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Outboard cooling fan for SWR Studio 220 ?? |c: ??

Chad Michael

Chad Michael

Sep 19, 2001
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Pacific Northwest USA
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#1
Just picked up an SWR Studio 220, very happy with the amp so far.

Was just contacted by some former band mates, they want to gig again, and that is potentially a very good thing. However: I bought the 220 thinking it would be a nice home practice head, and with the preamp out - add a healthy (fan cooled) power amp for gigs...

Now I'm wondering if I could run it as a stand - alone for band practice, or 'coffee house' stuff? Really like the 220, just don't want to cook it by pushing it over the top.

Hence the title - does anyone know of a small 120v. fan that could blow air through the chassis? (something that would fit above or below the chassis, inside a rack case)
 
#3
Thanks for the link. Have purchased a 5" or so 120v. box fan.

Moves a ton of air, but makes a ton of noise... thinking of adding a speed control, something small and simple that is compatible with the fan.
box fan.png
tjernlund fan speed.png
 
#6
I have owned a 220 since 1990. Unless something sounds horribly wrong, you don’t need to get it biased. You don’t even need a fan. What you DO need to do is insure that there is adequate airflow (some space) on both the bottom and top of the amp. I leave a half rack worth of space underneath (amp rests on wood shims, a little more than a half inch) and the rest of a four space rack on top. I usually run it with an 8 ohm 4x10 and have done plenty of very loud gigs with no issues. It gets warm. What you don’t want to do is run it up where the power amp clip light (over the master volume) is coming on a lot.

Sometimes I run it with 2 15s and then...look out! Thunder on stage.

My SM400 is essentially two of the 220 power sections bridged together, and that amp does require a fan (I use a 6” clip on in the back of the rack) and with that amp, if it gets hot (and it can get REALLY hot) then it’s worth taking to a tech to bias it, but you shouldn’t have to do that more than once. It’s not anything like a tube amp where the power section is constantly changing as the components age.

FWIW, I gigged my 220 outdoors last week. I usually use an MB500 but make a point to take the 220 out every couple of months. And the 220, well, let’s just say I don’t bother bringing a backup. Can’t say that about the GK.
 
#10
First thing, verify that you have 4 of the 0.1 ohm, 5 watt resistors on the power amp PCB. Don't change anything yet. The most common power amp PCB is #170002 (maybe with an A or B). There MAY be a different board in your amp if it was repairs with an updated module.
 
#12
arbiterusa said:
Oh goody. I’m taking notes. Thanks agedhorse!
Click to expand...
I'm being careful because there are possible versions that I may not be aware of. That original module had a series of revisions all the way through the Fender era. There are significant differences. Also, on at least the earlier versions, an intermittent bias pot can result in destructive bias levels so there is always some risk. I don't recall if later revisions changed this or not.
 

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