Mx-135 Subwoofer outputs are dead,....please help..

[macman007]

Yesterday while listening in Pure Stereo my Subwoofer outputs abruptly stopped working. There is only a little output at full volume/bass/loudness/sub gain, almost like a popping and vibration timed with the bass notes. I tried all positions for Music/Cinema/External, same thing, but a bit louder than Pure Stereo. I have 1 PS-112 and 1 XLS 112 and switched them in and out between balanced and unbalanced outputs same issue. I also tried a third Velodyne sub, same issue. All other balanced and unbalanced speaker outputs in A and B work fine, both in and outs.

Every other balanced in and out work fine for every other component. I have been thru the entire menu setting and option with no success I was running in Pure Stereo, with XLS 320's and XLS 112 listening to my turntable. All other digital and analog inputs when selected have the same issue. I tried different speakers and amps/speaker cables/interconnects/sources, everything, ..no dice..

I tried a factory reset, tried changing the crossover frequency in the OS menu, large, small speaker settings, gain, MC Bass on and off, different crossover points, same issue. All 3 subs work fine on a different preamp. I checked the balanced and unbalanced interconnects and swapped in known good ones in all positions, same issue. Other than the Subwoofer outputs everything works fine for now.

I bought the unit brand new in 2005 From my local Certified McIntosh dealer, and it has been babied all it's life. I even tried a light DeOxit treatment with pipe cleaners on the balance and unbalanced connectors, on the off chance I had a dirty connection,.. no go. This unit has been phenomenal since day one and is the hub of my analog and digital system, without it I'm dead in the water unless I want to hook up my big XRT's which I have no room for currently.

I do my own work on My Mc gear and for others as well, plus other audio gear as a side gig now. Mostly older gear as the newer stuff has proved to be very reliable and trouble free. I have signal generators, scope, meters counters and all manner of test equipment, but this unit is MINE and it's much more modern than what I am used to. I don't mind going inside at all. I've never had to on this unit or my MC501's, Mc Dac, transports, servers, and so on, so it's a bit unsettling to have a reasonably new unit act up like this. I know these are very complicated, so I was hoping either this was a common issue, or to get a starting point, something to start on.

Any and all help is and will be greatly appreciated. I know much of the electronics inside these newer pre-amps are sealed relays and chip driven, I'm praying it is something that wont require a trip to the local service center or Binghampton, as I'm retired and on disability now, which is why I do my own work and work for others as well, to provide a much needed income....

Thanks to all.

 

[macman007]

As an aside and an update, I'll post the following..

Going forward this sounds more like motor-boating, like when a cap goes leaky or bad, or a switch has high resistance. Tired of waiting and thinking about it, I removed the cover with an anti static wrist band on. My first venture inside this unit in 10 years or more it is as I suspected a big processor board in the center with Texas Instruments chips all over. Multi tiered boards towards the rear and ribbon cables everywhere,.this unit seems to be built modular with an eye toward servicing. Many of the chips on the motherboard are socketed as are many on the daughter boards. Quick disconnect ribbon cables are everywhere between boards.

So after a cursory cleaning with minimal dust mostly on the rear top-most board, but little everywhere, as this unit has been kept well by me in a filtered humidity controlled environment. So I removed and cleaned every cable I could get to and then some, on both the socketed connector and pins with Deoxit and a spare terminal smaller pin. That is a lot of pins. I also removed and cleaned each chip socket and chip pins, then carefully re-installed each. That's a lot of pins, and I followed Electrostatic discharge protocols all the way with a ground on my wrist. I noticed many of the socketed chips on the mother board for the speakers are the same part and series numbers. I was considering swapping two after clearly marking them so I can replace them if it doesn't affect the issue. After reassembly I did a hard reset then set all the parameters again and ran the unit.

It worked! Amazingly enough I had full Subwoofer in Pure Stereo again, as well as all the Music, External and Cinema modes, all but 2 Channel as it is supposed to be. After a long warm up it began to fade away again and motorboat a little in time with the bass, almost like an oscillation. It never got as bad as before no did the sub signal go away entirely. I haven't hooked up a function generator and scope, but I've heard oscillation enough to know what it is. I would like to see if there is any DC mixed with the signal though out of curiosity. The caps in this unit are Wima's and what looks like Nichion, all high end, so I wouldn't think any caps are failing just yet but you never know. The build quality and components used are of amazing quality, every bit what you expect from McIntosh..

The more I switched between the Zone A inputs and surround modes the less the problem occurred, to the point after a half hour of total run time all issues are now gone away completely and sounds great., scary great better than ever. Not believing in "Magic Fixes", I fully expect it to revert to it's issue before long, or after shut off and power up again. If it doesn't, maybe it was a dirty connection I De-Oxited. I don't get stupid and spray it everywhere and get it on everything, and you can't tell anywhere but the contacts it's been used sparingly and properly. Delayed action perhaps after soaking in , its happened before after a soak on other gear, or maybe it is a sealed relay that is bad and responds to actuation.

I have no reply's yet to the thread, and I'm sure I'm not the only person this ever happened to, but there are only one or two instances I could find anywhere on the net, and neither one posted the correction, or what was done to repair the unit..aside from a trip to Binghampton.

