Dynaco ST70 rebuild with Triode boards

[nj pheonix]

Just a side comment.
6.8 for your filament is on the high side. This isn't unexpected. Because the amp was built with 115-117 (early 1960s)
Typical line today is around 122-123
The amp will work fine but you'll shorten the tube life. Ideally you should make yourself (or buy) a bucking transformer.
At the very least add a couple of current limiters on the line in to drop the incoming line voltage.
Short term it's fine. It should be addressed sooner than later.

 

[Cabdiver]

I went ahead and put all the tubes back in and remeasured. The voltages at pins 1 and 3 (of the EF86s) are in range. At pin 6, I get 113 on the left and 129 on the right which is just a touch high (80-110.) I went ahead and hooked up a preamp and played a CD through my $15 test speakers. Never knew they could sound so good. Tomorrow, if I'm brave, I'll put the amp in my main system and let it drive my Cornwalls. Fingers crossed.

 

[s-petersen]

The readings make sense with the tubes removed, You could just insert the driver and preamp tubes and measure, if you want to, it would be a little high, or you could install all of the tubes and try it.
Edit.. a little late.., forgot to hit post reply

 

[Cabdiver]

Thank you again. I'm going to put in line today and will report back...

 

[Cabdiver]

First listening - so far, so good. Very minimal background hum, which I didn't notice until I actively listened for it, and good sound overall. Spacial separation is excellent, highs are more clear and musical. Mids and bass not much different than the stock amp, but the EL 34 and EF86 tubes are all brand new, the amp's caps are obviously new, and the Bryston pre-amp has sat idle for 3 months, as I've been using a SS integrated while doing this rebuild. In other words, I look forward to the sound evolving in the upcoming weeks.

Many, many thanks to Scott and everyone else who guided me through this process. What a great community this is!

 

[s-petersen]