Help with BK 1635 PS , excess voltage ?

[KD0CAC]

I picked up this unit from a friend helping move this was something he had .
I plugged in and hooked up to my Fluke meter to check voltages , it seems to work fine until it gets around about 5.9 - 6.2 volts [ depending on the setting of the 3 pots V fine & coarse , A .
When it hits that voltage above , a relay will click & voltage will jump 43 volts , then have to turn both voltage pots to min. , get the voltage to drop .
Any ideas ?
Thanks John

[KA9JLM]

You may want to put a load on it for testing.

[KD0CAC]

About the only thing loading does is drop the meter reading by about 3v from 43v to 40v , but it will jump to max v - 40v at 4v , its a 30v max PS .
And with a load the amps will go to about 5.4 amps , which is above unit limit of 3 amp .

[K8ERV]

Do you have a diagram?

TOM K8ERV Montrose Colo

[KD0CAC]

That's one of the problems , I downloaded a manual , but not diagram and did not find one yet in the net .

[K8ERV]

I picked up the manual too. Dunno why these companies are so afraid to publish diagrams.

TOM K8ERV Montrose Colo

[KA9JLM]

It may not be that hard to figure out.

It sounds like it may have a shorted Pass Transistor.

That constant current/constant Voltage Mode relay may be what you are hearing.

if CC or CV indicator seems to follow the jump in voltage I would check for a shorted Output Transistor.

If it has a shorted pass transistor the current normally would not read more than the load connected, But the Voltage would go high like you describe. A 120V light bulb may be a good light load tester.

[KE3WD]

Use of 120V lightbulb as test load is a good idea. Also, might want to clean those pots and controls before getting down and dirty with it, a dry pot or one with an area on the carbon that is not conducting might cause the same symptoms.

[KD0CAC]

Yes it sure would be nice if they would have a diagram in the manual .
I used a large wire-wound ceramic resistor .
And used Deox spray , the 2 part cans on the pots & switcher , that was the 1st thing I did , after a new neg. binding post , it was broke off when I got it .

[KA9JLM]

Yes it sure would be nice if they would have a diagram in the manual .
I used a large wire-wound ceramic resistor .
And used Deox spray , the 2 part cans on the pots & switcher , that was the 1st thing I did , after a new neg. binding post , it was broke off when I got it .

The Neg Post should not be ground and should be floating.

Is the one that you replaced insulated from ground ?