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Q & A / Re: '69 sunn solarus issues (warning: long post)
« Last post by _peter on February 01, 2018, 07:55:51 am »

if the problem depends on the cab but the cab itself is fine, I would suggest to disconnect the negative feedback wire for testing purposes.

It is coming from the output transformers secondary and sends a part of the output signal back into the preamp.

If the weird sound disappears, it might be an oscillation that only occurs when the amp is paired with the complex impedance response of your cab.

So that may help to isolate the bug.

Q & A / '69 sunn solarus issues (warning: long post)
« Last post by cosmic erosion on January 31, 2018, 05:55:24 pm »
Hello and good day! First, this post will take some time to read as I will give as much info as possible.

So, to start I have a '69 Sunn Solarus (2xel34) that I adore. I've owned a lot of sunns, ampegs, vintage fenders, etc etc. Never have I had this problem. So 2 shows ago, the handle decided to give out on the head and it fell maybe mid calf (i'm 5'8") and hit the ground as I picked it up from the ground. So not far and not too quick. Amp fired up afterwards and I thought nothing of it. 

A week later, it starts making this insane voltage sound (almost like the proton packs in the first ghostbusters movie), almost like a speaker is bad, and cuts out a bit soundwise. It over takes at least 75% of the sound. It starts right away when the amp is fired up. I usually run it at 6 on the volume into a sunn 4x12 loaded with wgs vet30s and et65s, 8 ohm cab. I assumed I had a voice coil rub or something like that, so I call my tech. I also should state that I tested this head into my 1x15 bass cab (8 ohm) and my traynor head into my sunn 4x12. No issues either way.

First, let me say that my tech has worked on numerous amps of mine, buddies of mine, and people I've sent to him. Been a tech forever, etc etc. I explained to him what happened. He has it a few days and says the 7199 tube needs replaced and he cleaned up some pots inside. Replace the 7199 with a nos ge. 

Take the amp to practice, it's better but still not right. We have a show in like 2 days so I just run the amp as is until I can take it back over. I explain a bit better what it's doing and he has me bring my entire rig over to troubleshoot. This is where, if you're still reading, it really starts to make our brains hurt. 

So I plug everything in and show him the sound. So again back to testing to see if it does it on other cabs and/or other heads into my cab. So 2 different heads into my 4x12. No crazy sound. Sounds just the way they should, even dimed they are fine. Ok. So my solarus into his 16ohm 1x12 cab, no crazy sound, amp and cab sound great. I should mention I ran into the 16 ohm cab from the 16 ohm tap on the head. Next up is the solarus into his 2x12, 8 ohm. No issues there. ok......

So back to the solarus into my sunn 4x12. Bam! There's the funky sound again. Which would lead me to believe there is a short somewhere in the cab or something funky with a speaker. I've blown alot of speakers, would not surprise me. Well, maybe in this case since the sunn before this into the cab was a 4xkt88 coliesum pa which I ran at 9. Anyway, cab measures just fine ohm wise at an even 7 ohms. ok..... so I leave the head with him and await his call. 

He hardwires the output tranny taps to the head, explained to me why. Cleaned jacks, replaced the amperex 12ax7 with a jj, reconnects the negative feedback loop in the amp, and calls me back. Says he thinks it's the 8 ohm tap on the head is going out. Explains that the wiring in the transformer ages and will break down and maybe the fall caused a short in it. Makes sense to me, but I know it's a rarity that transformers go out. So I head back over and we fire everything back up. We get the volume to 7 before it makes the bad sound. Which is doable since I run it at 6 usually. We disconnect it all and hook up all the heads to my 4x12 and and the solarus to his cabs to test. It still only does it with my head and cab. He lets me know that he thinks it's the output transformer and to do some soul searching if I want to replace that or move on. I didn't pay much for the amp from a buddy, who bought it nonworking and this tech brought it back to life. 

Fast forward to yesterday at practice. Head fires up, no sign of sound. Drummer and I are baffled. I dime the solarus, no wacky sound. Again, what?!? We practice for maybe 2 hours before it starts to do the sound, barely this time tho at volume level 6. I put it down to 5 on the volume, no crazy sound. Swapped heads at our spot (sovtek mig, my traynor) and try other cabs. You've read the above, same story on that. No wackiness.

So, long story short, here's some thoughts on my end. 

1.) If a transformer is bad, why wouldn't it make this sound in all cabs and at both 8 and 16 ohms? He did crack open the transformer and tried to clean it out a bit and see. He said the 16 ohm tap looked brand new, could I just respeaker my 4x12 to be 16 ohm and be fine? As it only does it on the 8 ohm tap. Do the windings for the different ohms affect each other inside? Say if the 8 ohm tap is bad and goes out, would the 16 ohm tap (and unused 4 ohm tap) be fine and run at full power?

2.) Bad rectifier tube? Maybe it's got a small leak in it and once it warms up, starts to misbehave? Or bad caps? It takes a 4 stage cap he explained. It tested fine, but again, who knows? 

3.) Or anything that jumps out at people? I've had caps, speakers, tubes, etc etc go out, this sound is driving me bonkers.

I just kinda want a 2nd opinion on what it could be. I paid very little for the amp and as I started amp shopping this past week, realized that I'd spend more buying another than just fixing this one. I mean, if a pickup in your guitar went out, you wouldn't just buy a new guitar would you? is kinda where I'm leaning. I would just buy another solarus anyway. The combo of solarus and my jazzmaster is the tone I've been hunting for, and we all know how expensive and time consuming trying to nail THAT sound is. I found it, now how do I fix it?

SUNN Sightings / Johnny Cash Show.
« Last post by DennyMcFastLane on January 28, 2018, 08:41:33 pm »
Carl Perkins playing a rare Microfrets Guitar through a Sunn Top & Bottom. Mark Farner used a Microfrets Guitar also.
Classified / Re: Sunn pre-'69 grill cloth 200s cab WTB
« Last post by bigobassman on January 26, 2018, 09:46:10 pm »
If you'll do a site search, you'll find detailed info thread(s) within.  The basic answer not available, but some stuff fairly close.
Classified / Sunn pre-'69 grill cloth 200s cab WTB
« Last post by thorner on January 26, 2018, 06:13:44 am »
Looking to buy pre 69 grill cloth for 200s speaker cabinet
Classified / Re: Sunn PA System Speakers
« Last post by loudthud on January 23, 2018, 01:39:59 am »
A quick check of the Dave's profile says he hasn't logged in here since 2009.
Q & A / Re: Overdrive or distortions pedals in Sunn Sonaro
« Last post by Isaac on January 22, 2018, 10:21:30 am »
My own experience, and that of almost every person I've heard express one, is that Sunn amps love pedals, and take to them as well as any amp out there, and better than most. Maybe you just don't like the sound of that pedal?
Q & A / Re: Overdrive or distortions pedals in Sunn Sonaro
« Last post by EdBass on January 22, 2018, 05:12:04 am »
I don't think so, ultra-linear refers to the output stage's interface between the output tubes and the load (Speaker). Shouldn't effect an outboard pedal plugged into the input of the amp.
Q & A / Overdrive or distortions pedals in Sunn Sonaro
« Last post by Tomm Williams on January 21, 2018, 07:48:45 pm »
Since receiving my Sonaro I've been enjoying the heck out of it. However with the one distortion pedal I tried in it, I did not care for the tone. I've read a couple of opinions about the ultra linear design not agreeing with pedals. Any truth to this ?
Classified / Re: Sunn Model T First gen
« Last post by Blight Moth on January 21, 2018, 12:59:12 am »
Hi there. Do you still have this amp? Email me at if you still have it! Cheers
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