(Chris Kilmer) wrote in message . com...
Hey folks, got a question: I just bought a S-38C and have replaced
most of the resistors. I will be replacing the rest of the capacitors
this week. I've also replaced all 5 tubes with new ones from AES. The
radio does work a lot better than it did when I first got it, but two
problems remain:

1) I only pick up 3 local AM stations (I live in downtown Washington,
DC.) Is this something I should be concerned about? I am new to all of
this, and I am still learning... but it seems to me that this radio
should be picking up more than 3 stations. I have a pretty big antenna
attached to it, so I'm pretty sure that's not the problem. Is living
smack-dab in the middle of downtown the reason why I can't pick up any
AM stations besides the local megawatt monsters? Or might the poor
reception be due to the fact that there are still 5 wax capacitors
that haven't been replaced? Bands 2 and 3 pull in tons of stations;
band 4 only pulls in a few but I'm not worried about that.

2) When I first got the radio, it worked but not very well. The
bandspread tuner worked fine, but after I operated it for a few hours
and then turned it off and started ripping out caps and resistors for
replacement, the bandspread didn't work the way it used to. Now, it
tunes just fine from 0 - 70, but when you turn it past 70 a very loud
crackle is heard, and then there's nothing but a soft buzz. If you
turn the knob back down below 70, the stations come back. Besides this
problem, the bandspread tuner works like a champ.

I've been having a great time restoring this thing, and learning from
my mistakes. I've got a shipment of the remaining capacitors that I
couldn't find at AES coming to me this week from Mouser... when I'm
done replacing those, there won't be much left to replace!

Thanks.
chris

Hello Chris,I think you should examine the RF coil assy. and check for
open circuit in BC input...think about this, If this receiver had an
external antenna connected and was sitting there on the BC
band,turned off,and a lightning charge came along it would most likely
burn out the BC RF coil,making it extremely weak on that band..I have
seen it happen many,many times. if the ant winding is open ,just take
some small wire,like 28 Ga. and wind about six turns on the form as an
antenna primary .. should work OK good luck W4PQW

In article ,
writes:

Hello Chris,I think you should examine the RF coil assy. and check for
open circuit in BC input...think about this, If this receiver had an
external antenna connected and was sitting there on the BC
band,turned off,and a lightning charge came along it would most likely
burn out the BC RF coil,making it extremely weak on that band.

This is good advice -- check that primary.
I'd like to add that many antenna primaries get blown out because someone
discovers that a ground makes a pretty good antenna -- because it's using the
hot side of the house power wiring as an antenna. If your line bypass caps are
leaky, you'll get excess AC current thrut he antenna to ground -- I've seen
sparks thrown, not big fat ones, jsut enugh to let you know it isn't good for
the coil.

And if you have a fancy antenna system with a baluyn coil, then for 60 cycle
AC, the "hot" antenna lead is as good as ground, so be sure to hook up the
ground side first. Which is just hte opposite of what PL-259 coax connectors
do ,,,
--Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

r (Mike Knudsen) wrote in message ...
In article ,
writes:

Hello Chris,I think you should examine the RF coil assy. and check for
open circuit in BC input...think about this, If this receiver had an
external antenna connected and was sitting there on the BC
band,turned off,and a lightning charge came along it would most likely
burn out the BC RF coil,making it extremely weak on that band.

This is good advice -- check that primary.
I'd like to add that many antenna primaries get blown out because someone
discovers that a ground makes a pretty good antenna -- because it's using the
hot side of the house power wiring as an antenna. If your line bypass caps are
leaky, you'll get excess AC current thrut he antenna to ground -- I've seen
sparks thrown, not big fat ones, jsut enugh to let you know it isn't good for
the coil.

And if you have a fancy antenna system with a baluyn coil, then for 60 cycle
AC, the "hot" antenna lead is as good as ground, so be sure to hook up the
ground side first. Which is just hte opposite of what PL-259 coax connectors
do ,,,
--Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

Thanks everyone for the advice. I have since replaced all but one of
the wax caps and lamentably, the AM band is totally shot now. All I
get are two very strong stations and then WMAL, which I used to get
fine, is all but dead (it usually comes in at 630 AM, but now for some
reason it is tuning in at 500 and very very faint...) I'm a total
novice at this but I guess it doesn't take a novice to realize that
this thing is horribly out of alignment. I am really going to need to
teach myself how to do an alignment. I just hope I don't electrocute
myself! ;-) Does replacing capacitors necessarily throw a radio's
alignment completely out of whack like this?

I hope I used the right kinds of capacitors to replace the old wax
caps. Although I am positive I ordered the right values (voltage, mmf,
etc.) and triple checked everything when I replaced the old ones, I
hope I got the right type of materials. I got mica caps from Mouser
and AES when available, but there was one caps that I got that is a
"polyester film" capacitor.

