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MC240 HELP PLEASE

Ive had a mc 240 for years, its never been a problem child, loud but never a problem.

I recently brought a 2nd one to drive my mids and tweeters.

I was useing the amp the other night,and it made some clicking/on/off type noise's near the 117/125 volt switch and then near or in the the tranformers,then it just went silent.No sparks, no smoke, no shock,just silence.And thats the way it stayed ever since just bloody silent.(now this one has become a problem child.Was useing cd player into c28 into mc240 in evo 40 speakers at the time

Ive checked the cd player the preamp the speakers with a second amp they are all fine.Tubes still light up, fuse seems to ok.

The amp had just been serviced before I brought it had new caps and more,the guy I brought it of on audiogon is 100% reliable and if he says it was serviced and caps replaced then it was .

Anyone got any ideas on what the problem might be.Bye Paulie.
Thank you to all that reply .
souterncross
s23chang
615 posts
 
Check if there are loose soldering joints.
alrau1's avatar
alrau1
56 posts
 
If your tubes light, the fuse and thermistor are fine. If the tubes light and do not self destruct, you either are missing the high voltage supply, or something else common to both channels (other than the bias supply) is wrong. Check the mono/twin amp/stereo switch (not that it's the only possible cause) if you have both 435 volts and 140 volts from the HV supply.
souterncross OP
18 posts
 
Thank you for all replys so far,no luck with it yet caps are new, amp was recapped by the original owner just a few weeks ago and was given a clean bill of health.

The only checking I can do is visual I removed the base to check for arcing ,and flick the switches I dont see any evidence of arcing and when I flick the switches it doesnt even give a static sound. thanks again Bye Paulie
souterncross OP
18 posts
 
Ive found a fuse inside the amp, I will try to discribe it. On one end it has a spring type set up, off that spring there is very very thin copper fusewire it is now absent without leave,and I dont expect its going to return to active duty.

This looks like it may well have been an original fuse, the serial numuber is ,


313 3AG 3-2/10A 125V (this fuse is on the inside of the amp accessed by removeing the bottom plate.

Is there a substitute,I can use because I dont like my chances of finding this exact type here.

Could it really be that simple ? I hope so.

Thanks everyone Bye Paulie.
aball
1,994 posts
 
That's right - now that you mention it, there is a fuse in there. I think it is for the bias stage in case a tube goes bad.

If a fuse blows, it is because there is a problem. You will have to find the problem before you're back to normal. It sounds like you have a tube that has gone bad. But which one? That is a tough one without a tube tester... Look at each tube very carefully and see if you see anything strange. I have seen some develop black spots and/or sometimes you will see a whitish film where the vacuum was lost (near the base typically).

Arthur
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