SVT 4 Pro Excessive Overheating

Headbanger1203 · #1 03-12-2011, 01:29 PM

I have read through threads about the amp overheating, but I was curious if the interior fan is supposed to be running all the time.

Mine has recently been cutting out when practicing for 20-30 mins at loud volume despite having a fan sitting behind it. Every time it cuts out, I can hear the interior fan cut on for about 15-30 seconds, which doesn't make a lot of sense to me. I removed it from my rack, put it on the floor with the top removed and ran two fans over it to double check and make sure it was cutting out because of overheating. I was able to play at constant loud volume without it cutting out, so I'm thinking maybe I need to replace the fan? It seems to me like it should be running more than just a short period of time everytime the thermal shutdown circuit shuts the amp off. Any help would be greatly appreciated!

DanRJBrasil · #2 03-12-2011, 02:20 PM

what kind of rack are you using?
the 4 pro has vents on the sides so if you are using a small skb or gator type of rack you are looking for trouble

xXColaXx · #3 03-12-2011, 02:22 PM

Quote:

Originally Posted by DanRJBrasil

what kind of rack are you using?
the 4 pro has vents on the sides so if you are using a small skb or gator type of rack you are looking for trouble

+1

If the intake vents are blocked then there is no air going through and whether the fan is spinning or not you are going to overheat.

Headbanger1203 · #4 03-12-2011, 02:38 PM

Ya I am using an skb rack which is why I took it out and took the top off. I just realized I left out a sentence earlier, it did cut out after about 40 mins outside the rack but only once at the end of practice last night. I felt the heat sinks and they were very hot despite the fan I had hanging above it blowing down into it.

It seems to have the symptoms of the thermal shutdown circuit I've read about, and that's why I was wondering about the interior fan and how it seems to only run when it cuts out and then for only 30 seconds at most. Does anyone know if it's supposed to run constantly, or at least a bit more than it is running?

Thanks for the replies!

DanRJBrasil · #5 03-12-2011, 02:52 PM

The fans work and get fast as the unit gets warm, you may experience overheat if you let the head with the top removed as the fans are put in a way to circulate the air inside of the head with the lid shut, if not this is tech time,

xXColaXx · #6 03-12-2011, 03:38 PM

Maybe put some new thermal paste on the heat sinks. The overheating could have caused it to melt a bit and cause separation so it isn't dissipating the heat correctly even though they are heating up.

Without having the amp in front of me, that's my best guess as something to do. be sure the van you are having blowing onto it is going to the intake vents and not the "exhaust" so it gets proper air circulation. The intake vents are placed where they are for that reason.

Jerrold Tiers · #7 03-12-2011, 05:26 PM

The fan should run at a low speed all the time.

When the unit begins to get hot, the fan should speed up gradually, stopping at the speed necessary to keep the unit cool enough.

if you have thermal cutout, sound will stop, and fans should be at maximum already, so no additional change.

Yes, with top off, cooling is a lot WORSE.

Yes, heatsinks will get very hot, hot enough to burn/scald you, much hotter than you can touch. The transistors are OK at that sort of temperature.

The fan circuit is quite simple, and works well. But if the wrong fan has been replaced in the unit, or if there is a problem, it may not work right. The right fan for a US model is a Rotron brand fan, I forget the number but can probably look it up.

Your problem may be that the fan does not run unless rather hot. That is wrong, it should be moving air all the time.

The outputs do not use thermal paste, but a special type insulator pad. In any case that would not affect this problem.

ButtUglyJeff · #8 03-12-2011, 05:37 PM

How old is your amp? I'm wondering how much dust build up you have inside, and if your fan is getting covered.

Headbanger1203 · #9 03-12-2011, 06:38 PM

Jerrold Teirs: It actually lasted a lot longer with the top off, but I think that's because the fan never runs until the unit already overheated. It doesn't move at all, the sound stops, then it speeds up to full blast for a bit. My buddy and I were thinking from the beginning that the fan wasn't working correctly, maybe replacing it will fix the problem? Because it definitely does not run constantly, far from it.

Jeff: I bought it back in '06 I believe, brand new.

Thank you guys for your help.

Jerrold Tiers · #10 03-12-2011, 08:30 PM

Maybe, maybe not....

if the fan is not a "Rotron" type, it might not start at the proper voltage, and might not run until too late.

if teh fan drive has a problem, it might not work right.

or, maybe the temp shutdown circuit is not right, and is shutting down early. Since we know the fan doesn't go, it's fairly unlikely, that would be two separate problems...... normally there is just one. But it "could" be.