Comments on: Restoring a Dynaco Stereo 70 – Part 1

By: Carlos da Cruz

Carlos da Cruz — Fri, 12 Oct 2018 14:55:15 +0000

A couple of decades ago, I acquired many parts related to the Dynaco 70, Four beautiful EL-34s. I even constructed a metal support base for all the components and as far as I know I acquired one of the last set of hand built transformers from a guy at EBay that took about a year to deliver (When I almost thought the money was lost). All these, plus parts, screws, etc. And an empty driver board have been kept all these years in a plastic bin, that survived two marriages, and lot of dream of enjoying it one day. I get excited when I read someone’s page like this, and the dreams aflore.

By: John Reekie

John Reekie — Wed, 16 Sep 2015 11:22:08 +0000

Hi Ed, unfortunately there won’t be a Part 2, as Bill Thomas has passed away.

By: ed webster

ed webster — Sun, 23 Aug 2015 03:02:46 +0000

where can i read part 2 ? this was a great help to me when 6 mos ago i bought st 70.

By: Fred M.

Fred M. — Sat, 23 Nov 2013 00:33:23 +0000

Doug wrote: “None of this major overhauling is necessary and is a waste of time.”

This article is intended for people who want their ST-70 to perform like new (or better) and not be a ticking time bomb, just waiting for a failure of a selenium rectifier, cap, or wiper in a bias pot to destroy matched EL-34 tubes, rare 7199 tubes, or other rare and expensive parts.

If you’re one of those people who just wants background noise and don’t care about the audible degradation that comes from old, dried-out electrolytic capacitors, out-of-spec carbon resistors, and selenium rectifiers which are dropping the forward voltage too much, then enjoy. But have a back-up amp for when some 40 year old part finally gives up the ghost and makes a mess of your amp.

By: Doug

Doug — Wed, 06 Feb 2013 07:10:06 +0000

None of this major overhauling is necessary and is a waste of time. I got my ST-70 bone stock and replaced the output tubes with a matched quad. It didn’t work on the left side and a tube plate glowed red and I couldn’t set the left side bias. I replaced the coupling caps on the PC board and bypassed the selenium rectifier with a silicon diode. It still didn’t work. It turns out that one of the 15.6 ohm wire wound resistors from terminal 8 to ground was shorted. I replaced both of them and it has been working just fine for four years now. Only replace what needs to be replaced. This amp is still, with the exception of the silicon diode bone stock. If it ain’t broke don’t fix it.

By: mike good

mike good — Fri, 03 Dec 2010 02:50:01 +0000

thanks for the great article, it was very precise and am glad to hear the next part is forthcoming. sorry to hear about your family medical issues, hope all is as well as can be. keep up the good work.

By: Bill Thomas

Bill Thomas — Fri, 05 Nov 2010 20:52:21 +0000

Hello, Friends!

Sorry about those infernal delays. Our second part of the Stereo 70 restoration article will be forthcoming. At present, we are shooting for it to appear in the December issue!

My sincere apologies for the delays. I’m afraid that family medical “issues” have shifted me into a “caretaker position” for the past few months, but I am gettin’ geared up for a real FLURRY of activity! Our Stereo 70 project will contain a surprise in the next article. I hope we can answer a “nagging” question.

More to come…

Sincerely,

Bill Thomas

By: mike good

mike good — Fri, 05 Nov 2010 02:11:41 +0000

now that i’ve torn apart my dynaco stereo 70 i am wondering when you are giong to publish part 2.

By: mike good

mike good — Sat, 25 Sep 2010 10:08:18 +0000

when is part 2 coming?

By: nunhgrader

nunhgrader — Wed, 23 Jun 2010 20:32:06 +0000

This is an awesome artivle – love the new web site as well!

Keep up the great work!