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To recap or not to recap...

Discussion in 'Radio Circuits, Repair & Performance' started by WM4MW, Feb 14, 2019.

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  1. WM4MW

    WM4MW XML Subscriber QRZ Page

    I am a new ham, and recently acquired a couple of old radios that I am trying to recondition and get on the air. In general, both currently seem to work. But, I'm trying to identify and perform whatever preventive, recommended maintenance might be a good idea. I've seen lots of comments about replacing electrolytic caps in old equipment, suggesting that this is a good practice after components get old. However, these things (Kenwood TS-440SATs) have nearly 150 small electrolytics in them, so replacing all of them is not a small undertaking. And, I've seen plenty of old (HP) test equipment that has survived decades without showing any sign of these kinds of problems.

    So... what's the collective wisdom regarding this issue? Close inspection of both units shows no sign of any problems -- nothing's bulging, leaking or otherwise currently causing problems (as far as I can tell at this point)… so, should I go to the trouble of recapping these things, or not? Aside from the obvious bulging/leaking symptoms, what other signs of cap-related problems should I be looking for in these old rigs? And, upon recapping them, I assume I'll need to perform a full alignment on them afterward, right?

    Thanks for any advice you can provide.

    Marty, WM4MW
    Gloucester, Virginia, USA
  2. G3YRO

    G3YRO Ham Member QRZ Page

    There is no simple answer this !

    I have a 40 year old FT101E that has never had a single fault . . . and I have never considered replacing any of the capacitors.

    Yet I have bought several LCD TVs just a few years old that have gone faulty (typically £400 TVs for just £20 - £30) . . . and the problem is just a few of the electrolytics. (On the PSU boards - easy to see which ones need replacing, as they were bulging on the top)

    So it's all down to the quality of the capacitors used . . .

    If you were taking this rig to a desert island, then maybe it would be worth replacing a load of the capacitors, just in case . . .

    But personally, if it's working fine, I wouldn't bother !

    Also bear in mind that OTHER devices can fail, including ICs or Processors that are often no longer available . . . so you could do a load of work, only to find the rig ends up as junk in a few years.

    For what it's worth, my other rig is a TS-930SAT . . . this has had LOADS of faults since I bought it 3 years ago . . . but none have been down to faulty capacitors! (Mainly dry joints, but also failed transistors or ICs)

    Roger G3YRO
    N1OOQ and W1TRY like this.
  3. K6LPM

    K6LPM Ham Member QRZ Page

    Yes, if its acting funny style try to identify what section of the radio it is effected by. I don't consider that radio to be so old , but I suppose it is.... I wouldn't just shotgun all the electrolytics for the sake of maintinence.
    You are more likely to have problems with dried out fouled up plastic trimmer capacitors that would likely be messing with alignment , selectivity and sensitivity.
  4. VK6YSF

    VK6YSF Ham Member QRZ Page

    I agree with Roger, if it is working fine leave it. I will change caps if they are in an area of the radio that I'm working on, particularly if it is even remotely possible that the cap is part of the problem. Most faults have turned out to be dry joints, bad wire connections and bad relay and switch contacts.
    Most importantly, every time you work on a radio there is always the chance of inadvertently causing damage, therefore if you don't need to go in; don't; just like surgery I guess.

    Peter vk6ysf
  5. N1OOQ

    N1OOQ Ham Member QRZ Page

    There was a bad batch of electrolytics in the 1999-2007 years ( "capacitor plague"). Other than that, it's mostly old, dried-up caps in old tube gear that were cooked dry over the years. Haven't traced any problem to a bad cap yet, myself. I wouldn't bother unless you're trying to solve a problem... Extensive repairs often cause some trouble that you'll have to cobble together a solution to... Like lifted PCB etch.
  6. K9ASE

    K9ASE XML Subscriber QRZ Page

    If it ain't broke don't fix it.
    ND6M and KC8VWM like this.
  7. WR2E

    WR2E Ham Member QRZ Page

    Yeah... leave it alone unless some symptom points to a cap.

    Those lil connectors in the 440 are prone to end up with bad connections if you mess with them.
  8. N7EKU

    N7EKU Ham Member QRZ Page


    Except for the "capacitor plague" electrolytics (which were limited to equipment that used cheap caps versus quality US or Japanese ones), I've had more problems with old tantalum capacitors. Some have gone up in clouds of smoke just turning on the unit. The old ones were really unreliable. Don't even try to use new-old-stock ones unless you measure their ESR first!


    KM1H and WB5THT like this.
  9. WM4MW

    WM4MW XML Subscriber QRZ Page

    Thanks, everyone. I was leaning this way myself -- lots of work, and a real risk of causing other problems in the process. But, it is very nice to hear everyone agree.


    Marty WM4MW
  10. K0OKS

    K0OKS Premium Subscriber QRZ Page

    If it’s a filter cap, with much ripple on it, I would always replace it if over 20 years old. Heat and ripple (which causes internal heating) are what kills electrolytics. That and sitting idle with no power applied.

    If it ain’t broke mentality leads to burned up transformers and other unobtainium parts. If your car ain’t broke do you not change its oil? Remind me not to buy a car from you... certain things require maintenance. Your mileage may vary...
    WQ4G likes this.

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