C 220 problem.

[Bill Ferris]

Yesterday morning, I turn on my Mac bedroom system, and it (the C 220 powers up like it normally has for 6 years.
But this time no sound other than mild hiss when I max out the volume.

All other room`s systems in the house are functioning properly, as all systems are being fed from the master rack`s source.
The preamp produces no sound from it`s connected Mac tuner next to it either, when selected, or the audio connected TV below it
I performed the micro processor reset indicated in the manual, but nothing changed.
I then did a master reset, and again, no sound other than mild hiss at max volume.
That`when I noticed that the preamp, when off, it`s standby light is not lighted.
I unplugged the preamp for about 5 minutes, then plugged it back in; still no standby light lighted and no sound when powered up.

Does anybody have any ideas about what`s going on with the C220 with it`s standby light not being lighted when off, but acting normally when powered up, other than no sound output.

Thanks, Bill Ferris

 

[damacman]

Bill - sure sounds like it’s due for service.

 

[Bill Ferris]

Bill - sure sounds like it’s due for service.

Well Sir, it sure looks like it..
I guess it`s time to take it down from the bedroom TV hutch and pop her lid, and fire up one of my benches.

Hopefully the 2 service manuals I have, after I print them off the pdf files, will help me find the path back to my important morning quality music fix.

Thanks damacman, for taking a look, and for your interest in my C 220 problem..
My first time, in quite some time, of an equipment issue/failure, especially Mac. gear
I hope not to have to sub another preamp whilst looking into it`s issues, as the C220 has spoiled me badly !!
Take care.
Have a great week Sir.
Kind regards, Billy Ferris

 

[4-2-7]

Does anybody have any ideas about what`s going on with the C220 with it`s standby light not being lighted when off, but acting normally when powered up, other than no sound output.

Well it's a tube pre so thats where I would start as you might have a bad one. Even just removing and reinstalling will help the contacts. For you, your not using the phono stage so those are extra tubes to work with or grab a complete set from your 275s. You would then pull a 220 tube out replace with one from the 275. Do this systematically one at a time leave the know working tubes in and test power up for each tube change till maybe you find the bad location.

 

[Bill Ferris]

Well it's a tube pre so thats where I would start as you might have a bad one. Even just removing and reinstalling will help the contacts. For you, your not using the phono stage so those are extra tubes to work with or grab a complete set from your 275s. You would then pull a 220 tube out replace with one from the 275. Do this systematically one at a time leave the know working tubes in and test power up for each tube change till maybe you find the bad location.

Well 4-2-7, those were a long my lines of thinking, but it is still a "micro processor controlled" preamp.

And it`s been well taken care of via my Panamax 20 ampere protector/ power on sequencer (surge/spike).

And though the 2 phono tubes were promptly disabled upon first power up programing, being no need for 2 phono tubes being active, when no application for them was needed, I have hundreds of 12AX7(both new and pulls) and a Amplitrex 1000 tube tester to check out the 2 line tubes, if their just not just merely substituted.
The preamp has lived a easy life since purchased brand new in sealed box, and in use, being a bedroom system that`s turned on in the morning for a hour or so, as part of my every morning wake up pre coffee ritual, since installation around 5 years ago.

There is still the no standby light on(normal, when operational) when the preamp is not powered up, along with the mild hiss when the volume control is maxed, which seems to imply that something is amplifying(like the 2 line tubes), but not getting signals routed to them. by the micro processor..

I will probably figure it out and repair, but was hoping some one here on AK might have had similar C 220 issues, and could provide a quick and direct path for me to address..

Maybe Ryan from Audio Classics, if he picks up on this post will have a suggestion/direction for me.

Analog preamp/amplifiers, no problem, been successfully working on them for decades..
But, micro processer controlled ones, well this is new territory for my repair skills. though I have both SM`s 1/2 for that preamp.

Anyway thanks for the interest and suggestion 4-2-7..

Take care.
Kind regards, Billy Ferris

 

[MACKIE1975]

A call either to McIntosh or Audio Classic maybe the shortest route.

 

[Bill Ferris]

A call either to McIntosh or Audio Classic maybe the shortest route.

