Mc 250 overheats help

Ballvalve

New Member
Just got a beautifull 250 the other day to try with my K-horns. Trouble is when i turn the gains up to 11 or 12 oclock (pretty loud)it plays for about 5 min then shuts down on thermal overload. The heatsinks closest to the terminal side get quite hot but the other 2 are cold. Is this normal? Am i pushing it to hard? Any comments appreciated. Here are some particulars.
15' of 12 gauge speaker wire per side connected to 8 ohm taps.
Black terminal on speaker to com on amp.
Plays all day at 9 oclock.
Thanks
 
Originally posted by Ballvalve
Just got a beautifull 250 the other day to try with my K-horns. Trouble is when i turn the gains up to 11 or 12 oclock (pretty loud)it plays for about 5 min then shuts down on thermal overload. The heatsinks closest to the terminal side get quite hot but the other 2 are cold. Is this normal?

No, that is not normal. It needs to be serviced.
 
A MC250 should be able to run with the volume down and have minimal warmth on the heat sinks, when pushed hard they should all warm up the same amount. I have never had mine thermal out no matter how hard I have pushed it, sounds like the one you have is ready for the shop.
 
MC250 is now very happy and will be going home on monday. Had an output transistor that had emitter to collector leakage not failed yet but on it's way - caused by a short on the 16 Ohm tap at the speaker terminal block.
Warning - if the screws in the terminal block get replaced make sure they are not too long, if they are they will short to the chassis and cause strange results/symptoms.
 
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