How to Repair 0-100V DC Power Supply? Need Help

[Noam]

Hi,

I have an old 0-100V (0.2A) HP power supply (HP 6116A), which is
broken. The output is always 0.6V (when on). Nothing is obviously
burned or exploded inside.

The problem started when one of the people in my lab connected a
capacitor backwards across the supply's output, giving it a large
negative voltage spike.

Any ideas on what could be the problem? The supply has a transformer
and several largeish capacitors. However, the inner circuit is pretty
complicated. My guess is something near the output is broken, but what
could it be?

Any advice would be greatly appreciated.

 

[James T. White]

Hi,

I have an old 0-100V (0.2A) HP power supply (HP 6116A), which is
broken. The output is always 0.6V (when on). Nothing is obviously
burned or exploded inside.

The problem started when one of the people in my lab connected a
capacitor backwards across the supply's output, giving it a large
negative voltage spike.

Any ideas on what could be the problem? The supply has a transformer
and several largeish capacitors. However, the inner circuit is pretty
complicated. My guess is something near the output is broken, but
what could it be?

Any advice would be greatly appreciated.

First, I would get an Operating and Service Manual for the 6116A off
eBay or one of the vendors that specialize in manuals for obsolete test
equipment. These are usually $30 or so. In addition to schematics it
will have circuit descriptions and parts lists which will make your
troubleshooting much easier. HP equipment of this vintage shipped with
this manual
but unfortunately lots of them have been misplaced over the years.

Second, HP supplies typically have lots of internal power and bias
supply voltages. One or more of those being out of spec can result in
lots of strange behavior at the main outputs. Unfortunately without a
manual you don't know where to probe or what is OK.

Third, I don't know specifically about the 6116A, but lots of HP
supplies have output over voltage protection that is implemented using a
comparitor and a SCR which crowbars the output to near zero and is reset
by power cycling the supply. I know the later model 6114A and 6115A
have that type of protection. If you managed to put enough voltage and
current back into the supply, you might have zapped the comparitor so
the the output is always shorted by the SCR.

Fourth, if it isn't the over voltage protection at the output, then you
might have zapped the output voltage or current sensing amps.

Hope this helps and let us know how your repair turns out.

 

[[email protected]]

Hi,

I have an old 0-100V (0.2A) HP power supply (HP 6116A), which is
broken. The output is always 0.6V (when on). Nothing is obviously
burned or exploded inside.

The problem started when one of the people in my lab connected a
capacitor backwards across the supply's output, giving it a large
negative voltage spike.

Any ideas on what could be the problem? The supply has a transformer
and several largeish capacitors. However, the inner circuit is pretty
complicated. My guess is something near the output is broken, but what
could it be?

Any advice would be greatly appreciated.

Sometimes power supplies have a diode accross the output terminals you
may have damaged that with the reverse current.