Going by memory.....you have a switched bias circuit in that amp. It comes
on and off with voice peakes. Enables a cooler operation. That circuit is
having a problem. Ive heard of this before. But since I don't have an amp
like that I can only go by what I remembered.

Dan/W4NTI

"Chuck (Jack) Hawley" wrote in message
...
A friend has an AL80B (bought new) and is on his fourth 3-500 in two years
or so. It just developed a grid-cath short. Supposedly there was a batch
of
tubes that were prone to go bad, but the latest ones from MFJ are supposed
to be ok. Apparently not or something is wrong with the amp. He's a good
operator and seems to be tuning and operating within safe limits for the
AL80B. The latest tube is an Amperex as was the first ones in the reported
bad batch. He reduced the filament voltage last time from 5.7 (from the
factory) to about 5 before the present tube was installed.
Any ideas?
Chuck, KE9UW

Ameritron AL80B eats tubes...
 

Going by memory.....you have a switched bias circuit in that amp. It comes
on and off with voice peakes. Enables a cooler operation. That circuit is
having a problem. Ive heard of this before. But since I don't have an amp
like that I can only go by what I remembered.

Dan/W4NTI

"Chuck (Jack) Hawley" wrote in message
...
A friend has an AL80B (bought new) and is on his fourth 3-500 in two years
or so. It just developed a grid-cath short. Supposedly there was a batch
of
tubes that were prone to go bad, but the latest ones from MFJ are supposed
to be ok. Apparently not or something is wrong with the amp. He's a good
operator and seems to be tuning and operating within safe limits for the
AL80B. The latest tube is an Amperex as was the first ones in the reported
bad batch. He reduced the filament voltage last time from 5.7 (from the
factory) to about 5 before the present tube was installed.
Any ideas?
Chuck, KE9UW

Hi Chuck
You already fixed it. 5.7V on the

"Chuck (Jack) Hawley" wrote:

A friend has an AL80B (bought new) and is on his fourth 3-500 in two years
or so. It just developed a grid-cath short. Supposedly there was a batch of
tubes that were prone to go bad, but the latest ones from MFJ are supposed
to be ok. Apparently not or something is wrong with the amp. He's a good
operator and seems to be tuning and operating within safe limits for the
AL80B. The latest tube is an Amperex as was the first ones in the reported
bad batch. He reduced the filament voltage last time from 5.7 (from the
factory) to about 5 before the present tube was installed.
Any ideas?
Chuck, KE9UW

Hi Chuck
You already fixed it. 5.7V on the

"Chuck (Jack) Hawley" wrote:

A friend has an AL80B (bought new) and is on his fourth 3-500 in two years
or so. It just developed a grid-cath short. Supposedly there was a batch of
tubes that were prone to go bad, but the latest ones from MFJ are supposed
to be ok. Apparently not or something is wrong with the amp. He's a good
operator and seems to be tuning and operating within safe limits for the
AL80B. The latest tube is an Amperex as was the first ones in the reported
bad batch. He reduced the filament voltage last time from 5.7 (from the
factory) to about 5 before the present tube was installed.
Any ideas?
Chuck, KE9UW

Sorry I press send too early, The 5.7 volts on the filament will eat tubes in
a hurry, also, (In the Dark) look for plate choke shorting out,
I find weak points are the Bias circuit and the Bandswitch. I see many of them
that come in for repair with these being the most common problems.
But the 5.7V is a good start, I just can't see tubes being all bad. 73 Chris
VE3NGW/W4 Florida

"Chuck (Jack) Hawley" wrote:

A friend has an AL80B (bought new) and is on his fourth 3-500 in two years
or so. It just developed a grid-cath short. Supposedly there was a batch of
tubes that were prone to go bad, but the latest ones from MFJ are supposed
to be ok. Apparently not or something is wrong with the amp. He's a good
operator and seems to be tuning and operating within safe limits for the
AL80B. The latest tube is an Amperex as was the first ones in the reported
bad batch. He reduced the filament voltage last time from 5.7 (from the
factory) to about 5 before the present tube was installed.
Any ideas?
Chuck, KE9UW

Sorry I press send too early, The 5.7 volts on the filament will eat tubes in
a hurry, also, (In the Dark) look for plate choke shorting out,
I find weak points are the Bias circuit and the Bandswitch. I see many of them
that come in for repair with these being the most common problems.
But the 5.7V is a good start, I just can't see tubes being all bad. 73 Chris
VE3NGW/W4 Florida

"Chuck (Jack) Hawley" wrote:

A friend has an AL80B (bought new) and is on his fourth 3-500 in two years
or so. It just developed a grid-cath short. Supposedly there was a batch of
tubes that were prone to go bad, but the latest ones from MFJ are supposed
to be ok. Apparently not or something is wrong with the amp. He's a good
operator and seems to be tuning and operating within safe limits for the
AL80B. The latest tube is an Amperex as was the first ones in the reported
bad batch. He reduced the filament voltage last time from 5.7 (from the
factory) to about 5 before the present tube was installed.
Any ideas?
Chuck, KE9UW

The grid to cathode short is a clue... You might want to review the
parasitic issues with this and similar amplifiers. A parasitic "bang"
might be the source of this and or similar problems.

Have a look at Rich Measures (ag6k) web page... used to be at
http://www.vcnet.com/measures but is now moving (or has moved to)
http://www.somis.org

There are protections for grid to cathode shorts in 3-500z amps. I like to
use a proper triple bypassed grid resistor and have never had grid/cath
shorts in any amplifier with said after an upgrade to the parasitic
network(s).

