CPR Method for a Boat Anchor

Discussion in '"Boat Anchor" & Classic Equipment' started by KA5SDC, May 18, 2019.

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  1. WB2GCR

    WB2GCR Ham Member QRZ Page

    My preference is to avoid the issue of the rectifier tube's filaments being lit.
    What I do is to make a solid state diode plug-in.
    If you don't have a fresh base, you can always take apart an old tube
    and use that (works fine on Octals or 4/5 pins) or need be, order one

    I use the solid state plug-in only for bringing the voltage up slowly, NOT for
    regular operation.

    This way you get B+ voltage up from zero, and can charge those old caps very
    slowly, without waiting for 60+ volts on the AC mains, and so about 1/2 B+ voltage
    coming on immediately.

  2. K6BSU

    K6BSU Ham Member QRZ Page

    You can re-form old electrolytics so that they work---sort of.

    You should also measure leakage current at full voltage. A leaky capacitor will not be "cured" by re-forming.

    Of course, the only way to measure leakage current is to dis=connect the capacitor and measure leakage current at rated voltage without anything else connected to it.

    Might as well replace it as long as you have it dis- connected.
  3. KD0DQZ

    KD0DQZ Ham Member QRZ Page

    One cheap (possibly even free depending upon your junkbox) piece of test gear every bench hosting a variety of tube gear should have is the good ol' Dim Bulb tester. They limit current rather than voltage and it's generally current that causes the release of the magic smoke.:)
  4. KE0ZU

    KE0ZU Ham Member QRZ Page

    I simply use a Watt meter and just monitor the input power consumption for a few minutes. The very first, and following 30 to 120 Seconds are the most cirtical.
  5. KE4OH

    KE4OH Ham Member QRZ Page

    I'm not a fan of the "bring it up slowly on a Variac" method. Along with others who have already posted, I'm a believer in replacing all electrolytic caps in old gear before initial power-up. It's just a matter of time before one or more goes bad, even if they have been reformed on a Variac. Good replacement caps just don't cost much these days. And it is amazing what one sometimes finds when you go under the chassis to replace the old caps.
    WQ4G likes this.
  6. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    I do have a Variac. It sits on a shelf, above my #1 workbench and hasn't been plugged in for years!

    Almost all of the equipment, that I work on, belongs to others and those people are paying to have reliably performing equipment. Therefore, I replace, not "reform", electrolytic capacitors, replace paper capacitors, replace silver-mica capacitors used as bypass and coupling, etc. The parts cost is minimal, when compared with the labor cost and, especially, shipping cost. The client does not want to have to return the equipment in a year, or two, for further work. A few dollars spent "up front" easily saves a LOT of dollars down the road.

    I do the same thing with my equipment. That is, I replace potentially problem components at the start. Of course, what any individual does with his / her equipment is up to that person. However, I prefer to err on the safe side!

    Glen, K9STH
  7. WB2GCR

    WB2GCR Ham Member QRZ Page

    Client? I think we're talking individual's equipment being brought back to life for themselves?

    Replacing every old cap in many radios is going to be many many man-hours of work. And if the old
    radio is full of MFP, I'd rather do the minimum amount of soldering.

    For an ultimate restoration I guess one would do what some people have done which is to
    strip the entire chassis, clean, polish and essentially rebuild the boatanchor as if it was a new
    build. Some have even gone so far as to remake the entire wiring harness.

  8. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page


    I did NOT say every capacitor! Disc ceramics capacitors almost never fail and silver-mica capacitors in tuned circuits are almost always fine. In most "boat anchor" equipment there are just not that many paper capacitors, etc., that need to be replaced, Typically between and hour and an hour and a half to replace capacitors. There are certain pieces of equipment, like the later Hammarlund Super Pro series (SP-600- units), and the Collins R-390- series, that do take longer. However, the vast majority of amateur radio equipment can be "re-capped" in well under 2-hours.

    Of course, having the correct parts handy and the proper tools does make things easier. A good soldering iron, diagonal cutters, needle-nosed pliers, etc., definitely speed things.

    I generally replace the capacitors one at a time. Where several capacitors connect to the same place (usually a ground lug), I solder the "far end" and then solder all of the leads that come to the common point. Also, modern capacitors are usually considerably smaller than the original capacitors. When one end goes to ground, I often look for a suitable point that is much closer than the original ground point. This saves time as well as cleaning up the under-side of the chassis. With the new capacitors, the wiring is often "wide open" where, before, it was very crowded.

    Some people may require considerably more time to replace the capacitors. But, in my experience, most people do work faster and the project does not take that long!

    Glen, K9STH
    WQ4G likes this.
  9. KA5SDC

    KA5SDC Ham Member QRZ Page

    Sounds like I need to leave the variac on the shelf and break out the soldering iron. I'll start by identifying the electrolytic and paper capacitors, then consider others. Should be a good experience for me. Thanks to all who have replied!

    Dee, KA5SDC
    KE4OH likes this.
  10. KE0ZU

    KE0ZU Ham Member QRZ Page

    As for Glen's statement regarding space availability after new caps are installed, heres an example, and yes all the caps are there.


    W1TRY and KE4OH like this.

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