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NOTE FROM ADMIN: This thread was split from OldRestorer's April Fool thread in Philco Home Radios at the request of Codefox1. It seemed we had two different conversations going in the same thread, so the Dynaco talk has been moved here.
Well Ron, not long ago I bout a Dynakit ST70, a Dynakit MkIII and a DynaKit ST30 for $19, not each but for all 3. So it does happen.
P.S. Add one of these to your old stereo wish list. No I'm not selling any.
"I just might turn into smoke, but I feel fine"
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Russ, I believe you...you seem to have all of the luck with the stereo gear! Hmph!   
As for Dynaco/Dynakit...back when I was looking at catalogs in my youth and admiring this stuff...Dynaco never impressed me. I understand they have a very good reputation, though.
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Ron Ramirez
Ferdinand IN
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They aren't much to look at but that ST 70 sure sounds nice. There is such a following now that you can get Everything for them and "MOD" the heck out of them, I don't know why you would want to other than the selenium rectifier in the bias.
"I just might turn into smoke, but I feel fine"
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The Dynaco stuff of the 1960's and 70's or so, and I expect that is what we are talking about were really good. So were the Eico and Heathkits, Harmon Kardon, and probably a few other DIY brands some of us misspent part of our youth on, and are still recovering from even after decades of lapse.
Suggest this thread might be better served on Vintage Hi Fi Stereo and Audio subforum here.
Best!
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codefox1 Wrote:Suggest this thread might be better served on Vintage Hi Fi Stereo and Audio subforum here.
Yes, that is a good idea. Done. 
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Ron Ramirez
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I have had Dynaco stuff for years and played 'em to death! My favorite was the Mk3 combined with a Pas 3 preamp. I had a set of 70's stacked, which sounded great. Just seemed that I always had problems with 'runaway' tubes in them. There was a fix, but was out of my budget at that time (and pre - internet, I was on my own for finding fixes). Found the Marks and loved 'em. But, when the kids came into the family, the space was needed for other things, so they got boxed up and stored. I also tried one of the NEW "Soundvalves" 70 setup, supposidly with all the fixes. It did the same thing. So I boxed it up. Still prefer the Mk. Oh, this was before the prices went crazy on this tube stuff, and you could still buy USA made tubes!
If I could find the place called "Somewhere", I could find "Anything"
Tim
Jesus cried out and said, "Whoever believes in me , believes not in me but in him who sent me" John 12:44
(This post was last modified: 04-05-2014, 09:58 AM by TV MAN.)
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Of course, problem is curent program content. Not enough worthwhile to watch or listen to anymore.
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They used a little bitty selenium rectifier for the bias. I know that became a problem, but is easy to fix now.
"I just might turn into smoke, but I feel fine"
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I have a ST-70, PAS-2, and FM-1 (with multiplexer) that my Dad built in 1961 and '62. I have been through the ST-70 and the preamp and have replaced all of the black tubular caps, the electrolytics, a couple of out of spec micas, and a few resistors> I matched component pairs where noted on the schematic or parts list. I replaced the electrolytics in the tuner, but not the other caps because they are all ceramic.
One of the EL-34s was missing, so I replaced them with a matched quad of Russian Mullards. After a while I replaced the 7199s with 6GHAs with the adapter. The whole system sounds great, given the mediocre quality of my speakers. The sensitivity of the FM is really impressive.
I've had intermittent problems with balance between the two stereo channels. Replacing the 12AX7s in the PAS-2 preamp with a matched quad seemed to work, but now, only a few days later, the ST-70 developed a balance problem! It's giving me fits. I'll probably start a thread on it once I've had a chance to dig into it and check a few obvious things.
And if that weren't enough frustration, the FM-1 suddenly developed a loud hum that is independent of the volume control. If I turn the tuner volume all the way up and the preamp volume way down, the hum is gone, but it is quite horrible with the volume controls set any other way. Another thread to be started later, I suppose.
John Honeycutt
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You never know. Sometimes it can be something simple and quite unexpected. The other day I was listening to my prized Sherwood and a channel went dead. All of the horrible possibilities, like having to find a new OPT went through my head. When I had it apart, I could not believe that the filament on a 6EU7 had opened up. Other than old battery radios, how often does that happen?! Well it gave me a chance to reset the bias. All happy now.
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I forgot to add that my Dad added a switch and a bundle of wires to the ST-70 that so he could switch between two sets of speakers and headphones. All that is undocumented. I thought of ripping it out and restoring all the wiring to original, but it didn't seam to be hurting anything so I left it in. I doubt that the new wiring is my problem, but it certainly adds complication to the troubleshooting.
John Honeycutt
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Running tube amp into open = bad. I would take out the switch(s).
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Good dynaco conversation--reminds me that I have a Dynaco pas-3 in the house--got in I think 1969 when I was in the USAF--paid like $30.00 to a friend---just saw a pas-3 at a swap meet for $300.00---guess I will rebuild it at some point
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when the kids came into the family, the space was needed for other things, so they got boxed up and stored
A lot more should do that with their kids. More room for radios.
Henry
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Madmurdok, about the runaway tubes in the Dynaco Stereo 70, I experienced the same thing with my Stereo 70 in the late 70s and eventually replaced it with a solid state Marantz DC120. In retrospect, although I originally blamed the problem on bad new tubes (grid leakage after warmup) I now know that there was an known problem with the quality of the tube sockets. Restorers now recommend replacing the output tube sockets with better quality sockets. The OEM sockets had a tendency for the grid contacts to spread easily and during warmup the contacts would fail to touch the grid pins of the tubes resulting in runaway conduction. I had some on my unit that got so hot the glass sucked in against the plate structure. That did not help the rectifier tube either. Of course the selenium in the bias circuit should be changed. I always hated the odor of failed selenium rectifiers.
Joe
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