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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
aball
2,016 posts
 
If the tubes light up, it isn't the thermistor. Everything will be off if the thermistor is dead.

There are many capacitors in there and I bet many people wouldn't replace all of them like I did. Look at the caps and see if they look like originals. It should be pretty clear. There will be two tall silver ones on the left of the choke inductor (looks like a mini power transformer, half the size of your fist). If they are labeled by engraved print, they are probably original - new ones have sticker labels in general. Then look at the two caps on the right of the choke. If they have paper outer coverings, they too are original. New ones have plastic wrap. If any of these 4 caps have a problem, your amp is in trouble and will need a specialist to assess the damage.

If all these caps seem ok, replace the fuse. Sometimes they can look fine but not be. If you replace the fuse and nothing happens, you need to have your amp checked out.

Good luck and keep us posted.

Arthur
s23chang
617 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.
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