[SignalOne] Who works on CX7s?

[Charles Hugg]

Dave,
Why don't I just box this thing up and ship it to you. You could fix this
problem and maybe check it out all around. I don't think that it needs much,
but I don't have any equipment and very little skills.
I would be willing to pay a reasonable, well a little more than reasonable,
price to get this rig up and running.
It deserves to be back on the air.
Just a thought. I am  not in a big hurry, so you could work it into your
schedule. Also, I know how pack so that it would arrive safely.
Thanks for considering,
Charlie
----- Original Message -----
From: David Bertman <davidbe@us.ibm.com>
To: <signalone@mailman.qth.net>
Sent: Tuesday, January 15, 2002 7:21 AM
Subject: Re: [SignalOne] Who works on CX7s?


>
> Hi --
>
>      Well, I'm not guaranteeing anything, but it sure sounds like this is
> the problem.
> It is not too hard to change, but requires some patience.
>
>      First, to diagnose the problem you need to check the 34v power
supply.
> This
> should be pin 132 or 131 of your power supply (I have only worked on old
> ps, but from
> schematic this is same on "B" ps).  If regulator is out the level will be
> over 40v (normally
> about 37v with no load).  If this is the problem, the 34 v regulation is
> out and you need
> to replace the pass transistor q4 mounted on rear of chassis.  The other
> transistors which
> determine its bias  could be gone too -- these are all on the ps board.
> All can be
> replaced without pulling pins on ps board (and I have replaced all!).  The
> problem could
> also be in other regulators.  On "B" ps these are three terminal devices,
> and are also
> mounted on chassis rear.
>
>      Best way to check for hum from this type of source is with a scope.
> You will
> see quite a dramatice angular form when regulation is out.
>
>      Hope this helps.
>
>      Dave AB7B
>
>
>
>
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