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mcs 3275 and 3125

yotems

Well-Known Member
i currently own a 3275 and have a 3125 on the way thats supposedly in good condition with its only flaw being a small amount of dust apparently.

the 3275 is incredible i gotta say. i personally love the look of it as well as the exoskeletal look of the 3125 with its dual exposed heat sinks... its like a MAC 6700 haha

i bought the 3275 about a month ago for my dad after we were talking about the realistic sta-2080 i had just purchased. he kept talking about how mcs made some of the best stuff back in the day that no one really knew about.. he kept saying he had heard the people behind the "quality" mcs receivers were some skunkworks experts, he just didnt know who (turns out NEC for some receivers and a couple other things).

though i didnt believe him as to their apparent unknown superstar status i knew i couldnt go wrong buying him what appeared to me at the time as simply mcs's second best receiver next to the 3125 which doesnt offer quite the classic aesthetic appeal the 3275 does, so im very glad it was the 3275 on ebay at the time because its still 70's if you know what i mean. after a quick search of it i learned of 75 watts rms and 5 band equalizers.

i also really wanted the closest mcs had to offer to my sta-2080 (short of the 3285, i didnt look into it despite knowing of it and dont mind because i believe the 3275 was the best receiver i could have bought him) so we could have equal receivers from respective manufacturers to see just how good the mcs was... at the time i didnt think it was going to be as good as the sta-2080 which since it was such a leap in quality from anything ive ever had, sounded overly confidently good through merely a pair of bose 201's (i have since upgraded, and my father currently uses BR-1's).

i got both receivers set up on a table, swapping speaker wire back and forth between the two to see how they do with certain songs. i had the 201's away from the wall enough to offer at least some bass, still too midrangy with the 2080 but i digress.. to note, the sta-2080 has never made a noise/hum/pop/static/abnormality in MANY hours of use now, this thing seems like the kind of receiver that stays on for 30 years straight in a shop...


needless to say i and the sta-2080 was humbled by that 3275. it actually pissed me off at the time, i couldnt believe the severe and significant difference between the two. the bose 201's are a terrible speaker for the sta-2080, but the 3275 didnt seem to care about the problems the 2080 had with the bose, it sounded incredible through the bose speakers, it didnt make sense to me. i had to have switched the two for "specific song listen sessions" around 20 times hoping i could come up with a reason the realistic did better but i knew every time the huge difference between the two. i dont know if its the fact that the 3275 is rated for a frequency response of 10hz-40khz vs the 2080's 20hz-20khz, or if the mcs is just producing more actual watts rms, or if the magic is in the five band equalizers... at that point in time i was certain it was mainly the frequency response.


after hearing both through a set of dayton BR-1's it was quite notable what a good crossover/ speaker design would do for the 2080 in terms of bringing the "tone" out of it, but the mcs was always able to be adjusted to produce numbingly intense noises.. it just seemed to hit harder with every instrument. it was such a difference that it actually played songs for me unlike i have EVER heard them before. notes were coming from places the realistic was just flat out missing them. dont get me wrong either, the sta-2080 is a quality sound, its bass is so instrumental vs boomy, you can hear/feel every rise/fall of the rhythm in such a nice way.. ive said it before and ill say it again, its hard to say where the realistic does better or even as good as the 3275 but its bass lines are really nice.

i still very much enjoy my sta-2080 and firmly believe i havent seen quite what its capable of without getting the right set of speakers. im currently listening to it through a pair of mcs 683-8295 40" tall 3 way floor speakers. they are a nice step above the bose 201's and for 55 bucks i had to have em. they are missing some wood trim but they sound great and the speakers are all dentless/appear nice and the grills/fabric are in one piece. they are having the excessive midrange problems the bose speakers had, but i think that might end up going away with the 3125. i think the 5 band equalizers were a nice way to compensate for wide varieties of speaker crossovers, and could make good use out of any crossover design, and could make not so great speakers sound incredible.

needless to say im not here just to write stories, id really appreciate the help/insight/guidance of those/someone/anyone who really knows the mcs units. while according to the seller, the 3125 shouldnt have any issues id really like a service manual for one of these along with possibly a list of things to watch out for.

i also really need a service manual for the 3275 as it occasionally drops the left channel. ive read this is almost certainly due to dirty switches and i really dont think my dad sprayed all of them, only the speaker selector switches. i read you really need to get them all but that was after he had it apart and back together. it seemed to fix it but it still occasionally goes out. i figure at minimum it needs all the switches cleaned and worked but the volume pot is also sealed.. i heard you can open it enough to spray deoxit in there but ive heard of these being trashed? the volume isnt scratchy or anything, no popping.. though id almost swear that the knob seemed to get ever so slightly "hung up" the very first movement after sitting for a bit after use.

if theres still anyone that knows these mcs units well, i could really use some help and id greatly appreciate it.
 
