My ST-70 Rebuild

Bought a couple of ST-70's for $100 bucks recently. Decided they do not sound very good untouched.....




The restoration has started. Here is what I had to work with....












As you can see, it is a little bit of a hackjob. Spray paint, terrible wiring job, ETC. Last night the rectifier tube exploded.

More to come...
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Took it apart today so I can get the chassis powder coated gloss black.










What a project.....took me all morning to get it down like this.

Growing a freshly painted transformer garden....

Bob Latino wrote:Hi Randy,

I like the blue color that you chose for your transformers. I love to see start to finish restorations of Dynaco tube gear. Keep this thread alive and show us photos as the rebuilt amp comes together.

Bob

I painted them gloss black Bob. The tape is blue. I would have liked to paint them blue, but it would border tacky. For my first tube amp restoration that many people would see I chose a more contemporary color.

Hey Randy,

I have the same SDS 6AU6 board in an ST70 I constructed a little over a year ago. If you keep that board, I'd like an opinion since you can compare the original amp and the one you are rebuilding. I like mine, but some resistor values need to be juggled in order to get the most from the board. Stock values could be a starting point, but cathode and plate resistors need tweaking in my opinion. I'm still working on mine, when I can find the time that is.

Good luck with your $100 purchase (no smiley for jealous)

Tony

Made some progress today.......

Got the chassis back form the powder coating place. Got the VTA board in the mail. Built it. Got a solder headache right now.....will assemble the amp tomorrow!

I like the sleeves on your cap leads and cut just right. Nice attention to detail.

harpy wrote: I like the sleeves on your cap leads and cut just right. Nice attention to detail.

Can't take credit for that one. Just following Bobs wonderful instructions.

And a teaser pic. Will do a full update once i finish everything...

And its finished. I put the front panel on upside down so had to fix that. I did the best I could with the wiring working with the old cloth wire from the transformers and my lack of experience with this(my first amp I have built). Anyways......let me know what you think!

Hi --

To me your craftmanship is superb!!

I guess the important question is "how does it sound??"

How much did the powder coating of one chassis and bottom plate cost?

Good Listening,
Stew

stewdan wrote:Hi --

To me your craftmanship is superb!!

I guess the important question is "how does it sound??"

How much did the powder coating of one chassis and bottom plate cost?

Good Listening,
Stew

it sounds great! alot better than I expected it to. The powder coat only cost $30. But the chassis was so pitted it did not turn out as good as i wanted it too....

Hi Again --

Nice to hear that they sound good to you. They should improve with continued breakin. You can also do some tube rolling. The center tube seems to make a lot of difference on the VTA70. There have been some posts about which 9-pin tubes sound the best.

I have some Dynaco Mark III Mono Amps and I have tried different Driver Cards on them. To me and others that I played them for, the best sounding driver was Roy's VTA/MK3 Low Gain Board, which is basically 1/2 of your ST-70 board.

Recently, I acquired a set of his VTA/MK3/Octal Driver boards that use 6SN7 tubes and am anxiosly awaiting some parts before I can complete the pair.

Enjoy listening to your "new" ST-70!!

Stew

your 2nd photo down (post 12), that's the kind of photo I like, that's the way I listen to my music,
dark, with just the tube glow and the music . . . .
permission to add another great customer photo on my website?
I might need to add my own gallery of favority customer photos!

tubes4hifi wrote:your 2nd photo down (post 12), that's the kind of photo I like, that's the way I listen to my music,
dark, with just the tube glow and the music . . . .
permission to add another great customer photo on my website?
I might need to add my own gallery of favority customer photos!

Sure thing! I would be honored!

thanks much!!