McIntosh - Hints and Kinks

Discussion in 'McIntosh Audio' started by dewickt, Jul 1, 2004.

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  1. quartersaw

    quartersaw Well-Known Member

    Messages:
    713
    Location:
    Albany, New York
    "New" Mc2300

    Terry,
    I was wondering if you would be so kind to give me some advice? I recently purchased Mcintosh Mc2300.that is in very good cosmetic condition. There is some rust on the power transformer (and maybe the Autoformers) that concerns me. Should I leave it alone, or try to clean it up?
    I was also wondering what components typically need to be replaced in a 42(?) year old first gen. Mc2300? (1Y983) I'd like to use the best possible caps, and whatever else might be necessary to bring this amp back up to spec.
    Any advice would be greatly appreciated!
     
    Last edited: Sep 27, 2013
  2. dewickt

    dewickt Will fix about Anything

    Messages:
    3,389
    Location:
    Knoxville, TN
    Rust is common and just cosmetic, never have seen it cause operational problems.
    Sensitivity may be low from bad capacitors on the preamp board, I use Nichicon Muse both the EH and KZ where appropriate.
    If in doubt on condition of the 2300 get it to a test bench with proper load resistors and a good distortion analyzer, then test to verify it meets specs, too capable an amplifier to test by ear.
     
  3. quartersaw

    quartersaw Well-Known Member

    Messages:
    713
    Location:
    Albany, New York
    Thank you for your time, and trouble, sir. Your advice is very much appreciated!
     
  4. Ajcrock

    Ajcrock New Member

    Messages:
    2
    Being new to Mcintosh I am not familiar with the type of wire used in the older amps. I recently acquired a MC225. Does anyone know what the wire was made of? Replacing it would be a awful mess so I would not want to if not needed but I do have some oxidation concerns if it is not made of silver.

    Thanks
     
  5. dewickt

    dewickt Will fix about Anything

    Messages:
    3,389
    Location:
    Knoxville, TN
    Pre-tined OFC copper I think with PVC insulation, used in all McIntosh, changing it out for silver wire would be a waste of time, the gains would be minute. The worst part would be the change in a known good layout and the possibility of fatal errors, change out the known bad bumble bee capacitors, and out of tolerance resistors. The brown dog bone capacitors are what gives the 225 it's fine sound, leave them alone.
     
  6. Ajcrock

    Ajcrock New Member

    Messages:
    2
    Thanks Terry. I will stick with that approach. I combed through this thread and documented those items along with the power supply. Sounds like a sensible approach.
     
  7. jlovda

    jlovda Things I loved from the 60's and 70's

    Messages:
    3,130
    Location:
    NE Ohio
    C34V turn-on noise

    I have a C34V that I bought on ebay several years ago with numerous problems. I thought I had them all corrected but now something else popped up. When I turn it on, one channel has an ~2 sec loud buzz followed by a snap/pop after which it is fine. Turn off is quiet. The other channel has no problem. It seems to be the monitor amp since the noise is not present when I send the line level outputs to another amp. I notice there are two FETs that shunt the audio at the input of the amps for two seconds. However, that would not silence any noise created downstream. It's very hard to get any probes onto the amplifier components. Would anyone have suggestions where to start looking? I have found a source for the J174 P-FETs used as the turn-on shunts so I will probably try changing them. That is however just a shot in the dark.
    Thanks
     
  8. paulram

    paulram Well-Known Member

    Messages:
    793
    I'm about to bring an old tube favorite back to life ( MC30) but before I start digging in anyone with testing procedures for the trannies? Regards..Paul
     
  9. pcrosewood

    pcrosewood AK Subscriber Subscriber

    Messages:
    148
    Location:
    Halifax, Nova Scotia
    Terry,
    I have an MX 114 tuner/preamp and it sounds dull and tired. What can be done to improve the performance?
    Thanks Terry,
    Paul
     
  10. dewickt

    dewickt Will fix about Anything

    Messages:
    3,389
    Location:
    Knoxville, TN
    Replace the electrolytic capacitors in the preamp and MPX sections, the originals are tired !! May as well do the power supply while you are into it.
     
