Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Old November 19th 03, 07:47 PM
RonE
 
Posts: n/a
Default Yeasu FT-990 runnaway power

I recently acquired a "dead" Ft-990.

I got the receiver running and found I had a bad T/R relay, got that
replaced, now I have 100++ power out on all bands no matter where the RF Pwr
knob is set. I have come a long way from a dead transceiver, but the rig is
still unusable as is since the output cannot be adjusted. I did see a
voltage change from ~-6 volts to about +.3 volts at a test point shown in
the service manual. I thought I'd drop a quick note in here to see if
someone may have run into a similar issue with the 990 in the past. I THINK
the problem is on the RF card, but am not sure. The service manual is great
for schematics and part numbers, but is seriously lacking in theory.

Anyhow, any help / suggestions would be great. remove the "spam" to email
me directly, if you like.

Ron E.
W0IFL



  #2   Report Post  
Old November 20th 03, 04:24 AM
Gary P. Fiber
 
Posts: n/a
Default

When I worked at Icom we saw a few that acted like your Yaesu does. On
the Icom's it was almost always the Power Amplifier was oscillating.
When that happens no power control adjustment is going to help. Some
of the times it was a transistor in the receiver switching circuit
that was causing the oscillation to happen.

Just a thought, I know Icom and Yaesu are not the same but I would
suspect circuit designs are not that dissimilar.




On Wed, 19 Nov 2003 18:47:06 GMT, "RonE" wrote:

I recently acquired a "dead" Ft-990.

I got the receiver running and found I had a bad T/R relay, got that
replaced, now I have 100++ power out on all bands no matter where the RF Pwr
knob is set. I have come a long way from a dead transceiver, but the rig is
still unusable as is since the output cannot be adjusted. I did see a
voltage change from ~-6 volts to about +.3 volts at a test point shown in
the service manual. I thought I'd drop a quick note in here to see if
someone may have run into a similar issue with the 990 in the past. I THINK
the problem is on the RF card, but am not sure. The service manual is great
for schematics and part numbers, but is seriously lacking in theory.

Anyhow, any help / suggestions would be great. remove the "spam" to email
me directly, if you like.

Ron E.
W0IFL



Gary K8IZ
Washington State Resident
Registered Linux User # 312991
  #3   Report Post  
Old November 20th 03, 04:24 AM
Gary P. Fiber
 
Posts: n/a
Default

When I worked at Icom we saw a few that acted like your Yaesu does. On
the Icom's it was almost always the Power Amplifier was oscillating.
When that happens no power control adjustment is going to help. Some
of the times it was a transistor in the receiver switching circuit
that was causing the oscillation to happen.

Just a thought, I know Icom and Yaesu are not the same but I would
suspect circuit designs are not that dissimilar.




On Wed, 19 Nov 2003 18:47:06 GMT, "RonE" wrote:

I recently acquired a "dead" Ft-990.

I got the receiver running and found I had a bad T/R relay, got that
replaced, now I have 100++ power out on all bands no matter where the RF Pwr
knob is set. I have come a long way from a dead transceiver, but the rig is
still unusable as is since the output cannot be adjusted. I did see a
voltage change from ~-6 volts to about +.3 volts at a test point shown in
the service manual. I thought I'd drop a quick note in here to see if
someone may have run into a similar issue with the 990 in the past. I THINK
the problem is on the RF card, but am not sure. The service manual is great
for schematics and part numbers, but is seriously lacking in theory.

Anyhow, any help / suggestions would be great. remove the "spam" to email
me directly, if you like.

Ron E.
W0IFL



Gary K8IZ
Washington State Resident
Registered Linux User # 312991
  #4   Report Post  
Old November 20th 03, 02:09 PM
RonE
 
Posts: n/a
Default

Thanks Gary,
I never even considered that. I did have to replace the T/R relay, it was
stuck in receive. I scratched my head over that for a while... 20Amp current
draw, and NO output.. Anyhow, got that replaced. Maybe the transistor that
drives that relay needs replaced as well..