I'll call McIntosh and Audio Classics tomorrow and see what they have to say, maybe they have seen this before and it's an easy fix or common failure. In the meantime any help or hints again are greatly appreciated.

 

[damacman]

I think you are likely the only AKer that is brave enough to attempt such a fix.

 

[macman007]

I think you are likely the only AKer that is brave enough to attempt such a fix.

I did switch the chips from the center channel to subwoofer. There are multiples of that chip on many of the 8 channels. I didn't look up the Op-Amp number, and I assume they are Op-Amp pairs. IIRC, the relays are self cleaning, so perhaps a combination of everything with actuating switches I typically haven't used in over 10 years or not more than a hand full of times since everything is primarily 2 channel LP or Tape that I play..I don't fire it up for movies though I invested in all the gear and a substantial amount at that..

Hey no guts no glory, its not as bad inside as it sounds,, mostly modular, though there is a lot of stuff in there and ESD precautions must be the number one thing on your mind since there are so many chips and processors inside.

I service and rebuild reel to reels and believe me compared to some of them, the MX135 is a pleasure to wade thru. Ditto with some of the receivers I do as well..the Mx135 just makes sense to me anyway,..

Lets hope I get a phone call back and its an easy fix, or it stays fixed...

 

[macman007]

It still motorboats/echo's/reverberates/pulsates after a while in Pure Stereo. If I switch to Music 1 or 2 and listen to 2 channel its fine. I set the effect to zero and it sounds like it should, but I shouldn't have to do that and come back it will be OK for an undetermined time, then begin again. Sometimes its OK for an hour, sometimes a few moments. Though it's pleasant sounding, it's not as accurate as pure stereo because of the Dolby effect. In music 2 with no extra channels selected, no Dolby or DTS soundfield options are illuminated, but there is a slight upper midrange bump and a bit of reverb added. While not bad, it's not the way I would want to listen to 2 channel analog sources given a choice.

I have a message in with Ryan at AudioClassics, we'll see what the experts come back with here. I'm amazed no one else has ever had this problem..maybe it's a fluke?

 

[macman007]

One reply after a week and no call back or email from Audio Classics,,either this is a one off issue or no one cares..there used to be a lot more traffic on this forum,,

 

[c_dk]

If I understand correctly, you believe unplugging and then plugging back in either a IC or interstage connector minimized the problem. Sounds like a cold/ cracked solder joint near the offending plugin connection. Not a uncommon issue in today's electronics when you have high thermal mass parts being soldered with low thermal mass parts.

 

[macman007]

According to Ryan at AC it's most likely a software issue. Got an email about an hour ago now. I was beginning to wonder what was up..

Swapping chips is likely coincidental with the issue, the last several days it only acts up a little bit at times and I have been able to listen in Pure Stereo with little or no sub issue, coming and going a small amount. Of course now I'm hyper sensitive to it and listening for it all the time!! I hate that once you hear a problem you listen for, it if you know what I mean. It messes up the joy of listening.

Today it's been on since 2PM, listening for nearly 6 hours now and other than a bit of echo an hour ago for am moment it's seemingly fine. This unit has the RS 232 port in the rear, is a software upgrade field serviceable, if possible I'd like to do it if at all possible. I hate the dealer, after a few bad experiences I don't trust them.

Where can I go to see if any software upgrades are available and what known issues they address? I can check the setup menu to see what version I am running, I have PC's and laptops and a network card with cat 5 capability but have no idea how MC does their software upgrades on the MX series and if the programs and installer are proprietary?

I'll call McIntosh directly Monday and see what they have to say. I'd hate to pack it all up and send it in or take it for service just for software, if that is what it really is. I cant believe they wont come out and say " yes we've seen that issue before, and XYZ% of the time it is software..

In the meantime, any information will be helpful..

 

[damacman]

Man I think you may be foraging new ground with respect to the regulars here ... But it would be awesome to discuss it further over some colossal blue crabs.

 

[macman007]

Man I think you may be foraging new ground with respect to the regulars here ... But it would be awesome to discuss it further over some colossal blue crabs.

The MD Blue Crabs are in season next month, fall is the best time as they are their largest, heaviest and full of meat. Likely we'll get a Bushell or 3 for Labor Day weekend, my father in law is part owner in a local Seafood Carry out and restaurant that's known to be one of the best if not the best in Maryland. If you ever get to town I'd love to sit down and gab about gear over Crabs and Beers.

I just got off the line with Binghampton. The firmware update for those who are interested is for a several issues/complaints and allows the unit to perform better. However it is not the main problem, but recommended just the same. If you do have the sub issue, or if you have a MX-135 that never had and needs firmware update, there is another issue that's been identified. In later runs of the MX-135 it seems there was a coupling capacitor that was identified as not needed for the subwoofer output. Evidently the cap either goes bad or something happens over time, but the repair is to bypass the coupling cap entirely, not replace it. My understanding is that later MX-135's bypassed this cap altogether and either the board was amended after a certain break point to eliminate this position or more likely they automatically jumper the caps +- terminals in production/update of the boards.

