I can restore your Dynaco ST-70 for $200.00
details at Dynaco-ST70.com
was always interested in tube audio and used a Lafayette LA-250
integrated tube amplifier for years. There was something about a Dynaco
that appealed to me. Maybe it was the chrome chassis, the brown steel
covering the tubes or just the way it looks. I finally went on a hunt
a Dynaco ST-70 amplifier, PAS-3 tube preamp an a FM-3 Stereo FM tuner.
The first item I found was the Dynaco ST-70. It was located in
I checked ebay and missed out on a few ST-70's and then I checked
After negotiating a price with the seller the ST-70 was mine. I eagerly
it to show up via UPS. The day finally came and I opened up the box.
removed and wrapped each tube individually and numbered them so I would
them in the same socket. After carefully unwrapping and installing the
connected my CD player directly to the input, connected vintage
and turned on the power. The amp sounded great. There was a very
slight hum which
was only heard when the music was not playing. That will get taken care
of after I
replace the filter capacitor can. I checked and corrected the
was set to high. A slight turn of the bias pots took care of that.
Here are a few photos of the unit. The transformers are the desired
wires. The chrome on the chassis is suprisingly in good condition. The
about this amplifier is that its all original except for the 4 coupling
that were replaced. Even the printed circuit board is original.
The tubes used in this amp are 4 6CA7's, 2 7199's and 1 5AR4
Who ever built this amp 40 years ago didn't really follow the wiring
practices as shown in the Dynaco assembly manual. A little sloppy
with the wiring but it works just fine.
When time permits I will take photos of my PAS-3 preamp and
FM-3 tuner. I replaced the voltage doubler circuit in the preamp
consisted of a selenium rectifier and 2 2000uf electrolytic capacitors
the filaments on the 12AX7's. The filaments are fed DC to eliminated
The FM-3 tuner is on my bench getting overhauled.