Re: 7704A (et. al.) Inverter Regulator Question


Until I get that bad transistor replaced, then I don't plan on trying it connected to the display unit as a load. I tried that before I was aware of the bad transistor. Once I get that, I do plan to test it connected to the display unit. If it's still ticking, then it's either a problem with the display unit or the PS. In that case, the external load resistors will at least eliminate the display unit from the equation. I'll report back once I get the transistor replaced.

Barry - N4BUQ

----- Original Message -----
From: "Göran Krusell" <>
Sent: Monday, September 13, 2021 11:29:02 AM
Subject: Re: [TekScopes] 7704A (et. al.) Inverter Regulator Question

Hi, I have not followed this discussion very closely but my guess is that you
are looking in the wrong direction.

You need to check U3105 pin 2, BAL SENSE, where the voltage should be 0V in
normal operation. If it deviates more than 200mV (+ or -) then the PS should
turn off.

Also check U3105 pin 13, I SENSE, where the voltage shall be positive,
perhaps +0.23V, in normal operation. In an over-current situation the
voltage drops below 0V and the PS should turn off.

If you hear a hissing and sparking sound you may have a problem with your
voltage multiplier.

Carry on and good luck

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