I’ve long been a fan of Dynaco stuff and have owned a couple of tuners, a PAS-3 and a PAT-4. Recently a friend gave me his old ST-70, an amp I’ve always wanted but never been able to afford. He was given it by another friend and never did anything with it.
I’d like to start the restoration but am a bit lost right now. I have basic electronics skills: I solder well, can read a schematic and have done a bunch of basic audio repairs in the past. But I’ve never worked on tube gear (Danger! Danger!!) and am out of my depth in terms of diagnosing whatever the previous owner did. Hopefully I can use this project to further my knowledge.
I know I’ll do the following:
• Replace or restore the driver board: I’m inclined to replace it with the Tubes4hifi ‘Classic’ board. I’ll buy the kit and solder it myself. It may take me a while to raise the $$ but I’ve heard it’s a great mod.
• Replace the missing multi-section cap. I know that the PO must have found another way to do the circuit, but I’d prefer to restore the wiring to the original. All the caps need doing anyway I guess.
• Reinstate the rectifier tube. Again, I guess that the PO found a solid-state solution, but I’d like to bring it further back to stock unless you guys advise me otherwise.
• The filter choke looks like it’s leaked most of its wax out, so I guess that’ll be on the shopping list.
• Should completely replace the bias circuit components?
• Replace the spring-loaded speaker terminals. I really hate the ones the PO added!!
It’s going to be a massive learning curve: technically it’s out of range of my skills, but if I can find a couple of patient people on the forum I’m sure I can get through it. I downloaded the original build manual and have been looking at as many photos of the original wiring as I can find.
Any advice is appreciated: I’d love to get this going and then pair it with my PAT-4, which is currently in a long process of modification. But that’s another story…………..
Thanks in Advance!!