A weird thing happened..... (SVT-CL owners)

[4StringShooter]

I should start by stating I use an SVT CL, with a Yorkeville 4-10.
Playing along the other night, my sound suddenly "dropped ". No sound, nothing.Standby light went RED. I hit the standby, waited a few seconds, clicked it back on and everything was fine. Green light.
It did it again, the next set. I did the same thing as before, and it carried on. While it was in the " dropped " mode, it did emit a slight buzzing. The amp had been benched a year before, replacing all 6 tubes, plus a new pre amp tube. It was also completely dis assembled, and the whole board gone over, fixing some ground issues with the Power Tubes (****** wiring from the " factory ").

Any other SVT users have this quirk happen?

[JimmyM]

Sounds like one of your new tubes pooped the bed.

[4StringShooter]

Power tube you mean?

[JimmyM]

Ya, power tube...that's generally the cause of those lights going out of whack. I could be wrong, and I'm certainly not the expert here, but going by what I know about the bias system, I think it's a likely culprit.

[BroKenSticKs]

SVT with yorkville 4-10? Did they ever make a 4-10 that was 4 ohm?

[BroKenSticKs]

Coincidently there is a thread about this on the front page right now. running 8 ohm speakers with a 4 ohm amp?

[okcrum]

Only one like this I ever saw was a blue line SVT that the B+ line for the preamp broke off inside, and it gently faded out on stage. Turned out to be a quick 'n dirty repair that was never followed up and fixed correctly until it died at a gig.

[Bermel]

I had a similar experience just two days ago with my SVT-VR. I was checking sound with my band at a club, when the owner of the bar suddenly turned on all the stage lights.

We heard a big "pop" and then no sound came from my amp. The same as the OP: the standby light was red. I turned down the standby, waited a few seconds, and clicked it back on and everything was fine. Green light for all the gig, with no problems then.

Hope everything is OK with my amp and with the OP's.

[Jerrold Tiers]

The VR problem is probably the silly low voltage cutoff that got put in (serious over-tech addition).

You likely heard the relay opening as it was 'expressed" through the speakers....

The amp is probably fine, but you should do the mod to get rid of that feature..... It's perfectly OK technically to do that.

"johnk_10" (is that right?) came up with a neat version that is just a wire harness you can make up and plug in. No more low voltage cutout "events", and the amp is not permanently changed, so you don't even void a warranty (if you remember to take it out before you take it in, should you ever have to).

I was going to say "search for it" but on a whim, I did, and found that the forum search cannot be used for "SVT" or "VR", because the search terms must be more than 3 letters. Go figure... Someone will have the search, or I suppose you could PM him.

It's not a hard thing, better than the soldered jumper I suggested.

[Bermel]

Thanks for your help Jerrold. I'm not exactly sure about what you are talking about that "low voltage cutoff". Is this some kind of fuse, like the one on the rear panel?

From the owner's manual: "The fuse helps protect the unit from damage due to overload conditions. If the fuse fails, replace it only with the same size and type. If the fuse fails repeatedly, check the line voltage or contact an Ampeg
Service Center."

Is this info relevant to the topic?

[Alex1984]

Originally Posted by Bermel

Thanks for your help Jerrold. I'm not exactly sure about what you are talking about that "low voltage cutoff". Is this some kind of fuse, like the one on the rear panel?

From the owner's manual: "The fuse helps protect the unit from damage due to overload conditions. If the fuse fails, replace it only with the same size and type. If the fuse fails repeatedly, check the line voltage or contact an Ampeg
Service Center."

Is this info relevant to the topic?

The amp will refuse to kick out of standby if the voltage supplied to it is too low.

John K's mod is explained on his page:
SVT-VR

[derridiandrift]

^^^^^

It's a simple mod. The hardest part is taking the amp out of the head case because it's so heavy. Be VERY careful because the voltage stored in the caps can kill you. I think John's mod also explains how to discharge the caps.

[4StringShooter]

Originally Posted by Bermel

I had a similar experience just two days ago with my SVT-VR. I was checking sound with my band at a club, when the owner of the bar suddenly turned on all the stage lights.

We heard a big "pop" and then no sound came from my amp. The same as the OP: the standby light was red. I turned down the standby, waited a few seconds, and clicked it back on and everything was fine. Green light for all the gig, with no problems then.

Hope everything is OK with my amp and with the OP's.

