Ever happened to you??

[nsgarch]

Just curious. Has anyone experienced this kind of early KT-88 failure (i.e shorting/arcing/popping sound, with or without accompanying resistor or diode failure)) in other than the OEM Russian KT-88's that come with all Mac tube equipment these days?

I'm sure it happens, but so far I haven't heard of it (except just now with vintage tube's remark about his GL reissue; which apparently did not put on any light show ;-)

 

[jdandy]

Wonder if McIntosh intends to "trickle down" the sentry monitoring which is a feature of the MC2301's?:scratch2:

SENTRY MONITOR TUBE PROTECTION
The output tubes have limits for the maximum amount of power they can handle. The MC2301 output stage and power supply have been designed to allow high current flow into properly matched load impedances. If, however, a short circuit or very low value of load impedance is applied to the output of the MC2301, destructive current levels could be reached. The Sentry Monitor circuit prevents this. The circuit senses the dynamic operating time, voltage, and current of the amplifier output tubes and confines it to nondestructive levels. Sentry Monitor does not limit the power output available from the amplifier. Sentry Monitor also protects the entire amplifier circuitry in the event that a failed Output Tube causes higher than normal current to flow. To prevent destruction, the MC2301 power is turned off. The protection mode is indicated by the flashing of the red standby indicator on the front panel. The Protect Mode is reset to normal operation by cycling the MC2301 power off and then back on with the POWER switch.


I know first hand this sentry monitor works -- or at least I believe it kicked in - as had one tube (GL Reissue) that would cause the left amp to go into shutdown (I decided to test all 15 remaining tubes on my tube tester -- they were fine). The one which caused the amp to shutdown failed several tests on my tube tester.

By the way, I recommend having spares -- I have 12 KT88's in reserve.

I did not realize the MC2301 had this kind of protection against power tube failures. This is a very good source of protection. Output power tube failure is a fact of life. A tube amplifier that can protect itself from additional circuit damage when tube failure occurs is fantastic. This feature offers a great deal of peace of mind when you're running 16 KT88's every time you hit the power switch.

 

[McTwins]

Does this only happens during the turn on of the amplifier or can it happen during operation?

Any experience on MC275

Something to be aware of:scratch2:

 

[W9TR]

KT-88's

I've had the following KT-88's fail:
1 Winged SED
2 Stock Mc tube
1 Sovtek

All the failures occurred after many minutes of operation, and blew the mains fuse with no other damage noted. When I've been there to see it happen, I can easily replace the offending tube. When I'm out of the room, it's a crap shoot to find the offender.

I've been running two Mc 2102's as monoblocs for the last two years and one in stereo for 2 years before that.

Some of the KT-88s have over 5000 hrs on them with no issues, others have gone TU in flash in under 100 hrs.

 

[vintage_tube]

Just curious. Has anyone experienced this kind of early KT-88 failure (i.e shorting/arcing/popping sound, with or without accompanying resistor or diode failure)) in other than the OEM Russian KT-88's that come with all Mac tube equipment these days?

I'm sure it happens, but so far I haven't heard of it (except just now with vintage tube's remark about his GL reissue; which apparently did not put on any light show ;-)

That was my FIRST tube failure in years (no offense McIntosh - but I always remove the stock tubes from day one and us NOS (or GL reissues) - so, no experience with stock tube failure).

In my case with the MC2301 GL reissue failure, at startup, the amp would turn on and after it "reached it's initialization/warm up feature" which takes 20 or so seconds, the amp would shutdown.

The Sentry Monitor is a fantastic idea w/o a doubt & am curious if there is room in the other tube amps for this feature at some point.

 

[Shane]

That was my FIRST tube failure in years (no offense McIntosh - but I always remove the stock tubes from day one and us NOS (or GL reissues) - so, no experience with stock tube failure).

In my case with the MC2301 GL reissue failure, at startup, the amp would turn on and after it "reached it's initialization/warm up feature" which takes 20 or so seconds, the amp would shutdown.

The Sentry Monitor is a fantastic idea w/o a doubt & am curious if there is room in the other tube amps for this feature at some point.

If a tube goes down, does the MC2301 tell you what tube it is?. How are you finding the MC2301's vs your old MC2102's are a few mnths now.

my old cj tube amps would indicate the naughty tube with a red light next to the tube. the MC2102's do not have this, so i would have no idea if a tube went down.

 

[vintage_tube]

If a tube goes down, does the MC2301 tell you what tube it is?. How are you finding the MC2301's vs your old MC2102's are a few mnths now. my old cj tube amps would indicate the naughty tube with a red light next to the tube. the MC2102's do not have this, so i would have no idea if a tube went down.

The MC2301's have no indicators specifying which tube is bad. On the MC2301 you can remove one side of tubes (4 each KT88's and the 12AT7) and turn the amp on -- if no issues, turn it off & reinsert those tubes and then remove the other set on the other side; turn on & my case, bingo --the amp shut off.

That at least narrowed it to 4 KT88's or the 12AT7. If you don't have a tube tester, you can then remove one tube at a time, repeating the remove/insert new/turn on sequence until you isolate the problem.

That feature is neat -- at least helps isolate a problem to one side of the amp or the other.

I do not know if you can do that with a MC275 or other McIntosh tube amps as with my MC275's I never had an issue with tubes. An owner of those amps would need to confirm with McIntosh if you can do a similiar troubleshooting regime as with the MC2301 -- I would not suggest doing so, until confirmed with McIntosh.

NEVER remove tubes while lit.

Briefly, the difference between the MC2301's and dual MC275's is:

--units are unbelievably quiet in-between passages
--a lot of air in the midrange – unrestricted, delicate
--soundstage has opened up more so than with the MC275’s
--Exceptional detail & outstanding attack when an instrument is struck or plucked
--Detailed Micro dynamics, musical and very linear even at low volumes