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  1. Gregory

    MC2255 Rehab Project

    This 2255 post was missing a photo https://audiokarma.org/forums/index.php?threads/mc2255-rehab-project.970640/#post-15041367 Contamination and grease on slide switch. See ratty insulation upper right, since trimmed off. -Greg
  2. Gregory

    MC2255 Rehab Project

    Got the RIGHT meter separated from the frame on Oct 7th and set on a microfiber cloth face down. Had trouble `breaking´ the adhesive at the lower corners on the back of meter and didn't want to crack the case, so decided to abort for now. The panel has a few `fixes´ on the possible `do´ list...
  3. Gregory

    MC2255 Rehab Project

    Many photos taken - few processed These are the recapped PO PCBs (driver boards). They are really the PREAMP INPUT, HEADPHONE & POWER OUTPUT boards. The black caps are all Nich VR, nice and small compared to originals. The input coupling caps are Nich FG (Fine Gold), and one each Nich ES...
  4. Gregory

    MC2255 Rehab Project

    The SN is CT5329 — unless I've mixed it up with another Mc unit.
  5. Gregory

    MC2255 Rehab Project

    Had John's 2255 from the first week in August till last Friday, for ~12 weeks and worked slow. Replaced nearly all PCB caps, except for a few on the 'double sided' Countdown board, and the 10% caps on the Meter board, probably the Meter Hold time delay circuit. Ripped a thru-hole and pad out...
  6. Gregory

    MC2255 Rehab Project

    2255 Powered On this morning after a pretty substantial tear down, inspection, and cleanup. Most all PCB electrolytics replaces. System Power On test completed successfully. AC line draw at idle is 50 Watts. -Greg
  7. Gregory

    MC2255 Rehab Project

    He's asking about a `drop-in´ Power Meter LED kit for the 2255 with the best and most authentic color match. The object here is for the unit to run cooler, especially when inside the walnut case.
  8. Gregory

    MC 2255 Service Manual

    The output caps hardware cleaned up beautifully with a dab of D-100 and a Dremel tool at low RPM. And there's that little disc ceramic cap, upper left. Before -Greg
  9. Gregory

    MC 2255 Service Manual

    Thanks for that, I haven't replaced or ordered new screws. The yellow oxidation came off the screw-heads easily with a touch of D-100 on white cotton cloth (i.e. patch from an old t-shirt).
  10. Gregory

    MC 2255 Service Manual

    A disc ceramic cap has broken from the copper side of the INPUT LEVEL board while removing the OUTPUT heat sinks. This is the only photo I have that shows the position of the cap, and it seems one leg is already disattached. The cap appears to be on the RIGHT channel in parallel to C104 ...
  11. Gregory

    MR80 display ranging

    Yes, comm engineers use what's called a Link Budget to describe or design RF/microwave systems. The general expression is: Received power (dB) = transmitted power (dB) + gains (dB) − losses (dB) https://en.wikipedia.org/wiki/Link_budget The biggest loss of course is Free Space attenuation...
  12. Gregory

    MR80 display ranging

    Found the FM station in Milwaukee Described earlier as WLTQ 97.3 MHz, is now WRNW. https://en.wikipedia.org/wiki/WRNW "Light 97 – Light adult contemporary became the format in April 1985 as "Light 97" with the WLTQ call sign." The transmission towers were 71.4 miles north of the 4408 FM...
  13. Gregory

    MC2255 Rehab Project

    More updates The Output Cap hardware cleaned up really well. The `buttons´ below had lots of surface rust. There's heavy pitting in the lower right below. Lots of elbow grease and the chassis came out better than expected. Best to remove dust and dirt from the chrome chassis every 5...
  14. Gregory

    MC2255 Rehab Project

    Recent updates The Input coupling cap on the right is a Nich FG (Fine Gold), the BLACK cap in the OVAL is a Nich VR: date code 1107, and the Green cap is a Nich ES Muse (bi-polar). The cap in lower left (red arrow) was replaced with a Nich VR. Here are those new VR caps installed (yellow...
  15. Gregory

    MC2255 Rehab Project

    We found last week that many Nichicon FG (Fine Gold) are out of stock at Mouser. So I'm using Nich VR which are black in color. -Greg
  16. Gregory

    MC2255 Rehab Project

    Yes, they're from my cap kits and are NOS, and JB is aware of it. You're reading date code 1124? That sounds right. Got to use them up! or not order so many at a time. -Greg
  17. Gregory

    MR80 display ranging

    Great photo! That is the finest McIntosh instrument I've ever owned. It's a work of art, not to mention engineering, and the performance in NW suburbs of Chicagoland was fantastic. There's a pot on the top panel where you can `calibrate´ the signal strength LED stack (12 units) to the strongest...
  18. Gregory

    MR80 display ranging

    JB added the MR80 oscillator transistors to the Mouser 2255 cap order. They (the transistors) were only 28 cents each, so four of them were 1.12 dollar. Got a ride in his Porsche 911 a few years ago and it's slick. The color is silver or gray metallic IIRC and it turns some heads, but I wouldn't...
  19. Gregory

    MR80 display ranging

    Here are some views from the Mc MR80 service manual, PN 039215 which is about 9/16" think. Schematic Circuit PCB Hope that's correct. How much will a new transistor affect the alignment? -Greg
  20. Gregory

    MR80 display ranging

    Which means: it's been sitting in the rack for about 10 years with a cover on top. :eek: The Antenna switch on the MR80 top panel wore out from swapping Omni vs Yagi, and Omni vs Yagi array, which are relative antenna gain or signal strength comparisons. That was part of the Chicago and...
  21. Gregory

    MR80 display ranging

    This is the results I got in the US: https://www.mouser.com/ProductDetail/onsemi-Fairchild/KSC1674?qs=%2Fha2pyFaduhp0ImzzPRatiIlyEUlQQH%2FYUeOE4f5Das%3D https://www.mouser.com/onsemi/RF-Bipolar-Transistors/KSC1674-Series/_/N-1z0zlrjZax1s5Z1yxk8hp Where to order from? NZ? Thanks
  22. Gregory

    MR80 display ranging

    Will get the Service Info out and locate Q205, IOW find out where the transistor is located, and get back to the discussion with diagrams. Next will be to find that part on Mouser. Update: Mouser is out of stock. Any cross reference? -Greg
  23. Gregory

    MR80 display ranging

    What Kev is basically saying: "Section 3, IF stage, Q205: replace this transistor with a KSC1674. Also make sure the RCA cable between the Display circuit and the IF stage is nice and clean." Thanks man, -Greg
  24. Gregory

    MC 2255 Service Manual

    It will take time to look through that inventory of yours. :rflmao: -Greg
  25. Gregory

    MC 2255 Service Manual

    The A-size 'taped' schematic pages are clear and good to highlight and make notes on. Need to take better pics of them. On bench and getting started Aug 2nd. Lots of detailing to do — not to mention deox and derust -Greg
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