If you have questions, you can contact me through the sonic server Email
icons or review Rich's web page and he will also reply to Emails.

cheers and good luck
skipp
http://sonic.ucdavis.edu

: "Chuck \(Jack\) Hawley" wrote:
: A friend has an AL80B (bought new) and is on his fourth 3-500 in two years
: or so. It just developed a grid-cath short. Supposedly there was a batch of
: tubes that were prone to go bad, but the latest ones from MFJ are supposed
: to be ok. Apparently not or something is wrong with the amp. He's a good
: operator and seems to be tuning and operating within safe limits for the
: AL80B. The latest tube is an Amperex as was the first ones in the reported
: bad batch. He reduced the filament voltage last time from 5.7 (from the
: factory) to about 5 before the present tube was installed.
: Any ideas?
: Chuck, KE9UW

The grid to cathode short is a clue... You might want to review the
parasitic issues with this and similar amplifiers. A parasitic "bang"
might be the source of this and or similar problems.

Have a look at Rich Measures (ag6k) web page... used to be at
http://www.vcnet.com/measures but is now moving (or has moved to)
http://www.somis.org

There are protections for grid to cathode shorts in 3-500z amps. I like to
use a proper triple bypassed grid resistor and have never had grid/cath
shorts in any amplifier with said after an upgrade to the parasitic
network(s).

If you have questions, you can contact me through the sonic server Email
icons or review Rich's web page and he will also reply to Emails.

cheers and good luck
skipp
http://sonic.ucdavis.edu

: "Chuck \(Jack\) Hawley" wrote:
: A friend has an AL80B (bought new) and is on his fourth 3-500 in two years
: or so. It just developed a grid-cath short. Supposedly there was a batch of
: tubes that were prone to go bad, but the latest ones from MFJ are supposed
: to be ok. Apparently not or something is wrong with the amp. He's a good
: operator and seems to be tuning and operating within safe limits for the
: AL80B. The latest tube is an Amperex as was the first ones in the reported
: bad batch. He reduced the filament voltage last time from 5.7 (from the
: factory) to about 5 before the present tube was installed.
: Any ideas?
: Chuck, KE9UW

I doubt it's a parasitic, but if you want to explore that, Measures has
his special parasitic kits for sale on his website.

Cheers as they say
Dale, K9VUJ






In article ,
Skipp can be reached through the sonic server
wrote:

The grid to cathode short is a clue... You might want to review the
parasitic issues with this and similar amplifiers. A parasitic "bang"
might be the source of this and or similar problems.

Have a look at Rich Measures (ag6k) web page... used to be at
http://www.vcnet.com/measures but is now moving (or has moved to)
http://www.somis.org

There are protections for grid to cathode shorts in 3-500z amps. I like to
use a proper triple bypassed grid resistor and have never had grid/cath
shorts in any amplifier with said after an upgrade to the parasitic
network(s).

If you have questions, you can contact me through the sonic server Email
icons or review Rich's web page and he will also reply to Emails.

cheers and good luck
skipp
http://sonic.ucdavis.edu

: "Chuck \(Jack\) Hawley" wrote:
: A friend has an AL80B (bought new) and is on his fourth 3-500 in two years
: or so. It just developed a grid-cath short. Supposedly there was a batch of
: tubes that were prone to go bad, but the latest ones from MFJ are supposed
: to be ok. Apparently not or something is wrong with the amp. He's a good
: operator and seems to be tuning and operating within safe limits for the
: AL80B. The latest tube is an Amperex as was the first ones in the reported
: bad batch. He reduced the filament voltage last time from 5.7 (from the
: factory) to about 5 before the present tube was installed.
: Any ideas?
: Chuck, KE9UW



--
Dale J.
Bloomington, Minnesota

E-mail:

I doubt it's a parasitic, but if you want to explore that, Measures has
his special parasitic kits for sale on his website.

Cheers as they say
Dale, K9VUJ






In article ,
Skipp can be reached through the sonic server
wrote:

The grid to cathode short is a clue... You might want to review the
parasitic issues with this and similar amplifiers. A parasitic "bang"
might be the source of this and or similar problems.

Have a look at Rich Measures (ag6k) web page... used to be at
http://www.vcnet.com/measures but is now moving (or has moved to)
http://www.somis.org

There are protections for grid to cathode shorts in 3-500z amps. I like to
use a proper triple bypassed grid resistor and have never had grid/cath
shorts in any amplifier with said after an upgrade to the parasitic
network(s).

If you have questions, you can contact me through the sonic server Email
icons or review Rich's web page and he will also reply to Emails.

cheers and good luck
skipp
http://sonic.ucdavis.edu

: "Chuck \(Jack\) Hawley" wrote:
: A friend has an AL80B (bought new) and is on his fourth 3-500 in two years
: or so. It just developed a grid-cath short. Supposedly there was a batch of
: tubes that were prone to go bad, but the latest ones from MFJ are supposed
: to be ok. Apparently not or something is wrong with the amp. He's a good
: operator and seems to be tuning and operating within safe limits for the
: AL80B. The latest tube is an Amperex as was the first ones in the reported
: bad batch. He reduced the filament voltage last time from 5.7 (from the
: factory) to about 5 before the present tube was installed.
: Any ideas?
: Chuck, KE9UW



--
Dale J.
Bloomington, Minnesota

E-mail:

"Dale J. " wrote in message ...
I doubt it's a parasitic, but if you want to explore that, Measures has
his special parasitic kits for sale on his website.

