[Kenwood] TS-50 problem

Sun Aug 5 15:09:09 EDT 2018

Thanks for the replies to my TS-50 problem.  I misspoke about bias being the issue, but my comment about a leaky cap or two matched with Clif's comments.  He is the expert, for sure.  I've seen caps in a TS-440 go South and the age of these rigs doesn't help much.

I forgot to mention that the VR(15-16-14) controls had zero effect on the power output measurements.  I'm going to check around IC-11 as well as the voltage rails and measure any electrolytics I see in the circuitry including the 6v rail.

I won't spend much time on the rig and if nothing obvious pops up I'll offer it up.

Thanks again, folks and Clif.

73
Chuck W4MIL

チャーリー ミルトン 

-----Original Message-----
From: Clif Holland <clif at avvid.com>
To: kenwood <kenwood at mailman.qth.net>
Sent: Sun, Aug 5, 2018 9:33 am
Subject: Re: [Kenwood] TS-50 problem

First, the bias circuit has nothing to do with power out. It determines the linearity of the final unit for SSB usage.The power out is controlled by the ALC circuit. There are several factors which can cause higher than normal power out. Most of which are traced back to leaking/open electrolytic caps. Leakage damages traces/thruholes. Open causes reference voltages to be incorrect, mainly the -6v supply.I'm not familiar with the 2SC5894's as the TS-50 and most Kenwoods of that era use the 2SC2879.Clif Holland KA5IPFwww.avvid.com214-850-0973On 8/5/2018 2:27 AM, Steef PA2A wrote:> Chuck,>> the 10 and 50 watt levels can be adjusted by variable resistors but > there must be some problem in the bias circuit of the finals where the > power level is set by fixed resistors. A cold solder joint or a > changed resistor value can be the cause of the changed bias.>> The 2SC5894 's can dissipate 250 watts of heat each so 200 Watts is no > problem for them except ferrite transformers will run a bit hot. In > SSB increased intermodulation products can appear but in CW there is > no big problem. The TS850 has the same amplifier and running 180 Watts > in CW was no problem.>> 73s Steve PA2A>> chuck via Kenwood schreef op 2018-08-05 00:59:>> I have a TS-50 that I recently brought back on line and found that>> everything worked...….except the output power into a 50ohm dummy load>> was a whopping 200 watts.  I immediately stopped, went to SSB mode and>> whistled up 200watts.  A quick try in CW and AM produced the same>> results.>>>> I had this rig repaired a few years back by Clif @ AVVID.  He put it>> in tip-top shape and I used it periodically afterward.  Fast forward>> to now (3+ years later) when I got it from the closet and found the>> above described problem.  It's been in a controlled environment and>> not subjected to humidity or high temperatures.>>>> I'm guessing an electrolytic has given up and the bias on the finals>> is in trouble.  But that's only a guess.  Anyone wish to comment?  I'm>> not equipped to service it unless there is something obvious that>> doesn't require precision work.  I'm one of the dinosaurs who is>> linked to BA gear where I still do my own repairs, etc.>>>> Thanks for the read.>>>> 73 de W4MIL>> Chuck>>>>>>>>>> チャーリー ミルトン>>>>>>>>>> ______________________________________________________________>> Kenwood mailing list>> Home: http://mailman.qth.net/mailman/listinfo/kenwood>> Help: http://mailman.qth.net/mmfaq.htm>> Post: mailto:Kenwood at mailman.qth.net>>>> This list hosted by: http://www.qsl.net>> Please help support this email list: http://www.qsl.net/donate.html>> Message delivered to pa2a at xs4all.nl> ______________________________________________________________> Kenwood mailing list> Home: http://mailman.qth.net/mailman/listinfo/kenwood> Help: http://mailman.qth.net/mmfaq.htm> Post: mailto:Kenwood at mailman.qth.net>> This list hosted by: http://www.qsl.net> Please help support this email list: http://www.qsl.net/donate.html> Message delivered to clif at avvid.com______________________________________________________________Kenwood mailing listHome: http://mailman.qth.net/mailman/listinfo/kenwoodHelp: http://mailman.qth.net/mmfaq.htmPost: mailto:Kenwood at mailman.qth.netThis list hosted by: http://www.qsl.netPlease help support this email list: http://www.qsl.net/donate.htmlMessage delivered to cemilton at aol.com