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 Post subject: Heathkit BE-5 repair attempt
PostPosted: Nov Sun 26, 2017 10:48 pm 
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Acquired a nice looking unit, that has OCT 1961 ink stamped date on the AMP gauge. Works fine on the 6 volt range, but not so well in the 12 volt. Can get only about 1 volt out of the 12 volt range and once got up to 4 volts.

Have only dabbled in fixing electronics before now, so not real proficient at this. Very much interested in learning more.

Not seeing any diodes in this unit as shown in the available on-line wiring diagram. Tested capacitors with the ohm setting with each one with a lug unsoldered, and all three seem to be good.

Not having luck in loading up images of the innards. Keep getting "The file is too big, maximum allowed size is 256 Kib".


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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Nov Mon 27, 2017 4:51 am 
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Will see if these images work..


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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Nov Mon 27, 2017 10:39 am 
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Location: Albuquerque, NM 87123
Could be bad capacitor (even though the ohmmeter test was OK), bad switch, bad selenium rectifier (the device with the heat sink fins), bad secondary winding (unlikely).


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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Nov Mon 27, 2017 4:34 pm 
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Every one of those I have worked on over the years has needed both the selenium rectifier and the electrolytic caps replaced to get full output voltage on 12 volts. It's a very marginal unit at best, but better than some of the earlier versions. You can use two modern full wave bridge rectifiers mounted to good heat sinks and rated 25 amps or so as replacements for the selenium, finding appropriate electrolytics that are affordable is another story.

Output voltage still drops severely under load with new parts, but it will work like it did when it was new.

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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Nov Mon 27, 2017 4:39 pm 
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Is there a better test for the capacitors, or best to just replace?

Both transformers look good, as in no charing.

Hope it is not the rectifier. Would like to keep the inner workings looking correct, but of course getting it working is more important. Suspected the capacitors first off and figured if tested bad would try gutting them to put in new ones inside the old casings.


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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Nov Mon 27, 2017 4:54 pm 
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Location: Dallas, TX
Sapphire Driver wrote:

Hope it is not the rectifier. Would like to keep the inner workings looking correct, but of course getting it working is more important.

Silicon rectifiers are so small you can put them on the underside of chassis. Disconnect the selenium and leave it in place.

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"Excellent!" I cried. "Elementary," said he. - Sherlock Holmes


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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Nov Mon 27, 2017 5:41 pm 
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Notimetolooz wrote:
Sapphire Driver wrote:

Hope it is not the rectifier. Would like to keep the inner workings looking correct, but of course getting it working is more important.

Silicon rectifiers are so small you can put them on the underside of chassis. Disconnect the selenium and leave it in place.



The kind of silicon rectifiers you need to use to replace a selenium of that size and with that many sections need to be mounted to a significantly large heat sink, there is no way the appearance of the unit can be kept original and no way to hide them.

On a piece of test equipment it shouldn't matter about the internal appearance as long as your work is neat, since you need it to be functional.

If you are concerned about maintaining original internal appearance, better off to leave it untouched, display it as-is and buy a different power supply that you can service to use on the bench. All of the ones that old are going to have capacitor issues, but starting in the mid-1960's many of them came with silicon rectifiers.

Note: If you want to verify the capacitors are causing a problem, you can temporarily disconnect all of the existing caps and connect new ones in their place. Also note that you can't use the much smaller modern tubular/radial type electrolytics of the same value and voltage to replace those, as they won't last. You need can type capacitors which are going to be pretty close to the same physical size as the originals to handle the ripple current from this supply.

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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Nov Mon 27, 2017 6:14 pm 
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Capacitors that old, I would replace whether or not they tested good. But that's just me. To do otherwise is asking to spend more time fixing your test equipment down the road, than using it to fix other stuff :)

You can get some pretty beefy rectifier replacements, stud mounted, for next to nothing if you go to hamfests. Probably close to next to nothing even on Fleabay. Properly insulated, and chassis mounted, the chassis becomes the heat sink.

Or, you can just get some overrated ones, even a stud type, and air mount it. Over rate it enough that you won't have to worry about heat sinking it.


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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Nov Tue 28, 2017 5:23 am 
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Location: Powell River BC Canada
The thing that is fatal on those packs is the transformer wiper that adjust the voltage. Look
at that carefully for charred insulation and contact pressure.