Cheers as they say
Dale, K9VUJ






In article ,
Skipp can be reached through the sonic server
wrote:

The grid to cathode short is a clue... You might want to review the
parasitic issues with this and similar amplifiers. A parasitic "bang"
might be the source of this and or similar problems.

Have a look at Rich Measures (ag6k) web page... used to be at
http://www.vcnet.com/measures but is now moving (or has moved to)
http://www.somis.org

There are protections for grid to cathode shorts in 3-500z amps. I like to
use a proper triple bypassed grid resistor and have never had grid/cath
shorts in any amplifier with said after an upgrade to the parasitic
network(s).

If you have questions, you can contact me through the sonic server Email
icons or review Rich's web page and he will also reply to Emails.

cheers and good luck
skipp
http://sonic.ucdavis.edu

: "Chuck \(Jack\) Hawley" wrote:
: A friend has an AL80B (bought new) and is on his fourth 3-500 in two years
: or so. It just developed a grid-cath short. Supposedly there was a batch of
: tubes that were prone to go bad, but the latest ones from MFJ are supposed
: to be ok. Apparently not or something is wrong with the amp. He's a good
: operator and seems to be tuning and operating within safe limits for the
: AL80B. The latest tube is an Amperex as was the first ones in the reported
: bad batch. He reduced the filament voltage last time from 5.7 (from the
: factory) to about 5 before the present tube was installed.
: Any ideas?
: Chuck, KE9UW



Sorry, but whats so complex about a 1 tube amplifier - if you have an
amateur license, you should have the theory to check it out - the
procedure for parasitics etc has been in the ARRL handbook for about
30 years or more - a voltmeter can be a useful instrument if its used
to check the specifications of the amplifier - and if it is playing
up, how do you know its not spraying garbage all across the spectrum?
- have you checked? -
de VK3BFA Andrew

"Dale J. " wrote in message ...
I doubt it's a parasitic, but if you want to explore that, Measures has
his special parasitic kits for sale on his website.

Cheers as they say
Dale, K9VUJ






In article ,
Skipp can be reached through the sonic server
wrote:

The grid to cathode short is a clue... You might want to review the
parasitic issues with this and similar amplifiers. A parasitic "bang"
might be the source of this and or similar problems.

Have a look at Rich Measures (ag6k) web page... used to be at
http://www.vcnet.com/measures but is now moving (or has moved to)
http://www.somis.org

There are protections for grid to cathode shorts in 3-500z amps. I like to
use a proper triple bypassed grid resistor and have never had grid/cath
shorts in any amplifier with said after an upgrade to the parasitic
network(s).

If you have questions, you can contact me through the sonic server Email
icons or review Rich's web page and he will also reply to Emails.

cheers and good luck
skipp
http://sonic.ucdavis.edu

: "Chuck \(Jack\) Hawley" wrote:
: A friend has an AL80B (bought new) and is on his fourth 3-500 in two years
: or so. It just developed a grid-cath short. Supposedly there was a batch of
: tubes that were prone to go bad, but the latest ones from MFJ are supposed
: to be ok. Apparently not or something is wrong with the amp. He's a good
: operator and seems to be tuning and operating within safe limits for the
: AL80B. The latest tube is an Amperex as was the first ones in the reported
: bad batch. He reduced the filament voltage last time from 5.7 (from the
: factory) to about 5 before the present tube was installed.
: Any ideas?
: Chuck, KE9UW



Sorry, but whats so complex about a 1 tube amplifier - if you have an
amateur license, you should have the theory to check it out - the
procedure for parasitics etc has been in the ARRL handbook for about
30 years or more - a voltmeter can be a useful instrument if its used
to check the specifications of the amplifier - and if it is playing
up, how do you know its not spraying garbage all across the spectrum?
- have you checked? -
de VK3BFA Andrew

As I mentioned before, a big clue is given in the grid to cathode short
description.

It takes a heck of a lot of energy to make these tube elements repeatedly
short. A parasitic bang is just such an animal.

Rich not only sells the kits cheap, but he provides the information to
"roll your own" on his web site.

cheers
skipp
http://sonic.ucdavis.edu

: Dale J. wrote:
: I doubt it's a parasitic, but if you want to explore that, Measures has
: his special parasitic kits for sale on his website.
: Cheers as they say
: Dale, K9VUJ

As I mentioned before, a big clue is given in the grid to cathode short
description.

It takes a heck of a lot of energy to make these tube elements repeatedly
short. A parasitic bang is just such an animal.

Rich not only sells the kits cheap, but he provides the information to
"roll your own" on his web site.

cheers
skipp
http://sonic.ucdavis.edu

: Dale J. wrote:
: I doubt it's a parasitic, but if you want to explore that, Measures has
: his special parasitic kits for sale on his website.
: Cheers as they say
: Dale, K9VUJ

"Voice In Wilderness" wrote in message news:iixYa.30982$ff.20061@fed1read01...
Ah come one guys -- he IS asking for advice as to how to repair the beast.
Why give em the old timers drill?
30 years ago many Hams were RF technical by occupation or the military.

Things and times have changed -- many are opting for the computer field.
Less and less RF savy in the Amateur Radio Service today and that is OK.

But when they come on asking for help --- you can Elmer or Bash --- the
choice is yours, but you know which one is correct in the spirit of Amateur
Radio

A refresher course inTHE AMATEURS CODE by Paul M. Segal, W9EEA (1928)


The Radio Amateur is:

CONSIDERATE..... never knowingly operating in such a way as to lessen the
pleasure of others.

