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CPR Method for a Boat Anchor

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

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  1. KA5SDC

    KA5SDC Ham Member QRZ Page

    Okay, I now have several boat anchors (mostly all-tube radios) that I must attempt to resuscitate. I have a variac but am not really sure of the most appropriate method to use. By that I mean X volts for Y duration, then Q volts for Z duration, etc.

    I will begin with equipment that is ultra-clean and looks like it could have been used recently. I do not know the history of most of this equipment. One set is the Kenwood T599D/R599D twins I have owned for many years. Those are the only ones I know worked the last time used.

    So...what do the experts say?
     
  2. KL7AJ

    KL7AJ Ham Member QRZ Page

    I use a Variac the same way I use a "Mexican Torque Wrench." Tighten it till it strips and then back off 1/4 turn.
     
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  3. W7UUU

    W7UUU QRZ Lifetime Member #133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    :eek::eek:
     
  4. W7UUU

    W7UUU QRZ Lifetime Member #133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Super important to know if the power supply is solid state (MANY "tube rigs" have solid state power supplies!) or tube rectifier.

    A Variac is a great way to bring an old radio up on the bench - but if it's a tube rectifier like a 5U4, unless you bring the filament up enough to cause the tube to conduct (and rectify!) it's pointless to bring it up too low. Put your voltmeter on the rectifier B+ output and bring the Variac up until you just see B+ happen - then leave it for a while. How long? Depends on how much smoke you then see ;)... but I generally go at least a few hours at that stage and see what happens. The raise it up a bit more. Not a bad idea to put a scope on the B+ and see how "smoothe" the DC is post-filter...

    If the radio has a solid state supply, all the above still applies but just at a MUCH lower level - the solid state rectifier(s) will start working at a much lower voltage - but same steps apply: SMOKE? TURN IT OFF!! :D If all seems well, monitor the DC output on your scope and verify it looks clean.

    After a day or two, keep ramping up and see what you have...

    Just how I've done it for years and it's worked well for me. I'm no expert by a long shot though.

    Dave
    W7UUU
     
  5. KA5SDC

    KA5SDC Ham Member QRZ Page

    Don't have a scope so I am on my own for now. The three radios I had in mind to start with are all Heathkit...Marauder, Apache, and Mohawk. I know the Marauder uses the 5U4 as that tube was broken when I got the transmitter. The other two I have not dug into yet but suspect they are similar.

    Thanks,

    Dee
     
  6. KK6IYM

    KK6IYM Ham Member QRZ Page

    I do not use a variac to bring the radio up slowly. I assume it needs new electrolytic and paper caps and replace those. I add a three wire power cord and replace the line caps with the safety variety. I add a fuse if it doesn’t have one and check to see that the fuse is correct if it does have one. I wire the hot to the fuse, then the switch, then the line caps, then the transformer. Heathkit (and other) transmitters benefit by having all the component mounting and terminal mounting screws loosened and tightened. I test all the tubes and make sure the proper tubes are in the proper sockets. I clean the chassis, tuning capacitor, switch wafers, tube bases, and all the exterior parts, panel, knobs, etc. I check the light bulbs and often replace with LEDs.

    After a final check of the power supply wiring, I flip the switch. I do watch for smoke and flashes of light, but as I said earlier—there is a proper fuse in place. I next proceed with an alignment by carefully following the manual instructions. If any of the alignment procedures does not work, I stop and fix the problem, then continue. I usually align a radio at least twice, as they can be pretty far off and it might take a few times through to get everything working properly.

    The Marauder is a difficult radio to work on as components are really packed tight in a few areas. Mine had a grounding problem that took me quite a while to locate—as the loose lug was on one of the filter studs so I didn’t get it when I went through all the mounting screws.

    Norm
     
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  7. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    SDC:

    The Marauder uses a 5U4 as the lower B+ rectifier and a 5R4 as the higher B+ rectifier.

    The Apache uses 2-each 5R4 tubes for the higher B+ rectifiers and a 5V4 as the lower B+ rectifier.

    Glen, K9STH
     
  8. K6BSU

    K6BSU Ham Member QRZ Page

    Listen to W7UUU. Vacuum tube radios that have a combined plate/filament transformer should not be run at low AC voltage. Tube heaters should be run at rated voltage. If you insist on using a Variac at less than about 80% line voltage, remove all tubes except the rectifier tube. Set the Variac at 80% line voltage so that the rectifier heater is hot enough to operate.
     
  9. KK6IYM

    KK6IYM Ham Member QRZ Page

    I actually really dislike “reformed” capacitors. It may work if you intend to use the radio on a regular basis, but let it sit on a shelf for a few months and you have bad capacitors. I have had more than one EBay electronic device that worked great when I received it and tried it out, but then when I left it sit for awhile and tried to use it, it immediately blew the fuse. How can that be? Because someone took the device, let it cook with some low AC, and then quick sold it as a working instrument. I say replace the electrolytics and you have a radio that can sit on the shelf for a few years and it will still work as it should with no worry about destroying a choke or transformer.

    Norm
     
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  10. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    There are those who like living dangerously, taking chances, etc. However, with any "boat anchor" radio, or even a more modern radio that is much over 20-years old, as far as I am concerned, the electrolytic capacitors are an automatic replacement as are any paper type capacitors, including bathtub capacitors, and any silver-mica capacitors that are used as coupling capacitors or bypass capacitors (in tuned circuits they are usually OK).

    It only costs a few dollars "up front" to replace these capacitors and such is definitely good insurance from when they go short and "take out", usually, hard to find, expensive, etc., other components. Paper capacitors are VERY likely to be leaky and that puts strain on other components. The unit "may" seem to be working OK. However, with the capacitors replaced, the performance is almost always considerably better.

    Of course, there are those individuals who have, so far, not suffered failures from not replacing these components. But, as for me, I prefer NOT to live on the "wild side" by taking chances that there will be no failure.

    Glen, K9STH
     
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