Solarus sound deteriorates

[Jack]

I have a 1970 or 71 Sunn Solarus (separte head and 2- 12" speaker cabinet).  After playing for about 20 minutes the sound deteriorates and becomes muddy.  A guitar tech just looked at it and said there is nothing wrong with it, just some dirty tube contacts.  He cleaned all the contacts but there has been no improvement.   Does anyone know a good amplifier technician who can get to the bottom of the problem in the New York tri-state area?  I am the original owner of this amp and it is cosmetically in mint condition.  Thanks for any help.

[Ryan Phelps]

Jack;
While I can't recommend an amp tech in your area, I would ask the following. If you are the original owner, have you ever had the filter capacitors replaced? How about the output tubes? If the answer is no to either question then I would strongly suggest that you have it done. A 30 year old amp with original filter caps and tubes will rarely sound right. Muddy sound is often traced to old, dried up filter caps that won't hold a charge. Ask your local guitar shops for a recommendation on an amp tech; this is not a do-it-yourself job (high voltages = death!)
Antique Electronic Supply in Tempe Arizona (check out their website) carries the multi-section filter cap that is a direct drop-in replacement for the original (no need to jerry-rig separate caps under the chassis any more). Just be sure to get the 525 volt rated capacitor to handle the high voltage that the power transformer puts out. Also replace the two negative bias caps (50uf @ 150 volt) while you are in there. I've done this to about a dozen Sunn amps (and MANY other brands as well) and it will make your amp sound like new! Don't forget to rebias the new EL34 output tubes to draw about 35ma or so.
Good Luck!
Ryan

[Jack]

Ryan,

Thanks for the help.  I am the orginal owner of this amp and the tubes have been replaced and re-biased.  I will look for a amp technician and give him your notes.  Thanks again.

Jack

[Bill Matthews]

If you are in NYC call Expert Audio Repairs and Service (212) 868-4357  These guys have a client list like the who's who of Rock&Roll  Trust me these guysa are the BEST..

[chev]

Hey looks like I need to do the same thing.

I just bought a 1970-71 Solarus wich is supposed to be 80w (from the catalog thread).

It has been cleaned up, re-tubed with 12ax7, 12au7, 6an8, GZ34 and 2 KT-88, re-bias and a Grounded AC cord have been install.

The problem is, if normal or not, I can't get the volume higher than 2 before getting some muddy crunch and this happens the all time it's on.

I also have a 1971 Sonaro 80w with the same tune-up did by the same tech but has 2 Sovtek 6550. This one has new caps inside and it stay clean till 7-8...didn't got pass this it's loud enough!

I would like to balance the Solarus volume with the Sonaro because I play both.

My Solarus  been sitting on a collectionneur shelf for 10 years...! so it need some good overhaul.

Just wondering what you guys think.

Thanks!

[EdBass]

Hey looks like I need to do the same thing.

I just bought a 1970-71 Solarus wich is supposed to be 80w (from the catalog thread).

It has been cleaned up, re-tubed with 12ax7, 12au7, 6an8, GZ34 and 2 KT-88, re-bias and a Grounded AC cord have been install.

The problem is, if normal or not, I can't get the volume higher than 2 before getting some muddy crunch and this happens the all time it's on.

I also have a 1971 Sonaro 80w with the same tune-up did by the same tech but has 2 Sovtek 6550. This one has new caps inside and it stay clean till 7-8...didn't got pass this it's loud enough!

I would like to balance the Solarus volume with the Sonaro because I play both.

My Solarus  been sitting on a collectionneur shelf for 10 years...! so it need some good overhaul.

Just wondering what you guys think.

Thanks!

I think you pretty much answered your own question...
Caps, caps, caps! 

[chev]

All right, I'll go on with caps caps caps...lol.

I was just wondering if those amp are suppose to be clean all the way up like a fender, not crunchy at 3-4? right?

there's just the 6an8 that's been replaced with a used Mullard by my amp tech, but it's tested positive, there's just no old-new stock of these, that's why.
I might buy another one because they're so hard to find.

If you know where I can get one in the new-old stock?! I would definitly buy another one just to make sure.

But still, the oldest parts are the caps...!

I'll let you all know if it resolve the problem for the well beeing of all Sunn Amps on this planet!

I love my Sunn's!

thanks again!

[loudthud]

Look on ebay. Search for 6AN8* (because some are called 6AN8A) in all categories and there are all sorts of hits.

[chev]

Ok I found a few on ebay, thanks.

Is it damaging anything if I play my amp at 2 until I let the head to my amp tech a.s.a.p.

I specially don't want to srew up my brand new JJ's KT-88! I've got them for a super low price that I wont get a 2nd time...

I've try a LPB-1 in front of my solarus to boost the volume without cranking the amp, it works a bit better.

thanks

[Soundmasterg]

You can find all sorts of 6AN8's at www.tubesandmore.com , new and used.

Ryan, the only issue I have with using the can cap they sell that fits in the Sunn amps is that at 525v it is often over-voltaged with the higher AC voltage coming out of the wall these days.....well that and price. If you used discrete caps inside the chassis it is cheaper for the parts, and you can hook up the first two cap stages with series connected 350v caps for a 700v rating, adn then no more over-voltage worries. The Sunn amps that used EL34's rather than 6550/KT88's often did have a lower voltage so they can be ok, but the 6550/KT88 amps are often at 560v and higher, which can make that can cap blow prematurely. Next time you get an old Sunn in for repair, measure the B+ voltage on the powe tubes and see if it exceeds the 525v that can cap is rated for. I bet it will.

As far as repair people in the New York area, Jess Oliver repairs vintage Ampeg amps,and he is in that area and very knowledgeable. Perhaps he will do Sunn amps too? Worth a shot.

Greg

[Ryan Phelps]

Greg,
9 years ago when I wrote this, I had re-capped several Sunn amps with 525V can caps with excellent results (I still own several of them). However, I've recently been running into the exact issue you raise....the B+ voltage from the rectifier can easily reach 560 volts and blows the $35 can cap! Two ways to handle this 1) install a new can cap, but replace the first cap-in-the-can with a totem stack (I use 2-100uf @ 450V in series with 220K 1 watt bleeder resistors....yields 50 uf of capacitance at 900V). Or 2) save yourself some $ and do as you suggest....replace all the filter caps with discrete caps! I did this last winter to a 1969 Sunn Studio P.A. I left the original can cap in place for appearance and, on the under-side of the chassis, pop-rivited two terminal strips and installed all new filter caps, bleeder resistors on the totem stack (as above) and new dropping resistors between the filter stages. This approach also allows you to use higher capacitances in the first two stages for better bottom end. I plan to use this approach in the future. While it is a bit more invasive, it provides for a stable amp for those that play them.

Ryan