LOYAL..... offering loyalty, encouragement and support to other amateurs.

FRIENDLY..... with slow and patient operation when requested, friendly
advice and counsel to the beginner, kindly assistance, co-operation and
consideration for the interests of others. These are the hallmarks of the
amateur spirit.

-------------------------------------------------------------------------


Point taken, and I readily concede that he is asking for help, and
hopefully from the replies he will be able to work it out.

Three
"The Amateur is progressive...He keeps his station abreast of science.
It is built well and efficiently. His operating practice is clean and
regular"

Thats from the 1961 ARRL Handbook - (no paricular year chosen, it was
grabbed out of the bookcase at random, and no, I didnt buy it new....)
I think its still relevant.



It seems to me that this problem has been going on for years -
consumed many tubes, and doesnt seem be solved except by "blaming"
someone - either MFJ, Eimac, whatever.

IF you have an Amateur license and IF you want to operate QRO then
there is a commensurate(sp) responsibility to be able to do that
WITHOUT causing harmful interference. That is in the terms and
conditions of your license. Fair enough, you can pass the exams on
crib sheets without any theory - but for heavens sake, this is
SUPPOSED to be a technical hobby!.

Buy a ARRL handbook, read the section on amplifiers, borrow a scanner
and see if its radiating anywhere else - not really high tech stuff,
just BASIC rf knowledge that is supposed to be a precondition of
getting a license.

In the interests of a good argument,

de VK3BFA Andrew

I get totally ****ed off when 2 amateurs, probably a few hundred miles
apart, insist on running QRO on 80m so they can chat to their buddies
in armchair comfort - wind the receive RF gain back to eliminate those
nasty atmospheric noises, and stuff the rest of the world trying to
have a QSO beneath them.

"Voice In Wilderness" wrote in message news:iixYa.30982$ff.20061@fed1read01...
Ah come one guys -- he IS asking for advice as to how to repair the beast.
Why give em the old timers drill?
30 years ago many Hams were RF technical by occupation or the military.

Things and times have changed -- many are opting for the computer field.
Less and less RF savy in the Amateur Radio Service today and that is OK.

But when they come on asking for help --- you can Elmer or Bash --- the
choice is yours, but you know which one is correct in the spirit of Amateur
Radio

A refresher course inTHE AMATEURS CODE by Paul M. Segal, W9EEA (1928)


The Radio Amateur is:

CONSIDERATE..... never knowingly operating in such a way as to lessen the
pleasure of others.

LOYAL..... offering loyalty, encouragement and support to other amateurs.

FRIENDLY..... with slow and patient operation when requested, friendly
advice and counsel to the beginner, kindly assistance, co-operation and
consideration for the interests of others. These are the hallmarks of the
amateur spirit.

-------------------------------------------------------------------------


Point taken, and I readily concede that he is asking for help, and
hopefully from the replies he will be able to work it out.

Three
"The Amateur is progressive...He keeps his station abreast of science.
It is built well and efficiently. His operating practice is clean and
regular"

Thats from the 1961 ARRL Handbook - (no paricular year chosen, it was
grabbed out of the bookcase at random, and no, I didnt buy it new....)
I think its still relevant.



It seems to me that this problem has been going on for years -
consumed many tubes, and doesnt seem be solved except by "blaming"
someone - either MFJ, Eimac, whatever.

IF you have an Amateur license and IF you want to operate QRO then
there is a commensurate(sp) responsibility to be able to do that
WITHOUT causing harmful interference. That is in the terms and
conditions of your license. Fair enough, you can pass the exams on
crib sheets without any theory - but for heavens sake, this is
SUPPOSED to be a technical hobby!.

Buy a ARRL handbook, read the section on amplifiers, borrow a scanner
and see if its radiating anywhere else - not really high tech stuff,
just BASIC rf knowledge that is supposed to be a precondition of
getting a license.

In the interests of a good argument,

de VK3BFA Andrew

I get totally ****ed off when 2 amateurs, probably a few hundred miles
apart, insist on running QRO on 80m so they can chat to their buddies
in armchair comfort - wind the receive RF gain back to eliminate those
nasty atmospheric noises, and stuff the rest of the world trying to
have a QSO beneath them.

In article ,
Skipp adds a little more wrote:

As I mentioned before, a big clue is given in the grid to cathode short
description.

It takes a heck of a lot of energy to make these tube elements repeatedly
short. A parasitic bang is just such an animal.

Rich not only sells the kits cheap, but he provides the information to
"roll your own" on his web site.

cheers
skipp
http://sonic.ucdavis.edu

: Dale J. wrote:
: I doubt it's a parasitic, but if you want to explore that, Measures has
: his special parasitic kits for sale on his website.
: Cheers as they say
: Dale, K9VUJ

Hows come mine (AL-80A) doent parasite? I don't want to make a big
argument of this, but this has frustrated me with this talk of parasites
curing all the problems.

--
Dale J.
Bloomington, Minnesota

E-mail:

In article ,
Skipp adds a little more wrote:

As I mentioned before, a big clue is given in the grid to cathode short
description.

It takes a heck of a lot of energy to make these tube elements repeatedly
short. A parasitic bang is just such an animal.

