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Ampeg SVT 3 Pro Fan Noise !!

Hawkeye

Hawkeye

Canuck Amateur
Aug 8, 2002
1,533
124
North of GTA, ON, Canada
Disclosures
Long & McQuade Sales Employee
#1
I just received my used Ampeg SVT III Pro head. It looks like it's a couple of years old.

I was surprised at how loud the exhaust fan is on this thing. I got my trusty Radio Shack SPL meter out and it measured 62db at the back of the unit.

Is this normal? It sounds like a Sopwith Camel about to take off.

The Ampeg website says:

"Pro Series heads are built for the long haul. The units remain cool with variable speed fans that only turn as the temperature dictates."

The fan on mine is on all the time. Sounds like something is wrong, OR is there an adjustment somewhere I've missed.

I haven't popped the top on it yet but is this fan easily replaceable with a whisper unit like in computers?

I was going to use the head in my church praise and worship band, but it's a no-go at this point with that racket.

Thanks,
 
#2
I just used my SVT 3Pro tonight at rehearsal and I didn't notice the fan noise at all. My band is a CCM praise and worship band and I run my volume at about 11 o'clock and the gain about 1 o'clock. I've never heard it kick in during rehearsal but I hear it when I practice alone, but it's still not that loud.

Have you checked for dust build up inside the head and on the fan? Even if you hear the fan I doubt anyone in the congregation would hear it.
 
#3
Hi there Megiddo. Thanks for the response. I think the unit I bought came from a studio. It was rack mounted and beat up a bit, and was probably left on all the time and fried the temp sensor making the fan work constantly. I should probably look at the tubes too.

From your experience it sounds like I should have the unit checked out. It's not what I expected from the sellers' description of "absolutely mint condition". Caveat Emptor.

The way this thing is droning on I think the congregation actually would hear it, it's that noticeable. I don't know if you know what 62db is but the whisper fans used in computers are about 22-24db. 60 - 70db is the approximate level of road noise at highway speed when you're in your car.

Not the best way to start out with a new amp, but serves me right for buying online.
 
#4
It's a great amp, I use one in church every Sunday. I use mine at 8 ohm load so it has an easy life in church, I never hear the fan come on. I would find a tech that knows that amp and have it looked at before I used it much. It's possible that the fan is running because it's actually too hot, I would not assume that it's the fan itself that's at fault.

I do like that amp, I have two of them.

Mike
 
#6
Eldermike said:
It's a great amp, I use one in church every Sunday. I use mine at 8 ohm load so it has an easy life in church, I never hear the fan come on. I would find a tech that knows that amp and have it looked at before I used it much. It's possible that the fan is running because it's actually too hot, I would not assume that it's the fan itself that's at fault.

I do like that amp, I have two of them.

Mike
Click to expand...

Excellent point. The symptom may not in fact be the disease. I know it doesn't FEEL hot, but that doesn't mean that some part of the chassis isn't. I appreciate it.

I'm enjoying these good suggestions.
 
#8
The fan is indeed temperature controlled on the 3PRO.

If it is running at high speed all the time, then either

1) the unit is hot

2) the fan driver has a loose connection or other problem

If the unit is hot, you would definitely notice that at the rear-panel exhaust vent. If you don't notice that, then it looks like #2.

Due to the way the 3PRO fan is set up, a problem with the fan driver might give the fan a higher than normal voltage, which could cause it to sound like it wanted to take off.

How old is the unit?
 
#9
Personally, I commend Ampeg for keeping an eye on these forums. Getting factual information directly from the manufacturer is very helpful to us, and I'm sure that our feedback to them helps greatly with their new product development and product improvement programs. It is a win/win situation.
 
#10
Ampeg Insider said:
The fan is indeed temperature controlled on the 3PRO.

If it is running at high speed all the time, then either

1) the unit is hot

2) the fan driver has a loose connection or other problem

If the unit is hot, you would definitely notice that at the rear-panel exhaust vent. If you don't notice that, then it looks like #2.