Ron E.
W0IFL
--

"Gary P. Fiber" wrote in message
...
When I worked at Icom we saw a few that acted like your Yaesu does. On
the Icom's it was almost always the Power Amplifier was oscillating.
When that happens no power control adjustment is going to help. Some
of the times it was a transistor in the receiver switching circuit
that was causing the oscillation to happen.

Just a thought, I know Icom and Yaesu are not the same but I would
suspect circuit designs are not that dissimilar.




On Wed, 19 Nov 2003 18:47:06 GMT, "RonE" wrote:

I recently acquired a "dead" Ft-990.

I got the receiver running and found I had a bad T/R relay, got that
replaced, now I have 100++ power out on all bands no matter where the RF

Pwr
knob is set. I have come a long way from a dead transceiver, but the rig

is
still unusable as is since the output cannot be adjusted. I did see a
voltage change from ~-6 volts to about +.3 volts at a test point shown in
the service manual. I thought I'd drop a quick note in here to see if
someone may have run into a similar issue with the 990 in the past. I

THINK
the problem is on the RF card, but am not sure. The service manual is

great
for schematics and part numbers, but is seriously lacking in theory.

Anyhow, any help / suggestions would be great. remove the "spam" to

email
me directly, if you like.

Ron E.
W0IFL



Gary K8IZ
Washington State Resident
Registered Linux User # 312991



  #5   Report Post  
Old November 20th 03, 02:09 PM
RonE
 
Posts: n/a
Default

Thanks Gary,
I never even considered that. I did have to replace the T/R relay, it was
stuck in receive. I scratched my head over that for a while... 20Amp current
draw, and NO output.. Anyhow, got that replaced. Maybe the transistor that
drives that relay needs replaced as well..

Ron E.
W0IFL
--

"Gary P. Fiber" wrote in message
...
When I worked at Icom we saw a few that acted like your Yaesu does. On
the Icom's it was almost always the Power Amplifier was oscillating.
When that happens no power control adjustment is going to help. Some
of the times it was a transistor in the receiver switching circuit
that was causing the oscillation to happen.

Just a thought, I know Icom and Yaesu are not the same but I would
suspect circuit designs are not that dissimilar.




On Wed, 19 Nov 2003 18:47:06 GMT, "RonE" wrote:

I recently acquired a "dead" Ft-990.

I got the receiver running and found I had a bad T/R relay, got that
replaced, now I have 100++ power out on all bands no matter where the RF

Pwr
knob is set. I have come a long way from a dead transceiver, but the rig

is
still unusable as is since the output cannot be adjusted. I did see a
voltage change from ~-6 volts to about +.3 volts at a test point shown in
the service manual. I thought I'd drop a quick note in here to see if
someone may have run into a similar issue with the 990 in the past. I

THINK
the problem is on the RF card, but am not sure. The service manual is

great
for schematics and part numbers, but is seriously lacking in theory.

Anyhow, any help / suggestions would be great. remove the "spam" to

email
me directly, if you like.

Ron E.
W0IFL



Gary K8IZ
Washington State Resident
Registered Linux User # 312991





  #6   Report Post  
Old November 20th 03, 04:14 PM
Clif Holland
 
Posts: n/a
Default

The -6 is the clue. It is a reference for the power control circuit and when
it goes away so does the control. At least on Kenwoods and Icoms.

--
Clif Holland, KA5IPF
AVVid
Authorized Kenwood and Icom Service Center
816 W Shady Grove Rd
Irving, TX 75060

www.avvid.com

1-800-214-5779
972-870-0630 (Local)
"RonE" wrote in message
...
Thanks Gary,
I never even considered that. I did have to replace the T/R relay, it was
stuck in receive. I scratched my head over that for a while... 20Amp

current
draw, and NO output.. Anyhow, got that replaced. Maybe the transistor

that
drives that relay needs replaced as well..

