Hickok 5055 bench supply restoration

[Nick56]

Alright, so I just picked up this old power supply from a scrapyard. This thing is from the mid 70's and has been out in the elements for probably 2+ years. The AC cord has been cut off of it, which is probably for the best for the time being..
I'm attaching some pictures of the interior, there are a few caps that look like they're leaking. They're an old style so I'm not positive if that's what it is. I found an old thread about this supply that recommended replacing all of the big caps:
https://www.badcaps.net/forum/showthread.php?t=11043
Are they worth checking or should I just change them all out?
Also some of the ratings are odd and hard to find good matches for, like 75V 150uF. Is it OK to use a cap that's higher in both voltage and capacitance, such as 200V 330uF?

The only other obvious problem I found is the horrible wiring going to the power transistors. What other things should I look for to replace/repair?

Thanks in advance for any advice.

[Robert666666]

Re: Hickok 5055 bench supply restoration

Alright, so I just picked up this old power supply from a scrapyard. This thing is from the mid 70's and has been out in the elements for probably 2+ years. The AC cord has been cut off of it, which is probably for the best for the time being..
I'm attaching some pictures of the interior, there are a few caps that look like they're leaking. They're an old style so I'm not positive if that's what it is. I found an old thread about this supply that recommended replacing all of the big caps:
https://www.badcaps.net/forum/showthread.php?t=11043
Are they worth checking or should I just change them all out?
Also some of the ratings are odd and hard to find good matches for, like 75V 150uF. Is it OK to use a cap that's higher in both voltage and capacitance, such as 200V 330uF?

The only other obvious problem I found is the horrible wiring going to the power transistors. What other things should I look for to replace/repair?

Thanks in advance for any advice.

Hi Nick56'. My name is Bob. I have the Hickok 5055 power supply you just posted pictures of. I would like a closeup of the smaller circuit board showing components and wiring hookup. I think mine is wrong. If you can help I would appreciate it. Thanks Bob

[ben7]

Re: Hickok 5055 bench supply restoration

Alright, so I just picked up this old power supply from a scrapyard. This thing is from the mid 70's and has been out in the elements for probably 2+ years. The AC cord has been cut off of it, which is probably for the best for the time being..
I'm attaching some pictures of the interior, there are a few caps that look like they're leaking. They're an old style so I'm not positive if that's what it is. I found an old thread about this supply that recommended replacing all of the big caps:
https://www.badcaps.net/forum/showthread.php?t=11043
Are they worth checking or should I just change them all out?
Also some of the ratings are odd and hard to find good matches for, like 75V 150uF. Is it OK to use a cap that's higher in both voltage and capacitance, such as 200V 330uF?

The only other obvious problem I found is the horrible wiring going to the power transistors. What other things should I look for to replace/repair?

Thanks in advance for any advice.

You should change all the capacitors, in my opinion.

It might be OK to use a higher capacitance rated cap for replacements. You can always use two or more in parallel to get as close as you can to the capacitance of the original. Just don't replace any with a lower voltage rating than original, ex: don't replace the 75V cap with a 50V cap. Replacing the 75V cap with a 100V or even 200V cap is fine, though the replacement cap might be bigger in physical size than the original.

The horrible wiring on the power transistors might be from a previous repair, I know the sockets that were used for TO-3 transistors would get bad contacts after a number of years. This especially causes problems in audio amplifiers xD

[Nick56]

Re: Hickok 5055 bench supply restoration

Hey Bob, I attached some pictures of that board. It's pretty cramped in there. Let me know if they're not clear enough, would be easy to draw up a diagram next time I work on it.
The single wire on the back of the board goes to the (-) lead of the nearest big cap.

I'm wondering if a couple parts on mine are fixes or addons. Can you check yours for the two three-terminal devices pictured? One is on the inside back of the chassis, the other on the side.


Ben:

Ok thanks I will give it a shot. The caps they used are huge in relation to their ratings, so I think I'll have enough room to put 2-3 in parallel for each to match values.
Yeah having sockets for metal power transistors always seemed a bit overkill to me. Those things are built like tanks, I've never needed to replace one. Now what we really need is socketed electrolytic capacitors for mainboards. :P

[Robert666666]

Re: Hickok 5055 bench supply restoration

Thanks Nick. Pictures are great. I'll take some pictures of those transistors and post them for you. Again thanks Bob

[Robert666666]

Re: Hickok 5055 bench supply restoration

Nick. Can't figure out how to upload pictures. Email me and I'll send them to you. Bob. Pj02090@yahoo.com

[Nick56]

Re: Hickok 5055 bench supply restoration

OK Bob, will do.

Took some time, but I got the whole thing working.
There were 5 separate circuit breakers, all with rusty metal cases. They were acting a bit weird, when I'd reset them, they'd change the output voltage! Just had to take them apart and clean the contacts, all work well now.

In the limited information I found online about this supply, I noticed several people mention the big 25W 100ohm power resistor that runs very hot. Sure enough, I checked the voltage and mine dissipates 21 watts of heat at idle. The fact that this is within the 25W spec of the resistor makes me think this is an intentional design choice and not a fault. Regardless, I don't see any reason to burn that much power at idle, so I put a switch going from the orange wire to the left resistor terminal. When I turn it off, it shuts off only the 400VDC section and reduces the idle AC watts from 52 to 25 with no apparent ill effects on the circuit. I used an old switch and mounted it in the gap between the 400V adjust dial and output terminals. I'm quite happy with it, IMO it looks almost like it was part of the original design!

Also a final pic of the supply on my bench with different types of lights hooked up to every single output.