"rahulkapoor" wrote in message
...

Hi

This is VU2YK.

Last week I used my TS-450S and it was in perfect working condition.
Amazing receiver and get unsolicited comments about nice TX audio
with stock mic. The lightning fast relayless Rx/Tx switching is
noiseless and any CW Ops delight. Full 100 watts out on all HF bands.

Yesterday I switched on the rig, and shock and awe ! Output power
reduced to 20 watts ! All else remains same. Low SWR, Power supply
rock steady. ALC indicator does not move, indicating some problem
inside. I did not touch the rig in the last few days.

The important symptoms are :

1. NO ALC movement of meter
2. Power output down to 20 W on 20 M, low on other bands
3. Shack temp had become very hot last few days. Day temp in shade is
40 degrees C plus.
4.I checked all power and antenna cable connections. Receive is 100 %
OK and power cable are clean. SWR is 1:1

Will appreciate any help in diagnosing and rectifying the problem.
Thanks !

73

Rahul
VU2YK
New Delhi

No ALC indication may be either low drive or low output since it derives
it's indication from the output stage to reduce the drive. IP is probably
low too.

Check Mic gain, DC Power (do the lights dim?) and mic connections first.
Other than that, check for loose screws on the boards. Or you may have PA
circuit board problems where solder joints go bad from heat or shock,
usually the grounds. Just a few thoughts.

"JB" wrote in message
...
"rahulkapoor" wrote in message
...

Hi

This is VU2YK.

Last week I used my TS-450S and it was in perfect working condition.
Amazing receiver and get unsolicited comments about nice TX audio
with stock mic. The lightning fast relayless Rx/Tx switching is
noiseless and any CW Ops delight. Full 100 watts out on all HF bands.

Yesterday I switched on the rig, and shock and awe ! Output power
reduced to 20 watts ! All else remains same. Low SWR, Power supply
rock steady. ALC indicator does not move, indicating some problem
inside. I did not touch the rig in the last few days.

The important symptoms are :

1. NO ALC movement of meter
2. Power output down to 20 W on 20 M, low on other bands
3. Shack temp had become very hot last few days. Day temp in shade is
40 degrees C plus.
4.I checked all power and antenna cable connections. Receive is 100 %
OK and power cable are clean. SWR is 1:1

Will appreciate any help in diagnosing and rectifying the problem.
Thanks !

73

Rahul
VU2YK
New Delhi

No ALC indication may be either low drive or low output since it derives
it's indication from the output stage to reduce the drive. IP is probably
low too.

Check Mic gain, DC Power (do the lights dim?) and mic connections first.
Other than that, check for loose screws on the boards. Or you may have PA
circuit board problems where solder joints go bad from heat or shock,
usually the grounds. Just a few thoughts.


Also check to ensure that you are not measuring power output while in the AM
or FM mode. Easy to overlook.

It has been too many years since I have operated my old TS-450/AT rig, to
remember the controls and options well.

Yours has fast T/R switching time? Wow. My TS-430 had to be modified in
order to work Amtor within less than 100 miles. I used the old AEA
modification plan, which worked great and was easy to do.

Isn't there an ALC adjustment on the TS-450? I would look into that and see
if it got bumped.

Ed, AJ4PJ

Hi

This is VU2YK.

Last week I used my TS-450S and it was in perfect working condition.
Amazing receiver and get unsolicited comments about nice TX audio
with stock mic. The lightning fast relayless Rx/Tx switching is
noiseless and any CW Ops delight. Full 100 watts out on all HF bands.

Yesterday I switched on the rig, and shock and awe ! Output power
reduced to 20 watts ! All else remains same. Low SWR, Power supply
rock steady. ALC indicator does not move, indicating some problem
inside. I did not touch the rig in the last few days.

The important symptoms are :

1. NO ALC movement of meter
2. Power output down to 20 W on 20 M, low on other bands
3. Shack temp had become very hot last few days. Day temp in shade is
40 degrees C plus.
4.I checked all power and antenna cable connections. Receive is 100 %
OK and power cable are clean. SWR is 1:1

Will appreciate any help in diagnosing and rectifying the problem.
Thanks !

73

Rahul
VU2YK
New Delhi


Just a Note here, I run a TS-690, which is the same basic Radio with a 6
Meter extension... Look at the second Knob in on the lower lefthand
corner of the Front Panel, at the Knob called PWR. It should be fully
Clockwise, to get Max Power Out......

--
Bruce in alaska
add path after fast to reply

Thanks gentlemen for your valuable suggestions. I am indeed grateful. I have had this rig for than a decade and never an issue.

Yes the 450S has PIN diode switching TX/RX. Works like a charm with full bk-in on CW. Even at 35 WPM I can hear the other station between my dits.

My friends have pointed out to a common problem with many Kenwood rigs of this era. Blown predriver and/or driver transistors ! They are both obsolete therefore need careful substitution with some peripheral component changes involved.

Since the problem occurred suddenly and not gradually I am inclined to believe that excessive heat cased one of transistors to rupture. While I have not yet begun work on this, I am collecting all possible documentation before I bring out the proverbial screwdriver from its hiding place.

Thanks again

73

Rahul
VU2YK
Hey - Just do an image/video Google search of my call