Also a question about tolerances -- how important is it to get a
capacitor with the exact tolerance? When I'm looking up part numbers,
sometimes a capacitor won't list any tolerance at all; other times, a
tolerance is listed (Say, 10%) and that's the only one they have with
the voltage/farad spec that I need, but the radio's parts list
requires a 5%. Will performance/safety be affected adversely if I go
with a capacitor with a 10% tolerance instead of the required 5% ?
Maybe it's a silly question, but it's hard to find some of these
tolerances, at least in my experience.

Thanks for putting up with these questions.

-chris

Chris Kilmer wrote:
r (Mike Knudsen) wrote in message ...

In article ,
writes:


Hello Chris,I think you should examine the RF coil assy. and check for
open circuit in BC input...think about this, If this receiver had an
external antenna connected and was sitting there on the BC
band,turned off,and a lightning charge came along it would most likely
burn out the BC RF coil,making it extremely weak on that band.

This is good advice -- check that primary.
I'd like to add that many antenna primaries get blown out because someone
discovers that a ground makes a pretty good antenna -- because it's using the
hot side of the house power wiring as an antenna. If your line bypass caps are
leaky, you'll get excess AC current thrut he antenna to ground -- I've seen
sparks thrown, not big fat ones, jsut enugh to let you know it isn't good for
the coil.

And if you have a fancy antenna system with a baluyn coil, then for 60 cycle
AC, the "hot" antenna lead is as good as ground, so be sure to hook up the
ground side first. Which is just hte opposite of what PL-259 coax connectors
do ,,,
--Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.


Thanks everyone for the advice. I have since replaced all but one of
the wax caps and lamentably, the AM band is totally shot now. All I
get are two very strong stations and then WMAL, which I used to get
fine, is all but dead (it usually comes in at 630 AM, but now for some
reason it is tuning in at 500 and very very faint...) I'm a total
novice at this but I guess it doesn't take a novice to realize that
this thing is horribly out of alignment. I am really going to need to
teach myself how to do an alignment. I just hope I don't electrocute
myself! ;-) Does replacing capacitors necessarily throw a radio's
alignment completely out of whack like this?

I hope I used the right kinds of capacitors to replace the old wax
caps. Although I am positive I ordered the right values (voltage, mmf,
etc.) and triple checked everything when I replaced the old ones, I
hope I got the right type of materials. I got mica caps from Mouser
and AES when available, but there was one caps that I got that is a
"polyester film" capacitor.

Also a question about tolerances -- how important is it to get a
capacitor with the exact tolerance? When I'm looking up part numbers,
sometimes a capacitor won't list any tolerance at all; other times, a
tolerance is listed (Say, 10%) and that's the only one they have with
the voltage/farad spec that I need, but the radio's parts list
requires a 5%. Will performance/safety be affected adversely if I go
with a capacitor with a 10% tolerance instead of the required 5% ?
Maybe it's a silly question, but it's hard to find some of these
tolerances, at least in my experience.

Thanks for putting up with these questions.

-chris


Questions are never silly. Well, maybe sometimes :-) The variances
between say an .05 and a .047 are nil. You could recap the whole darn
radio with .01 or .02 and rarely notice a difference.

You're looking for the fly on the elephant's butt while ignoring that
he's in the room (Yeah, I heard that from Bill Maher). I'm going to
give you credit for having chosen the correct value caps and putting
them in the right place but CHECK THAT ANTENNA COIL and CHECK THOSE
TUBES if you haven't done so already.
Has anyone mentioned that maybe you should check the antenna coil for
continuity? If not, I'd recommend checking the antenna coil. Checking
th antenna coil would be a good idea. Maybe it has a problem and
checking it would allow you to confirm or refute that common problem.
Schematics are on nostalgiaair.com and BAMA. Get dirty with the radio,
don't try to rationalize it. Check the antenna coil or better still
check your own work and then CHECK THE ANTENNA COIL.

-BM

Chris,
Let us know where you are located and maybe someone from the list who lives
nearby can meet with you and share some of their experience showing you how to
debug a problem radio in a systematic manner. If that doesn't work out, get a
copy of an old tube radio servicing bk (Marcus wrote some classics) and read up
on what each stage does and what the symptoms to look for are. A new book
called "All American Five" is also very good. Your enthusiasm is good, but some
assistance may help. By the way, the S-38 series has a "hot" chassis so use
what is called and isolation transformer when working on and using it. 73 Mike
KF6KXG

"Chris Kilmer" wrote in message
om...

[snip]

. All I
get are two very strong stations and then WMAL, which I used to get
fine, is all but dead (it usually comes in at 630 AM, but now for some
reason it is tuning in at 500 and very very faint...)

[snip]

I'm confused. Where are you reading 500? I don't think this radio
indicates any tuning below 540kc.

Frank Dresser