Mod'ing a tube circuit (from early 60's stereo turntable)

[trem]

Oh Man....... you lucky so and so.
You literally found that in the trash somewhere.?

I have made 2 cool amps from old PA heads, but NOTHING as bitchin' as what you have there.
Did you replace the speakers in that or are they original or recons.?
Are the speakers round or are they......not sure what the term is.... oblong.?

This is awesome..!!!

[Chuck H]

The strange thing is Rose Metal has a melting point of 98c, yet on one of the schematics I have for this thing it says 125c.
Just got the caps and diodes I need to rebuild this PS and get rid of this selenium rectifier.
Anyone replaced a selenium with diodes before? - I understand I need to put a high-watt resistor in series since the silicon will put out more voltage.
I also have some 5 and 10 ohm thermistors, I was thinking to add one to the PS (after fuse and switch on the AC line) in an effort to take it easy on this old thing when its switched on.
Would love some feedback from anyone familiar with these 3 things! Cheers.

Not at all familiar with selenium rectifiers in the real world but what I've read is that they are made from the stacked plates and each one has a reverse voltage rating of 25V and a FVD of 1V. I also read that most units comprise six or eight plates. Though I'm sure there were different designs and I can't say about what might have been used in guitar amps. Using this info eight plates means a RV of just 200V and a FVD of 8V. Considering the number of units that would be necessary for a tube amp I'd have to guess a voltage drop not dissimilar to any tube rectifier.

I didn't revisit the whole thread but I believe an EL95 tube (if that's what's in the amp/s) should be ok in this circuit at 300 to 320ish volts. You'd gain a little power though probably not a noticeable amount. The amp might sound a little tighter. Probably not in a bad way. If you notice an undsireable change with silicon diodes you could add something like a zener string to reduce voltage back to where it was. If you use a resistor for voltage drop it will add sag that wasn't there before and also change the feel/sound. So do measure your plate voltage with the rectifier you have now in case we need a target to shoot at after changes are made.

[The Dude]

Here's a good article on selenium rectifier replacement.

https://w5rkl.com/wp-content/uploads...BSelenium2.pdf