Mc2301 turning off
 

Hey guys,
I'm having an issue with one of my c3201's. Here's what happens - i turn on my system, start playing music and after a minute i here a crunchy sound' the unit turns off with a blinking red light.

It's always the same unit, and only happens when i have just turn it on first time that day. When i turn the unit off and on again it's fine.

The tubes are all new from may this year - could this be a bad tube that acts up when it's cold?

Any help is appreciated,
Luk

Yes, it can easily be a bad tube. I would not turn it back on until all tubes have been checked. Sentry Monitor is turning your Amp off for a reason.

Do you have access to a tube tester? If not, is there a friend or possibly an audio store you frequent or your dealer who has one? If not, are you in the states? I could possibly send you 8 KT88's and 2 12AT7's to get you back in the game -- you send me your 10 and I'd test 'em for you. Anyway, could work out the details.

Let me know -- general comment here in this thread & PM me details.

Best Sir,

Bob

Luk,
Many tube issues happen on warm up. Elements inside the tube expand and move as the heater warms the inside of the tube. Probably one of the grids is hitting the plate or cathode, causing a short. Sentry monitor is saving your amplifier. Re-tube the offending amp and then get the tubes you pull tested. This problem may not show up using a tube tester because all the voltages and how the tube is operated are different than in your amplifier. But it's worth a try.

Tubes often fail when they have low hours, so called infant mortality. If you get past the first 100 hours or so, you'll be good a long time.

Tom

Okay -- you can try this to help isolate the KT88 and 12AT7's. I'm somewhat leaning on making a bet it's the 12volt 12AT7's - they work pretty hard in the MC2301's and for your amp to shut down so quickly, my bet is there -- may not be correct as too many variables, but I'm here, you're there & so it's a guessing game from my end.

First off -- do you have any spare KT88's or 12AT7's?? If not, you should make that a priority acquisition -- like yesterday.

Here we go (from our AA member W9TR -- TOM when he was much younger:D):

"First, swap all the tubes into your good amp. If it shuts down, you've got a tube problem. If not, stop and get help from McIntosh service.

Let's say you swap the tubes and the problem follows the tubes. So you know it's a tube.

First swap out the 12AT7's to see if it is one of them. Replace both 12AT7's tubes with a matched pair if one is bad. These little guys work hard.

If the amp still shuts down, isolate the bad KT88. Here's how.

The 8 power tube slots are labeled V1-/V1+, V2-/V2+, V4-/V4+ and V5-/V5+ with the + tubes on the left bank, and the (-) tubes in the right bank.

The tubes are grouped into two quads, one in the front of the amp, one in the rear. The front four tubes (V5+, V4+, V1- V2-) are one quad, the rear four tubes (V1+, V2+, V5-, V4-) a second quad.

Each quad can be removed and the amp powered up and operated. This allows you to isolate down to a quad with out swapping in different tubes. So pull either the front or read quad, the one you most suspect, power up the amp, and if itstays powered up, you've isolated the bad quad. If the amp still shuts down, the bad quad is in the amp.

The next step further isolates the bad tube. Power down the amp and put all the tubes back in. Tubes V1&V2 are in parallel, and tubes V4&V5 are in parallel. This means that you can pull one of each of the parallel tubes and the amp will still run. On the bad quad, pull V1 and V4, leaving V2 and V5 in the amp. Power up the amp. If the amp shuts down, you know either V2 or V5 is bad. If the amp keeps running, it is V1 or V4 that are bad.

Now you've isolated it to two tubes. You'll need a single new tube to find the bad tube by swapping the good tube for one of the known bad pair. Swap it and if the amp stays running, you are done. Congrats. If the amp shuts down, the remaining bad tube is in the amp. Swap it out and the amp will run.

Trust me, it's easier to do than write about, and with all the protection circuitry in the MC2301's, you're not likely to cause collateral damage. You turn on the amp a max of four times.

McIntosh amps, especially the 2301, are not picky about tube matching, so no worries there."

Best Sir,

Bob

Mc2301 turning off
 

Bob,

While I follow your experimental design to isolate the offender(s), isn't that putting a lot of faith in the Sentry Monitor to be your 'yes/no' trigger? If it hiccups, you could toast a $9,000 amplifier...

I would simply unplug it, order a full set of new tubes and have the others tested. Then cross your fingers, say a pray to the McGods and turn it on.

Honestly, every time I turn my system on I say a little prayer the tubes are working.

I like the idea of trying all the tubes from know OK amp to test with.


sounds like a tube is goofy??? :(

I had several conversations with the designer, now retired Ron Evans. He was gracious enough years ago -- maybe 8 -- to take the time to email me troubleshooting steps in isolating the faulty tube such as W9TR (Tom) posted back in 2013 & reiterated above.

My PC HD crashed and so lost his electronic email but have it printed out. Easier to copy & paste than retype.

There's always a gamble -- but from those conversations, Sentry Monitoring is pretty slick. Not to make someone feel bad when they see $9K for a new MC2301 -- the current price is closer to $12K each.

Best Sir,

Bob

"I say a little prayer to Joe Pesci that the tubes are working."....

fixed that for ya....

:yes:

LMAO - George would appreciate your humor, may he Rest In Peace.