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32blownhemi

Tubes bad in 80 days on new Mc275? Are they BS'ing me?

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Call the store first and read them the super detailed letter you will be sending McIntosh with the amp.  Accept any good suggestions from the store concerning editing, as long as they don't water down the letter.  Ask them if they have the name of someone at McIntosh who is understanding, detail oriented and non-defensive who you should ask to talk to.   Ask the store to pay shipping, and get reimbursed by McIntosh, if they can.  The store should handle the packaging, as well.  Then call McIntosh and tell them the amp is coming, along with the letter.   Once I had an issue like that (with a tape recorder company) and the store technical service guy (an engineer) and I called the company together, which seemed to help.  That could deter any temptation a less than optimum person at the company might have to use electromythological mumbo jumbo. 

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Thank You guys! I e-mailed the guy at McIntosh that agreed to send me the tubes by replying to the last correspondence we had. He had added 3 other people from McIntosh to receive copies of our e-mails. So 4 people at Mc read everything we write back & forth. I think this is the best/quickest way to handle it. The stereo shop I got the amp from is quit a drive from where I live (the local place didn't have an amp in stock). Dealing directly with Mc cuts out all the middle men...  Oh, I checked the fuse & it's good...     Bill

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Please keep us informed when you have time. I'm very curious to see what they do for you. That's such a sweet amp. It's a shame to see you having issues like this. I assume this is not normal. They seem very well built. There's a video that shows them being made on YouTube I just watched last night. Pretty cool. 

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Another Genalex KT88 on a different amp went bad.  Not even 100 Hours on it.

 

Turned it on.  Noticed a cracking sound in one of the speakers.  Looked at the amp and one Kt88 was freakin bright red.  I swear I thought it would start a fire.  I shut down the amp.

 

The 3 other Kt88s barely warm at all.  The one that turned red was insanely hot.  Wasn't on 30 seconds.  I can't believe a fuse didn't blow.  WTF man.

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19 hours ago, babadono said:

Ah...the pleasure of tubes😎

 

I've only had trouble with two tubes since 1998. That is not bad. You can upgrade tubes pretty easily but if you have solid state that is all you get 8-)

 

 

 

 

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Okay, inquiring minds want to know.  How did this all turn out?  I just read through this whole 4 page thread with great enthusiasm and interest.  Please don't let it end here!

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Guest wdecho
On 6/13/2018 at 12:19 PM, jwc said:

Another Genalex KT88 on a different amp went bad.  Not even 100 Hours on it.

 

Turned it on.  Noticed a cracking sound in one of the speakers.  Looked at the amp and one Kt88 was freakin bright red.  I swear I thought it would start a fire.  I shut down the amp.

 

The 3 other Kt88s barely warm at all.  The one that turned red was insanely hot.  Wasn't on 30 seconds.  I can't believe a fuse didn't blow.  WTF man.

Doubtful it is tube, more likely something wrong in amp when one turns that hot. Likely being biased to high.  Should be easy fix for someone knowledgeable. 

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What a mess, sounds like the guy that did the repair didn't do you any favors. Of course this amp is all but new so Mc isn't blameless either, knowing what a guy spends for one of their amps this is totally unacceptable. They better go above and beyond for you this time.

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On 8/12/2018 at 8:25 PM, Cornwalled said:

Okay, inquiring minds want to know.  How did this all turn out?  I just read through this whole 4 page thread with great enthusiasm and interest.  Please don't let it end here!

I though I read that Mac took care of it as you would expect them to.

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Yep, the factory fixed it free BUT it just quit working for the 3rd time! I have a $6400 lemon... 

 

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On 11/29/2017 at 12:53 AM, 32blownhemi said:

Brand new from an approved McIntosh dealer. I'll report back after I talk to him tomorrow.... One time I accidentally left it on for 8 hours.  Including those 8 hours II wouldn't be a bit surprised if the amp didn't have any more than 50 hours on it...   Thank You!   Bill

 

Well, that is a terrible terrible design.  The problem was the dumb engineering at McIntosh,  to operate output tubes so hard.  There is no excuse for that. 

 

Are you able to adjust the amp's bias on your own, with a pot??  If so, DO THAT and run maybe 30% less current than " stock" . 

 

It would be nice to see a schematic, with operating voltages, and determine / compute precisely how hard they run that tube, versus the tube's maximum rated dissipation.

 

Anyone got that data ?  Can someone do the computations?  ASK the people at McIntosh to tell you dissipation. 

