HELP ON MY AMP!

timenbacker · Post by **timenbacker** » Sat Nov 06, 2004 4:05 am

guys:

Last night my SWR Workingman's 400 watt amp was cutting in and out on me in my second set. I was only running at at about at 65%-70% of power, but it got REAL hot (and the compressor I had under it). This happened to me twice before, but not since March. can heat do this? Is this indicate a problem with my amp?? I'm wondering whether I need to get rid of this and buy another. Thoughts? Help? I was frantic!

timenbacker · Post by **timenbacker** » Sat Nov 06, 2004 4:21 am

I didn't put the complete model number it's a 4004.

Do you think merely hooking up an external fan blowing in the back would help? or do I have a larger problem?

This is really disconcerting - the model has such high reliability ratings.

I had no problems in the last set, as I turned it off after the second set. but gosh..to be playing and have the sound cut out for 4-5 seconds? it was making me panic.

incubus2432 · Post by **incubus2432** » Sat Nov 06, 2004 4:30 am

My opinion would be that your amp is doing what it should....shutting off when the thermal load gets too high. I'm not familiar with the head but if it has a fan check to make sure it is working properly and that it is unobstructed. From your description it sounds as though it is rack mounted so make sure there is room above the head in the rack for it to vent heat (if it is doesn't have a fan and has "vent slots" on it's top). By saying that you are running it 65%-70% of it's power do you mean that that is the position of the master volume? If that is the case I would recommend getting a more powerful amp since I think if you have the master that high you are pushing the amp a little hard....hence the overheating. I am no expert JMO. Example....I have 1000 watts feeding three cabinets with my preamp master set at about 30% and my amp (with output peak voltage LED's) is running at about 75% power on average....so if my master was at 60%-75% I'd be asking too much of my amp.

Hooking up a fan might help but if there is no where for the heat to vent out it may not help much.

timenbacker · Post by **timenbacker** » Sat Nov 06, 2004 4:56 am

no, it has no internal fan.

yes, I meant the master volume was at about 65% and the gain at about 55%

ojobob2 · Post by **ojobob2** » Sat Nov 06, 2004 5:10 am

No fan? that is unusual Tim

hmm my ashdown 180w head and trace elliot 150w combo both have proper fans in them.

And this is a 400w amp?

timenbacker · Post by **timenbacker** » Sat Nov 06, 2004 5:12 am

yup. Apparently SWR added a fan in the 4004S version, but no internal fan on this. There are sort of grates that stick out the back. Got REAL hot.

incubus2432 · Post by **incubus2432** » Sat Nov 06, 2004 5:28 am

That's a heat sink. They should get hot since their job is to "absorb" heat and dissipate it externally. A fan blowing across them may help some but there is still the issue of why the amp is getting so hot that the thermal cutoff trips. I'd spend a few bucks and have an amp shop take a look at it (or get it checked under warranty if it still applies) and if it comes back as OK then I'd start amp shopping because I think it may be time to upgrade.

jwr2 · Post by **jwr2** » Sat Nov 06, 2004 5:40 am

I had a similar problem with an ampeg ... I sent it in for repairs twice ... I replaced the fan ... it still malfunctioned ...

the problem was the $5 on off switch ...

atomic_punk · Post by **atomic_punk** » Sat Nov 06, 2004 6:52 am

I would have it looked at also. A fan might help, but something like this is something you dont want to mess with on stage. I had an Ampeg that had "reliability issues", and out it went. You just can't take that chance onstage. It might be something simple, but to risk blowing it outright by overheating it would be a bummer.
A fan in the back would be helpful, I used to have a power amp that would do this, put a clip-on fan on the back of the rig, no worries. But I can't guarantee this is what is wrong with your rig.

jnbass · Post by **jnbass** » Sat Nov 06, 2004 8:05 am

the position on he vol/gain knob does not really indicate how hard the amp is running. it needs to be set on a bench and given diagnostics.

better to start looking for another amp or a slave if you like the SWR's front end.

jblakey · Post by **jblakey** » Sat Nov 06, 2004 9:39 am

I would pull it out of the rack.. and rule out your other components.. you say the compressor was hot too.. You'd want to make sure that your compressor is not malfunctioning and heating the amp into shutdown. Disconnect all other components and try it out, then add them into the line one at a time. I had a similar disaster that had me panicked and shopping last year but it turned out to be an eq with problems.

timenbacker · Post by **timenbacker** » Sat Nov 06, 2004 11:07 am

is that possible? If I purchased, say another 300W amp, could I hook them together and would this take the pressure off my SWR? I didn't realize that was possible.

jnbass · Post by **jnbass** » Sat Nov 06, 2004 11:34 am

see if the SWR has a preamp out.

gbenner · Post by **gbenner** » Sat Nov 06, 2004 11:48 am

I also have been wondering about this. Do you use the preamp out of the lower powered amp to the preamp in of the higher powered amp?

jnbass · Post by **jnbass** » Sat Nov 06, 2004 11:56 am

in most set-ups the preamp out goes to a slave, a poweramp with no tone shaping.

the old daisy chain was made popular by a guy named hendrix...