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    Problem with Kenwood TS-850

    Posted In: Technology

    • Participant
      Anonymous on June 25, 2010 at 1:59 PM #11227

      Hello, I have a problem with this TCVR, it transmits on the frequency I set on the display, but receives a few kHz higher, and the display still shows that frequency a few kHz higher.. I write a few kHz because this frequency changes… one morning it is 6kHz, evening 12kHz, another morning 4.5kHz and so on… So far, I have not found that it is caused by temperature influence…
      I warn that I am not working in split and also have RIT and XIT at 0.
      On the control unit, 2 electrolytes leaked, which I replaced, but the problem persists...
      I would be very grateful if you could contribute suggestions on what else to look at… Thank you
      73, Martin S.

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      Participant
      Anonymous on June 30, 2010 at 12:12 PM #12971

      Martin, try to properly clean the control board with alcohol to wash away the electrolyte residues. Probably that is causing the shorts. 73 Miro OM3CU

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      Participant
      Anonymous on June 30, 2010 at 12:47 PM #12972

      Hi, I forgot to write… I cleaned it right after I desoldered and soldered in the new ones… that electrolyte has already started to damage the connections and the PCB…

      the radio still does not work as it should… on CW the RX and Tx frequency is shifted by about 3.5kHz and on SSB by about 12kHz…
      and recently something new has happened… SSB cannot be listened to, because it seems there is no sideband filter and I hear about 12k width…
      So far, I have tried to check according to the service manual:
      reference oscillator at 20MHz… that is okay, I also checked VCO1-4 they are also okay… everything so far on the PLL unit…
      I do not see deep enough into that electronics to know exactly where the fault is, so if someone has a suggestion on what I should focus on, please write
      I read on a foreign forum that such and similar errors can be caused by DDS chips on that control unit, so either they burned out due to the leaked electrolytes or I don't know... those IOs are no longer available, so if anyone happens to have this radio with some other error, I would buy the whole control unit, possibly also the chip(s) Kenwood 6631.
      Thank you
      Best regards
      Martin S.

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      Participant
      Anonymous on July 2, 2010 at 21:26 #12973

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      Participant
      Anonymous on July 3, 2010 at 8:42 PM #12974

      So thanks for the comment... Maybe I already know where the error is, but I'm not sure at the same time... yesterday and today I had a bit of time, so I really got down to it... I looked again at the VCO, which I delivered to exactly 3.2V as it is in the repair kit, before that I had a bit of a clue... (before I started with the trimmer, I tried different voltmeters and shielded cables and it always came out the same... 2.5V instead of 2.30V /+-0.03). So I adjusted the VCO voltages and they are fine, but there is no difference in the RX/TX frequency.
      I measured everything that comes from the CAR unit... First with an oscilloscope... everything nice sine wave then with a homemade reader... some signals had a slightly lower amplitude, so the reader had a problem with them, but I will verify it with another... but despite that, I found one difference from IC4, there is a car signal coming out that goes to the IF board... it should be 455kHz, for me it is 457.38kHz, and on one foreign forum I read that he had the same problem as I did and replaced it with YM66312 and everything worked well again... but he had that signal at about 600kHz which is a much bigger difference than mine2kHz... so I don't know if it's an error or an allowed deviation...
      As I said, I will try to measure everything again with some original meter and let you know if so...
      By the way, I looked at those chips and I really don't know where to get them... I also looked at Avelmak, but they didn't have them in the database, and I had no idea they could even get a whole board...
      So thanks for the info, if you could advise me on anything else, I would be very glad... It was such a good radio...
      Thank you
      Best regards
      Martin S.

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      Participant
      Anonymous on July 3, 2010 at 10:25 PM #12975

      As for Avelmak, you won't find anything in the offer, I contacted them by email. Regarding the defect, I think nothing will help anymore, only chip replacement. For now, maybe just that one will be enough, but it's just a temporary solution. Forums say that if those capacitors leak, all 6631 will gradually fail in a short time.
      I threw away those SMD electrolytes even before leaking. On each
      I also have an adhesive cooler for the RAM.
      As for the TS850, I have a pretty 'worn' piece. I had to replace the capacitor in the VCO, do the ALC mod, replace the electrolytic on the LCD board, do the NB mod, and clean the radio after a heavy smoker. Additionally, I bought a 'TXCO' crystal heater from DE for 15 euros and currently
      I seem to have some problem at the RX input. After tuning the tuner, the signal increases by about 2 seconds on the directional antenna. But it can be lived with.
      Despite the problems, it's a great radio.

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      Participant
      Anonymous on September 14, 2010 at 2:59 PM #12976

      Did you manage to get that radio working?
      Preliminarily, it looks like YM66312 will be available. The price would be around 50 euros each, depending on the USD exchange rate, shipping, and customs. Delivery in 14 days.

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      Participant
      Anonymous on September 14, 2010 at 9:00 PM #12977

      @XXL wrote:

      Did you manage to get that radio working?
      Preliminarily, it looks like YM66312 will be available. The price would be around 50 euros each, depending on the USD exchange rate, shipping, and customs. Delivery in 14 days.

      Sorry... I even forgot to let you know how I ended up... Currently, I'm at a point where I probably can't try any more... In the summer, I got a good soldering station, so I tried some fun... I swapped those chips several times, but the problem persisted... so it probably isn't in those chips... I tried everything possible... I measured various signals to see if they corresponded to the service manual... everything is okay.
      I then focused on the RAM memory, the main processor, etc., but nothing ever happened that could somehow be related to my problem... there is still a difference between the Tx and Rx frequency, SSB is unusable and overall it behaves even more strangely... From nothing overnight, not even FM works... reception is completely silent - not even a hum...
      Until now, I thought that the broadcast was ok, but from a colleague, he learned that during the broadcast, there is a crack in the modulation with a frequency of about 1Hz... at the moment, I don't even have the strength to look into it, I will definitely look into it again, at the moment, I prefer to look at another radio station.
      VY 73 de Martin OM1ADX

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      Participant
      Anonymous on September 15, 2010 at 4:53 am #12978

      That doesn't look good. The initial problem was definitely in those chips, but other problems could have joined it. If you would like to get rid of it for parts, let me know.

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