Ron E.
W0IFL
--

"Gary P. Fiber" wrote in message
...
When I worked at Icom we saw a few that acted like your Yaesu does. On
the Icom's it was almost always the Power Amplifier was oscillating.
When that happens no power control adjustment is going to help. Some
of the times it was a transistor in the receiver switching circuit
that was causing the oscillation to happen.

Just a thought, I know Icom and Yaesu are not the same but I would
suspect circuit designs are not that dissimilar.




On Wed, 19 Nov 2003 18:47:06 GMT, "RonE" wrote:

I recently acquired a "dead" Ft-990.

I got the receiver running and found I had a bad T/R relay, got that
replaced, now I have 100++ power out on all bands no matter where the

RF
Pwr
knob is set. I have come a long way from a dead transceiver, but the

rig
is
still unusable as is since the output cannot be adjusted. I did see a
voltage change from ~-6 volts to about +.3 volts at a test point shown

in
the service manual. I thought I'd drop a quick note in here to see if
someone may have run into a similar issue with the 990 in the past. I

THINK
the problem is on the RF card, but am not sure. The service manual is

great
for schematics and part numbers, but is seriously lacking in theory.

Anyhow, any help / suggestions would be great. remove the "spam" to

email
me directly, if you like.

Ron E.
W0IFL



Gary K8IZ
Washington State Resident
Registered Linux User # 312991





  #7   Report Post  
Old November 20th 03, 04:14 PM
Clif Holland
 
Posts: n/a
Default

The -6 is the clue. It is a reference for the power control circuit and when
it goes away so does the control. At least on Kenwoods and Icoms.

--
Clif Holland, KA5IPF
AVVid
Authorized Kenwood and Icom Service Center
816 W Shady Grove Rd
Irving, TX 75060

www.avvid.com

1-800-214-5779
972-870-0630 (Local)
"RonE" wrote in message
...
Thanks Gary,
I never even considered that. I did have to replace the T/R relay, it was
stuck in receive. I scratched my head over that for a while... 20Amp

current
draw, and NO output.. Anyhow, got that replaced. Maybe the transistor

that
drives that relay needs replaced as well..

Ron E.
W0IFL
--

"Gary P. Fiber" wrote in message
...
When I worked at Icom we saw a few that acted like your Yaesu does. On
the Icom's it was almost always the Power Amplifier was oscillating.
When that happens no power control adjustment is going to help. Some
of the times it was a transistor in the receiver switching circuit
that was causing the oscillation to happen.

Just a thought, I know Icom and Yaesu are not the same but I would
suspect circuit designs are not that dissimilar.




On Wed, 19 Nov 2003 18:47:06 GMT, "RonE" wrote:

I recently acquired a "dead" Ft-990.

I got the receiver running and found I had a bad T/R relay, got that
replaced, now I have 100++ power out on all bands no matter where the

RF
Pwr
knob is set. I have come a long way from a dead transceiver, but the

rig
is
still unusable as is since the output cannot be adjusted. I did see a
voltage change from ~-6 volts to about +.3 volts at a test point shown

in
the service manual. I thought I'd drop a quick note in here to see if
someone may have run into a similar issue with the 990 in the past. I

THINK
the problem is on the RF card, but am not sure. The service manual is

great
for schematics and part numbers, but is seriously lacking in theory.

Anyhow, any help / suggestions would be great. remove the "spam" to

email
me directly, if you like.

Ron E.
W0IFL



Gary K8IZ
Washington State Resident
Registered Linux User # 312991





Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wanted: Power Supply for TR-4C KA9S-3_Jeff Boatanchors 20 December 16th 04 08:51 AM
Wanted: Power Supply for TR-4C KA9S-3_Jeff Boatanchors 0 December 8th 04 10:31 PM
Current in loading coil, EZNEC - helix Yuri Blanarovich Antenna 334 November 9th 04 06:45 PM
Derivation of the Reflection Coefficient? Dr. Slick Antenna 104 September 6th 03 02:27 AM


All times are GMT +1. The time now is 08:58 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 RadioBanter.
The comments are property of their posters.
 

About Us

"It's about Radio"

 

Copyright © 2017