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H7864 Power supply just stopped working

C

Crawford

Experienced Member
Joined
Oct 21, 2008
Messages
275
Location
Maryland
Folks,

As part of getting my franken-PDP11/53 running again, my H7864 power supply croaked. Rather than letting go in a smelly or spectacular manner (as some others have done) it just stopped working. The circuit breaker and internal fuse both register continuity, and the insides all look pristine.

Any pointers on where to start with this thing? I was flipping the power on and of relatively often (don't have a run/stop or reset switch wired yet), and the last click to 'on' did nothing.

Thanks,

? ; - )
 
Hi All;
I would check the obvious things as well as the stupid things first.. Like the Plug is not plugged in All the way, it just slipped out half way.. Ask me How I know..
THANK YOU Marty
 
yeah I try to check that first

yeah I try to check that first

Marty said:
Hi All;
I would check the obvious things as well as the stupid things first.. Like the Plug is not plugged in All the way, it just slipped out half way.. Ask me How I know..
THANK YOU Marty
Click to expand...

Yup - I do that first so I don't embarrass myself publicly (as much)
 
One more really obvious thing to check (which has caught me out on one occasion) the MCB/fuse feeding the power circuit you are feeding your PDP from hasn't tripped/blown has it?

This is easily checked by plugging a known good electrical device into the socket you are feeding the PDP from (I state the obvious).

I was once repairing a piece of equipment. I found the fault with the power supply and fixed it. Everything was working fine on the bench. I re-installed the power supply and it didn't work once I had installed it. I removed the power supply and went through the fault-finding checks again only to discover after a short while that the MCB feeding the ring main had tripped for no apparent reason. I reset the MCB, tested the power supply once again (OK), re-installed it and (hey presto) everything worked as expected.

So now - when something like a lack of power seems to occur - I always plug in my socket tester (just as a first check) before disassembling anything.

It is unlikely to be this type of fault, but you can never rule it out...

Dave
 
Folks,

We'll it turned out to be something relatively simple. The filter board had cold solder joints on the spade lugs. I resold erred them and the rest of the board for good measure.

Back in business... Thanks all for the inputs!
 
Crawford said:
Folks,

We'll it turned out to be something relatively simple. The filter board had cold solder joints on the spade lugs. I resold erred them and the rest of the board for good measure.

Back in business... Thanks all for the inputs!
Click to expand...
The easy fixes are the ones I like. But rarely does that happen.
 
Ah... the "Cold Solder Joint" fix... never used to be thankful for those. Last one I had was a few years ago on my Laser Printer's Fuser control board.
 
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