Should these resistors be replaced? Pic

[GlennW]

They look a little used to me, but I don't know...should they be replaced?

I've already ordered a replacement for the gold cap that's leaking (also in picture).

[tubeswell]

I'd replace that cap, then see how it goes.

[52 Bill]

Are you talking about the five black things with the blue lines?

If you are, they are diodes, not resistors. Check them with a multimeter that has a diode test function.

[Don Moose]

Where are they in the circuit? - could be burnt resistors, but it seems odd they would all have burnt in a way that the only color band surviving on all of them is the blue. Odds are they're diodes, like 52 sez, but it's good to cover bases.

Hope this helps!

[GlennW]

Thanks everybody. Since they're diodes, that might be them in the bottom right corner of the schematic. I'm guessing that's an example of the diode rectification I read about a while back. It looks like the leaky cap right next to them, 100uF 50v.

I'll try to test the diodes. I didn't see a spec for them on the schematic...anyone know what value they are?

Here's the schematic. It's a Magnatone MP-1.

Edit: On Line 1 of the Notes in the schematic it says something about High Voltage Rectifiers 600 PIV 600MA. Would they be the diode specs?

[tubeswell]

Ordinary old 1000V diodes oughta be alright (1N4007)

[GlennW]

I tested them just like in the picture, didn't disconnect anything, and got readings of about 530 with the leads one way and 1 with the leads the other way so I guess they're good.

Thanks again.

[metalangst]

1N4007 diodes will work. in the picture the four lower diodes are the B+ rectifier, the top diode and the cap are for the bias voltage. Watch the polarity when you replace these, or else you'll watch the smoke.

[GlennW]

It's alive.

I replaced the cap, hooked up a speaker, and turned it on for about 1 1/2 hours with a light bulb in series between the amp and the wall.

Then tested straight into the wall and plugged in. It was pretty quiet and sounded good for the short time I played with it.

I'll put a 3-prong cord on it next.

Thanks again.

[Dave Curtis, dB AudioTech]

Then tested straight into the wall and plugged in. It was pretty quiet and sounded good for the short time I played with it.

I'll put a 3-prong cord on it next.


While you're at it, either clip the .047/600 death cap out of circuit, or replace it with a proper "safety" cap (X/Y).