 

Thanks.

 

 

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Two thousand seventeen...

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About 10 years ago I tried going back to tubes with Cary products and went through tubes like candy on Halloween. It was frustrating and embarrassing and eventually maddening. I sold it all and went high end solid state, Accuphase. Could not be happier. My 0.02$.

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Manufacturers design and sell amps to the public based on Watts Per Dollar.  And the public is naive enough to buy them on that basis and live with the consequences..

 

To get the Mc 275 to be 75 Watts per channel, they most likely PUSH the tubes' rated dissipations.  Sure, it meets the spec of " power" when new.  But as the amp gets any hours on it, the tube degrades. 

 

What kind of engineering is that !!!???????>?>?

 

Do the Manufacturers' EE / O-Scope jockeys ever listen to what happens when a tube is operated even NEAR its rated dissipation??  There is a " thermally stressed sound " I hear with such operation.   It is not a relaxed and at-ease sound, with the same tube operating at a lower plate dissipation. 

 

The best 2A3 amp I have ever heard operates a 15 Watt Maximum rated 2A3 plate at about 10.5 Watts, or 70 percent of rated maximum.   

 

Probably 99 percent of existing 2A3 amps are sadly running 14 to 15+ Watts of plate dissipation,............... and they all sound worse that way - to me.  The designers are clueless. 

 

I am SO happy that I have been able to DIY my own amps, last 40 years., to avoid the Manufacturer's foolishness.  In another thread, I am operating the Output tubes on a new Single Ended Direct Coupled KT88 amp build at about 10.5 Watts dissipation.  This is only 25 % of the tube's rated  42 Watt plate dissipation.  It eliminates the "thermally stressed " sound.   The amp 's tubes should run a LONG time, maybe a decade or so, before they may need to be changed. 

 

Conservative plate dissipation operation is what we need to have, in my experience.   As a general goal, I like 62% of maximum, a Golden ratio proportion, for Finals tube plate dissipation.  ( its like driving your car, capable of 100 MPH, at 62 MPH continuously. )

 

Another question I have is, .............Haven't you ever heard vintage Mac 60s??  Has two tube rectifiers.  A pair of MC60s always sounded better ( to me ) than any similar-vintage Mac 275 !!! 

 

 

 

                                                                                  1709848246_Mac60s.JPG.43fc9c3445b0223033da25f24405b578.JPG

 

Note, all of the above is written either " in my opinion" or " in my experience".

 

 

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One of the things I did when approaching the idea of owning tube gear, and deciding which tube gear that I would own, was serviceability. Just as I would do with ANY other product I would consider owning, I would research painstakingly to determine whether or not that product was reliable. Amps AND tubes.

 

I owned two different sets of McIntosh MC30s, and once those amplifiers were properly/thoroughly rebuilt, I had ONE service problem with the amps themselves - a CE Engineering can that failed and that I had replaced. This was over a combined total of 25ish total ownership years over two amp pairs.

 

I own a pair of VRD amplifiers and have two friends close (and not on forum) that own the same. In over a decade of each amplifier pair of ownership, ZERO trips to the shop from amplifier failures. ZERO. I did have a Sonicap Platinum cap fail in my VRD pair shortly after inserting these as we found out that the 600VDC rating wasn't true to the real world - turned out that the manufacturer had to back off that claim as they subsequently only spec'd them to 400VDC (not enough for the specific application). Inserted Cardas Gold Ratio 600VDC caps and no such issue since. VRDs don't have trouble in the field. Maybe a tube, but not the amps.....

 

When tubing those amplifiers, once I determined what tubes I wanted for those amplifiers, I set about stocking up my stash with the specific tubes that have a good reputation for long/good service life and sound. But even in that effort, I lost some tubes, too. Had a couple of Genelex Gold Lion KT88 repro tubes go into a blue flamed spark show (and scared the hello out of me in the process) in my pair of VRDs - but it did nothing to hurt the amplifiers themselves. I quit using those brand tubes afterwards, though. Reliable tubes that I like in sound, I stocked up on (for VRDs - Mullard 5AR4s, Penta Labs KT88SC, Amperex/Philips Holland 12AX7/12AU7) and just ran with those. I haven't had a tube fail in YEARS. I've replaced a couple sets in total over time from wearing them out, but no problems of any noteworthy discussion. Once I found out how good the Penta Labs tubes were, I had Doug at Doug's Tubes sell me a matched (at least in close range) set of THIRTY at $125ish per quad (because that's what they sold for back then) and a set of 20ish Valve Art KT100 from AES  at just over $100 per quad and will never buy a KT88 type tube again unless I luck into a value priced set of Genuine Tung-Sols. Have about 30 Mullard and similar era 5AR4 and will never buy another. About 15 pairs of Amperex Holland Bugle Boy NOS 12AU7/12AX7 and will never buy another.