Due to the way the 3PRO fan is set up, a problem with the fan driver might give the fan a higher than normal voltage, which could cause it to sound like it wanted to take off.

How old is the unit?
Click to expand...

I appreciate your post AI, and your thoughtful response. Thanks for monitoring the forum for Ampeg questions. I've noticed in some other posts that you have been very helpful and forthcoming with good tech information on Ampeg gear.

The question re age of amp is a good one and an answer has yet to be forthcoming from the somewhat reticent Ebay seller. It looks a couple of years old.

I'm going to phone one of the local Ampeg dealers and inquire re service. I'm a bit miffed at having to do this with an amplifier that was described as being "absolutely mint condition". Harrummpphh! Serves me right for buying online.

It's times like these that you appreciate the support and service that is offered by bricks and mortar dealers.
 
#12
You can get the age yourself...from the serial number.

Look at the serial number 5th and 6th position.

The system started in 1988, which is year "A". So 1989 is "B", etc.

If that were only 2 years old, it would be coded for 2002, which would be an "O" in the 5th position.

The sixth position is the month, 1-9, 0, A, and B.

So "O5" would be May 2002, for instance.

Since you actually have the unit, you can look and see what year and month it was made.

The warranty would have started when it was sold. But obviously if it is less than 5 years old, sale date isn't important.......
 
#13
Thanks again AI. Serial # is BDVDM60067, "M6" makes it June 2000 right? Knowledge is power they say.

Seller says he doesn't have the original sales receipt. I assumed that it was necessary to have that for warranty work to be authorized.

Question: Would Ampeg authorize warranty work (assuming that the issue was deemed to be a factory defect and not misuse) based on the fact that the manufacture date (serial #) indicated it was obviously within the factory warranty period?
 
#15
The SVT-3 PRO uses a Comair Rotron Sprint DC ST24A3 for the fan
(at least mine does). This can be found at the [Invalid or Expired Link Removed].
It uses sleeve bearings (cheap).

However, it appears that there is a fan equivalent to the Sprint DC
ST24A3 but with ball bearings. That fan would be the [Invalid or Expired Link Removed].

And it appears that Invalid Link Removed for $39.58 (versus $21 for sleeve bearing version).

I haven't tried this myself but it sure looks like a better-than-original
drop-in replacement to me. Maybe one of you guys with a noisy fan
wants to try this out.

My SVT-3 PRO fan is a little noisy but you definitely can't hear it when
I'm playing. :p If I ever replace the fan, I will try the ball bearing version.
 
#16
i have the st24b3 fan in my svt3 and it is still relatively noisy.
the reason is in the design.
if you remove the fan attachment screws,then switch on with the fan isolated from the metal cabinet,the fan is fine.as soon as it makes contact with the metal brackets it gets loud as the sound and vibration reverberate.
if you can isolate the connection points this will help using e.g. rubber
maybe a case lined with sound absorbing material would help(dont impede air inlets or outlets)
it can be annoying at low sound levels
 
#17
We actually did NOT choose the fan with sleeve bearings to be cheap...... You seem to have discovered the reason, though.....

The ball bearings are NOISY. They tend to rattle and they transmit the rattling through the chassis. It is nasty.

We picked the sleeve bearings for their quiet operation..... Quiet at lower speed, at least. But the particular fan actually is fairly quiet even at full speed... Other fans that move the same amount of air sound like a Learjet....complete with the whistling whine.

Any temp-controlled fan that is running fast and loud at idle is evidence of a problem. Either the amp really IS hot, possibly from dust, etc, on the heatsink, or the fan circuit has a problem.

Either one should be fixed.
 
#18
Here is my solution:
IMG_9811.JPG
IMG_9815.jpg
 
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#19
just got a 1995 blue logo svt3 pro and fan was noisy...found that raising fan up helps.....little angle brackets and fan were touching bottom of case...so i filed off just a little from the bottom edge of the bracket...mounted them back on to fan pushed down so fan sits higher off the case ...make sure top bolts go in to holes and brackets screw hples are aligned...remove fan and tightened bottom bolts..replace fan tighten the bracket screws then top bolts...it did help
 

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