Rebuilding R-390A Power Supply Caps. Step by Step With Photos

Discussion in '"Boat Anchor" & Classic Equipment' started by KC8VWM, Apr 16, 2016.

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  1. KC8VWM

    KC8VWM Ham Member QRZ Page

    Oh I did... Just showing them to you. Show and tell sort of thing. I also have a pair of Centrons for it too. Anything is better than the Chinese tubes I guess.

    Say any word on how those new Taylor's work?
    KD2ACO likes this.
  2. KM1H

    KM1H Ham Member QRZ Page

    OK, just in case there is still any confusion...that Raytheon 572B has a stepped glass, commonly called shoulder, so it is a Cetron. You will also find some round tops with the Cetron name, they couldnt keep up with orders and had United make them. Those are mostly found in SB-200's with the original tubes, Heath did not have their name on them as did Dentron. Waters sold a lot of the UE version with the Waters name.

    When Taylor (the real one in IL) sold the rights to the T-160L design around 1960 it went to UE as the 572A/T-160L and Cetron as the 572B/T-160L. UE didnt have a high production capacity and didnt push them to OEM's as hard as Cetron so the Cetron was the most common one. Soon the T-160L part was dropped and just 572B was on the tubes. Some 572A's still show up on Fleabay, etc and are a direct swap for those who didnt know the history.

    Ive only heard good things about the new Taylor/RFP versions but they havent been out long enough for life tests. Im still working thru the US versions Id been stockpiling plus older good type Chinese I bought in quantity direct from China so havent ordered any more yet.

    Richardson Electronics in Chicago still has the original Cetron manufacturing equipment and wont sell it last I heard.

    AF6LJ and KC8VWM like this.
  3. W9GB

    W9GB Ham Member QRZ Page

    I think the bomb shelter is still available ... hard to say whether it should be refurbished.

    I have my popcorn order (cheese and carmel/Chicago mix) for January 20th.
    Always enjoy a good adventure and mystery reel .... beverage yet to be selected.

    AF6LJ likes this.
  4. N2EY

    N2EY Premium Subscriber QRZ Page

    Probably better than new, because of higher-quality replacement parts (filter caps and rectifier diodes, in particular).

    KC8VWM likes this.
  5. KC8VWM

    KC8VWM Ham Member QRZ Page

    Just a quick note to inform everyone that I had many requests and shipped out A&M meters for the R-390A from my source, but the supply has almost been entirely depleted.

    There's now only 2 of these meters left, but 1 of the remaining meters has a small ding on the outside metal cover, and the other one has a bad movement and it isn't working properly so it's probably only good for its cosmetic parts.

    The rest of the meters I have acquired and shipped out are now living happily inside some

    AF6LJ and KD2ACO like this.
  6. N3DT

    N3DT Ham Member QRZ Page

    Good on you. I hate to say it, but I haven't gone any farther than getting the meters, thanks. I got interested in the Apache lately, but now that all seems resolved, so it's time to get back to the 390's. Besides they're still taking up a whole bunch of desk space. Trouble is I can't remember where I was. Seems to me I was putting the tube rectifiers back in one of the PS units and re-wiring it to original, it was a mess.

    Did I tell about repairing one of the main tuning knobs with brass bushings and epoxy glue? It's holding up fine after a few years. I might have done that on the 390 list, can't remember (anything).
    KC8VWM and AF6LJ like this.
  7. KC8VWM

    KC8VWM Ham Member QRZ Page

    Yup you're welcome. Feel free to post photos in this thread of your meter install progress as it will help others.

    One thing people need to be aware of is the two large knobs on the R390a for tuning and bandswitching look identical but they are not. I noticed the large knob shafts are different sizes too and the reason why the "fingers" will often break at the back of the knob is because the large knob is being installed on the wrong shaft.

    If there's any resistance when putting the knob back on, don't force them on or else the knob fingers will break!! It's likely you are putting the knobs back on in the wrong order and try switching the two large knobs around with one another instead. ...Just something to be aware of.
    Last edited: Mar 5, 2017
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  8. N3DT

    N3DT Ham Member QRZ Page

    I didn't know that. Thanks. I had a broken one that came that way.
    KC8VWM likes this.
  9. KC8VWM

    KC8VWM Ham Member QRZ Page

    I had one break before. I ended up just replacing the knob with another one for the sake of originality. Not really a big fan of how they are using those fingers and clamp arrangement to hold the knob on the shaft and I think they could have found a better way. I have often wondered if they did it that way because if a set screw ever did get rusted stuck, or the head of the set screw become stripped (more likely) then it's still possible to "break the clamp" which will facilitate knob removal. Alternatively, if another design used a set screw installed directly against the shaft then the knob will be next to impossible to remove without sledgehammers and brute force methods instead which will of course damage the shaft in the process. So the clamp seems to provide a "break away" point in the event something like that happens.

    The fingers on the knob are made from pot metal and can become brittle and develop stress cracks and eventually the fingers can break. They are most likely to break whenever the situation arises when removing the knobs to do anything to the radio. So if you never do that, you won't have any problems with these knobs lol. :)

    Like I said earlier, I just ended up replacing my knob but the broken one's can be repaired by drilling out the shaft hole and making it larger on the back of the knob. This is done to accommodate a shaft bushing with a set screw that slides over the shaft. Sounds like that's what you did too and I think I got that information from the R-390 list in the past.

    The bushing will need to be installed permanently inside the hole at the back of the knob with nothing less than a good quality outdoor marine epoxy. I prefer using epoxy made by Permatex and using cheaper products like JB Weld is a pointless endeavor. It might be possible to tack weld the bushing on the knob but I never tried it, so I don't know.

    Of course you have to ensure you line up the bushing set screw with the Bristol wrench hole in the side of the knob, but you already knew that before the epoxy hardened right? lol.
    Last edited: Mar 5, 2017
  10. N3DT

    N3DT Ham Member QRZ Page

    Yeah, I ordered a couple bronze bushings and drill from ebay to drill out the old knob and epoxied the bushing in place after I hack sawed 2 slots in it, so it mounted with the original Bristol screwed clamp just like before. It's been holding up for a couple years now. Forget what epoxy I used but probably Permatex. I got the idea off the 390 list. Those large knobs are expensive if you want to buy one.
    KC8VWM likes this.

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