 

I dug like crazy to see who had issue with any of these amps, or any other amps in the field I was considering that got any amount of pub that I was considering. Being a Mac fan, I did of course investigate the newer build MC275s, and saw a lot of complaints of early power tube failures, and when those tubes would fail, take out resistors along with them. I saw enough of these reports that I didn't buy those, but bought something else. Seen a number who didn't have much issue, but enough that did to decide they were not for me.

 

Yes, tubes are inexact. Yes, they can be a painindeazz. But when I researched thoroughly I found out through gear selection and tube selection how to minimize those issues and have been sufficiently successful as to not consider ownership a painindeazz at all. Just a bit of rare and educated maintenance (test tubes on rare occasion to see if in need of replacement). Tube gear is much like any other mechanical device - some extremely reliable, some not so much, and some in the middle, with varying ramifications as to what happens when they DO fail. Investigating how parts of the circuit are designed and how that affects normal operation (IOW, is it maxing out the tubes or design to stretch or squeeze that performance out of the amp, or is it overbuilt for the purpose) is another aspect of tube gear worthy of investigation. These are only operationally as good as their weakest link, and if that weak link fails too often it will drive many out of ownership of specific gears often, and tube gear in totality occasionally (which I discourage because that's throwing out the baby with the bath water). That can be avoided with thorough investigation.

 

All in my experience, of course - tube gear need not be a bother or annoyance. Hell, I'm not even a "circuit genius" either. But I DO understand "limits", "reliability", and "worse case scenarios". And in that research and experience the end result is

 

:: insert picture of content tube gear owner on reclined La-Z-Boy here ::

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In Europe, we have 2 years of warranty, no questions asked, most of the time.

Any brand selling expensive, high end gear, will make great effort to satisfy the customer.

It's American companies, such as  Apple, that are unwilling to comply - first they even refused to list the two year option on their website.

 

Edit:

McIntosh' warranty is 3 years for hifi gear, except for tubes.

I just checked. It is the same in Europe.

Also other tube sellers in Europe only give limited warranty, or none...

It's the same for batteries, I guess.

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McIntosh is sending me a shipping label & I'll send it back to them. I told them it was a lemon & I wanted a new one. We'll see what happens. I looked & the 2nd time it broke it flashed the power transformer thermal protection switch. No idea what that is... The first time it had an 'Open Transformer', that it 'dead shorted' & it blew 4 K88 tubes. One tube had 'flashed', One tube had an 'open filament' & two tubes had 'low emission gain'. No idea what this means either. And that it had excessive wear on it. Which is BS, I had & still have very few hours on it...  Thank You for the replies!    Bill

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40 minutes ago, 32blownhemi said:

McIntosh is sending me a shipping label & I'll send it back to them. I told them it was a lemon & I wanted a new one. We'll see what happens. I looked & the 2nd time it broke it flashed the power transformer thermal protection switch. No idea what that is... The first time it had an 'Open Transformer', that it 'dead shorted' & it blew 4 K88 tubes. One tube had 'flashed', One tube had an 'open filament' & two tubes had 'low emission gain'. No idea what this means either. And that it had excessive wear on it. Which is BS, I had & still have very few hours on it...  Thank You for the replies!    Bill

It seems that you have either a wiring issue or a bad power transformer to me!...or both!  Don't worry about it....after all you can find almost all the forum tube guys always saying that Tubed Mac's and heritage Klipsch are a match made in heaven...just lean back on that heavenly cloud and relax!  And maybe search eBay for a good used H/K 430 twin-powered receiver for "MAC-back-up" …"just in case".  Honestly...it would be SO MUCH NICER if all the U.S. companies which USED TO MAKE TUBES (RCA, Westinghouse, etc...)...still did so!  Does Telefunken still make them???...or just re-badge Chinese made tubes nowadays??  I'm not even sure if Russia and the former Warsaw Pact countries even still make them, anymore!  My take is that if they DID still make tubes, it would cost even more of a fortune to run them! 

 

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