Rich not only sells the kits cheap, but he provides the information to
"roll your own" on his web site.

cheers
skipp
http://sonic.ucdavis.edu

: Dale J. wrote:
: I doubt it's a parasitic, but if you want to explore that, Measures has
: his special parasitic kits for sale on his website.
: Cheers as they say
: Dale, K9VUJ

Hows come mine (AL-80A) doent parasite? I don't want to make a big
argument of this, but this has frustrated me with this talk of parasites
curing all the problems.

--
Dale J.
Bloomington, Minnesota

E-mail:

"Dale J. " wrote in message ...
In article ,
Skipp adds a little more wrote:

As I mentioned before, a big clue is given in the grid to cathode short
description.

It takes a heck of a lot of energy to make these tube elements repeatedly
short. A parasitic bang is just such an animal.

Rich not only sells the kits cheap, but he provides the information to
"roll your own" on his web site.

cheers
skipp
http://sonic.ucdavis.edu

: Dale J. wrote:
: I doubt it's a parasitic, but if you want to explore that, Measures has
: his special parasitic kits for sale on his website.
: Cheers as they say
: Dale, K9VUJ

Hows come mine (AL-80A) doent parasite? I don't want to make a big
argument of this, but this has frustrated me with this talk of parasites
curing all the problems.


Its been pointed out to me that I have been an unhelpful old grump -
and, re-readinfg the Amateurs Code, I can see its true. My aplogies
all round - should have engaged brain before opening mouth.

Its an interesting fault - have downloaded the MFJ manual and will
study it when I have some spare time. However, a few comments in the
meantime...

1. If there was a faulty batch of tubes, they would have been cleared
out by now - MFJ would have had words with Amperex, so they can be
eliminated as future fault causes.

2. is it a design error - possibly, but then again MFJ would be aware
of it by now and offered a correction - this company would not stay in
business in the Amateur Radio marketplace if it didnt.

3. The filaments high at 5.7 volts - it can be safely assumed that MFJ
would have set them up properly at the factory - this suggests that
the AC line voltage is high - variations are not unknown (here its
plus/minus 10% on 240VAC - fine, except when it causes marginally
rated 220V European equipment to die - took me a while to figure
that one out....). Check the AC line voltage with a KNOWN ACCURATE
voltmeter (I like Fluke, because they come out of the factory set up
properly) and adjust transformer taps if necessary.

4. is it a parasitic oscillation - the traditional check is to swing
the plate tune capacitor acrtoss its range and check for multiple
small dips - if so, there is one. A more scientific way is to use a
spectrum analyser if available, a cheap way out there is to sit a
scanner near it and tune across every band etc and look for birdies
etc.

5. the dynamic bias (good way for QSK switching) and ALC circuit in
this thing looks interesting - possibly a fault there (which would
explain why the AL80A doesnt have problems - its fixed bias) - but
this is speculation, as I said I havent had time to check/compare both
circuits or analyse how the AL80B circuit is suppossed to work.

Anyway, again my aplogies to the group for being a Grump - will try
not to do it again.

73 de VK3BFA Andrew

"Dale J. " wrote in message ...
In article ,
Skipp adds a little more wrote:

As I mentioned before, a big clue is given in the grid to cathode short
description.

It takes a heck of a lot of energy to make these tube elements repeatedly
short. A parasitic bang is just such an animal.

Rich not only sells the kits cheap, but he provides the information to
"roll your own" on his web site.

cheers
skipp
http://sonic.ucdavis.edu

: Dale J. wrote:
: I doubt it's a parasitic, but if you want to explore that, Measures has
: his special parasitic kits for sale on his website.
: Cheers as they say
: Dale, K9VUJ

Hows come mine (AL-80A) doent parasite? I don't want to make a big
argument of this, but this has frustrated me with this talk of parasites
curing all the problems.


Its been pointed out to me that I have been an unhelpful old grump -
and, re-readinfg the Amateurs Code, I can see its true. My aplogies
all round - should have engaged brain before opening mouth.

Its an interesting fault - have downloaded the MFJ manual and will
study it when I have some spare time. However, a few comments in the
meantime...

1. If there was a faulty batch of tubes, they would have been cleared
out by now - MFJ would have had words with Amperex, so they can be
eliminated as future fault causes.

2. is it a design error - possibly, but then again MFJ would be aware
of it by now and offered a correction - this company would not stay in
business in the Amateur Radio marketplace if it didnt.

3. The filaments high at 5.7 volts - it can be safely assumed that MFJ
would have set them up properly at the factory - this suggests that
the AC line voltage is high - variations are not unknown (here its
plus/minus 10% on 240VAC - fine, except when it causes marginally
rated 220V European equipment to die - took me a while to figure
that one out....). Check the AC line voltage with a KNOWN ACCURATE
voltmeter (I like Fluke, because they come out of the factory set up
properly) and adjust transformer taps if necessary.

4. is it a parasitic oscillation - the traditional check is to swing
the plate tune capacitor acrtoss its range and check for multiple
small dips - if so, there is one. A more scientific way is to use a
spectrum analyser if available, a cheap way out there is to sit a
scanner near it and tune across every band etc and look for birdies
etc.

5. the dynamic bias (good way for QSK switching) and ALC circuit in
this thing looks interesting - possibly a fault there (which would
explain why the AL80A doesnt have problems - its fixed bias) - but
this is speculation, as I said I havent had time to check/compare both
circuits or analyse how the AL80B circuit is suppossed to work.

Anyway, again my aplogies to the group for being a Grump - will try
not to do it again.

