Bridge rectifier problem

[jimi]

I have what looks like an old Selmer little giant amp. It has a bridge rectifier rather than tube Im not sure how unusual this is the diagrams I have seen have a tube rectifier. The problem is the HT seems to be low. I have 300vac from the transformer and only 190 volts dc after the rectifier. The whole amp is drawing 47ma so its not loaded heavily. I tried 4 in4007s the HT went up to 360v which is too high. The main cap is only rated at 300v. I have a schematic which is very similar but uses a tube rectifier. It has the HT at 282 volts. The BR is a sealed unit with aluminium around it and gets too hot to touch. I measured 10volts accross it before it starts to conduct. Is it just a bunch of diodes in series? It seems to be dropping ALOT of voltage. What could I replace this with so the HT will be around 280v?

[Bruce / Mission Amps]

...the HT seems to be low. I have 300vac from the transformer and only 190 volts dc after the rectifier. The whole amp is drawing 47ma so its not loaded heavily. I tried 4 in4007s the HT went up to 360v which is too high. The main cap is only rated at 300v.

Do you know the difference between a full wave bridge and a full wave rectifier?
The tube version is using a full wave rectifier not a bridge.
Is your amp running on 220v-240v?

I suspect a bad diode in the rectifier and bad choice of filter cap specs.

[jimi]

Yes it's a full wave bridge rectifier. I tested it on a variable power supply. Each diode(s) starts conducting between 12-12.6v. reversed biased at 20v it looks ok. I'm assuming it is faulty despite this test. Surely this is not made up of a string of 18-20 diodes to have such a high forward voltage? What will it be made up of? The amp is from the late 50s I think.

[jimi]

I've done some investigating. I think it's a selenium rectifier. Seems like they have them in some old radios they just replace it with a modern rectifier and a dropper resistor. Is that a good way to go?