  11. pcrosewood

    pcrosewood AK Subscriber Subscriber

    Messages:
    148
    Location:
    Halifax, Nova Scotia
    Thanks for the quick response Terry. Any recommendations for best capacitors to replace the electrolytics with.
    Thanks,
    Paul
     
  12. dewickt

    dewickt Will fix about Anything

    Messages:
    3,389
    Location:
    Knoxville, TN
    I like the Nichicon Muse - ES, KZ, and FG, normallly I buy them from Handmade Electronics http://www.hndme.com/
     
  13. pcrosewood

    pcrosewood AK Subscriber Subscriber

    Messages:
    148
    Location:
    Halifax, Nova Scotia
    Terry,
    In the MX 114 service manual, the preamp printed circuit board diagrams show C305 and C307 in the left channel and C306 and C308 in the right. The caps list show these to be electrolytic caps # 066-048. In my MX114, they're actually Tantalums in those slots. Should I replace these or leave them be?
    Thanks,
    Paul
     
    Last edited: Dec 2, 2013
  14. dewickt

    dewickt Will fix about Anything

    Messages:
    3,389
    Location:
    Knoxville, TN
    Tantalums were a good cap in their day, as they aged they develop problems like shorts and bad ESR, replace any you find !!
     
  15. dubai2000

    dubai2000 Active Member

    Messages:
    145
    Location:
    Germany
    MA6200 question

    I would like to replace the electrolytic caps on both driver boards - does the amp need to be recalibrated after that or is it a 'simple' swap job?

    Any feedback will be appreciated.

    Wolfram
     
  16. RShackleford

    RShackleford Active Member

    Messages:
    179
    Maybe you don't know, but tantalums are a type of electrolytic. And yes, I'v also heard they tend to fail.
     
  17. pcrosewood

    pcrosewood AK Subscriber Subscriber

    Messages:
    148
    Location:
    Halifax, Nova Scotia
    Replace the tantalums with aluminum caps?
     
    Last edited: Dec 3, 2013
  18. RWright

    RWright New Member

    Messages:
    7
    More info on MC40s

    Hello,
    I also have a pair of MC40s that I recapped years ago. I also changed out the selenium rectifier on the bias power supply. However, I never added any resistor in series with the rectifier diode as you mention. I used a variac and adjusted the pin 3 of the 6L6 t 470v. Now I get -168 and -58 volts on the bias lines. Should I put a pot in series with the transformer/diode to trim this, and then replace with fixed value? It seems like it would be alot higher than 470-ohms, but I calculated on the dc side.

    Since I originally posted this, (without replies) I have tried to adjust the bias by setting the 6L6 voltage to 470v, then using a pot in series with the AC side of the bias voltage I adjusted for -52 volts on the bias. However, when I do this the 6L6 voltage drops to 460v. Is there another issue with the amp I might be overlooking? Thanks.
     
    Last edited: Dec 5, 2013
  19. pcrosewood

    pcrosewood AK Subscriber Subscriber

    Messages:
    148
    Location:
    Halifax, Nova Scotia
    I replaced all the electrolytic caps in my MX 114 as per Terry's suggestions, with Nichicon KZ caps and wow. The MX 114 went from being dull and lifeless to being dynamic, detailed, rich highs with solid bass, smooth with rich warm resonant mids...I'm trying to describe what you can only appreciate by listening. People have suggested to me not to put money and effort into this preamp. "They weren't all that great to begin with" I was told. Well, I beg to differ and this preamp with my Mac 2105 is providing me with listening bliss...it's all I'll ever need or want. Many thanks to Terry and all on this site for being so open and generous with your experienc and knowledge. Can you tell I'm happy with the resuits :)
     
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