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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Nov Tue 28, 2017 7:11 am 
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If you replace the rectifiers and capacitors, be sure to use capacitors with a higher voltage rating. Mine goes up to almost 40 volts with no load on the 12 volt setting. I put my rectifiers on a heat sink from a computer CPU. It gets hot at full load. Don't skimp on the heat sink.

It is possible to redesign this unit to use a full wave bridge and still have both voltage ranges. There are enough switch contacts left over to add a multiplier resistor to the voltmeter so that it's range changes with the voltage switch. Why Heath didn't do this is an open question, perhaps patent issues.

I used ordinary tubular electrolytic capacitors. At full load they heat up. They won't last long like that. Find the large size or only use it at low current.

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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Nov Wed 29, 2017 11:05 pm 
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Another common problem with those is dirty or burned contacts on the voltage selector switch; it's a little small for the job. At one time, Heathkit sold a replacement rectifier assembly which used silicon diodes, mounted on a heat sink.

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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Nov Thu 30, 2017 8:14 pm 
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Found this capacitor for sale. It is a bit smaller dimension wise than the original ones.

https://www.ebay.com/itm/10000uF-100V-4 ... 1438.l2649


See any problem with using in this project?


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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Nov Thu 30, 2017 9:00 pm 
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Location: Dallas, TX
I'd see if I could find one with a little lower voltage rating. It would work, but I believe over time the capacitor might "reform" and change value. I think you could find 50V or 25V versions. Caps like these were used in linear high ampere 5V power supplies used in large digital devices like computers. Not so much anymore however.
http://www.surplussales.com/Capacitors/ ... 000uF.html

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"Excellent!" I cried. "Elementary," said he. - Sherlock Holmes


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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Nov Thu 30, 2017 9:17 pm 
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Location: Mpls, Minnesota
Notimetolooz wrote:
I'd see if I could find one with a little lower voltage rating. It would work, but I believe over time the capacitor might "reform" and change value.
That is ancient technology, modern electrolytics do not change.
As mentioned before, the major problem with these is the switch contact assembly.

Dave


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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Dec Sun 03, 2017 1:28 am 
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Well I have had no luck in finding a lower voltage capacitors just to CYA against the possible reform problem. So will just buy the previously posted ones.

Have probed around the contacts of the switch to see if any caused the 12 volt circuit to work suddenly. No change.

Did hear three random electric snaps from what seems to be in the direction of the rectifier.

Had previously tested the unit only with voltmeter. Decided to try load testing it with a small 12 volt bulb. Then the 6 volt range is fluctuating up and down about 2 to 4 volts!

Any recommendations on rectifiers I can buy on line for this?
Thanks!


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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Dec Sun 03, 2017 6:15 pm 
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I have used full wave bridges in epoxy or metal packages, you don't necessarily use all 4 diodes in each package for this type of application. A minimum of 25 amps and 100 PIV would be good, you can get the best prices on 50 amp 1000 PIV ones, if you are patient about waiting for delivery from China for about a buck apiece on eBay, higher prices from US shippers. Need about 20 square inches of heat sink (or more) on them, with the heat sink bolted to the chassis if you plan to run the unit near maximum load rating. I used some scraps of 1/4" thick aluminum plate.

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Experience is what you gain when the results aren't what you were expecting.


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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Dec Mon 04, 2017 12:08 am 
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And don't forget the heat sink grease.

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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Dec Tue 05, 2017 3:16 am 
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Did not have much luck finding 50 AMP rectifiers! Some of 35 and lots of 150 AMP ones listed on Ebay. So for now have some 25 AMP ones ordered up. Probably going got take over a month to get here direct from Asia.

Now going to order up the 100volt capacitors. Could not find ones in the 50 volt flavor that had near the same length and width dimensions.

Looking forward to getting this running. Have a project Airline table top radio model 62-338 that was produced about 1936-38 (if on line info is correct), that was designed to run off 2 volt wet battery cells. Probably for the back woods farmer or hunting cabin... With this power supply hope to see if it works or get it fixed. Fellow whom I bought it from claimed it worked, but I did not believe him. Still for $20.00 could not walk away. Will start another thread on the radio, probably as soon as the power supply is working.


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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Dec Tue 05, 2017 3:48 am 
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Thanks for the reminder on the heat sink grease. Got it now ordered!


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 Post subject: Re: Heathkit BE-5 repair attempt
PostPosted: Dec Tue 05, 2017 3:58 am 
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Location: Mpls, Minnesota
25 amp rectifiers is really cutting it close, just be careful you don't accidentally touch the leads together. The seleniums wouldn't care but the silicons will short very quickly.

Dave


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