Ampeg SVT 4 pro - problem, or normal?

twssbassman · #1 01-23-2013, 08:40 PM

I got a used SVT 4 Pro recently. When I first power it on, the low end is weak. After some time, it kicks in and all is well. At first, it took a few minutes (10-15). Lately, it's taking longer and longer (20-30 minutes). In the owners manual under "Thermal Considerations" it says "When the amplifier is first turned on, the fan runs at a low speed. AS THE POWER OUTPUT INCREASES AND THE AMP WARMS UP, the fan gradually increases in speed..." (the emphasis is mine).

So, is 20+ minutes for the amp to warm up and deliver full power normal, or does my unit have a problem? Could it be a tube going bad? Am I in danger of it failing completely sometime soon (like in the middle of my gig tomorrow night)?

Thanks for any/all help!

**Bass 45** · #2 01-23-2013, 08:43 PM

Mine never acted like that. It sounds like it needs to be checked out. Hopefully you are covered by a warranty.

chaosMK · #3 01-23-2013, 09:43 PM

I've known a few all-tube amps to flavor up a bit over a period of time like that, but your SVT-4 should be 100% within the first 10 seconds. Transformer issue?

BoogerHook · #4 01-23-2013, 09:50 PM

Quote:

Originally Posted by Bass 45

Mine never acted like that. It sounds like it needs to be checked out. Hopefully you are covered by a warranty.

Even when dealing with warranty products Loud Technologies wants to know much info about the amp before they cover it. I had problems when I told them I wasn't the original owner of the unit (SVT-4 Pro). Just an FYI.

**sleevey55** · #5 01-23-2013, 09:55 PM

Thats NOT at all normal. Sorry bud...

Jawbone · #6 01-23-2013, 10:32 PM

Mine whines a little after about 12-18 seconds but it comes to full power in easily 22 seconds. I timed it after I read your post - no minutes needed.

**Bass 45** · #7 01-24-2013, 12:05 AM

Quote:

Originally Posted by BoogerHook

Even when dealing with warranty products Loud Technologies wants to know much info about the amp before they cover it. I had problems when I told them I wasn't the original owner of the unit (SVT-4 Pro). Just an FYI.

I believe the Ampeg warranties are no longer transferable. For a while, they were 5 years no matter who owned it and you could be covered simply by the date coded serial number (no proof of purchase).

I got real lucky with my SVT-4. I bought it as a B-Stock for like 1/2 price. When I received it, one of the power sections was not working. I called Ampeg and told them of the issue and they sent me a brand new one to my house within three days. They just asked me to put the defective unit in the package the replacement came in and they supplied a return label. That replacement performed flawlessly for five years in a very busy working band I was in.

If you get a good one, the SVT-4 is a fabulous piece of equipment.

twssbassman · #8 01-24-2013, 10:41 AM

Thanks all. So, definitely an issue. I get the same behavior whether in stereo, one side mono (either side), mono bridged, or biamp mode, so I'm thinking it's in the preamp. FWIW, with the lid off when I power it on from cold all 3 tubes do glow right away. I'm thinking I'll pick up some new tubes, but this is my first go at tube replacement. I'm seeing references to GENERIC, PRIMO, and ULTRA tube sets. Any way to tell what I've got currently? Any real difference between these types in reliability or tone, or is it just marketing? Ampeg tech support said they can be swapped out with no calibration/bias adjustment. Anything else to watch out for? I need a clue fast. Happy to read up if you can point me to where to read.

Jawbone - I get that same initial whir/whine, too. Pretty sure that's the fan kicking in at low speed at startup. I think that behavior is normal, not related to my issue.

Again, thanks for any/all help!

B-string · #9 01-24-2013, 10:56 AM

Pull as straight up as you can when removing the tubes, a very small circular rocking motion can be used. Line up the pins on the new tube to the socket (there will be a space with no pins to locate the position). Push the new tube straight down till it fully seats in the socket (again a very slight rocking may be needed but avoid if you can). "Tube sets" sold often include things like section matching on preamp tubes and are a waste of cash for instrument amp use. As long as the tubes are good quality (as good as new production tubes could be) premium matching is a waste. If a low noise testing is offered that can be easier to get a replacement if one or more winds up noisy.

twssbassman · #10 01-28-2013, 06:33 PM

Update: I replaced the tubes last Thursday (thanks B-string for the timely advice!) and now all is well. I get full power from startup. Had to rework my settings a little to find my tones again, all part of the fun. Replaced a Fender Groove Tube in slot 1 and 2 Sovteks with another GT and 2 JJ's, all Russian. I saw a refernce to having a GT in slot 1 on an ampeg faq, and that's what I found when I opened it, so that's what I put back. The GT cost a little more than the others. Does it really make any difference in power or tone? If I have time, I'll experiment with swapping them around, but maybe someone else already has?

B-string · #11 01-28-2013, 06:43 PM

Excellent! Glad you are back in the thunder.

BasturdBlaster · #12 02-02-2013, 10:12 AM

I have a 4-pro and mine acts the same as decribed in the 1st post, I guess I should try some new tubes as well.

Jerrold Tiers · #13 02-02-2013, 07:48 PM

Quote:

Originally Posted by twssbassman

I saw a refernce to having a GT in slot 1 on an ampeg faq, and that's what I found when I opened it, so that's what I put back. The GT cost a little more than the others. Does it really make any difference in power or tone? If I have time, I'll experiment with swapping them around, but maybe someone else already has?

It's really more about NOT getting a noisy tube there..........

twssbassman · #14 02-02-2013, 08:38 PM

Ah. Thanks for explaining!