bandmaster rectifier diode type?

[r0bo01]

well, once i started digging, under the doghouse cover found one of the 20uf caps had a mound 'o schmutz on its endplate. now am committed 'cause firing up to poke around probably wouldn't be good idea...
so, replace all the caps w/those in the kit (100uf x 2, 20uf x3, 25uf x 5) as well as the rectifier diodes. find a few suspect connections/solder joints, fix. fire up, check b+ @ + end of caps and stdby switch - 444v +-1 or so. let run w/o pwr tubes (on stdby) for 1/2 hr as nod to filter caps. check grid bias - 42ma and...
happy days! she's a worka! seems more power than before and better tone.
then, about 15 min into session notice low level squealy oscillation rising and falling. oh crap. shut down discouraged. next day, take apart and poke around looking for obvious problems, none. put back together and fire up.
worked fine. played thru a practice set am working on. sounds fine.
could it be caps had to "settle in" somehow? in particular, the 25uf 25v caps from kit that go to ground in para w/resistor from each cathode of preamp & vib tubes?
kit also had 100uf 100v electrolytic i couldn't find on board or in schem. used in older bandmaster?
anyway, thanks again to all for help/encouragement (and putting a fire under my tail).

[Dave Curtis, dB AudioTech]

"kit also had 100uf 100v electrolytic i couldn't find on board or in schem. used in older bandmaster?"

That's for the bias supply.

[r0bo01]

That's for the bias supply.

the higher values ok? mine's 25uf @ 50v. resistors (15k, 10k l-pot, 470 1w) handle it?
while about it, can i use one of my 1n4007 to replace the diode there?

thnx again.

[MWJB]

Use a 100v cap ("+" to ground), rather than 25 or 50v. You might see -60vdc+ when all biased up with some brands of power tube.

Yes a 1n4007 will be fine in the bias supply, remember stripe goes to the PT.

[Dave Curtis, dB AudioTech]

the higher values ok? mine's 25uf @ 50v. resistors (15k, 10k l-pot, 470 1w) handle it?

Yes, 100uF is going to stiffen up the bias supply (you really don't want a squishy bias supply). On some other amps (without a separate bias tap on the PT), it would be too much, but not on the Bandmaster. If you're worried about it, test and see how long it takes the bias voltage to charge the cap. I have a 220uF in this spot in my Pro Reverb.

while about it, can i use one of my 1n4007 to replace the diode there??

Yes, remember this is a negative supply, so the cap and diode are installed "backwards" (positive and anode to ground).

[r0bo01]

Yes, 100uF is going to stiffen up the bias supply (you really don't want a squishy bias supply). On some other amps (without a separate bias tap on the PT), it would be too much, but not on the Bandmaster. If you're worried about it, test and see how long it takes the bias voltage to charge the cap. I have a 220uF in this spot in my Pro Reverb.

Yes, remember this is a negative supply, so the cap and diode are installed "backwards" (positive and anode to ground).

k. i was afraid of somehow zitting the 470 1w resistor as 100uf charged up. in retrospect, silly, so will prolly go for it this wknd.

thnx for your reply and everyone's, am learning something new every day here! (& i got a lot to learn...)