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Ampeg SVT-CL protection/blinking LED at very loud volume

T

threehz

Feb 25, 2009
9
0
#1
hey all,

i have an ampeg svt-cl that i've had around 10 years now. first some background and then my issue.

it has always been what i consider to be the best amp ever. i've cranked it to the limit many times and it never failed me.

well, until recently. one day in practice it went into fault protection/blinking LED mode. tried to turn it on and off but it kept kicking out.

i noticed one of my power tubes was flashing and going out, so i turned it off and assumed i needed new tubes (i had never replaced them). i ordered svetlana 6550's, a matched sextet, and installed them. after playing it for a while, one of the brand new tubes blew out too.

so i had it serviced by a certified ampeg tech. apparently some screws had come loose and welded themselves into the circuitry (crazy!). the issue was fixed, and the tech installed one new tube to replace the blown out one.

now, i have my amp back and it sounds great, the bias lights work great (actually better than before) but when i try to turn it up to the volumes i used to (very, very loud, pregain and master volume both at 2-3 o'clock), it goes back into protection mode, LED's blinking and no sound. i turn it off and back on and all is well until i try to play really, really loud through it again. like i said, its working fine unless i totally crank it. and it's still pretty loud, just not AS loud.

any ideas why this might be happening? anyone think its possible the new tubes may have been damaged too when my amp was still broken? are the new svetlana's crappy (ive heard they arent the best... these are not the winged C's)? i used to have sovtek 6550WE's, which lasted for years and were louder than all hell, and never, ever made my amp go into protection mode no matter what i threw at it.

any advice? im ready to just order a new set of sovtek's but thought i'd see if any experts out there had an opinion.

thanks a lot!
 
#8
so i got the amp back from the tech, who replaced the power tubes with a new set of electro harmonix 6550EH tubes. he had it hooked up to a dummy load and some kind of testing equipment in the shop, said it was running at "full power" and that it was fine. i saw his scope doing it's thing and all seemed well.

so, i went to play a show on friday and the same exact thing happened again. tried to turn up loud and right back to the blinking led again. amp worked at lower power (< 50%) without cutting out but needless to say i was barely audible over the drums and everything else.

i forwarded the info from jerrold to my *new* tech (2 strikes was enough for me), and hopefully it helps, but im still throwing this out there to see if anyone had the same issue ... which now seems to only happen when hooked to a real speaker (vibration?). amp sounds GREAT till it kicks out (usually whenever i hit a note thats really loud, ie a chord thru my big muff). my speaker is a ampeg 410hlf, i replaced one speaker with an eminence bp102-4 (4 ohms) when i had blown one out.

thanks guys
 
#9
Perhaps an intermittent cab? When I wired up my cab, I had accidentally shunted my circuit and I could get low volume and then the protect light on my 1001RB would kick on as soon as you tried to actually play the thing.

Inspect your wiring, check your head on a different cab, then check a head on your cab.

It sounds like your cab could be shorting your amp.
 
#15
Jerrold Tiers said:
There is an old service bulletin on those, just FOR the protection acting up......

The bulletin is date in 1997, so the problem is older than 10 years ago, and a 10 year old unit should have everything OK......... But you never know.
Click to expand...
I played a rental SVT-CL a month and a half ago that did a similar thing...every time you touched the gain or master, it would go into protection and shut off. Bought new a year ago and made by LOUD. Funny thing is it had just come back from the shop for that exact problem. Not my headache anymore, but very annoying at that gig.
 
#16
well, mines a SLM version. lets hope that info is useful to my tech. im gonna open my speaker up soon and see what i can see. this issue did appear shortly after i replaced a speaker, so even if it's the right speaker maybe it's loose or something.
 
#17
just wanted to update this thread, jerrold's pdf's were a huge help to my tech and my amp is back to normal, loud and reliable. if you're having this problem feel free to contact me for those pdf's!
 

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