BG116 - MC240 Amp Amplifier - Replacing power supply capacitors, selenium rectifier, rebuild bias supply. Replace electrolytic bypass caps, some aged coupling caps, test all 6L6GC and small signal tubes, bench test.
Hello! I hope you are feeling well. This is a great video. I restored an MC40 last year and looking at a C11 preamp to refurb. You have great advice and practical intel to share, and it is most appreciated. I re-run this video as a sanity check for new projects. Thanks!
I fully restored a Tandberg Solvsuper 10 hybrid tube amplifier from 1968, it took 5 days and a lot of coffee. Only 6 watts per channel, actually gets way loud on some 70s 8 inch speakers I bought for $70, basically a $150 stereo system. The sound quality is insane, better than a $1000+ modern stereo system I heard a couple of weeks ago in a store.
I love the MC240. I've been fortunate enough to work on two of them over the years. The first had the classic leaking bumblebee cap problem. The other had aging power supply 'lytics. By the way, I have a severe case of test bench equipment envy.
Great video for sure, it was so interesting to watch reminds me back in the days when I was learning how to fix those vacume tube amplifiers from my fanatic dad especially the Marshall band amps. And yes I still have my vacuumed amps and still love the acoustics that comes out of them. It's really ashamed that our new generations have no idea what they are missing out on this amazing technology. Thank you for this awesome video.
Great video !!!! The only thing I do different is I never Snip Wires I use a solder sucker. That way you don't need to Re-Strip them.I do snip those tabs.
Great video ! I’m a retired electronic Engineer and own a Mc275 I purchased New 1970 . Thinking about recapping it because of the year although it sounds great . But excellent video . !!!!!
That old handwired stuff is the best. McIntosh uses pc boards now, like most other manufacturers. They may function the same but the mojo is in the handwiring!
very nice work. Many of the Russian ebay sellers have run out of the 600v rated K40 PIO caps, so have tried the Jupiter vintage tone, or the Jensen Copper foil caps. Some time try the MC240 with KT88s in place of the 6L6 outputs; more dynamic, with more of an ease to the sound.
You said it makes a difference in sound as to what kind of caps you use as to sound or bass. For coupling, if you use any brand of polypropylene cap with a good esr that tests good for voltage, will that sound good. Will it sound different if its polyethelyene or ceramic, oil, etc?
Hi, love your videos, what do you think about replacing the 2 black capacitors in the voltage doubler with the authenticap 330MFD 250V instead of the 250MFD/250V?
If you ever start doing customer work again, I am in NC and I have two MC-240s and a MX-110 that most likely need to be serviced. They were serviced about 9 or 10 years ago, but have been in storage since then. I also have a new chassis for one of the MC-240s, but I know that would be a huge job.
I pulled mine out after many years with audio research pre amp .and found I had to turn the volume up alllll the way up to get the slightest sound out of it? Had phone to pre amp what would you say that is. Could you your input. Great video man thanks
Great video! I have my father's 240 and other components out for refurbishing right now. I hope they are doing as good a job! Unfortunately, mine is not near as pretty as this one. Does anyone do cosmetic restoration on these?
It's easy to underestimate how much time it takes to rehab tube stuff; especially if you have a nice high-end piece and you're working in the high voltage section and you want to do a good job. It's just amazingly time-consuming.
Thanks for the video. However, I notice you mention the chassis of the 240 is the same as that of the 275. I have both MC275 and MC240 so I know it is not true.
Another great video Mark. I have really been enjoying your videos and have learned a lot from them. I do have a question for you on capacitors substitutions. I have a bunch of new Mallory yellow caps and a bunch of orange drops for a Magnavox 8802 amp I'm recapping. Will either of them be fine or is there an advantage of one over the other? Thanks, Tony
I imagine there is no difference in sound, as long as the specs on each cap are reasonably close. There may still not be an audible difference even if one cap has less leakage and different Q and D. As it's only 4 caps, I would do one channel with orange and one with yellow and test on a scope and load, see if there are any measurable differences while swapping pairs of tubes to cancel out the effects the tubes may have on channel imbalance. Then listen to some tunes on speakers and see what's up! Report back on Audiokarma with detailed notation of the measurements, and settle the great tube amp capacitor debate once and for all! Probably too much error for real science, but better than people listening for differences, hours apart.
Evan Fitzgerald the caps are all the same values just rated for higher voltage. It will be an interesting test and I will put it out on AK. Thanks for the input.
Hi Thank you for your generous sharing of your skills. I live in Riverside, California and have a C39 preamplifier with a “humm”. Can you refer me to a capable and ethical technician in my area? Kind regards Ref Tomerlin
Nice video! Did you ever do a video on your variac? It looks like a custom unit. Love to see the construction details and circuit. The built in load limiter is intriguing.
You added one of the 470 ohm registor with one diode on Power rectifier mini board. How many watts 470 ohn? Is it 1watt or 2 watts or1/2 or 1/4 watt. Please let me know. Thanks.
I looked up the eBay price for this kit... 250 dollars is a bit of cash! Mouser has equivalents by Vishay at perhaps 40 dollars. Wouldn't look nearly as nice, however.
Yeah, I'd just do a Mouser order, and I'd get the can caps from Hayseed Hamfest. Save some money. Or save a LOT of money and just use regular electrolytics under the chassis instead of can caps.
I tried a lot of tube combinations on this amplifier.....................here's one set , a combination i like very much. 5751 RCA ( black plates triple mica ) - ECC83 telefunken - 12BH7A GE - ECC83 Telefunken ( flat plates ) _7027A Sylvania .
42:56 nice quick discharge haha you touched the earth by mistake before your magic resistor pen. That was funny. Not so good for the cap though. But your making nice video's and good repairs enjoyed watching it.
