Hickok 5055 problems..

[BaasDNB]

Hello all,
I'm new to the forum, and enjoying the content a lot... I've read a lot and fixed a broken LCD thanks to the users on here. : D

My next project is I am working on is an old power supply. I found it in a junk pile at my school where they dump old equipment. Its a Hickok model 5055.

I've searched a ton online for schematics but cant find anything. The power supply has a 0-40V DC (up to 1amp) supply, a 0-400V DC(up to .15 amp) supply, a 0- (-100) V DC and a AC source.
The problem is the 0-400V DC source. There is a missing capacitor(which I'm assuming blew out and they took it out..) and the thing that bothers me is that there are 3 wires(shown in pic). My initial guess was that green is ground and black is negative and red is positive to the output . I traced the green wire to the middle of a bulky transformer, so im guessing that is the isolated ground(pic attached)? The black wire goes to the negative terminal of the 0-400V supply output, and the red is a little confusing.. It goes to this strange "wooden" resistor(pic shown)as well as some other spot on the circuit board. It does not go to the positive output as I thought.
If I turn the supply on, there is a constant 38V between the red and black wire, no voltage reading at all between green and black or green and red. The ammeter and voltage meter pulse as if the 0-400V supply is trying to turn on...
One last thing, that strange resistor gets very hot in only a matter of half a minute or so... Maybe there is some short?
Any direction of what to check next would be much appreciated! Thanks,
Anthony

[Toasty]

Re: Hickok 5055 problems..

Welcome to the Forums!

They have a website. See if someone can help you there. http://www.hickok-inc.com/

The "wooden" resistor is actually a ceramic wirewound type.

You may want to join the forum at audiokarma.org. The post link that follows is 2-1/2 years old, but they have 1600+ posts, so I figure they are somewhat active. They have one of these and may be able to tell you of the missing values:

http://www.audiokarma.org/forums/sho...d.php?t=148547

Strictly from an age standpoint, I would be prepared to replace all of those large can caps. Their filtering ability has most likely faded due to their age and probably what caused the failure of the removed one.

The power coming to that cap would be rectified somewhere, but one leg of the transformer could be the neutral/ground leg. That makes sense to see the green wire direct from the trafo to the cap. It's likely a full-wave rectifier, center-tapped. Depicted in the 3rd diagram down, here: http://en.wikipedia.org/wiki/Rectifier

Going by the voltage (38v) you read there, this is more likely the 40v supply section.

The high voltage in this supply, as indicated by the front panel, is limited to 150 milliamps. That resistor may be the limiter. Where does the wire from the other end go?

You will find there is little need for 400v in a bench supply. Remember these were used in a electronics classroom setting following a guide of "How to build this circuit". "Hook wire A to meter B terminal X1"... etc. They really aren't up to the caliber of what is needed today.

Happy Hunting!

Toast

[JimNarem]

Re: Hickok 5055 problems..

I just got one of these, haven't even fired it up yet since one of the caps has
a bizarre little mushroom of electrolyte oozing out of the 2500uF/75V cap.

The cap you are missing is 500uF/75V. The negative side has three black
wires, a braided ground line to the HV- and a green wire going to a transformer.
The positive side of the cap has three orange wires. One goes to a bleeder
resistor near the cap, one goes to a huge 100 ohm power resistor and the
last goes to the regulator board.

The six can caps should be replaced with short, fat snap-caps, the two
HV caps (50uF/450V) should also be replaced. Looks like there are two
dipped tants on the meter board that should be checked.


Yes, normal people don't need a 400V bench supply. It's designed for tube
equipment. That's why it's got two filament supplies, a 2mA negative
supply and a variac. It's like a better version of the heathkit IP-2717.

...................jim (narem@narem.com)

[matros_kolya]

Re: Hickok 5055 problems..

Hi Everybody, I see that quite of few people attempted to repair and restore this PS. I have some problems with my own PS as well. Need some assistance if possible... I bought my Hickok PS 5055 at local flea market and I see that someone already attempted repairs and left with cut wires, missing transistors, etc. Does anyone can help with getting a schematic diagram for this model? You are help is appreciated! Thanks, Nick