Yes, that`s on my mind too.
Thanks

 

[Bill Ferris]

Yes !! , I fixed it all by myself, and didn`t need the SM, Mac support, A/C, or my very helpful A/V dealer whom I bought it from just shy of 6 years ago !!

My Mac C 220 bedroom`s system preamp LIVES AGAIN !!



My first ever use of the dancing banana`s ever, but applicable in this situation !!

 

[feinstei]

Well... how did you fix it? We want DETAILS!!!!

 

[Chubba]

Congrats and man we are not hanging here at all.

 

[Bill Ferris]

Well... how did you fix it? We want DETAILS!!!!

Well fienstiei, it was simple, and if I was working for the Government, and told you, I would have to kill you !! Just Kidding !! LOL !!
Just kidding !!
The problem, turned out to be no filament lighting of the 2 main 12AX7 main line tubes, which was totally unexpected, being that when the preamp volume control was maxed out, mild hiss was heard!!
Thus implying that they were functioning, at least in my 2 brain cell`s mind...
So, I saw the two unused, in my non-bedroom application`s, phono preamp 12AX7`s filament`s fully lighted nearby, I first checked the 3 circuit board mounted fuses to see if they were popped, but they were fine..

So I said what the Hell, let`s just try 2 new NOS Groove Tubes 12AX7 replacements, and see what happens !! (I was a Groove Tube dealer from 1988 until they sold out to Fender Musical )
So I did, and all looked good on the audio analyzer, except the left channel appeared to be a fraction of a db lower than the right channel.
So I went and retrieved two NIB/NOS USA Groove Tubes 12AX7A`s, to see if there was any change in the level off set, but it remained, so I proceeded to not worry about it and ran THD+N tests on the C 220`s both channels for a period of time..

After a beer and two cigarettes timed THD bench burn in time(30 minutes, or so), I hooked the preamp up to my signal source from my Mac. MA 6100`s tape out and hooked it up to my workshop`s Sencore PA 81 audio analyzer/active dummy load for over night burn in..
if it looks good tomorrow, she get`s her skirt put back on and re-installed back into my Mac bedroom system.

Anyway, thanks for the interest, and input folks.

Kind regards, OKB

 

[4-2-7]

Well it's a tube pre so thats where I would start as you might have a bad one. Even just removing and reinstalling will help the contacts. For you, your not using the phono stage so those are extra tubes to work with or grab a complete set from your 275s. You would then pull a 220 tube out replace with one from the 275. Do this systematically one at a time leave the know working tubes in and test power up for each tube change till maybe you find the bad location.

Well 4-2-7, those were a long my lines of thinking, but it is still a "micro processor controlled" preamp.

And it`s been well taken care of via my Panamax 20 ampere protector/ power on sequencer (surge/spike).

The problem, turned out to be no filament lighting of the 2 main 12AX7 main line tubes, which was totally unexpected, being that when the preamp volume control was maxed out, mild hiss was heard!!
Thus implying that they were functioning, at least in my 2 brain cell`s mind...

and?

 

[Bill Ferris]

Well it's a tube pre so thats where I would start as you might have a bad one. Even just removing and reinstalling will help the contacts. For you, your not using the phono stage so those are extra tubes to work with or grab a complete set from your 275s. You would then pull a 220 tube out replace with one from the 275. Do this systematically one at a time leave the know working tubes in and test power up for each tube change till maybe you find the bad location.

Thanks for the suggestion and input 4-2-7, but I don`t need to rob/borrow tubes from other gear to test the C220, as I have plenty of NIB/NOS + Amplitrex 1000 tested pulls tubes, and if there had not been hiss(indicating active circuit function, via tubes, I would have gone straight to the Mac C 220`s Chinese line tubes as suspect, while the preamp was still in my bedroom..

Again, thanks for your interest, and suggestion.

Take care.
Kind regards, Billy Ferris

 

[Bill Ferris]

Congrats and man we are not hanging here at all.

OK ...

