My Sunn Amphead Is having Issues Please help...

[Matt Nonyabuisness]

Hey everyone,
I got a problem I hope someone on here has the answer to. I have an old amp head, a Sunn Sentura II to be exact. Now my problem is that the thing sounds like it has a heart beat. After its on for a while, there is a slow bump... bump... Its really odd. Could the tubes be the problem? Any ideas would be helpfull. Also what tubes does this amp have?

[Matt Nonyabuisness]

Sorry Everyone, also whats the Ohms for the speaker outputs?

[stanner]

get thee to a tech-
allquestions answered
and you end up w/ a great playable amp.
s

[mckinnon audio]

  Hi there,sounds like you have a filter cap. going bad.Did you try playing the amp while the bump is happening?There aren't many sources of low freq. oscillations in amps.If you're not familiar with tube electronics,you should take it to a tech.Good luck Mel.

[JoeArthur]

Yep, based on the description it certainly sounds like motor-boating to me.

As Mel mentioned, normally caused by old electrolytic caps.

And since you don't know what tubes it uses, I second (third?) the suggestion to take it to a tech.

[basiklybass]

Add another voice for bad caps. Look to the ones around the 6AN6 tube. I just replaced the .25uf in my 200S and stopped some Putt Putting.

I agree with Joe, take it to a tech if you have never done anything like this before.

Most of the Sunn tube amps have an 8 ohm speaker jack and a 4 ohm speaker jack. The 4 ohm is the outside one. There were some that were 8 and 16 though, mostly the PA heads as far as I have read in this forum. Plug into the inner jack with any 8 ohm speaker and the outer  and inner ones with 2 - 8 ohms or the outer one with 1 - 4 ohm speaker.  I would think the Sentura II used 6550's. The Sentura used EL 84's but I believe by the end of the series run, everything was the same and used 6550 and solid state rectifiers.

[Isaac]

That's a 6AN8, not a 6AN6. And yes, the Sentura II uses 6550's. Mine does, anyway.

[basiklybass]

Thanks Issac, I was typing fast and part of the 8 flew away making it into a 6.