BXR300R Noisy Cooling Fan

bonedaddio · #1 03-12-2013, 05:19 PM

Hi all, recently bought a BXR300R head and a SWR 4x10T cab for $200.00. After cleaning up the head, deoxiting the pots and switches, I have a decent sounding rig for cheap...

EXCEPT the cooling fan is noisy and I would assume it's on the way out. I'm shade tree engineer and I'm sure I can rig something up to cool this with, but anybody have an idea where to look for a replacement part?? Will my next adventure be trying to rebuild a freakin fan??!!

Thanks

craig.p · #2 03-12-2013, 05:24 PM

Lotsa places. Mouser, Allied, Digi-Key, Jameco . . .

bonedaddio · #3 03-14-2013, 07:17 AM

It's an amp from the 1990's, so I'm thinking that it might be a little hard to find that particular fan.... but if I can determine manufacturer and model, I may get lucky.

I guess I'll take it apart and see what info I can find on the fan... any resources for a schematic for this beast??

Thanks

wcoffey81 · #4 03-14-2013, 07:35 AM

i doubt if you will find the schematic. look for any markings or decals on the fan its self. fan size, rpm and voltage are the big three and add the number of leads to the equation. if you have any soldering experience at all it should be a fairly easy swap out.

bonedaddio · #5 03-14-2013, 07:28 PM

Thanks for the replies, gents.
Yes, I've repaired pcbs, replace/repaired/modded stuff in the past, so I'm not as concerned about that part as I am about finding an appropriate replacement part.

BassmanPaul · #6 03-15-2013, 11:02 AM

A new fan requires that you replace the old one with one of identical specs. RPM is unimportant, it's the amount of air the fan can move, CFM, that matters. You also need to match the voltage and current draw.

bonedaddio · #7 03-15-2013, 05:43 PM

I guess it also will matter that this is a two-speed fan, with a higher speed kicking in when things get internally hot.
Thanks again all. I appreciate it.

BassmanPaul · #8 03-15-2013, 05:47 PM

Quote:

Originally Posted by bonedaddio

I guess it also will matter that this is a two-speed fan, with a higher speed kicking in when things get internally hot.
Thanks again all. I appreciate it.

That's why the current draw is important. You don't want to burn out the fan controller.

B-string · #9 03-15-2013, 06:11 PM

I highly doubt it will be a two speed fan. I have NEVER seen a small fan with 2 speed winding. The amp's fan control circuit controls the fan's speed by the voltage sent to the fan.

bonedaddio · #10 03-15-2013, 08:42 PM

Thanks, BassMan Paul, and B-String, (B, that is probably my bad. I'll post tomorrow when I have it apart again and can do some research re: what's in it, and leads and voltages).

I did have it apart for pot and switch and general cleaning (at which time I thought the fan got a lot quieter... but it still sounded bad when I had it back together). I have a vague memory of the fan having more than two leads and OF COURSE I DID NOT get the info off the fan which had labels and mfg. info on it. Sigh.

B-string · #11 03-15-2013, 08:49 PM

I just want to make the point clear for anyone who has a fan in their head that is controlled speed.

Very possible with the amp opened up the free air flow was not placing as much load on the fan. If it has a label it should be no trouble to locate a replacement.

bonedaddio · #12 03-16-2013, 12:41 PM

Good point, fan "under load" in closed box could be noisier.
B-String, right you are, two leads, it's an 110v AC fan. After some digging, found the same model on ebay which I'm getting in next week. Hopefully this will have OK bearings, and that will be it.

The BXR300R really is a great old amp head; the degree of tone shaping and the raw power of it (and it's made in USA with pretty good parts) are really good.

Thanks guys

Hactar · #13 03-16-2013, 12:59 PM

Interestingly enough, the manual says that the BXR300R/C fan does in fact have two speeds. It appears to be throttled by a resistor that is bypassed by a temp sensor when temp > 200ºF

Schematic:
http://music-electronics-forum.com/a...702-bxr300.gif

Appears to be redrawn from this:
http://guitarwork.ru/electronic/firm...plifier%20.gif

B-string · #14 03-16-2013, 01:28 PM

Quote:

Originally Posted by Hactar

Interestingly enough, the manual says that the BXR300R/C fan does in fact have two speeds. It appears to be throttled by a resistor that is bypassed by a temp sensor when temp > 200ºF

Schematic:
http://music-electronics-forum.com/a...702-bxr300.gif

Appears to be redrawn from this:
http://guitarwork.ru/electronic/firm...plifier%20.gif

The fan is single speed (note only one pair of wires/winding). The dropping resistor lowers the voltage to the fan to lower the fan's rpm. To some that may sound like splitting hairs? To someone looking for a replacement it becomes a BIG difference!

bonedaddio · #15 03-16-2013, 05:07 PM

Thanks so much, now I have a schematic to use!
I never thought this was splitting hairs, I got the two-speed idea from the PDF manual which was all I could find. Great to know how it works, and to be able to do further repairs, mods as needed. I will have the replacement fan this coming week. I can only hope it isn't noisy, in which case I'll send it back and maybe look at a replacement mod. I did eventually also find a good PDF spec sheet for the fan, so I have all the info re: CFM, RPM, etc.
This stock fan is a really nice heavy duty unit, I'm hoping the new (used) one will work.

Thanks again guys! This is an awesome forum!

Hactar · #16 03-16-2013, 11:41 PM

Quote:

Originally Posted by B-string

The fan is single speed (note only one pair of wires/winding). The dropping resistor lowers the voltage to the fan to lower the fan's rpm. To some that may sound like splitting hairs? To someone looking for a replacement it becomes a BIG difference!

I guess I could have been more clear that the fan is in fact a single-speed, but run at two speeds.