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Dynakit ST-35 - quiet static (popping noise) in one channel. Help!

As Dave suggested early on and I foolishly forgot to do it when I was trying everything else...

Just tried it without the front 7247 tube on the left side and NO popping noise. Swapped the tubes and put them both back in and the popping is back! Does this mean it is one of the mica caps next to the the 7247 tube?
 
Nice to have narrowed down the area. I don't have a ST35, so can't advise further, but I'd be tempted to replace all those smaller caps (C2, C6 and C7). Someone with one of these might give more specific advice.
 
Yup. That's my plan. Since there are only 3 and no disassembly required, easy enough to swap one and see if it fixes things.
 
Well one thing I learned by this whole process is that I don't have a true Dynakit ST-35, but rather a frankenstein. The chassis, output transformers and multi capacitor are Dynakit. The power transformer is Triode. The boards are labeled ASC. I can't find any information on those. Anyone familiar with ASC or know where they would have come from?
 
they are marked "Dynaco" so I wouldnt worry much. all the rest is dynakit . triode transformers are used in dynakits.
if I am wrong about this someone will correct me.
U do have something goin on with the amp making noiise tho.
sounds like part weakening or solder joint lose, or god only knows whaht else.
If U do not have the manual U shoud get one. they are a necessity for these things.
 
DAMNIT! New silver mica capacitors arrived. Replaced them one at a time... and no difference. Still that popping noise. Back to the drawing board.
 
Aright! Success I think. I found one resistor (R5) that measured differently (basically no resistance) from the same on the good board. It’s: Orange, Black, Yellow, Silver (300k?). Pictures attached. I tested it (briefly) by swapping in a 1/4 W that I have, and no popping! I’m assuming it is supposed to be a 1/2 W resistor? Note: the resistor on the good side reads on my meter as 319K. Is this right?


IMG_3784.jpg IMG_3785.jpg
 
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Interestingly, googling Dynaco ST-35 and R5 does discover a few threads where the R5 resistor goes bad. Must be a weak spot of sorts.
 
Before you go big on the resistor you should make sure its not protecting something down the line by failing. Someone who's more familiar with these should chime in.
 
I can't say enough good about Kevin and Dynakit. Super helpful and fast responses. He even suggested a Canadian supplier for the parts. Wow!

Trav,

Feels good to know you can trouble shoot & fix your own amplifier.


Yes...this resistor should be 300K 1/2 watt. Resistor appears to be a Xicon brand 1/2 watt 1% metal film.


319K is more than 5% tolerance. I would suggest replacing both these resistors. Parts Connexion in Burlington, Canada stocks this value in PRP brand. Cost 0.45 each USD.


PRP Half Watt Resistors


Kevin




Dynakit, Inc.

55 Walman Ave.

Clifton, NJ 07011 USA

PH: 973-340-1695

FAX: 973-340-8216

Email: dynakitparts@aol.com

Web: www.dynakitparts.com
 
Another positive is I added some banana jack binding post in place of the screws on the back. That's going to be a major improvement for me!
 
I don't want to hijack this thread but are those Dynakit as good as a vintage ST35?
 
Yes, seems like it.
It is really a question of are those output transformers as good as the original vintage one.
That will be my decision point it I decide to try one.
 
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