Re: HP8657B doubler issue
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It's a small world I guess.
If I had that doubler I might try to reverse engineer it a bit to see if the problem is tractable.? It seems you have no trouble with the doubling circuitry, but the control circuit is messed up.? When the supply dropw, is it due to overload or insufficient available current?? Or perhaps voltage instability.? Lift the appropriate wire and insert a milliammeter.? Without a diagram it's more challenging.
I have a similar problem with a 3455A voltmeter.? It works great excapt it won't switch into 4 wire Ohms mode.? I have the cover off and am trying to see how that works.? I think there are relays involved so I might look for a burnt out relay driver or a bad connection.? It could also be a logic problem, and if so I am out of luck.
Bob
On Monday, April 8, 2019, 1:44:10 PM PDT, Ted Cuff <tcuff65@...> wrote:
I think that was my post on EEVBlog. :)
On Sat, Apr 6, 2019, 12:26 PM Bob Albert via Groups.Io <bob91343= [email protected]> wrote:
I suggest you go to EEVblog and connect with a guy there who has what seems to be the same issue.
As you probably know, HP has no available information on the innards of the doubler.? I repaired mine but it had a different problem.? The factory, even when it was supporting the unit, required that the doubler be returned to the factory for repair or replacement.? I don't know how much they charged for that but I suspect it would have been well over $1000, since the whole generator went for something like $13k.
I think this guy already tried relacing the regulator.? Anyway perhaps between you two a solution can be found.
Bob
On Saturday, April 6, 2019, 6:02:34 AM PDT, < tcuff65@...> wrote:
I read through a lot of the posts on the 8657b doubler issues, but haven't found any ideas that match my issue.
I seem to have the same issue VE2ZAZ had with his.
When my doubler acts up, a red led lights up inside the doubler, and the -5.2v supply gets loaded down.
Then after a little bit, the led goes out and the -5.2v supply recovers, and all is well again.
There is a power resistor by the 723 regulator that has overheated some.
I'm guessing that the led is tied to that regulator somehow.
But I have no idea where to begin with no service data available.
Also, is the 38v supply only for the doubler as well?
Thanks for any help.
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