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In Reply to: RE: GZ34/5ar4 question posted by M. Vidal on July 19, 2016 at 12:28:25
Vidal
It can cause an oscillation if there are issues with the tube.In your preamp you emailed me about,the biggest issue I had on the Suprateks are broken wire connections on the function switch..Look closely and you may see a solder connection that came loose on the switch..I meant to email you back but I just got back.
You need to do this as well.Go up to the 5881 regulator tubes and see if you have 305vdc in pin 3..If you don't,readjust the pots in the regulator until you get 305vdc.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 07/19/16 07/26/16Follow Ups:
"the biggest issue I had on the Suprateks are broken wire connections on the function switch..Look closely and you may see a solder connection that came loose on the switch"
Do those issues appear to be factory defects? That's unforgivable for a unit in the Supratek price range.
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Buy Chinese. Bury freedom.
Jack
The problem with them in a sense is a factory weakness out of a very fine preamp..I do a lot Supratek upgrades and repairs..I actually have all the schematics to the units but the function switch is turned and works itself loose and if you don't retighten it,it tweaks on the solid stranded wire which connects to the switch.I put a special washer in to lock the switch down and change some of the wires that could potentially become brittle..It is a first rate preamp tho.
The other issue I have,if any of them use battery bias in the phono stage cathodes,I remove it and put a resistor in its place because it causes oscillation as well.The 1.5v battery used for the negative voltage on some tubes,you leave that alone.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 07/20/16
Michael Samra, may I have your contact info for future reference in case I ever need work on my Supratek, that is if you are still accepting work.
Don't all rotary switches now have a mechanism to prevent rotation if the nut isn't properly torqued down? Either a D shaft or a pin that protrudes through the panel? In any event, this is an indicator that they weren't paying attention to details when designing the gear. That's the problem sometimes with small companies. You're at the mercy of the often limited experience of one or two engineers. Things look good, but they fail later.
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Buy Chinese. Bury freedom.
You are right they do,but this was only on a couple early models of the Chenin and the cortese
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
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