Blown Threshold S/300 Stasis II

I over drove it tonight and it went quiet without warning.The on/off light works.
I was really pushing it but I heard no distortion or clipping.I've never played it this loud,but I feel I still had head room.
Im using a re-built Dynaco ST-70 on top.
The Dyna seems fine.
The Threshold has a breaker for a on/off switch but I didnt notice if it had tripped.
One thing I did notice,is the left channel heat sinks were considerably warmer (not hot) than the right channel heat sinks.
Anyway,the amp is dead quiet.
Could it be the breaker/on/off switch 'burned' and a simple replacement may cure the problem?
Or am I in trouble?
Thank you for any advice.

Hi David,
Sorry to hear of your dilemna. Did you check the fuse(s)? Is the Dyna ST-70 a tube unit? If so, maybe there was some DC leakage. I don't know first hand, but, I've heard that the Thresholds can be sensitive about that sort of thing. Best of luck sorting it out. Do you have a back up amp?
I used to have a forte amp that I believe was made by threshold. Inside that amp each channel had 2 fuses.
Try taking the top off and see if they are blown. If so, you might find replacements at radio shack.
Thanks Unsound for the fuse tip.
The two 5 amp fast blow fuses on the negative rail blew.
Problem fixed.
Email Jon Soderberg at Vintage Amp Repair.
Perhaps you should listen to music without blasting out your eardrums and your masterpiece Threshold amp? Even so, I can't imagine driving this amp to failure. Check fuses and/or preamp.
Perhaps you should listen to music without blasting out your eardrums and your masterpiece Threshold amp? Even so, I can't imagine driving this amp to failure. Check fuses and/or preamp.
Perhaps you should listen to music without blasting out your eardrums and your masterpiece Threshold amp? Even so, I can't imagine driving this amp to failure. Check fuses and/or preamp.
I forgot all about this old thread.
I replaced 2 rail fuses and the Threshold was in action again.

safeharbor,the S/300 isnt a 'masterpiece' amp.
I bought a asw-3000 B&W sub and with my curcio modded Dynaco amp there's no comparison.
The Threshold sounded hard and grainy compared to the Dynaco,and I can 'still' blast my eardrums out with the sub in the mix.
I sold the 'masterpiece' Threshold.

Many respectable audiophiles would seriously disagree with you regarding the S/300 Series II. When balancing dollars with quality, this amp is considered by many to be a masterpiece. I hope that you enjoy your new setup.
I can only use my Threshold S500/II as a reference here, and while I have sincere respect for David99's opinon, I don't hear "grainy", perhaps a bit hard, but my Threshold could only be described as smooth. I would go as far as to say, very smooth.
Hi all,
Safeharbor,I never said the S/300 wasnt a very good amp.
I bought Thiel 3.5's @ 4ohm 86-88dB?
and started out with a Electrocompainet Amp Wire 75 to drive these power hungry speakers.
The AW-75 did a decent job of driving them with 96 peak amps.
I then got a steal on a mint,silver S/200 series II and this amp really opened up the Thiels and I could tell then,I should have gone with a higher powered amp to begin with.
I then got an incredible deal for a mint,black S/300 series II and I sold my S/200 to a bud in town.(he was begging me for it)
The S/300 drove my Thiels without a hint of effort and the combo sounded very good.
I could detect a bit of hardness though.
Soon after,I sold my Thiels for my present speakers which are much easier to drive.
I bought my Dynaco soon after and I used the Dyna for the top and the S/300 for my bass amp.This set-up sounded very good.
I tried both the dyna and S/300 alone with my speakers and the S/300 still sounded hard and with these present speakers I noticed slight grain in the midrange.
The S/300 sounded very good with my 90dB 7ohm speakers but when I ran the Dynaco alone, the hardness and grain was gone and the Dynaco sounded smoother and more pleasing.
Of course at 35wpc the Dynaco didnt have the power or bass of the S/300 'but'the Dynaco didnt do a bad job.
My speakers only go down to 29hz and I craved deeper bass from my experience with the 20hz Thiels.
I decided to go the sub route for the first time ever,and can honestly say,I'll never go without a sub again.
I now have a all tube system that sounds very refined on top and with clean,well integrated bass down to 18hz,and it rocks!
The S/300 is a very good amp and it hurt to see this incredibly built,black beauty go. But I like the sound of my current set up better.

Im glad you finally have your rig fine tuned.
I know how hard you worked at getting it to sound the way that pleased you most.
Your Threshold amp and preamp mods make these already fine pieces go to a level hard to beat.
Good job..and dont forget to keep your CD's VERY neat and in order :>)

David99, your right to point out the mods. I bought the Threshold gear with the mods so I can't say how much effect they had on the original sound. I do believe the modifications are fairly minor.
I own the S/300 and it's one of the finest pieces of equipment I've heard. Sure there will be better amps, but this one's a keeper.
. . . and if your old Threshold amp, S/xxx series or older, still has it's original electrolytic caps in it, you have no idea how good it will sound once you change them out with new. Be sure to change out both the large PS caps, and while you are at it, upgrade their capacity as well, and the small with some Blackgates or Rubycon ZA or ZL.

You have to figure that in these 20+ year old amps, the small electrolytics are pretty well dried out and shot, and the larger ones may still work, but are well past their prime.

The same goes for older Threshold pre-amps as well. I replaced all the small electrolytic caps with Blackgates in my SL-10. That change alone took it to a new level which now makes it a keeper, too.

I have three Threshold pieces; a Stasis 2 amp, an S/150 II, and the above mentioned SL-10. The cap upgrades to all of these Thresholds made big improvements, but the improvement to the SL-10 was over the top.