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TS-850S Car board question...

Discussion in 'Radio Circuits, Repair & Performance' started by KB1MM, Jun 29, 2020.

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  1. KB1MM

    KB1MM Ham Member QRZ Page

    Hey folks....

    I'm in a quandry...

    I have a TS85os that works fine, S/N series 40 million. It has the old series DDS IC's on the board but years ago, I replaced the bypass caps before they exploded their guts onto the PCB.

    I am considering buying an aftermarket board that I know work as well as the original, just in case those IC's fail.

    I guess my question is, what caused the failures? Has it ever been determined definitively ? Other than the guts eating away the traces underneath the caps, was it the caps failing which caused problems with bypassing noise/glitches on the VCC lines that went to the IC's. I've had this radio since the mid 90's and except for the tuner motors squealing which I fixed, the radio just works.

    I have since bought a TS590SG which I like a lot but I also can't let the 850 go so it is my back up radio which I still use once or twice a week.

    Is my 850 living on borrowed time? The replacement is about $300. I don't have a problem buying one if one or more of those DDS IC's demise is inevitable. I guess if I buy a replacement board and I never need it, I can probably sell it for close to the price is now...

    Thoughts???
     
  2. VA2GK

    VA2GK Ham Member QRZ Page

    The CAR board can have two different DDS ICs, the YM6631 or the YM66312. The caps were a problem but it was fixable (Actually, 99% of the problems in this radio are caused by caps, either electrolytic or the chip 0.01µF filterring cap thas is found throughout the radio) the main problem with the early versions were a bad DDS chip that was failing, the original YM6631.
    If you have the chance of having a late version with the YM66312 chip, I'd say you're pretty good to go, I have mine since 1993, and even if I had to ressucitate it a couple of times, at least the DDSs are holding up.
     
  3. KB1MM

    KB1MM Ham Member QRZ Page

    The one I have has the YM6631 chips, not the 66312 chips. I believe the S/N range for the new chips started at 50 million or thereabouts. I guess my question was, do these YM6631 always eventually fail or can I assume if it's made it this far that I'm good to go. I have used this radio countless hours and except, as I mentioned in the OP, the squealing motors in the tuner which I fixed, the radio just keeps chugging along.
     
  4. KA5IPF

    KA5IPF Ham Member QRZ Page

    I have repaired 850's (YM6631) where the Car board was eat up by the caps leaking and ones that were pristine. From that observation my guess is the IC's are the problem, not the caps. Hours of use, not age.
     
  5. VA2GK

    VA2GK Ham Member QRZ Page

    I tend to agree with you, they upgraded the DDSs during the production because they have a tendancy to fail, maybe they are only good for so many warm-up / cool down cycles, who knows.

    What kind of pi$$ed me off about kenwood, I saw two 850s that got repaired at the factory in the late 1990s because of that problem and in both cases, they changed only the defective chips, not the four of them (one in a case and two in another) Talk about cheap, you know they will gail eventually, replace them all!
     
  6. NN6D

    NN6D Ham Member QRZ Page

    once the internet lore is born the repeaters will just keep repeating the same worn out unsubstantiated disinfo forever

    the 6631 dds ic's don't just fail on their own for no reason

    it's virtually always because of the caps

    long long before these caps start spewing acid their rated values change wildly

    stop believing and repeating the nonsense
     
    VA2GK likes this.
  7. KA5IPF

    KA5IPF Ham Member QRZ Page

    I'll put my experience up against yours anytime. There is a problem with the IC's.
     
    VA2GK likes this.
  8. NN6D

    NN6D Ham Member QRZ Page

    my experience is probably a tiny fraction of yours and hovers around 6 ts850s
    there may very well be a problem with them but that doesn't mean that every single (6631) one will fail or even that one will fail in every radio
    or are you saying that as well?

    is there any data which one of the 4 fails the most? same for the two in the ts-450?

    have you by chance ever measured the value of caps on the pristine looking boards with failed ICs? I'm sure you've replaced the caps proactively...
     
  9. KD0CAC

    KD0CAC Ham Member QRZ Page

    I had a guess some time a ago that the caps may help the old chips fail and that there maybe some type of protection circuit in the new chips / besides the newer caps and chips at the same time ?
    But that was a guess , SWAG Scientific Wild Ass Guess . theory .

    I would keep an eye / ear on Cliff's experience .
    And would like to hear from the the tech that has produced the new replacement boards , maybe more ideas down this road ?

    But NN6D , you are near or past the line of bad behavior with your post , you could have just stated your idea , but you basically made an attack .
     
  10. NN6D

    NN6D Ham Member QRZ Page

    feel free to make your own "attacks" LOL

    I've also looked at the quality of surface mount soldering under a good microscope and found 2-3 pins per at least two of the chips on couple of the early 6631 boards virtually just laying on top of the board not held by any solder
    seems not enough solder was used and/ or they had issues with temperature profiles for the reflow -or however they did it- process during production
    after acid attacked the surfaces under the pins and made them hard dull and brittle manually resoldering them en-bulc per side and sucking off excess with a wick proved impossible
    had to scrape traces in front of each pin and blob to top of each scraped pin individually
    some traces had voids making them half as wide and vias with no connection to the trace
    it was either that or unsoldering the whole chip scraping all the surfaces and resoldering it from scratch...
    these boards were deemed as having "bad chip"
    they only had bad soldering, marginal vias, acid and leaking capacitors and still survived
     

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