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ampeg SVT issue.

takhammer

takhammer

Jan 17, 2011
390
11
Columbia, SC
#1
Hi everyone,
I would like to start off by saying thanks in advance, for any help provided. Now, onto my issue.

Last night at my gig, I used my SVT-CL and Aguilar GS412. Halfway through our second set, my amp stopped making sound, and the LED started flashing green and red, which indicates a fault. i quickly turned it off and back on, and it worked for the rest of the show. I started thinking about it today, and I'm pretty sure I forgot to change the impedance selector back to 4ohms from 2ohms. I have done this once before on accident.

Do you think I could've messed my amp up really bad, or is this likely a tube issue? I replaced the power tubes not too long ago, with a very lightly used set of matched Tung Sol 6550's, purchased here on TB, and in the heat of the moment last night, I didn't think to look and see if all the tubes were glowing or not.
thanks,Cory
 
#4
BassmanPaul said:
Have a look now. There should be a blue glow in the output tubes if they are operating properly. Did you reset the bias to suit the newly installed tubes??
Click to expand...

Yes I rebiased after changing the tubes. i see the blue glow, so it seems like they are all working, but the amp doesn't seem to be as loud as usual. I could be mistaken though. I definitely had the impedance selector on 2 ohms, running into a 4 ohm cab, when it stopped making sound and the LED started indicating fault.

Anybody got input?
 
#5
Chances are, your amp wasn't damaged. By setting the impedance at 2 ohm and connecting a 4 ohm cab, your tubes saw twice the impedance that they would normally see. THe mismatch would be like someone connecting an 8 ohm cab into a 4 ohm cab. People report that they run SVT's like this all the time. But you weren't doing it for that long.

I would make sure that the impedance switch is set correctly for the cabinet that is connected. Then I would try to re-bias the amp again. If you are not able to set the bias, there could be an issue with the tubes. If you can set the bias and if you think that the amp is not performing as it used to, you should have a tech check out the amp just to be safe.
 
#7
I've ran 8 ohm cabs in a CL set to 4 ohms before (rentals, not my own, although I did accidentally hook up the Heritage 810e to where it ran only 4 speakers at 8 ohms the first gig I took it to) and it was fine. However, I'm not running it very loudly. If you're running it on the louder side, you can take out the tubes and/or output transformer (or I guess make it shut down in newer ones now). So yeah, I could see that being the problem.
 
#10
Mines a US made. 2004 I believe. I told the tech that.

I didn't think they had a thermal protection either, but that's what they said on the phone. They also verified, that if the green lights on the rear(for biasing) light up, then the tubes are working properly.
 
#11
The CL's do have some protection circuitry. I have the exact same amp, same year. My only experience with it going into fault mode has been waiting too long to change tubes and losing one or more. More than once, this has resulted in blowing a screen resistor or two. If your amp sounds like it should and it biases, I would say it's ok.
 
#14
wonder if a loose connector would make the fault lights do that?

my svtII was doing the intermittent cutting out thing, first time it was the preamp out/amp in jacks being corroded

one time was a bad preamp tube, tung sol reissue lost one of the halves

third time was a loose connection in the connector that goes from the preamp board to the main board

i wasn't sure if it was the same problem all three times, and this was over about 1.5 yrs.
but every time i could plug my bass into the amp in jack and get a good strong sound, so you might try that when it is giving you problems. will let you know if it's the preamp section or the power amp section that has the problem.
 

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