 

[feinstei]

Well fienstiei, it was simple, and if I was working for the Government, and told you, I would have to kill you !! Just Kidding !! LOL !!
Just kidding !!
Kind regards, OKB

I bet you feel like I did when I was able to fix my own MC-275 Mk VI, MR-88, and MX-119. I find that McIntosh equipment breaks down much more often than say a Yamaha receiver.... Luckily, with all of the resources available all over the Internet, one can quite often fix the stuff.... I'm really happy for you. Shipping these things are a bitch. I sometimes wonder if McIntosh is worth all of the trouble.

 

[Bill Ferris]

I bet you feel like I did when I was able to fix my own MC-275 Mk VI, MR-88, and MX-119. I find that McIntosh equipment breaks down much more often than say a Yamaha receiver.... Luckily, with all of the resources available all over the Internet, one can quite often fix the stuff.... I'm really happy for you. Shipping these things are a bitch. I sometimes wonder if McIntosh is worth all of the trouble.

Well feinstei, I don`t know about your experiences with Mac gear, but this is the first time in many, many years, that any of my in daily use for decades(some have been running nonstop) 24/7/365 failure free Mac gear.

My Mac gear seems to be relatively happy and trouble free, even unrestored vintage (over 50 years old C 22) Mac tube preamp.

My C 220, after just shy of 6 years of ownership, being turned on every morning, and run for as many as 12 hours a day since installation..
That Sir. is a lot of hrs. on it, and it didn`t fail me, but the Chinese tube(s installed in it) did.

I suspect, but could be wrong, that the replacement of the original Chinese) tubes, now with the NOS USA ones, will probably outlast me before they fail..

I don`t ship any electronic gear I own for repair, as I can usually repair my self, as I did this for a successful living for over 42 years, and posted in hopes of finding a lazy easy way out quick suggestion/fix, but was not forthcoming, so I had to investigate myself.
Your experience with Mac gear may be different, but I`ll stick with my Mac gear.

 

[Bill Ferris]

Oh, BTW; I had a chance to test the Mac. factory original Chinese tubes that I pulled out of the C 220 preamp today on my trusty Amplitrex A 1000 tube tester, and compare it with an substitute NOS/NIB USA 12AX7A Groove Tubes to the still working 3 out of factory tubes installed.

Boy, were the original Mac selected/labeled & Installed Chinese tubes testing weak and not even near balanced triode to triode on the 3 three functioning out of four !!
And with approx. 1000 hrs. in use..

The forth 12AX7 filament was, in fact open, hence my C 220 preamp`s original failure.

A original set of factory installed " weak ticket" tubes were found, in my tests, even the un-used, in my application phono 2 Mac labeled Chinese ones were very unbalanced to each other(L/R , and even within section to section !!

Oh well Mac, you`re only as good as your parts suppliers, especially vacuum tubes !!

I`m surprised the C 220 sounded as good as it did before the tube failed, or I would have tube rolled, as it`s called, years ago !

I guess Mac can`t get consistent quality tubes anymore ?

I`m glad, in a since, that I have quality substitute tubes to restore my latest Mac tube based audio equipment to better than factory expected/delivered performance..

Trust me AK Mac heads, I like, and enjoy, and use lots of Mac stereo gear, or wouldn`t own and use the many daily in use pieces that I do.

So I`m no trashing them, just surprised at what I found in this situation after decades of owning, enjoying, & using their gear..

Take care Folks.

Kind regards, OKB

 

[TSmith8605]

Oh, BTW; I had a chance to test the Mac. factory original Chinese tubes that I pulled out of the C 220 preamp today on my trusty Amplitrex A 1000 tube tester, and compare it with an substitute NOS/NIB USA 12AX7A Groove Tubes to the still working 3 out of factory tubes installed.

Boy, were the original Mac selected/labeled & Installed Chinese tubes testing weak and not even near balanced triode to triode on the 3 three functioning out of four !!
And with approx. 1000 hrs. in use..

The forth 12AX7 filament was, in fact open, hence my C 220 preamp`s original failure.

A original set of factory installed " weak ticket" tubes were found, in my tests, even the un-used, in my application phono 2 Mac labeled Chinese ones were very unbalanced to each other(L/R , and even within section to section !!

Oh well Mac, you`re only as good as your parts suppliers, especially vacuum tubes !!

I`m surprised the C 220 sounded as good as it did before the tube failed, or I would have tube rolled, as it`s called, years ago !

