Ampeg SVT CL Power Fault Issue with too much volume?!

[metro_area]

I've got a '94 SVT CL that has been with me a long time. It's been functioning fine for a long time, and been consistently re-tubed and serviced by a certified tech.

Anyway, this weekend I was playing an outdoor show. I was running through a Samson power conditioner using an Essential Sound Products MusicCord Pro (as I always do, so I should have had the cleanest power available). I powered the head up, let it warm up for 5 or so min, and then turned the standby off. Given that it was outside, I had both the Gain and Master past half, each at about 7 or 8 (out of 10) to get the proper stage volume.

About 90 seconds into sound check, my sound cut out. I looked back, and my head is flashing the Standby/Power/Fault light - flashing between red and green. I clicked it back into standby, but it just kept flashing, so I turned it off. After giving it 10 minutes, I turned it back on (warmed it up, then standby off) and it was working again. However, only for about another minute - then it did the same thing again.

This continued repeating until I turned down both the Gain and Master to about 5 or 6, and then I had no issues the rest of the night - aside from the fact that no one in the band could hear the bass. If I turned the volume up any more than that, even slightly, it would cut out and flash again. One of the main points of lugging around a 90 lb head and 810 cab is for volume as well as tone, and we were all super bummed that I couldn't properly turn up.

This rig has been to more dive bars than I can count, sharing one single outlet with 2 AC-30's and a 212 Deville, without any issues. So I'm not sure what was different this time. Is this an issues that the JohnK Mod would fix? (SVT-VR) His mod seems to fix an issue where the head won't come out of standby, and that wasn't an issue for me. It worked fine, except when I turned up.

Help!

[rickdog]

Mmm, playing outdoors... where was your power ultimately from? If you were at the end of a long extension cord, you may have been causing enough voltage sag at high volume to trigger the low-voltage protection. Can the Samson regulate a low line voltage back up to normal?

[wvbass]

Essential Sound Products MusicCord Pro...



I suspect this is a power issue, but am curious to hear the concensus here.

[billfitzmaurice]

Originally Posted by wvbass

Essential Sound Products MusicCord Pro...

Well of course we could bring up the fact that you should never run an amp through a power conditioner, and that the ESP cord is pure unadulterated snake-oil, but that's not going to help the OP.
Power might have been an issue. I've heard of some amps not being happy with under-voltage, and under-voltage is common with outdoor gigs. I'd just try the amp under normal conditions and if it works OK I wouldn't worry about it.

[metro_area]

Tell me more! I've not heard anything about not running an amp through a power conditioner. I would actually like to hear more about that.

As far as the ESP, I got it for free because this SVT didn't have a power cord when I bought it. Snake oil or not, it's been the only power cord I've ever used with this head, so it's not the independent variable here.

rickdog, my power was coming from an outdoor wall outlet, and was the only thing plugged into the outlet (not sharing with anyone else). I had a 10-12 basic orange extension cord running to the Samson power conditioner, which my head was plugged into. I always run it through there, so I'm guessing the extension cord was the issue?

[okcrum]

The VR fix is not applicable to the CL. You'll need to figure out which if any output tubes are bad, and also find any other failed components, before you can construct a failure scenario. Until then it's all guessing.

An output tube overcurrent is what normally trips the fault relay in the CL.

[billfitzmaurice]

Originally Posted by metro_area

Tell me more! I've not heard anything about not running an amp through a power conditioner. I would actually like to hear more about that.

It gets beaten to death here on a regular basis. Power conditioners can starve amps for current, and well made amps don't get any benefit from them.

my power was coming from an outdoor wall outlet, and was the only thing plugged into the outlet (not sharing with anyone else). I had a 10-12 basic orange extension cord running to the Samson power conditioner, which my head was plugged into. I always run it through there, so I'm guessing the extension cord was the issue?

The wire feeding that outlet could also be feeding a dozen other outlets, with who knows what plugged into them. As for your extension cord, that's only the tip of the iceberg, who knows how many more feet of wire lay between the outlet and the breaker box powering it. Then there's the matter of your needing to use four times the power outdoors to achieve the same perceived volume as indoors. Add up all the little bits and you probably end up with the reason for your problems.

[metro_area]

Originally Posted by billfitzmaurice

It gets beaten to death here on a regular basis. Power conditioners can starve amps for current, and well made amps don't get any benefit from them.

Thanks for the heads up, I'll look into it.

Originally Posted by billfitzmaurice

The wire feeding that outlet could also be feeding a dozen other outlets, with who knows what plugged into them. As for your extension cord, that's only the tip of the iceberg, who knows how many more feet of wire lay between the outlet and the breaker box powering it. Then there's the matter of your needing to use four times the power outdoors to achieve the same perceived volume as indoors. Add up all the little bits and you probably end up with the reason for your problems.

Also good to know. The entire head was re-tubed three months ago with EHX 6550s and GT preamp tubes, and had been running perfectly on them up until this incident. I'd have to guess it was the questionable/crap power source that was the cause for all my issues. Would I have been better served to use a 20ft nice gauge extension cord and plug into the outlet nearest the breaker box?

But is this an overkill protective feature that Ampeg created, or is this legitimately just 'how the amp works'? Other guys who have had power fault issues with their SVTs have done some mods to override Ampeg's stock circuit to keep it from shutting down in situations like this. Is this something I can do? Or is this a different scenario than those the JohnK mod is based on?

[Bassmec]

Originally Posted by metro_area

Thanks for the heads up, I'll look into it.



Also good to know. The entire head was re-tubed three months ago with EHX 6550s and GT preamp tubes, and had been running perfectly on them up until this incident. I'd have to guess it was the questionable/crap power source that was the cause for all my issues. Would I have been better served to use a 20ft nice gauge extension cord and plug into the outlet nearest the breaker box?

But is this an overkill protective feature that Ampeg created, or is this legitimately just 'how the amp works'? Other guys who have had power fault issues with their SVTs have done some mods to override Ampeg's stock circuit to keep it from shutting down in situations like this. Is this something I can do? Or is this a different scenario than those the JohnK mod is based on?

What damage can be done to a newer ampeg svt that protection against under voltage, protects against.
It must be something to do with the idiot light based bias system.
Its quite common in studio to use a variac to reduce voltage on an all tube amp, thus providing earlier onset of distortion.