Like many I had a Dynaco ST-70 in my youth. I was given one in college and used it all throughout and then left it with one of my roommates when I graduated.
Now I'm a bit nostalgic and decided I wanted to fit one into my system. Doing a search and wow. These guys are expensive! Looks like free was out of the question, but I found one without tubes for $330 and I actually have a matched set of EL34's for a different amp anyway.
So after research, I realize there are some first things first, such as replacing the selenium rectifier and upgrading the cap. I ordered the bias kit and a quad cap from Dynakitparts and will check the transformers. Then I plan on striping everything off the chassis and cleaning it up and repainting the transformers. I am optimistic based on the other posts I have seen.
This is not going to be a VTA70 build. I would like to build one of the VTA120 or M-125 sets after this though. I will just use one of the ebay 6GH8A boards to keep it as stock as possible.
I would like to get a recommendation of what chassis resisters to use if I replace them and where is a good place to buy them. I am also on the fence about weather it is necessary to use new tube sockets or retension and re-use the existing ones.
I got these values from the following article.
https://www.hifizine.com/2010/06/restoring-dynaco-st-70/
Quantity | Value | Description | Source | Part Number |
2 | 10 ohm | 10 ohm resistor on power socket | ???? | ???? |
2 | 15.6 ohms | precision resistor (for bias set) | Dynakitparts.com | BRWW-15D6 |
2 | 5.1 K | 5.1 K ohm 1 watt resistor | Digi-Key | PPC5.1KW-1CT-ND |
4 | 1000 ohms | 1000 ohm 1 watt resistor (On EL34 socket) | Mouser | 71-CMF601K0000FHEK |
1 | 6.8 K | 6.8 K ohm 1 watt resistor (filter capacitor) 6800 ohm | Digi-Key | PPC6.8KW-1CT-ND |
1 | 22 K | 22 K 1 watt resistor on Capacitor | Digi-Key | PPC22KW-1CT-ND |
2 | 475 K | 475 K ohm 1/2 watt resistor (socket to ground) | Digi-Key | CMF475KHFCT-ND |
With out further adieu. Her is what I am starting with.
The amp with cover:
Cover off
The underside
Look at those original Dynaco caps!
My first shipment from Dynakitparts