[sdiy] Roland CMU-800R transformer query

[Chromatest J. Pantsmaker]

Have you tested the transformer itself?  Check for AC voltage on both the
input and output of the transformer.  Are the voltages what you expect?
With power disconnected, check for continuity on each side.  You should
have continuity on each side, but not from one side to the other.

Check these at whatever point is closest electrically to the transformer.
Try to avoid measuring on the other side of fuses, voltage regulators, etc.

On Sun, Feb 26, 2023 at 8:10 PM Todd Sines via Synth-diy <
synth-diy at synth-diy.org> wrote:

> I have two CMU-800R’s, one 120v, the other 220v. The 220v model is rock
> solid, whereas the 120v model is somehow DOA but in mint cosmetic
> condition. 220v has a 245-231D (21114A) transformer and 117v has a 245-231C
> (30414A) transformer. I can swap the 291-451 power supply boards to either
> unit and get the main PCBs to function correctly; but I cannot get the 117v
> transformer to function at all. There’s not much happening on that 052H348B
> sub board; a thermal fuse, a glass fuse, AC in, power switch, and DC output
> (white, brown, red)
>
> When I measure the PSU board from the 220v I get l 20v, GND, 45v, GND,
> and 15v off CN1 pins 1-5. When measuring the 117v transformer, I get
> nothing on all pins.
>
> Where might you investigate— or find a compatible replacement 117v
> transformer, which I suspect to be the culprit?
>
>
> Todd
>
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