Ampeg B2R - fan...or not??

[Blenin]

Picked up a late 90's USA made B2R, sounds great, but I noticed the fan is not on. I have run it for nearly an hour and still not on......well??

[kosmicwizard]

I am not a fan ... LOL. Sorry I just had to. Is it hot to the touch? I found I had to really push my B4r before the fan would come on, but it always did once I got it warm/hot to the touch. If your head is hot and the fan doesn't come on, go get it repaired. Cheers.

[Blenin]

It's hot on top, but not terribly. Maybe I'll leave it on over the next couple hours and just see what happens.

[audiomitch]

I picked up the same head, a '98 SLM B2R, and the fan was always on. Not just on, but blasting at full speed. I replaced the fan and now it's on high for about 3 minutes when I first flip it on, then it slows down. But it never stops completely.

Here's my thread on it -

Ampeg B2R fan question

Hope there's something in there that helps.

[Blenin]

Got mine on now to test it. Had it on for about an hour earlier, was heating up but the fan never came on.

[Inconnu]

I used to have a B2 combo. The fan was always on... and pretty noisy. You bought the B2r used... maybe the original owner got annoyed by the fan and simply disconnected it. Have you checked?

[Jerrold Tiers]

it should be on, but low speed, just wafting air through. When it gets hot, the fan should speed up.

If the fan is not on at all, then either it is wrong, bad, disconnected, or the fan circuit is messed up.

There are only about 7 parts in the fan drive, so it is pretty reliable. and the low speed is set by resistors in series.

My bets are on wrong/bad/disconnected.

With any of the Ampeg fan variable speed circuits, the fan must be capable of running at reduced speed. Quite a few fans can, but if the fan is replaced with one that does not, it may not come on until the amp is stinkin hot..... which is bad.

[impactwrench]

I had a B-2R from around 2002 or so. I am pretty sure the fan ran full time. I thought my first GK head (that replaced the B-2R) was so quiet because the fan only came on as needed.

[Daveydude]

I just sold one.....
The fan ran all the time. It sounded like a weedeater

[Jerrold Tiers]

Not saying it didn't, but if id did, something was wrong.

Wrong fan, bad drive circuit, whatever.

[5not4]

I've got an SLM version that worked great until some solder joint issues. Took it in for repair and the tech said he also adjusted/modified the resistor on the fan circuit to have it run a bit more at the lower power levels.

I don't recall the fan ever being on before and the amp did run a bit warm. However, the fan is very quiet now so I would suggest looking into that area for sure.

Good luck.

[Blenin]

Okay, so I took it in and they couldn't get the fan to work. I was told not to worry about it and it should be fine without.....does that sound correct??

[Jerrold Tiers]

Not if it never runs..... we didn't put it in for looks, you know......

You only need it if the unit could otherwise overheat, but it is expected that is the case.... i.e. you could overheat the amp if the fan were not there/not running.

There are so few parts in there, that it seems the fan ought to work easily, unless the fan drive is bad or the fan has been replaced with one that is way different.

If teh fan drive is bad, watch out. The fan drive comes from the same over-temp sensor device that senses heatsink temp and shuts down if the temp gets too high. There is a chance the over-temp may not be working either, in which case you could cook the amp into a failure with no protection.

[Blenin]

Thanks Jerrold, that's what i needed to know. Thought about getting a clip on fan for it and just attaching it to the back, but my gut feeling is that this isn't gonna work out.