TS-450S output reduced
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 |
TS-450S output reduced
"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. |
TS-450S output reduced
"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 |
TS-450S output reduced
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 |
TS-450S output reduced
In article ,
rahulkapoor wrote: 3. Shack temp had become very hot last few days. Day temp in shade is 40 degrees C plus. Rahul- Unless you ran it key-down for an extended period in CW or FM mode, it is unlikely that your ambient temperature caused a transistor to fail. Power transistors normally operate somewhat higher than 40 degrees C. Lack of any ALC reading is most likely the result of low power. The cause of low power could be a bad transistor, but is more likely a leaky or shorted capacitor loading down the voltage supply to an RF stage, or a voltage-dropping resistor that has gone high in value. Another problem you might look into, is a connector on the rear panel, where a transverter would normally be connected. Some Kenwoods have a closed-circuit switch built into the connector, and sometimes the switch contacts get oxidized from lack of exercise. There would have been a mating connector in an accessory packet that came with the radio. If you still have it, try plugging it in several times. The wiping action of the switch should clean up any oxide coating. 73, Fred K4DII |
Hi Rahul and all,
did you get your TS450 fixed? What was the problem? I have same symptoms in my TS450: no ALC reading and power output reduced to about 20 watts. Thanks and 73s Cesar |
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