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so the "small amount of dust" turned out to be full blown dusty/dirty knobs.. neither channel works unless you play with the tone defeat switches and even then they are temporarily there with the sound quality being quite dreadful.

bought this on ebay (no affiliation) under the impression "it functions great"... so much for that

but i need some info on this thing. a service manual would be pretty killer right about now

best way to access EQ switches/ tone defeats?
 
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Yup. dirty controls most likely, and the two defeat buttons are known weak spots.
I don't know about the 3275, but the 3125 is not exactly easy but I've done two of them. The hardest part with the 3125 is getting out the board that holds the 10 eq dials and the the two defeat buttons. It's a bit of a wrestling match and care must be taken to not overbend and break that control board. It's important to clean ALL controls while disassembled and not just the eq dials and defeats...clean the speaker control, on/off, loudness, tape monitor, volume control, even the mic level...all of them. Better to do them all when you have it disassembled rather than have to go back in again.
This thread....
http://www.audiokarma.org/forums/index.php?threads/mcs-3125-control-cleaning.49994/
has been of great help to me with cleaning the controls on both of my 3125's.
Rick at stereomanuals.com has a nice repro 3125 service manual if you want more in depth technical stuff. I don't see a listing there for the 3275.
Good luck!
 
thanks man i really appreciate it. really glad theres still people out there interested in this stuff as much as i am (even more so lucky for me)
 
I had a pair of MCS 3-ways once. Not bad speakers! I put a pair of BR-1's together myself. They play pretty nice with everything I have except for one low watt tube amp I have. I still have one of the weirdest audio/video components I've ever seen and its a MCS. It's a combo of closed circuit B&W monitor/vhf-uhf TV/ monitor when recording VHS/ stereo O-scope. The one I have was built in '78 and came to me with NASA calibration stickers on it and labled "launch Pad 6". Must have been used as a closed circuit monitor, kinda cool.
 
I had a pair of MCS 3-ways once. Not bad speakers! I put a pair of BR-1's together myself. They play pretty nice with everything I have except for one low watt tube amp I have. I still have one of the weirdest audio/video components I've ever seen and its a MCS. It's a combo of closed circuit B&W monitor/vhf-uhf TV/ monitor when recording VHS/ stereo O-scope. The one I have was built in '78 and came to me with NASA calibration stickers on it and labled "launch Pad 6". Must have been used as a closed circuit monitor, kinda cool.

yeah the br-1's arent very sensitive speakers, my sta-2080 took a little more juice to drive them to the same "loudness" as the bose 201's i have but the quality was such a big difference it was incredible. the br-1's really showed me what i was missing without a good set of speakers.

that closed circuit monitor sounds extremely cool, id build that thing a filtered/heated bunker and still dust it every day if i were you
 
The stereo scope watt meter is the coolest part. L/R channel is split on the screen. It was just too weird to pass up. :D
 
I have my eye on a 3125 locally, going into protection. If the price becomes right I may have to grab it and fix it.
 
well the filter caps have got a solid bit of greenish sandy corrosion on the leads with stalactite like electrolyte dripping.. looks like something it had been doin for a while as it had built up on the bottom cover. its a shame it really wasnt horribly dusty like i thought it was from looking at the tops of the transformer and filter caps.

i havent cleaned the controls yet as its just sitting up side down. i managed to make more work for myself by lifting on a lead of solder on what appears to be the volume/balance switch that was placed on the solder mask and i tore the solder mask. it looks like someone peeled back the solder mask at some point if not at the factory and jumped over the exposed board with a tiny length of solder as a means of reaching an area of the board on that circuit that still had a good "insulation" as there is a pretty messy spot at lead #60 on the volume/loudness board. #60 is missing about half a cm of solder mask coming off the lead. around the left side of the lead it seems to be missing is insulation or whatever separates solder mask circuits.

im not sure if i want to even get to cleaning the controls and reassembling it once i fix this part of the circuit board.. im definitely going to work some D5 into all the controls but im not sure if im going to put it back together yet or if im going to go about replacing the filter caps first.. i feel like i really ought to. i looked over all the other caps and aside from some old dried booger glue they all look really good.

when i got it to play by messing with the controls i found that i had to hold the balance just off center for best results, maybe that has something to do with what i found at lead #60.. it also seemed to be capable of quality sound but it was certainly missing a lot.

would it be okay to replace just the filter caps before replacing any others or could that be a problem? my rationalization is new and better filter caps should be an improvement over these even with all the other original caps but i could be wrong.