When I know the software update numbers, I will post them here along with the capacitor location and disposition. If I do it myself I'll take photos along the way to show others if they are interested or need to do this or are curious what is done.

Reminds me of my MS300 and MS750, I ended up doing both power supply's (replacing bulging, leaking or shorted electrolytic caps), since the backlog at the repair facility was extensive and no one wanted to touch them anymore. Since I replaced the caps they too (MS-300,750) have been as perfect as the day I bought them. I wish the site hosting for Gracenote was as reliable....!

 

[damacman]

The MD Blue Crabs are in season next month, fall is the best time as they are their largest, heaviest and full of meat. Likely we'll get a Bushell or 3 for Labor Day weekend, my father in law is part owner in a local Seafood Carry out and restaurant that's known to be one of the best if not the best in Maryland. If you ever get to town I'd love to sit down and gab about gear over Crabs and Beers.

I just got off the line with Binghampton. The firmware update for those who are interested is for a several issues/complaints and allows the unit to perform better. However it is not the main problem, but recommended just the same. If you do have the sub issue, or if you have a MX-135 that never had and needs firmware update, there is another issue that's been identified. In later runs of the MX-135 it seems there was a coupling capacitor that was identified as not needed for the subwoofer output. Evidently the cap either goes bad or something happens over time, but the repair is to bypass the coupling cap entirely, not replace it. My understanding is that later MX-135's bypassed this cap altogether and either the board was amended after a certain break point to eliminate this position or more likely they automatically jumper the caps +- terminals in production/update of the boards.

When I know the software update numbers, I will post them here along with the capacitor location and disposition. If I do it myself I'll take photos along the way to show others if they are interested or need to do this or are curious what is done.

Reminds me of my MS300 and MS750, I ended up doing both power supply's (replacing bulging, leaking or shorted electrolytic caps), since the backlog at the repair facility was extensive and no one wanted to touch them anymore. Since I replaced the caps they too (MS-300,750) have been as perfect as the day I bought them. I wish the site hosting for Gracenote was as reliable....!

Grew up in Beltsville sir. I used to get back to MD for business but not any longer. We would take the water taxi to Bo Brooks and eat like kings. Nothing else like it ... my mouth is watering just thinking about it.

 

[macman007]

Grew up in Beltsville sir. I used to get back to MD for business but not any longer. We would take the water taxi to Bo Brooks and eat like kings. Nothing else like it ... my mouth is watering just thinking about it.

Yea Buddy! If you know Maryland and good food then you know Gibbys seafood. That's the place I'm talking about. Their seafood market is about the best around. they have a plant in Florida and a bunch of boats they own, they catch pack and ship seafood and such fresh to their store and restaurant in Maryland, best stuff ever!

OK, the capacitor in question is C215 on the analog bass management section of the main board. I'm going to remove and bypass it when I can get someone to help me physically pull the unit and put it on the bench. Can't do it myself anymore because of a back problems/ disability due to a bad car accident. Can't lift over 10 pounds (not supposed to anyway) which is why I don't work in the automotive business as a tech any longer. I'll report back once it's done. It also needs to have the firmware updated and for those interested in looking at theirs the current firmware is V1.1.63, my unit has version V1. 1. 61 which is what it shipped with. I'll let the local Pro's From Dover in Lancaster do that, in case it gets screwed up and bricks the unit, they are responsible and have to make good on it.

A well deserved thank you and shout out needs to be acknowledged as Landon Mullen at McIntosh service in Binghampton is unbelievable to deal with. He get's my highest praise and marks for the quick reply's, accurate information, and working with me. He even sent me a copy of the service manual in PDF form! The McIntosh service just doesn't get any better and they always seems to blow me away with how helpful and easy to deal with they are. Ryan Kilpatrick at Audio Classics gets the same kudos due him and his company. Dealing with Audio Classics is always a great experience with either information, sales, or buying parts and equipment. It's no wonder they work so closely with McIntosh. It just doesn't get any better than this!

Hopefully this thread will help others, or at the very least serve to reassure those with the same problem that the the repair isn't a major ordeal and lets them breath a bit easier.

 

[Pablo2k]

[QUOTE="macman007,
Hopefully this thread will help others, or at the very least serve to reassure those with the same problem that the the repair isn't a major ordeal and lets them breath a bit easier.[/QUOTE]

Hi Macman007, it's been a long time since you posted this thread, but I'm hoping you'd be able to answer some of my question about my MX135.

1) I have problems with my subwoofer too; it works great during movies and music, but if I'm using analogue outs from my bluray player to MULTI IN, I have zero sub/lfe output.
2) My MX135 "Set up" menu only shows on my TV if I use composite out, s-video or component does not show "set up" on TV? But I know they work when I use them for regular video source.
3) How do I hard reset a MX135? I know I can go on set up menu and do "Factory Reset" is that the same?
4) Im thinking about "upgrading" to MX121 or if I get lucky MX150/151, but I do all my video switching is done thru my TV and Projector because they are all 4k/HDR and those two newer units cannot handle them anyway, So Im looking for sound quality only.

Thank you Macman007!