Mosvalve 500 getting hot after a few hours...

SveinungL · Post by **SveinungL** » 26 Apr 2001 2:55 am

I have converted my Mosvalve 500(Mv 942 2x250 watts) to run on 220 volts. (I live in Norway). After a tip from Dag Wolf I rewired the input wires, so that the transformer can handle 220v.

I keep it in a 5 space soft-rack and there is really not too much space for air flow within the rack.
After a few hours the whole rack (Mosvalve, Mesa studio preamp and Lexicon MPX 500) gets pretty hot. Could this damage any of the components?
I run the amp into two Mesa Boogie Ev 12" cabinets (8 ohm 200watt per side), so I don't think I run the amp too hard.......
Is it common that the Mosvalve 500 gets hot after a while?

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Thanks SveinungL - Norway
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Kentucky Riders

Dave Smith · Post by **Dave Smith** » 26 Apr 2001 4:13 am

Hi SveinungL - I experienced the same problem when I played the first gig with a new 4-space rack that I got. I use a TubeFex, Lexicon MPX-100 and a Mosvalve 1500 on this particular system. The new rack case was specially made so I could plug in a power cord and speaker cables on the side without having the case open. The case was made with a 1/4" extra space between the power amp and the adjacent component for air flow but that wasn't enough. I started noticing the system losing power about the 3rd set. At the end of the set I felt the Mosvalve and it was HOT to touch. I shut it down and opened up the case to let it cool during the break. We finished the gig but I just barely made it and at greatly reduced power. I thought I'd blown it.

The next day I fired it up and everything was OK. Now I play with the door at the bottom of the case OPEN and I shut the whole system down during break. This seems to have corrected the problem. As you know, there is no fan on the Mosvalve so it needs plenty of 'breathing' space. But, what an amp!!!!!!

Bill Crook · Post by **Bill Crook** » 26 Apr 2001 4:14 am

<SMALL>I keep it in a 5 space soft-rack and there is really not too much space for air flow within the rack.</SMALL>

Considering that you dont have much room for air flow,I would think it would get more than somewhat hot.

Remember,these power-amps demand fan and air-flow. It seems that you have a few other things in the rack too. Yea,I would say it would run hot.

Jack Stoner · Post by **Jack Stoner** » 26 Apr 2001 4:38 am

One of the things the Genz-Benz (Mosvalve) tech told me (cautioned me) was to allow for adequate air flow. The cooling fan in the MosValve 500 draws air from the bottom of the chassis and expels it out the front.

I have mine mounted in a 4 space rack with a Transtube Fex. I cut out 6 inch circular holes on each side of the rack and installed 6' round speaker grilles. My MosValve 500 power amp is mounted with the bottom next to one side, so it can suck in adequate air. There is a space between the top of the MosValve 500 and the Transtube Fex. The Transtube Fex is mounted one rack hole from the opposite side. This allows adequate air flow and avoids the heat from each unit affecting the other. I have my rack sitting vertically on my right side where I can reach the Transtube Fex controls. My MosValve 500 can run for an entire 4 hour gig and gets warm but not hot. There is a picture of the front of my rack, on my web page. http://tampabaydsl.com/~jestoner/eq.htm

Do not run any equipment without adequate ventilation. "Baking" the equipment will ultimately lead to failures.