Re: CBM 3032 (PET 2001N-32), no video?

On Sun, Feb 25, 2018 at 7:43 PM, Sherry Haibara <v.castelli92@gmail.com> wrote:
>> the heater of the monitor is really independent from the main PET
>> board. It should light as soon as you apply the AC power to the
>> monitor PCB, even if no PET is connected. It's fed with the regulated
>> 12V DC through a dropping resistor only.
>> If it doesn't come on, there is no 12V dc on the monitor PCB or some
>> connection is broken (wires going to the CRT neck, the dropping
>> resistor, etc.)
>
> The pins of the regulator seems indeed to be in a very sorry state. I'm
> attaching a picture (let me know if it's visible). It looks like someone has
> attempted to replace it but didn't do a very good job, those traces might be
> broken at this point. How should the pins and the traces look like? Are they
> supposed to be connected, and in what order? My guess so far is that the
> left pin (top in the image) should be connected to the trace with the 'U'
> shape, the right pin (bottom in the image) should be connected to the bottom
> trace and the central pin should be connected to the trace on the left.

that is correct.
You should measure only between the center pin (negative) and the
other pins: one is the input coming from the rectifiers and the
smoothing capacitor, and the other pin is the output.
On the input you have to measure at least 17V, more likely about 20V,
on the output pin, you should have about 12V.

> After having applied some fresh solder to the pins, I now see 8V DC across
> the two side pins and between the left pin and the central pin. There are 0V
> between the right pin and the central pin. It sounds like the central pin
> and the right pin are shorted together.

your measurement is strange and only compatible with a shorted 12V
rail (or broken rectifiers or maybe dead capacitor).
Power down everything and measure the resistance between the output of
the 12V regulator and ground (center) pin.

Frank

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