73 de VK3BFA Andrew

Andrew VK3BFA wrote:

1. If there was a faulty batch of tubes, they would have been cleared
out by now - MFJ would have had words with Amperex, so they can be
eliminated as future fault causes.

2. is it a design error - possibly, but then again MFJ would be aware
of it by now and offered a correction - this company would not stay in
business in the Amateur Radio marketplace if it didnt.

3. The filaments high at 5.7 volts - it can be safely assumed that MFJ
would have set them up properly at the factory


How can it be safely assumed? You seem to be assuming too much of the
manufacturers. Their business is not humanitarian relief - they're in
this for the money. They would certainly not be the first one to make an
amp with the filament voltage too high.


73 .... WA7AA

--

Anti-spam measu look me up on qrz.com if you need to reply directly

Andrew VK3BFA wrote:

1. If there was a faulty batch of tubes, they would have been cleared
out by now - MFJ would have had words with Amperex, so they can be
eliminated as future fault causes.

2. is it a design error - possibly, but then again MFJ would be aware
of it by now and offered a correction - this company would not stay in
business in the Amateur Radio marketplace if it didnt.

3. The filaments high at 5.7 volts - it can be safely assumed that MFJ
would have set them up properly at the factory


How can it be safely assumed? You seem to be assuming too much of the
manufacturers. Their business is not humanitarian relief - they're in
this for the money. They would certainly not be the first one to make an
amp with the filament voltage too high.


73 .... WA7AA

--

Anti-spam measu look me up on qrz.com if you need to reply directly

In article ,
Zoran Brlecic wrote:

How can it be safely assumed? You seem to be assuming too much of the
manufacturers. Their business is not humanitarian relief - they're in
this for the money. They would certainly not be the first one to make an
amp with the filament voltage too high.


73 .... WA7AA

Perhaps you're on to something. My AL80A was mfg by Prime Instruments
which made a fine amplifier, still with the original Eimac tube.

--
Dale J.
Bloomington, Minnesota

E-mail:

In article ,
Zoran Brlecic wrote:

How can it be safely assumed? You seem to be assuming too much of the
manufacturers. Their business is not humanitarian relief - they're in
this for the money. They would certainly not be the first one to make an
amp with the filament voltage too high.


73 .... WA7AA

Perhaps you're on to something. My AL80A was mfg by Prime Instruments
which made a fine amplifier, still with the original Eimac tube.

--
Dale J.
Bloomington, Minnesota

E-mail:

"Dale J. " wrote in message ...
In article ,
Zoran Brlecic wrote:

How can it be safely assumed? You seem to be assuming too much of the
manufacturers. Their business is not humanitarian relief - they're in
this for the money. They would certainly not be the first one to make an
amp with the filament voltage too high.


73 .... WA7AA

Perhaps you're on to something. My AL80A was mfg by Prime Instruments
which made a fine amplifier, still with the original Eimac tube.

The vast majority of 3-500z amps have the filiment voltage set too
high from the factory. Probably 80% of them. Maybe more... most
henrys, including my 2k classic, TL-922's, SB-220's, most Ameritrons,
etc, all are guilty. You can stretch the tube life out a good bit if
you lower the voltage. MK

"Dale J. " wrote in message ...
In article ,
Zoran Brlecic wrote:

How can it be safely assumed? You seem to be assuming too much of the
manufacturers. Their business is not humanitarian relief - they're in
this for the money. They would certainly not be the first one to make an
amp with the filament voltage too high.


73 .... WA7AA

Perhaps you're on to something. My AL80A was mfg by Prime Instruments
which made a fine amplifier, still with the original Eimac tube.

The vast majority of 3-500z amps have the filiment voltage set too
high from the factory. Probably 80% of them. Maybe more... most
henrys, including my 2k classic, TL-922's, SB-220's, most Ameritrons,
etc, all are guilty. You can stretch the tube life out a good bit if
you lower the voltage. MK

In article ,
"Chuck \(Jack\) Hawley" wrote:

Good tips...all of these. By the way, this is the worst schematic I have
ever seen on any piece of electronic equipment.
I take it that the 80A was built by another company which was bought by MFJ.
I'm beginning to think we should convert this amp to an 80A even if the
active bias ckt is not the culprit here.

Thanks,

Chuck, KE9UW


As I understand, Ameritron first came out with the AL-80 which wasnt too
good, then Prime Instruments bought out Ameritron and upgraded and
improved the AL-80 into the AL-80A. After that it gets cloudy. I think
MFJ bought the ham stuff from Prime and came out with the AL-80B. Even
though my AL-80A says Ameritron on the front the back says Prime
Instruments.

If anyone knows better please come forth.

The AL-80A is a good amp for the money, $500-$800 . Power out 800 to
1000. I don't like to push mine too much so I keep it down around 800
in SSB. Also I usually don't use a amp, 100-200 watts gets the job done
most of the time.

73
Dale, K9VUJ

--
Dale J.
Bloomington, Minnesota

E-mail:

In article ,
"Chuck \(Jack\) Hawley" wrote:

Good tips...all of these. By the way, this is the worst schematic I have
ever seen on any piece of electronic equipment.
I take it that the 80A was built by another company which was bought by MFJ.
I'm beginning to think we should convert this amp to an 80A even if the
active bias ckt is not the culprit here.

Thanks,

Chuck, KE9UW


As I understand, Ameritron first came out with the AL-80 which wasnt too
good, then Prime Instruments bought out Ameritron and upgraded and
improved the AL-80 into the AL-80A. After that it gets cloudy. I think
MFJ bought the ham stuff from Prime and came out with the AL-80B. Even
though my AL-80A says Ameritron on the front the back says Prime
Instruments.

