Just finished recapping another ST-70 today

[Sal Brisindi]

Today I completed another recap of a ST-70 for a friend, took a few hours. I replaced all the capacitors including the quad cap with a 40/80/30/20uf quad cap. I also replaced the bias selenium rectifier with a 1N4004 diode. Sounds great. It has the original circuit board. I noticed this chassis is a little different than my 2 ST-70's.

Where the preamp plugs in the front it says PAM 1 power (5 watts). Also in the rear under the speaker connections is says 35 Watts. I wonder if this is a real early 1959 model...

I was testing the amp out with a 5U4 for a short while then I installed a 5R4. I could adjust the bias but it was at one end of the travel. I then tried my 5AR4 in it, what a difference, now the bias control is just about midway on the potentiometer. I guess the voltage drop of the 5R4 was a little to much.

I just started recapping my other ST-70 about 1 hour ago. I replaced 8 caps on the circuit board, I have to order a 390pf cap as I was short 1 in my stock. Tomorrow I will replace the quad cap, selenium rectifier and the bias caps.

Regards,
Sal Brisindi

[Sal Brisindi]

Make that 2 restored ST-70's in 2 days!

Sal

[parabellum]

oh crap I just noticed the trans am on your site..... nice!