I just got this Magnecord M90 mono reel to reel and I was wondering if anyone had any schematics available. I looked all over the net and can't find any. I plan on reworking this unit into a mic pre/tape simulation unit and the original schematics will go a long way in helping me plan the revised circuit. I have tried tracing it out but the unit I have is a bit of a basket case. It has been messed with extensively in the past and some of the wires are hanging free, even what is hooked up is a rats nest. I think this unit is very similar to other models like the M60, M80, and M900. At least they look the same on the outside from the small amount of info available. Even the M90 had an A, B, and C revision so really schematics of any of these models would probably get me a lot further than where I am now. I appreciate any and all info those of you out there may have for this interesting bit of tech. Plus, if anyone wants the transport for free it is not in the best shape, but would be great for parts and I would be willing to give it away, you just pay for shipping and packing materials.
Magnecord M90 Tube Reel to Reel: Any Schematics Available?
- Thread starter xfmr
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tubologic
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The Magnecord M90 was their top of range pro recorder and an excellent unit,in the same league as the AMPEX 350/351 series but with a more refined tape transport. (automatic tape lifter,etc...) It certainly worth restoring and I would not discard the transport if it is in a restorable condition. The preamp unit is similar (but not identical) to the M75/M80 series. The good news is that the M90 preamp has a built in good quality mic input transformer which is often missing (because optional) in the other versions. AFAIK,differences between B/C versions are trivial. I have the complete manual but it's about 50 pages long. Attached a low resolution scan of the preamp schematic. Full res scan available but doesn't fit here due to the attachment size limitation to 300k. PM me if you need the full size document.
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I don't get it, I don't see any schematics at that link. Am I missing something?
Also, thank you for the low res schematic and info posted but I can't really read the parts values, so yes can you e-mail me a hi res copy? My e-mail is xfmr AT xfmr DOT org Thanks so much, now I'm getting excited about restoring it!
tubologic
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xfmr said:
You need to be a member to gain access to the (often) inacurate and incomplete infos available on this website. Even for french speaking people, registration is a tedious,complex and discouraging process: a donation is required AND you need to prove them you're a "true" Radio-Collector by sending various info's and justify your motivations. If you're successful you'll have access to the hidden contents mostly available (free) elsewhere on the web. Great deal ! IMO this site s***s and should be avoided.
directdriver
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I need the full size schematic of the Magnecord M90. Please PM me. I'd really appreciate it. Thanks!
lapslide2010
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I know a long time has passed, but wondering if anyone has access to the high res schematic for the P75C, which looks to be the recording/reproducing amplifier in the M90 console setup? Tubes are 5Y3, 6BK7, 6BK7, 12AU7 and 12AU7A, 12AX7, 12AU7. Octal plugin sockets for input and output transformers. Front panel looks exactly like the amp unit in the M90.
directdriver
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Last edited:
lapslide2010
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Fabulous D! Much appreciated!!
hpyle
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@lapslide2010 Here's the P75 service manual. Not a great quality scan, I'm afraid, but I hope you find it interesting.
lapslide2010
New member
What great timing! I'm just getting ready to go over the record/reproduce unit on this, I'm sure there will be some valuable information in it. Thank you very much, easy enough to read!!
C.B. - Boudio
Well-known member
Electrolytic caps, especially the first one right behind the rectifier, and grid coupling caps (unless they are film instead of paper, or something alike the Philips mustard caps - which they are probably not, with this vintage) as well.
tablebeast
Well-known member
I always wondered about the 6BK7 tubes in this circuit. Its the only audio device I've ever seen with that tube. Its normally a TV tube, used in cascode, which is how its used here. But look at the 6BK7 and 12AU7 cascode circuits at the front of the input and playback stages. They are the SAME exact circuit! Why didn't they just use 12AU7s in both those positions? Or if the 6BK7 is somehow so much better, why not have them in both spots? Did they get a great deal on a truckload of TV tubes?
tablebeast
Well-known member
Yes, always replace those ticking time bombs! That is one thing I always replace without even checking. Its like disposing of asbestos properly. There is no grey area. You're lucky it hasn't already killed you.
