I recently acquired an original Dynaco ST-70 power amp and PAS-2 preamp. I've been checking them out, downloading docs, checking the tubes, etc.
I'm starting to think that EICO did a better job of documentation than Dynaco did. My docs on my EICO ST70 seem much more clear.
Is there any documentation on the above Dynaco amps where the schematics actually label the tubes, and layout diagrams indicate which tube is which? Just because I can do it the hard way, I don't think it excuses that documentation.
-- KW
I'm starting to think that EICO did a better job of documentation than Dynaco did. My docs on my EICO ST70 seem much more clear.
Is there any documentation on the above Dynaco amps where the schematics actually label the tubes, and layout diagrams indicate which tube is which? Just because I can do it the hard way, I don't think it excuses that documentation.
-- KW
If you look at the hand-drawn diagrams of the layout in the pdf manual, the chassis mounted tube sockets are numbered V1, V2, V3, V6, and V7.
The two 7199 sockets (V4 and V5) on the preassembled pcb are also numbered on the second diagram, which includes the pcb.
The kit was very simple, and I assembled many of these without ever using the manual at all.
A novice could successfully assemble the amplifier just from the hand-drawn diagram on the last page of the pdf manual (originally a separate sheet),
which gives all the necessary information. That was intended to be the main reference for assembling the kit. If you have a printed manual but not the
separate large hand-drawn layout diagram, it is included in the pdf manual posted here as the last page. The preamp manual has a fold-out diagram instead.
Both the amp and preamp were in full production as kits for about 20 years with great success.
https://hafler.com/pdf/dynaco/Dyna-ST70.pdf
The two 7199 sockets (V4 and V5) on the preassembled pcb are also numbered on the second diagram, which includes the pcb.
The kit was very simple, and I assembled many of these without ever using the manual at all.
A novice could successfully assemble the amplifier just from the hand-drawn diagram on the last page of the pdf manual (originally a separate sheet),
which gives all the necessary information. That was intended to be the main reference for assembling the kit. If you have a printed manual but not the
separate large hand-drawn layout diagram, it is included in the pdf manual posted here as the last page. The preamp manual has a fold-out diagram instead.
Both the amp and preamp were in full production as kits for about 20 years with great success.
https://hafler.com/pdf/dynaco/Dyna-ST70.pdf
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The Dynaco manual includes layout diagrams. As for tube placement there is self-evident in the mentioned amps. In the PAS you only have one type of tube (ECC83) on the circuit boards, the remaning 7 pin 12x4 will only fit in the rectifier socket. As for st70, the 7199 will only fit on the circuit board, and the only issue is the GZ34, it is in the sole socket in the back, all other octals is filled with EL34.
Ah! I didn't see the tube numbers in the middle of the sockets in the layout diagrams -- that helps. Thanks!
It's interesting that I can't see the tubes (or anything else) numbered on the schematics though. I mean, why? Who does that?
I'm now that I have official numbers I may update the schematic accordingly. I inherited these amps and was starting out by testing all the tubes, writing down the results -- and making up numbers to keep track. Meh.
It's interesting that I can't see the tubes (or anything else) numbered on the schematics though. I mean, why? Who does that?
I'm now that I have official numbers I may update the schematic accordingly. I inherited these amps and was starting out by testing all the tubes, writing down the results -- and making up numbers to keep track. Meh.