I guess Mac can`t get consistent quality tubes anymore ?

I`m glad, in a since, that I have quality substitute tubes to restore my latest Mac tube based audio equipment to better than factory expected/delivered performance..

Trust me AK Mac heads, I like, and enjoy, and use lots of Mac stereo gear, or wouldn`t own and use the many daily in use pieces that I do.

So I`m no trashing them, just surprised at what I found in this situation after decades of owning, enjoying, & using their gear..

Take care Folks.

Kind regards, OKB

McIntosh cannot really sell new equipment with used or "NOS/NIB USA [] Tubes". They have limited options wrt tube sources. Early on I put used Telefunken tubes in my C220 and they've been fine since. Seems like the sound improved with those, less tizzy treble maybe. Or maybe I just imagined that part.

Just out of curiosity: that the failure of one tube filament caused both channels to quit means either each tube is used in both channels (12AX7s are dual triodes), or the filaments are wired in series so an open filament in one tube caused the other good tube to go dark.

Also curious about why you heard hissing if both line-level tubes were not heated. The C220 is a hybrid preamp meaning it has both tubes and transistors (ICs) in the signal path. The hissing may have come from a transistor circuit (IC) that comes after the tubes in the signal path. But that you had to turn the volume up all the way means that either the volume control also comes after the tubes or that some small amount of signal gets past the dark tubes to the output. But then you might expect to faintly hear some of the music signal as well hissing. Could be that the microprocessor detected the bad tubes and shut off the inputs or outputs or something.

Anyway just curious - I don't have a service manual and a simple functional diagram would answer a lot of these questions.

 

[Bill Ferris]

McIntosh cannot really sell new equipment with used or "NOS/NIB USA [] Tubes". They have limited options wrt tube sources. Early on I put used Telefunken tubes in my C220 and they've been fine since. Seems like the sound improved with those, less tizzy treble maybe. Or maybe I just imagined that part.

Just out of curiosity: that the failure of one tube filament caused both channels to quit means either each tube is used in both channels (12AX7s are dual triodes), or the filaments are wired in series so an open filament in one tube caused the other good tube to go dark.

Also curious about why you heard hissing if both line-level tubes were not heated. The C220 is a hybrid preamp meaning it has both tubes and transistors (ICs) in the signal path. The hissing may have come from a transistor circuit (IC) that comes after the tubes in the signal path. But that you had to turn the volume up all the way means that either the volume control also comes after the tubes or that some small amount of signal gets past the dark tubes to the output. But then you might expect to faintly hear some of the music signal as well hissing. Could be that the microprocessor detected the bad tubes and shut off the inputs or outputs or something.

Anyway just curious - I don't have a service manual and a simple functional diagram would answer a lot of these questions.

Interesting observations TSmith, though I have the SM, both parts, 1/2. and recently printed both from a pdf provided by my A/V dealer as a courtesy, whom I purchased the preamp from, just shy of 6 years ago.
Had not needed, nor considered until a couple a days ago.

And though I glanced at it during printing, I couldn`t tell if it was hybrid or not, though I`m under the impression that it`s signal path is tube amplified, but controlled by a micro-processor, though the balanced outputs use IC`s, though their not used in my particular application.
I know Mac is not going to use NOS USA tubes in their production, I was implying that more tube useful life should have been available for the running hours, from my sale and use of the same Chinese 12AX7A tubes over 20 years in much more demanding applications(Guitar amplification, as an example, IMHO/E, that`s all, especially thinking they were selected/graded by Mac.
And the fact that these tubes tested specifications would be so dismal, for the easy hours on them was disturbing !!

And the 2 Line 12AX7A`s filaments have to be power fed in series, as both were cold after 10 minutes of being powered up.

Since I did a full micro-processor reset , the IMHO, stupid under lighted with bright green LED`s hampered visual confirmation of filament glow, so I waited for a period of time( like getting a beer, and puffing on a couple of cigarettes, and came back to feel the questionable tubes for proper warmth..
It(the C 220 preamp ) is hooked back up and playing to my satisfaction in my bedroom for about 8 hours now, so all else is Academic to me..
Though, thanks for your interest and comments..

Kind regards, OKB