If anyone knows better please come forth.

The AL-80A is a good amp for the money, $500-$800 . Power out 800 to
1000. I don't like to push mine too much so I keep it down around 800
in SSB. Also I usually don't use a amp, 100-200 watts gets the job done
most of the time.

73
Dale, K9VUJ

--
Dale J.
Bloomington, Minnesota

E-mail:

For what it is worth there is a mod for AL-80B's to get rid of the "dynamic
bias circuit used to cut off the idle
current and reduce heat"

There was an apparent problem with the dynamic bias circuit introducing SSB
distortion. See URL:

http://ham.shineline.it/i3fue/mods-a-d/al80b.txt
Proceed at your own risk. Caveat Modifcatious !!
Remember most mods posted on the web are conjured up by Amateurs !!!

I bought my AL-80B used and it has this mod -- left it alone -- been
pouring out the Watts w/o a problem for 2 years now.

AL-80's were (still are ?) an Ameritron Design as far as I know. Affiliated
with MFJ somewhere along the line.
======================

Good tips...all of these. By the way, this is the worst schematic I have
ever seen on any piece of electronic equipment.
I take it that the 80A was built by another company which was bought by
MFJ.
I'm beginning to think we should convert this amp to an 80A even if the
active bias ckt is not the culprit here.

Thanks,
Snip

For what it is worth there is a mod for AL-80B's to get rid of the "dynamic
bias circuit used to cut off the idle
current and reduce heat"

There was an apparent problem with the dynamic bias circuit introducing SSB
distortion. See URL:

http://ham.shineline.it/i3fue/mods-a-d/al80b.txt
Proceed at your own risk. Caveat Modifcatious !!
Remember most mods posted on the web are conjured up by Amateurs !!!

I bought my AL-80B used and it has this mod -- left it alone -- been
pouring out the Watts w/o a problem for 2 years now.

AL-80's were (still are ?) an Ameritron Design as far as I know. Affiliated
with MFJ somewhere along the line.
======================

Good tips...all of these. By the way, this is the worst schematic I have
ever seen on any piece of electronic equipment.
I take it that the 80A was built by another company which was bought by
MFJ.
I'm beginning to think we should convert this amp to an 80A even if the
active bias ckt is not the culprit here.

Thanks,
Snip

"Mark Keith" wrote in message
om...
(Andrew VK3BFA) wrote in message

Wow, I wonder if we are talking about the same thing here - what I was
refering to was the bunch of lids starting their scheduled net (which
the rest of the world should know about anyway, after all its "Their "
frequency ) all running high power with the rf gain wound right back
and not even noticing that they are QRM ing people underneath them
-and these same lids then get really ****ed off when someone with more
power does it to them. You arent one of these people are you?

I doubt it. I don't do nets.

- the
ones I was speciffically reffering to were about 2 years ago (the most
noticeable) when I was operating portable on 80m in the middle of a
forrest in the middle of winter (bloody freezing cold and wet,
operating QRP) during a safety net for a car rally and two Americans
came up and started their QSO - no way they could hear anyone under
them, and I dont think it would have made any difference to them
anyway. We couldnt QSY as the QRO guys didnt leave breaks, just kept
on yakking for hours and hours and hours........ dont ya just love
em....

If you were using the freq first, then yes, they were lids. But also,
you did most likely have a puny signal if you ran QRP on 80m. They
might not have heard you with the rf gain full up. Did they actually
say they had the gain rolled back?

But hey, this is the way it is - in psychology its called the "law of
comparative advantage" - If I have a big SUV then those nasty little
foreign cars wont bother me when I hit them - but eventually these
drivers get a big SUV as well so eventually everyone is stuck in
traffic driving gas guzzling trucks going nowhere. Same applies to QRO
- if nobody used it, then maybe, just maybe, no one would need it.

Probably so. I don't need it. I have good antennas. But you are going
to have to expect things like that when running a peanut whistle on
75m. I wouldn't lose much sleep over it.

BTW - whats the radiated power adjacent channel from a amplifier
putting out 1300 watts - assuming its well designed and has -35
supprseeion (sorry, cant think of the right word here...or the right
spelling....)

Dunno, not sure the question you are asking. MK

Only way to run QRP on 80m is in the dead of winter at 2-3am in the morning.
Most of the time QRP on 80 means 400 watts output.

Dan/W4NTI

"Mark Keith" wrote in message
om...
(Andrew VK3BFA) wrote in message

Wow, I wonder if we are talking about the same thing here - what I was
refering to was the bunch of lids starting their scheduled net (which
the rest of the world should know about anyway, after all its "Their "
frequency ) all running high power with the rf gain wound right back
and not even noticing that they are QRM ing people underneath them
-and these same lids then get really ****ed off when someone with more
power does it to them. You arent one of these people are you?

I doubt it. I don't do nets.

- the
ones I was speciffically reffering to were about 2 years ago (the most
noticeable) when I was operating portable on 80m in the middle of a
forrest in the middle of winter (bloody freezing cold and wet,
operating QRP) during a safety net for a car rally and two Americans
came up and started their QSO - no way they could hear anyone under
them, and I dont think it would have made any difference to them
anyway. We couldnt QSY as the QRO guys didnt leave breaks, just kept
on yakking for hours and hours and hours........ dont ya just love
em....

