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Behringer EPQ1200 My Impressions/Need Help (Thermal Runaway?)

6K views 2 replies 3 participants last post by  Lucky7! 
#1 ·
Hi everyone,

I purchased a Behringer EPQ1200 recently and I think it's going into thermal runaway after a fan swap.
I would like to ask for your insightsas well as offer my impressions. I'm hoping someone else might also have an EPQ or a similar experience.

I apologize for the long post. I've sectioned it up to help :)


Why EPQ?

I've looked at multiple solutions and went with the EPQ for several reasons:
  • VERY cost-effective (main reason actually :p), especially since RCA/XLR adapters and Speakon cables are not necessary due to the existing RCA jacks and regular speaker terminals :spend:
  • small size fits on my rack
  • 425W RMS/600W Peak is plenty for my needs
The not so secret plan is to power a pair of sealed Shiva-X subwoofers :bigsmile: (yet to be built :doh:)


My Impressions

I picked up the amp a few days ago and I must say, the fit and finish is excellent. From the good looking metallic silver faceplate to the rubberized feel of the knobs - it exceeded my expectations in this regard :)

I have them hooked up to my main (and only) system, a pair of Ascend Sierra-1s, to do my testing.
In terms of sound, I haven't had time to do extended/detailed listening yet. Nevertheless, compared to my gainclone and TA3020, it doesn't miss a beat. It does sound different from both of these amps. I haven't done any A/B listening, so I'll reserve my comments in this regard. I will say that it indeed sounds very good overall, especially considering the cost and the number of watts available.


The Internal Layout

Despite the fact that Behringer claims back to front airflow, the design is actually quite different, as you'll soon see in my pictures below. Air flows from right to left, with fan in the center drawing air from the the SMPS/small smps heatsinks on the right side and pushing it through the amplifier/the large heatsink on the right.


The Problem

As most of you must know, the Behringer amps have rather noisy fans.
In the case of the EPQ, this also rings true. It came with a Bi-Sonic 0.25A 24VDC fan (BP802524HL-03) which makes quite a racket. I find it unacceptable for quiet scenes and quiet sections of music.

I've replaced it with a quiet 1900rpm, 21db NMB fan (P9739-ND), and although it's very quiet, I think it's going into thermal runaway. One of the SMPS side heatsinks gets hotter and hotter (too hot to touch for more than a second) The large amplifier side heatsink is not even lukewarm. After a while of playing (less than a few hours), I could literally see the power consumption rise several watts every few seconds even though the material/volume is the same. Of course, I pulled the plug (figuratively) before doing any damage.

I suspected the transistors on the SMPS side heatsink wasn't being cooled properly, so I flipped the fan around to blow air directly onto them - no dice. Next, I tried to duct most of the airflow through the overheating heatsink and so far it's been stable at my casual music listening volumes (70-80db at one meter). I'll do some more extended testing tomorrow, for tonight is already gone :crying: I'm slightly afraid to crank it up for for testing though. :help:

Another observation: I noticed amp draws 50W at idle after a cold start, but rises to 60-70W at idle after playing material for a while. I hope this is normal. :huh:


Now to my questions:

  • Do you think I should try the old fan and see if it still overheats? (I really should have done more testing before voiding the warranty by replacing the fan :hissyfit:)
  • I've read something about oscillations as the possible culprit for overheating on someone's EP4000. What are those? And is there any easy way to test/remedy it?
  • Do you think a bad transistor could be at fault or is this more like a case of poor thermal design? i.e the EPQ requires a crazy loud fan for a reason (even in HT use :unbelievable:)
  • I would appreciate any further insights!

Pictures

Pics will follow soon (hopefully tomorrow) It's getting pretty late tonight.
I'll be sure to show both the external and internals :)

Edit. LOL first post since joining in August 2007 :ponder:
 
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