Old Dyna amp -- Worth Repairing??

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,

Thank you for your responses. The amp is an SCA-35. Unfortunately, I'm having trouble locating info. on it.

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".

Good advice, even though you remain "Clueless". BEWARE working on the amp yourself unless you do your homework as it contains "lethal" amps (even many weeks after being unplugged). Though Clueless remains so, he/she is far from, again good advice.

Contact Audio by Van Alstine,he has been modding these amps for years,he's reliable and priced right,good luck,Bob

I assume by Dyna you mean Dynaco? Dynacos are great old amps! Some of the best values in all of audio if you ask me. They can be very musical if taken care of. Well worth repairing and one of the favorite hobbyists amps of all time.

Take a look at www.Curcioaudio.com. Joe Curcio invites you to e-mail him with a description of the problem at his site. He is also a regular at the audioasylum.com DIY tube section. If you ask your question there he is likely to answer you online.

What model Dynaco do you have? I'll assume an st70 as it is the most popular.

There are a number of things you can do to identify and fix the problem like swapping tubes and speaker wire and things like that. I am not going to go through it all because it is all available in very nice manual form at Joe's site. At the first page of Joe's site click on "Doctor Dynaco". At the new page scroll down until you see "Stereo 70 Repair Guide." This guide walks you through step by step method to identify and eliminate hum if you have a ST70.

There may be other guides there for other models but I am not sure.

Be careful poking around because tube amps carry high voltage even when unplugged.

The first thing I would do is read through the manual completely. Then do the simply things advised. Remember that there is lethal voltage even when the amp is unplugged. If you do not fix it post your question at the www.Audioasylum.com diy tube section. You will have narrowed down the possible problems a great deal by going through the process described in the manual and it will be easier to diagnose the problem over the web if it still exists. Joe has been there in the last day or two answering questions about hum and stuff in Dynacos. There are a lot of other folks who know a lot about Dynacos there too. Also you can e-mail him at his site.

If it's not an ST70 look at Joe's site for your model and ask at the Asylum in any event. Let us know what model it is too!

I'll look for you post at the Asylum but I hope all goes well and I don't see it!

Cheers,

I remain

Most repair shops, with good reason, charge an estimate refusal fee. I think that's fair. If you like art, then you should get the Dynaco repaired and enjoy. Just my 2 cents, as they say.

you did not state model, but even given that probably a very minor problem tnat would be easily repaired by most any tech, and I would think at around $50 or so, depending on who you find. Probably should repair to keep some other damage from happening that would be a lot more costly. Great old gear. Good luck