McIntosh 240 sparked then stopped

[BMSIII]

Last night I was listening to LP's and accidentally turned the power off on the preamp (the amp is directly plugged into preamp) and then immediatly turned it back on. I heard a pop and my son said he saw sparks then power to the 240 was out, preamp and turntable still worked fine. I checked the 240 fuse and saw that it was blown.

Today, I found a 3 amp slo-blow fuse and replaced it hoping it would resolve the problem. I had power and started listening to another LP when I started hearing static through the speakers and noticed a couple of the tubes were very hot and glowing bright orange. I shut everything down and now I don't know what to do next.

Anybody know what might have happened?


System:
McIntosh 240 amp/McIntosh C20 preamp/JBL-L100 speakers/Music Hall 5 TT w/Ortofon red cartridge.

 

[ron-c]

Check to see all voltages match on the MC240 schematic. Check that the 220 ohm, 5 watt sandblock resistors are not open.
If your output tubes arced over they are most likely shot now. What tubes were you using? Turning a tube amp on-off-on quickly can send over 600 volts through the tubes and some will not like this much.

Thanks,
Ron-C

 

[BMSIII]

Ron-C, thanks for the response. I am a complete novice and this does not sound like something I can check out on my own. I was hoping there might be a simple fix but it sounds like I need to let a professional check it out. Looks like the tubes are probably the original McIntosh tubes.

 

[ron-c]

If the 6L6 tubes say McIntosh on them they are original. Many parts will be worn out on an original MC240. It is best to send it to an expert which would be MR DeWick listed at the bottom of the page and have him go through the amp. A properly serviced MC240 will last another 50 years and retain or appreciate its' value.
In the meantime just use another amp or whatever while the Mc240 goes to the electronic spa. You may want to send the C20 along with it at the same time.

thanks again,
Ron-C

 

[BMSIII]

I inherited this amp and preamp from my father a couple years ago. First thing I did was send them both to DeWick for a complete tune up. Everything was working fine until I turned it on/off/on. Live and learn....the expensive mistakes are the ones you don't forget!

 

[wajobu]

On the positive side...it can be fixed and Terry is the right man for the job!

 

[ron-c]

I suspect you will need some new output tubes. You can power it up with a new fuse but remove the output tubes first. Does the fuse hold?

thanks,
Ron-C

 

[dewickt]

Sure sounds like a 6L6 has bit the dust, hot turn on shock was more then one of them could take.

 

[BMSIII]

Follow up to original Post:
Turns out it was a blown fuse and output tubes. I replaced all 4 output tubes and fuse and everything is working fine. The blown tubes were the original McIntosh tubes and I suspect they have been in the amp since the late 60"s, early 70"s. Thanks to everyone for the help!