The centre piece of the right hand capacitor is not ground. It is 475V. This is the top capacitor in the voltage doubler. Positive terminal is B+ voltage, negative terminal is half that, which is why you need an insulated case.
No it wouldn't. You should use modern components. You're not looking at the amp, you're listening to it, and you're relying on capacitors not to leak. You may as well leave the old ones in there if you want to just preserve the look. And not turn it on.
On all the MACs, I change out those 10k/2 watts to a 10k 3 w CF and 12K / 2 watters in the phase inverter to voltage amp. I change out the 12k 2 watt PI to voltage amp resistors to 5 watt CF or WW. only reason I do is because the 2 watters always run warm to me.
You can also get can capacitors from Hayseed Hamfest. They'll make whatever you need. I just got a new one to replace the old one in a Heathkit AA32 that I have.
@@danielthomas3057 Yeah I was thinking the same thing too. Maybe Solene or Mundorf caps perhaps? Orange drops? Trouble is, the music signal flows through theses caps, apparently contributing to the sound of the Mac. I dunno how much though. If they need to be replaced then they need to be replaced! The others, I spose if they're still good after 50 years they should probly last another 20?
I would never leave a single bumble bee cap in an amp. They are terrible for reliability. Especially plate to output grid, where even a micro -amp will cook the output tubes. While I will keep an open mind regarding the tone of caps, my engineer's hat calls BS. I have never seen any compelling evidence that a good modern cap would make any 'sonic' difference at all.
bit overrated disappointed they didn't put any rubber grommets should have done! have you come across any Russian valve amplifiers now they should be superb. anybody!!
The whole business of establishing a firm "physical" connection before soldering is nonsense that was taught by trade schools and in kit building instructions back in the previous century -- I know, I was there -- but, given a proper soldering job, it's totally unnecessary and just makes future repair work harder for the next tech.
This is absolutely TRUE. When I was building the Dynaco PAT-4, Dynaco absolutely admitted this in the instruction for building the 4 position "Hi Filter". There is no way the build this multi-wafer switch with that restriction. The "secure mechanical connection" procedure was an attempt to allow people with poor soldering skills to build a projects that would work. (at least to the end of the warranty.)
5 лет назад
Wrong, solder should never be relied on for a physical connection. This is basic stuff, leads should always be wrapped first then soldered. Do it right or don't do it at all.
Cool amp indeed. But can someone tell me why people are selling these for up to 5K on EBay? Some $499, is it really worth it? With a blind test could anyone tell the difference from another way less expensive amp? I doubt it. I bet if I set my PC with my monitors, played the same media, NO-ONE could tell the difference. Never used the MC240 in this test, but a friend (an audiophile nut, who pays $276 for RCA cables, lol), we did a blind test with them and a set of $5 Phantones, he lost every test :)
Sean Spark Your friend is tone deaf. McIntosh amps are premium and have been for ages. If you compare "a complete analog" set up vs. your computer would yield much different results I'm sure. Try the Mc amp, McIntosh preamp/receiver stage with a nice turntable and some good old 4311 JBL speakers- this setup will not only blow out the windows in your home but will exhibit the warm, throbbing, spacious sound of true top quality analog gear will have you throwing your computer out of said windows.
+Patrick Foster I do agree analog has a warm feel, lived through the whole era of change, still prefer valves for my guitar amp. But I also am not opposed to the fact that good sound, is good sound. Whether it be from electrons flowing through expensive gasses, iron, or silicon, it will sound good, if both media and hardware are good. I would think the final and important factor involved is what turns those electrons to kinetic energy, the transducers. Of coarse garbage in , garbage out :) . But definitely difficult to tell the difference to the blind eye. A good digital/analog recording, tube/transistor hardware, can be hard to detect, either way. I do not lean toward either system, only a good sounding, fair priced one :)
Sean Spark Didn't know you are a guitarist, as am I. It is the age old debate really. The good old days vs. change. In reality you are correct in that the digital tech has really caught up in a sense. The "A vs. D" really started in the early 80s in the pro studios: keep using the great Studer recorders or go with the new Sony or Panasonic 48 track digital recorders that were built to fight Studer's dominance of the market. They failed. Digital recording did not make inroads into the pro studios until the rise of the pc and pro tools in particular (we'll skip the Adat crap). My friend and I have built a really nice "home" studio and I am aware of the incredible power of technology giving us poor people the chance to have our own studio that rivals some of the great old dedicated "48 track" studios! Having said all that, I would not trade my old tube Fender (my "go to" amp is an old Bassman 10, which sounds as good for guitar as it does for bass) and Marshall amps for anything. Clearly now we can see it's not A vs. D but it is A + D. Cheers!
Patrick Foster Sweet, I try, not so good, lol. Yes, I think it has become more of a football team like thing, go Digital !, Go Analog ! lol, both teams are capable of winning. I was in that flow of tech change in the 70's & 80's. Saved paper route $ for a MOOG. (never made enough). 90's were on the doorstep, as you said, home recording equipment was affordable, available, to the not so rich. SO, I too, built a home studio in efforts to setup a kind of bed & Record-fest, failed...By the turn of the century, for a few hundred bucks in a pre-amp and mics, software, a lappy, or smartphone, could make a hell of a recording. Hey, I have a pristine, very low hour ADAT XT & a Mark III for sale, if your interested.. lol :) They have been replaced by $99 hard drives and $15 SD cards. Ah remember the ole CD burning days... another shiny coaster.
@@patrickfoster4586 Yeah, which is why when you mention double-blind testing on most audio forums you get banned. McIntosh stuff IS Premium, I know this because I've seen the price tags, but I would take the pepsi challenge against this amp with some class D stuff in my stereo, in a double blind test.