If you were using the freq first, then yes, they were lids. But also,
you did most likely have a puny signal if you ran QRP on 80m. They
might not have heard you with the rf gain full up. Did they actually
say they had the gain rolled back?

But hey, this is the way it is - in psychology its called the "law of
comparative advantage" - If I have a big SUV then those nasty little
foreign cars wont bother me when I hit them - but eventually these
drivers get a big SUV as well so eventually everyone is stuck in
traffic driving gas guzzling trucks going nowhere. Same applies to QRO
- if nobody used it, then maybe, just maybe, no one would need it.

Probably so. I don't need it. I have good antennas. But you are going
to have to expect things like that when running a peanut whistle on
75m. I wouldn't lose much sleep over it.

BTW - whats the radiated power adjacent channel from a amplifier
putting out 1300 watts - assuming its well designed and has -35
supprseeion (sorry, cant think of the right word here...or the right
spelling....)

Dunno, not sure the question you are asking. MK

Only way to run QRP on 80m is in the dead of winter at 2-3am in the morning.
Most of the time QRP on 80 means 400 watts output.

Dan/W4NTI

Seventy five meters sounds like CB these days. I don't bother going there
any longer.

Ed, NM2K

"Dan/W4NTI" wrote in message
...

"Mark Keith" wrote in message
om...
(Andrew VK3BFA) wrote in message

Wow, I wonder if we are talking about the same thing here - what I was
refering to was the bunch of lids starting their scheduled net (which
the rest of the world should know about anyway, after all its "Their "
frequency ) all running high power with the rf gain wound right back
and not even noticing that they are QRM ing people underneath them
-and these same lids then get really ****ed off when someone with more
power does it to them. You arent one of these people are you?

I doubt it. I don't do nets.

- the
ones I was speciffically reffering to were about 2 years ago (the most
noticeable) when I was operating portable on 80m in the middle of a
forrest in the middle of winter (bloody freezing cold and wet,
operating QRP) during a safety net for a car rally and two Americans
came up and started their QSO - no way they could hear anyone under
them, and I dont think it would have made any difference to them
anyway. We couldnt QSY as the QRO guys didnt leave breaks, just kept
on yakking for hours and hours and hours........ dont ya just love
em....

If you were using the freq first, then yes, they were lids. But also,
you did most likely have a puny signal if you ran QRP on 80m. They
might not have heard you with the rf gain full up. Did they actually
say they had the gain rolled back?

But hey, this is the way it is - in psychology its called the "law of
comparative advantage" - If I have a big SUV then those nasty little
foreign cars wont bother me when I hit them - but eventually these
drivers get a big SUV as well so eventually everyone is stuck in
traffic driving gas guzzling trucks going nowhere. Same applies to QRO
- if nobody used it, then maybe, just maybe, no one would need it.

Probably so. I don't need it. I have good antennas. But you are going
to have to expect things like that when running a peanut whistle on
75m. I wouldn't lose much sleep over it.

BTW - whats the radiated power adjacent channel from a amplifier
putting out 1300 watts - assuming its well designed and has -35
supprseeion (sorry, cant think of the right word here...or the right
spelling....)

Dunno, not sure the question you are asking. MK

Only way to run QRP on 80m is in the dead of winter at 2-3am in the
morning.
Most of the time QRP on 80 means 400 watts output.

Dan/W4NTI

Seventy five meters sounds like CB these days. I don't bother going there
any longer.

Ed, NM2K

"Dan/W4NTI" wrote in message
...

"Mark Keith" wrote in message
om...
(Andrew VK3BFA) wrote in message

Wow, I wonder if we are talking about the same thing here - what I was
refering to was the bunch of lids starting their scheduled net (which
the rest of the world should know about anyway, after all its "Their "
frequency ) all running high power with the rf gain wound right back
and not even noticing that they are QRM ing people underneath them
-and these same lids then get really ****ed off when someone with more
power does it to them. You arent one of these people are you?

I doubt it. I don't do nets.

- the
ones I was speciffically reffering to were about 2 years ago (the most
noticeable) when I was operating portable on 80m in the middle of a
forrest in the middle of winter (bloody freezing cold and wet,
operating QRP) during a safety net for a car rally and two Americans
came up and started their QSO - no way they could hear anyone under
them, and I dont think it would have made any difference to them
anyway. We couldnt QSY as the QRO guys didnt leave breaks, just kept
on yakking for hours and hours and hours........ dont ya just love
em....

If you were using the freq first, then yes, they were lids. But also,
you did most likely have a puny signal if you ran QRP on 80m. They
might not have heard you with the rf gain full up. Did they actually
say they had the gain rolled back?

But hey, this is the way it is - in psychology its called the "law of
comparative advantage" - If I have a big SUV then those nasty little
foreign cars wont bother me when I hit them - but eventually these
drivers get a big SUV as well so eventually everyone is stuck in
traffic driving gas guzzling trucks going nowhere. Same applies to QRO
- if nobody used it, then maybe, just maybe, no one would need it.

Probably so. I don't need it. I have good antennas. But you are going
to have to expect things like that when running a peanut whistle on
75m. I wouldn't lose much sleep over it.

BTW - whats the radiated power adjacent channel from a amplifier
putting out 1300 watts - assuming its well designed and has -35
supprseeion (sorry, cant think of the right word here...or the right
spelling....)

Dunno, not sure the question you are asking. MK

Only way to run QRP on 80m is in the dead of winter at 2-3am in the
morning.
Most of the time QRP on 80 means 400 watts output.

Dan/W4NTI