I had the same thing happen one night when I stupidly unplugged my Bass ( at the Bass ) while the Amp was in " go " mode. BIG ...BOOM...then nothing. I almost scorched my drawers , thinking I had blown my new amp. Turned it off, waited a few minutes, and it came back. The problem I had was while playing. The standby went RED. Shut it off, waited a few seconds, flipped it back on and it worked. But....it did it again a little later.
I also noted that my 4-10 is NOT the same impedance as the Amp. Time for a new cabinet. Time for an 8-10 !!!!!!

[Bermel]

My cabs are a mesa 410 and a mesa 115, both at 8 ohm. So 4 ohm in total. I dont think any problem lies there. Im thinking if the mod we are talking about is worth it. What happened to the svt-cl of the first poster?

[rickdog]

The SVT-CL Owners Manual (available from the Ampeg web site) says:

STANDBY/POWER/FAULT INDICATOR LED: This is a multi-function LED. In Standby Mode, it glows red. In the On mode (when the high voltage comes on) it glows green. If it does not turn green in the On mode, there is no high voltage present and the unit needs servicing. If the amp detects a fault in the power tube circuit, the high voltage is turned off and the LED flashes between red and green. This usually indicates a bad power tube. The amp will remain in this condition until the unit is turned off.

I have a partial schematic for this amp that has a penciled-in mod with the notation "to slow fault trigger." Jerrold?

4StringShooter, how old is your CL?

[4StringShooter]

My Amp is less than 4 years old. Just last year, it was worked over at a major Music Shop. I had all 6 power tubes replaced, AND a new Pre Amp Tube. The Tech told me there were issues with the ground wiring for the Power Tubes. He told me he stripped the head right down, and checked all solder joints. But Tubes can go bad.....

I think I'll just buy the dam Traynor 8-10 Cab, and be done with it. Their warranty is amazing !!!

It does weigh as much as a Bus, though.

Now, if I can get rid of this Yorkeville 4-10 /w tweeter cheap....and yes, it does work great. It HAS suffered damage from the Cats ripping the fuzzy blue covering, though.

[FrankLowend]

As I live in Brazil () is so difficult to have good equipment, so, my head was manufactured according Ampeg Customer Service in 1996... The black face head yet. It's funny because could be crazy pay in US about U$3.600 for this amp and 1X15 + $X12 cabinets...Used!! Very Used!! Unfortunatelly this is our reality... But comebacking to the point: I always use a local power conditionner (similar to Furmann) and I think that never I plug or unplug the bass cable (I'm using specific cables for bass from Dominator and Monster cables and the difference is very significant from the normal ones) before push the "mute" buttom. A few years ago I went to US and I bought new valves (the 12AU7 I not find, but last year i found one in England). The cables for the cabinets are specific for cabinets, not instruments cables. I never had this problem in my Ampeg. I was a little afraid to force it since I'm using one DBX Compressor + BBE Maximizer + V-Amp Bass Pro Behringer in the FX in/out - But after almost one year doing this, I have no more doubts about the robustness of my old 96 SVT III...

[4StringShooter]

Sherwood Music, Kitchener, Ontario, Canada for the 12AU7 s.

I shop there.

[4StringShooter]

Originally Posted by 4StringShooter

My Amp is less than 4 years old. Just last year, it was worked over at a major Music Shop. I had all 6 power tubes replaced, AND a new Pre Amp Tube. The Tech told me there were issues with the ground wiring for the Power Tubes. He told me he stripped the head right down, and checked all solder joints. But Tubes can go bad.....

I think I'll just buy the dam Traynor 8-10 Cab, and be done with it. Their warranty is amazing !!!

It does weigh as much as a Bus, though.

Now, if I can get rid of this Yorkeville 4-10 /w tweeter cheap....and yes, it does work great. It HAS suffered damage from the Cats ripping the fuzzy blue covering, though.

To add to this, the Amp worked perfectly the other night. All night. Observed the leds in the back while playing , and they appeared as they did just after last shop.

[Jerrold Tiers]

Originally Posted by 4StringShooter

To add to this, the Amp worked perfectly the other night. All night. Observed the leds in the back while playing , and they appeared as they did just after last shop.

If you have low voltage issues, any time the voltage is OK, it will work fine..... but that is typically ONLY with VR.

A CL that does it is a different issue, most likely.

But it CAN be a problem with that same relay as with the VR, the relay just isn't set to respond to undervoltage in the CL.

Problem is that teh CL has a complex fault detection circuit, and if you do the bypass to IT, you lose that protection....