sucks i gotta fix the solder mask i tore but at the same time i dont like how it was set up/previously repaired and im glad its a manageable repair. i also found the leads of something just a little to the right and down (if down is going toward faceplate and up is filter caps) touching each other. i separated them with my fingernail but i havent seen the other side of this board yet so im not exactly sure what it is, maybe it needed jumped like that but it really didnt look like it.

and as to it even having original caps, they are rubycon 85 C filter caps and the 4 bigger caps on the channel output boards are light blue rubycons as well. bottom board is a lot of purple.. looks like ill need one of those manuals from that one site
 
Are you talking about the 3125 or the 3275?
It sounds like you have way more technical/electrical knowledge than I do. Assuming you are talking about the 3125, those filter caps on the 3125 are easy to access and changing them out should be easy for you.
Based on my experiences, to REALLY clean the controls you have to do a full faceplate and eq board disassembly. The eq controls and defeat buttons are not easily accessed without removing that particular board. It's not that bad with help from the link above takes me maybe 3 hours.
If you do go for the full cleaning, let everything dry really well before applying power to the unit. And test/work all the controls back and forth many times and make sure all is well before reassembling the unit.
 
im talking about the 3125. in the above link it shows you how you can remove the volume/balance board that is underneath the eq board so you have access to the bottom side of the eq pots and tone defeat switches without removing the eq board from the chassis. i stopped after i broke the #60 trace lead on the volume board so i could 1. learn the best way to fix that trace lead and 2. better assess what exactly needs done.

any ideas on what brand caps i should go with? im looking at some cornell dubilier 6800 uf 80v 85c .049ohm snap in at the moment
 
I'd be interested in knowing what caps you end up using, I don't have a recommendation other than a name brand from a trusted source.
I've seen talk online about going larger with filter caps (not just this particular receiver but most any receiver) like replacing the 6800uf with 10000uf. Supposedly a little bigger is ok and may give slightly improved performance. I'd want to research that some more before doing it though.
There was something on the left side of the 3125 that was held in with little teeny screws, maybe the tape monitor switch board, or maybe the mic level, I can't remember, but I swore I'd try not to remove it again as it was a pain to get it lined back up and getting a screw started, one of those deals where a finger in back of the main plate to hold the assembly but no room, etc....since I've already forgotten what it was I hope I don't do it again.
As for the balance/volume pot, I think that's the one that you need to remove a LONG screw and shoot deoxit into the screw hole, you need to really work that switch and make sure the deoxit does it's thing. And if I remember correctly....those long screws go into a nut that is recessed into the back of that housing....I found it best/easier to keep a finger over that nut so it doesn't fall out, but maybe that's just me.
 
i ended up buying 4 panasonic UP 6800uf 80v 85c .046 ohm off ebay for 22 bucks shipped before i found a site called www.percyaudio.com where i found and bought 4 nichicon KG series 6800uf 80v caps for 48.99 shipped. i didnt cancel the order on the panasonics because thats a darn good price for 4 of that value cap shipped.

im not sure yet if im going to jump a wire from the broken circuit track/trace lead to the pad or what yet. ive still got to clean up the affected area a little bit and im considering doing the entirety of the board repair after i clean all the controls.
 
Have you received the nichicon caps yet?
How do they compare size wise with the original MCS caps?
Both of my 3125's are ok now but who knows I may want to replace filter caps in the future.
 
not yet but they are 35mmx50mm vs panasonic UP series 30mmx50mm

ill probably use 2 of these panasonics in this mcs 3226 (if and when it needs it) i just picked up off ebay. ive also got a marantz sr220 25 rms wpc, and a realistic sta-78 22 rms wpc that both sound very very good that use similar sized caps as each other and the sr220 i saw used 6800 uf 60v filter caps. im unsure on the realistic but its caps are a similar size so id imagine a similar value.
 
good you upped the voltage for the ps caps. If residual or other noises in the signal path testing like in a tone control circuit or board. Elna simic II's for caps in the signal path should fit nicely. Hopefully transistors are still good. If any rear mounted transistor types on the chassis? you should re paste them and try to save the mica as just apply the paste to the mica to chassis side.
heat dissipation/ cooling.

90+ percent of mcs stuff is NEC and their suppliers back then. Bought a tape and tuner from a guy who said he paid a grand for his system back then refused to part with his amp. separate. but threw in a pair of speakers that I repaired and sold. I use both tuner and tape deck for testing on amps and not enough listening.. :D
 
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i didnt up the voltage i stayed at 6800uf 80v. if thats what the factory used i dont see a reason to change it
 
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