2. amps-preamps
  3. 1015621599

Old Dyna amp -- Worth Repairing??

I was given an old Dyna tube amp which seems to work well except, on occasion, there is an intermittent hiss or hum in one channel. Does this sound like a common or simple problem? I enjoy the use of this amp in my painting studio, so ultimate fidelity is not absolutely critical. However, I don't have the money to spend on a major repair. Typically, will I be charged a fee to even have someone open up and look at this piece of equipment? Or, should I ask for a free estimate? Any bits of advice on finding a fair and competent repair shop?

I am very glad I found this forum, as I enjoy music, but know very little about electronics, etc. (am a newbie), but am learning as I go. TIA.
dog581b
usblues
1,217 posts
 
Contact Audio by Van Alstine,he has been modding these amps for years,he's reliable and priced right,good luck,Bob
maxgain
526 posts
 
Dog, the first thing to look at on a Dynaco amp would be the tube sockets for an intermitent "hiss/hum". Try wiggling the driver tube gently(the small one, it's a 7199 if it's a ST 70)on the channel that makes the noise. If it goes away or makes the same noise when wiggled, you found it. Clean the tube sockets and the pins on the tubes. Feel free to e-mail me with questions, I dont know everything there is to know about them but I fooled around with Dynas for a very long time and know some of their "habits".
dog581b OP
1 posts
 
Thank you for your responses. The amp is an SCA-35. Unfortunately, I'm having trouble locating info. on it.
clueless
763 posts
 
Dog
The SCA used one 12ax7 tube for each channel in the pre amp. It used two tubes for each channel in the amp, one 6BQ5 an one EL84 for each channel. It might be as simple as a loose tube or a bad tube. If you switch the tubes around and the noise moves to a new channel/speaker its just a tube problem and you just need to buy a new tube. If you switch the tubes make sure you only change like kinds of tubes.

You could open it up and at least see if you can identify the tubes. If they are easily identified as above just rotate the tubes. Do not touch any of the capacitors.

Ask over at the asylum. I don't see your post there yet. There is bound to be someone with a lot of experience with that unit there. They might even have a manual for you. It is a very helpful group.

I remain,
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