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SVT CL - No high Voltage

K

Kaspergreenday

May 19, 2010
63
0
#1
Hi TalkBass!

My Ampeg Svt - Classic stopped working. When i turned the standby switch off, it just still lid red, which in the manual means, that there is no high voltage present. It was fine just yesterday.

I know many of you will tell me that i have to go to a tech, but i want to make sure that i have done everything in my power to fix it before hand, since them damn technicians always are way overpriced, at least in my area.

My amp had a problem earlier on, where it the lid switched between red and green, which means according to the manual, that something is wrong in the power tube circuit. I fixed it by changing the tubes myself, but i guess this i kinda different.

Well, i hope you could help me, would aprecciate some good tips if there are any! (Poor student here)

-Kasper
 
#2
Check the fuses. If the one for the B+ is blown, replace it with the same type and fire it up. If it works, go forth and conquer. If it blows again, take it to a tech.
 
#4
If you had taken it to a tech in the first place, you might not have had to spend all that money on a new set of power tubes. Taking it to a tech may cost you a bench charge, but at least you'll get it fixed right (provided your tech is any good).
 
#5
Checked the fuse, and unfortunately, it should be OK to go. I just can't figure out how the amp could be hurt, it was working perfectly yesterday, and it's standing safe in my room, so with my unexperienced logic, i would think that the damage can't be that bad?
 
#6
Probably isn't. Could be as simple as one of your new tubes going out on you. But it could also be more complex. And that's where the tech comes in...a good tech can pinpoint what exactly is wrong and fix it, whereas you're guessing. If you guess right, then it's all good, but if not, you could end up spending money needlessly.
 
#8
I would assume it is a tube thing, but with a serious amplifier like that, don't touch it without being totally qualified. This thing is pretty complex and fairly dangerous. You can easily mess it up worse than it is.

I honestly wouldn't even take it to a tech that I couldn't vouch for, in my experience "qualified" means nothing more than working at a store front, I need a good first hand experience and/or review
 
#9
Hmm, as i said i changed the power tubes earlier on, and if i am correct, the SVT Classic is made, so you could easily change the tubes without needing a tech, but since it's not the same error im getting this time, i guess i really need to send it to a damn tech..
 
#11
BassmanPaul said:
Tell me Kasper, if your microwave stopped working would you even think of opening it up to see of you could "fix" it? I know I wouldn't and I've been working with tube electronics for more than fifty years. Please take your amp to a tech. His bill will be so much less than your live is worth!!
Click to expand...

Looks like i only got one thing to then! Well, thanks for the quick responses as ussual! Will give a call to my recommended tech :)..
 
#12
IME- Peace of mind is worth a $70.00 or so bench fee, to know that it's right. IMO- Its worth the small entry fee to not have to worry about plugging it in at a gig, and it not work. Plus the potential extra expense You could incurr by messing up $200 worth of parts for a $5 problem or losing life/limb.
 
#14
Could be a bad standby switch, poor solder joint. Wouldn't you feel silly if you bought a couple hundred dollars worth of tubes for a $10 switch or a cold solder joint.
Logic has little place in electronic failures. Just because a light bulb worked yesterday, does that mean it MUST work today? :)
 
#18
nashvillebill said:
Where are you located? Perhaps somebody here could recommend someone.

Or, perhaps somebody here might be qualified and close enough to you to that they could look at it and help you out. If you were close to Nashville, I'd take a peek at it for you.
Click to expand...

The thing is, i live in Denmark, where everything is much more pricier by the way :). But i contacted a new recomended tech, hope he works on ampegs.
 
#19
Hi again! My father insisted that i first changed the cheap preamp and driver tubes first, so i shipped 3 x 12ax7b Bugera home, and 2 x JJ AU7, and changed the preamp tubes, (1 x 12ax7 + 2 x AU7), and turned it on, and it worked! I know you guys said i needed to talk to a technician, but i guess it was one of the times were you just got lucky!

Well anyway, when i wanted to change both the driver and preamp tubes (because i know nothing of tubes, and had recently changed the power tubes, so it must have been either one of thoose 5 tubes), i couldnt really locate the 2 driver tubes, but i guess i was lucky that it was the 3 preamps that was something wrong with. But just on a curious note, where are theese 2 driver tubes placed?

I dont know if people are monitoring this thread, or if i should start a new one, but i also noticed that the fan is not on, and is the fan supposed to be on at all times, or is just when it detects warmth or something?

And another thing, which like the fan, is not new, my SVT CL is making a decently loud noise when i turn standby on, and it just idles, and even when i play (but you do not notice it because the bass sound is louder), and is this normal and what could it be? When i biased the amp very low it was nearlly gone, but when its at a correct bias its pretty loud. Here's a sample, theres alot of background noise, but you get the difference:
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and again, thanks for all the good replies, hope you guys can give me some enlightment on theese questions too :)
 
#20
The driver tubes are the ones next to the power tubes in the lower chassis, there should be three tubes there, the splitter/inveter and the two drivers. Just for reference, the pre-amp tubes are the ones located in the upper chassis behind the gain/tone knobs.
 

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