Dynakit ST70 with Welborne Mod
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Face
Posts: 14,340
Yesterday I managed to pick up a Dynakit ST70 with what appears to be a Welborne ST70 mod kit. http://www.welbornelabs.com/st70.htm
The unit powers up, but the left channel has a low pitched hum and also sounds to be slightly lower in gain than the right channel. Someone told me the coupling capacitors needed to be replaced.
Before yesterday, it hasn't been powered up in years, so the bias is probably off too. Does anyone have any idea how to and what to set it to on this unit?
Here it is, in all it's ugliness.
Thanks in advance,
Mike
The unit powers up, but the left channel has a low pitched hum and also sounds to be slightly lower in gain than the right channel. Someone told me the coupling capacitors needed to be replaced.
Before yesterday, it hasn't been powered up in years, so the bias is probably off too. Does anyone have any idea how to and what to set it to on this unit?
Here it is, in all it's ugliness.
Thanks in advance,
Mike
"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
Post edited by Face on
Comments
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To set the bias, gently tap on the tubes with a hammer.....
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I thought I was supposed to put vice grips on the tubes and twist till they sound good?"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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I would donate that to Trey so he and his friends can make a home video out of it.
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I think it looks cool.
It has a ton of potential.
If it was cleaned up and painted it would look just like my jolida only with more tubes.
It looks like the same deal but with a different tube configuration.
If you get it working correctly and want to keep it send me a PM and maybe we can see about getting it painted for ya.;) -
I wouldn't just plug that into the wall....got a variac?CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
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Took to bottom plate off and found a bad cap on the L side input RCA. Also found the bias screws, they're also on the bottom. You would think they'd put them somewhere more convenient.
I can't make it through 20 seconds of one of his videos, so that would be pointless.SolidSqual wrote: »I would donate that to Trey so he and his friends can make a home video out of it.
I have a few local body shop connections, thanks for the compliment and offer though.nikolas812 wrote: »I think it looks cool.
It has a ton of potential.
If it was cleaned up and painted it would look just like my jolida only with more tubes.
It looks like the same deal but with a different tube configuration.
If you get it working correctly and want to keep it send me a PM and maybe we can see about getting it painted for ya.;)
No I don't, but I can plug it into my UPS and it will tell me how much current it's drawing.I wouldn't just plug that into the wall....got a variac?
I'm going to email the seller again and ask him when was the last time this thing was fired up. There really isn't that much dust on it for something that's been sitting in a attic."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
Congrats on scoring a true audio classic.A little TLC and you should have a good sounding little amp.There should be tons of tweaking info online as they are one of most modified units of all time.Testing
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Well, make that two burnt caps in the input side. They appear to be polarized, because when I replaced them with caps of the same value, two of the preamp(little) bulbs didn't light up and I had no sound. Off to Rat Shack tomorrow until I can get some new replacements from Sonic Cap.
I had a idea of what I was getting into when the guy wasn't sure what kind of amp it was and that I only paid $100 for it. He claims it was built by a good friend of his who recently passed away, so it could have been in use a few months ago for all I know."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
Nice grab Mike.
Here's a few places that may be of help to you.
http://store.triodestore.com/
http://www.curcioaudio.com/dynadr_3.htmPolitical Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
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Thanks to Jeff at Sonic Craft, she's up and running again with no more hum in the left channel.
Both channels are nearly silent now.
Tomorrow I'm going to have a friend help me bias it and soon I plan on giving it a complete recap.
"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
OK, Ill bite. How did Jeff help you?Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
The caps that were bad, aren't even necessary for my application. I bypassed them for the time being until I receive a new set from him."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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Most excellent!Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
6 capacitors and 4 tubes later, it sounds wonderful!
Upon inspection, it appeared 2 caps were burnt. I replaced those along with a few others with Sonic Caps.
Sound quality improved, but the amp still broke up after being pushed. I swapped the tubes from one side to the other, and the breaking up followed.
Today I received a set of quad matched Mullard Reissues. Put them in and the bias was VERY low, not even close to the 1.5v the old tubes were set to. Set the bias, let it warm up for 15 minutes, then hooked it up, WOW!
The sound is impressive, and the new caps aren't even broken in yet. Bass is improved, mids lush, and the highs better than I expected. Music also seems to have more impact. I'm in love. As a disclaimer, the amp that this is replacing at the moment is one of Mac's older and less desirable models. My other 2ch amp, the 7270 needs a recap, so it would be a unfair comparison at the moment. But it looks like I found a new source of amplification for the time being. And to think, it cost less than my interconnects and only has 35 watts. "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
And to think, it cost less than my interconnects and only has 35 watts.
I'm sorry, you are 165 watts short. Please try again -
Great to hear you have it up and running.
Sometimes 35 watts is all you need.:DTesting
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I love it.
Nice grab.I like speakers that are bigger than a small refrigerator but smaller than a big refrigerator:D -
Very cool indeed!!
Glad to hear you got it going. -
Thanks guys!
Since I got it up and running, I guess it's due for a nice cleaning/polishing.
I eventually plan on having a new face plate made and maybe having parts of it powdercoated."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
Ok, I have 20 hours on the new caps.
Some music sounds fantastic and much better than before, such as Zeppelin, Floyd, etc... But it doesn't do as well for some Metal and Industrial.
Regardless, it's definitely a keeper for the time being."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
Did the Sylvania's arrive yet?Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
No, but the set from upstate did. I'm going to test those out in a bit."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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That was fast and I'm glad it worked out. I look forward to your impressions.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Finally had it cleaned up.
Dark shot.
"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
Not bad, doesn't look like you were dumpster diving anymore.
Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Looks great, for a second there I thought I hit the wrong favorite button and I was viewing Audiokarma. A quick scroll to the bottom of the page told me otherwise. Nice job.
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MillerLiteScott wrote: »I love it.
Nice grab.
I love it even more.I like speakers that are bigger than a small refrigerator but smaller than a big refrigerator:D
