Dynaco-Doctor Forum Welcome! Need support, you got it. Or share your ideas and experiences.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Dynaco-Doctor Forum ]

---

[ Alert Moderator ]

---

RE: Pas 2 balance bypass

Posted by Flyquail56 (A) on March 29, 2014 at 15:35:48

In Reply to: RE: Pas 2 balance bypass posted by Cleet Torres on March 24, 2014 at 11:26:34:

Almost everything you need is here, at the top of the Dynaco Doctor page. I would recommend starting with reading the ST-70 Restoration Manual to verify proper operation of the amp. It may or may not need a new quad filter cap. Next, read the Bias Expansion Mod, which is usually necessary if you are going to replace the selenium rectifier in the bias supply. Beyond that, a stock ST-70 in proper order sounds quite good.

For the PAS, I would do the following (again, all linked at the top of the page): Restoring The Filament Supply (wouldn't hurt to increase capacitance to double or more the original value), Correcting RIAA Response, Removing The PAS Tone Controls. Will all due respect to the author, I would recommend one change in the tone control removal: instead of jumper wires from eyelets 6 to 7 and 12 to 13, I would instead install 1.0 uF/100V film caps. Otherwise, there will be a small amount of DC at the output after modification, and the ST-70 does not have a blocking cap on the input.

As for resistors and coupling caps, there is no need to change resistors in either unit unless they have drifted badly and your voltage measurements are way off. The PAS already has 1% metal film resistors where they're needed.

I'm not a big fan of high-dollar coupling caps, especially when they're inside a feedback loop like they are here. CDE, Matsushita/Panasonic, Illinois, and Sprague orange drops all do fine for not a lot of money. All readily available from Mouser, DigiKey, Antique Electronic Supply, and others.

Almost forgot, assembly manuals are also available here, and have schematics with the voltage charts you will need.

Hope this helps, and that all goes well with your foray into uncharted Dynaco waters!

Mike

This post is made possible by the generous support of people like you and our sponsors:

Herbie's Audio Lab

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---