More Amplifone woes ...

From: Dave Langley <robotron_at_ntlworld.com>
Date: Thu Aug 22 2002 - 16:52:23 EDT

Hi again,

I've been looking at my Star Wars 25" Amplifone HV again.

I tested the regulators with the BU406D removed and I'm getting +/- 30v
fine. The +24v reads a little under 25v (is this OK off load?), however
I'm getting -31v instead of -24v at the 7924. If I remove the 50ohn 5w
resistor the regulator now produces -24v perfectly (though off load). The
resistor seems fine out of cct but maybe it's breaking down when there's a
load on it? Either way I guess it will get replaced now as I have no
confidence in it.

Moving on to the waveforms from the oscillator cct:
(remember my scope is old and wont have seen Cal for a number of years)
I'm getting a nice 10v(ish) square wave at pin 3 of the 555
I'm getting a 60v? rounded square wave at the collector of the MPSU07
AT the base of the BU406D I'm only getting a 4v rounded square wave IS THIS
CORRECT?

Thanks in advance for any help

Dave Langley
www.robotron-2084.co.uk

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Received on Thu Aug 22 14:54:54 2002

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