Stereomour II blowing fuse [resolved]

[TexFlood]

Terminals 19 and 20 free of connections and fuse intact.  I do hope the poor diodes survived.

[Doc B.]

OK there must be something pulling excess current in the power supply. Do any filter capacitors look swollen on the end cap?

[TexFlood]

No.  Perhaps I should have tested once more before disconnecting 19 an 20 to determine if reflowing 29L made any difference.

[Doc B.]

Don't reconnect them yet. Measure resistance from T41 to T44. You may see cap charging/discharging  behavior, where the meter climbs up or down. That's OK. We're looking for a really low ohms reading somewhere, that shouldn't be low.

It's really stormy here at the moment and my monitor just flickered like the power may fail. If I don't answer right back it's not because I am ignoring you.

[TexFlood]

Between 41 and 44 is high 2 M ohms and dropping.

[Doc B.]

OK, now measure resistance between T41 and T42, and T44 and T45.

[TexFlood]

Both start in the 2 M ohms and drop.

[Doc B.]

I am looking at one of your photos that shows the resistor connected from T27 to T30. In the manual it is attached to the lower terminal holes. In your picture it looks like it might be attached to the upper holes (difficult to tell) and the lead of the resistor connected to T30 might be touching a capacitor lead at T29 that it should not touch. This may all be wrong and it's all connected correctly, it's hard to tell from the angle of the shot.

[TexFlood]

Resistors are both lower.  There is just the reflection off the black wire from 29L to 41L going under the resistor.

[TexFlood]

One more thing - While doing the last resistance checks, I noticed that as I put pressure on the terminals with the leads, the terminal strip would move and as it did I would get 0.L reading then back to  dropping M ohm reading.  This would happen with pressure and movement of the terminal strip.

[Doc B.]

The measurements across 41 and 42 and across 44 and 45 should not go to zero. Sounds like something is shorting out as the strip is moving, and that could definitely take out a fuse. An very thorough visual inspection around that T strip seems like the next step.

[TexFlood]

Reflowed 30L and 31L where resistors attach and cross over to 44L .  Readings are now M ohm and dropping.

[Doc B.]

Ok, it sounds like it might be time to reattach the rectifiers at 19 and the white wire at 20 and try it to see if the fuse holds.

[TexFlood]

Fuse blows.

[Doc B.]

OK, unplug amp. Clip black meter lead to 8U and remeasure resistance of T21 thru T35 and T41 thru T45, looking for discrepancies from the numbers in the manual.