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Post new topic Mesa Boogie Mark 1 early 1975
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Author Topic:  Mesa Boogie Mark 1 early 1975
Ken Fox


From:
Nashville, GA USA
Post Posted 9 Aug 2017 4:49 pm     Reply with quote

By special request I am bringing serial #121 back to life. This is a rare model with reverb and no mid control. Also no graphic EQ section. From what I have found on the net only a handful were made with reverb.

All early 1975 transformers and choke. Altec speaker. Contacted Mesa and they were stumped, had no recall if seeing one quite like it.

Got it up and running this afternoon. Carlos Santa, Black Magic Woman amp for sure

Did a filter cap job, one bad preamp rube, one bad screen grid resistor and a new reverb transformer.
Going give a good checkout tomorrow and make aschemetic by hand of the amp.





.






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Bob Lawrence


From:
Beaver Bank, Nova Scotia, Canada
Post Posted 9 Aug 2017 8:31 pm     Reply with quote

Ken,

Would the schematic for that amp be different that this one?

Mesa/Boogie Mark I
Preamp (11kb)
Poweramp (16kb)
Mark IA (90kb)
Mark IB (52kb)
Mark I Reissue preamp (40kb)
Mark I Reissue poweramp (43kb)

http://www.tubefreak.com/fschema.htm
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Josh Braun


From:
Minneapolis, Minnesota, USA
Post Posted 10 Aug 2017 5:04 am     Reply with quote

Awesome - I'm a huge Mesa fan!
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Ken Fox


From:
Nashville, GA USA
Post Posted 10 Aug 2017 6:59 am     Reply with quote

Seen all those schematics. I will blueprint the amp. Even Mesa did not have a schematic, as so few were built like this. Will be easy to draw up a schematic for it. Power supply and preamp are very similar to the existing schematics. Will just have to draw in the reverb section and a few other tweaks,
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Last edited by Ken Fox on 11 Aug 2017 3:36 pm; edited 1 time in total
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Tom Gorr


From:
Three Hills, Alberta
Post Posted 10 Aug 2017 8:40 pm     Reply with quote

Nice!

Please give more details on the Altec.. also how it sounds clean and dirty
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Ken Fox


From:
Nashville, GA USA
Post Posted 11 Aug 2017 6:27 am     Reply with quote

From what I have gathered the Altec was the early first choice speaker for these amps. He also has the original extension cabinet. Oddly the original speaker was reconed to 4 ohms in the main amp. Verified with a true impedance meter.
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Brint Hannay


From:
Maryland, USA
Post Posted 11 Aug 2017 10:08 pm     Reply with quote

I had an original "Boogie"--no "Mark" anything. The terminology when I ordered it was that it was a "Boogie Hun-Rev" ( hundred-watt, w/reverb), with graphic EQ, and Altec 12. The only option I didn't go for was the hardwood cabinet with cane grill "cloth". I went with the cream-colored Tolex.

I lived in San Francisco in 1975, and ordered it direct from Mesa/Boogie, which was the only way to get one in '75. I picked it up at Prune Music in Mill Valley, CA, the only retail outlet in the country (or the world!) at that time to pick one up. I loved it, and it was my pride and joy, until it was stolen from my car in about 1980.

I have the original schematic that came with that amp, if it might be helpful.
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Ken Fox


From:
Nashville, GA USA
Post Posted 12 Aug 2017 6:03 am     Reply with quote

Wow, that is great info. Learning more with each post. A copy of the schematic would be awesome. If you can scan and email that I would be every so grateful. I started checking it against the earliest schematic I could find and there are small differences for certain.
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Ken Fox


From:
Nashville, GA USA
Post Posted 13 Aug 2017 10:01 am     Reply with quote

Thanks for the schematic. I started drawing out the amp last week and I can tell this is either right on or very, very close to the amp. I will get back to my shop in Ray City tomorrow and start checking it closer
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Lefty


From:
Grayson, Ga.
Post Posted 14 Aug 2017 11:45 am     Reply with quote

The speaker is like the one in my 1-15 model (only a 12). Mine has reverb but no EQ. It does have the 60/100 watt switch so I believe it to be a IIb.
Great sound, but you need a buddy to help load it.
Lefty
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Jerry Korkki


From:
Arizona, USA
Post Posted 14 Aug 2017 9:12 pm     Reply with quote

Never seen a mk1 with reverb. Bought a 60w mk2b in '80. I thought I sounded like a new guitar player. Still have it and it makes me sound like a newer guitar player. A few years back, got a 60/100w '79 mk2a that sounds even better, just weighs a lot more. I'm a Boogie man for sure. In many ways it's a heavy little amp. And from my experience, great customer service as well.
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Ken Fox


From:
Nashville, GA USA
Post Posted 16 Aug 2017 3:43 am     Reply with quote

Got it back together. Old reverb tank was causing lots of problems. Temporarily checked it with a long Fender tank and it was awesome! Got a new short tank coming for it. What a sweet amp! Making me a new Boogie fan for sure.
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Jerry Korkki


From:
Arizona, USA
Post Posted 21 Aug 2017 5:07 pm     Reply with quote

Ken, you might look for a solid wire going from the back of I think the master volume pot to the chassis. Both of my amps had some issues breaking up at volume when I added a little more bass. I replaced the solid wire with braided and problem solved. I always use another single 12" cab with my setup (I like low end) and these things sound outstanding.
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Steven Paris


From:
Los Angeles
Post Posted 21 Aug 2017 11:30 pm     Reply with quote

Just curious why you changed the reverb transformer. Never heard of one going bad---???
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Ken Fox


From:
Nashville, GA USA
Post Posted 22 Aug 2017 4:45 am     Reply with quote

Open primary winding on the reverb transformer. Seen that a few times as well in Fendet amps. The reverb drive tube gets it plate voltage thru that winding and it was most definitely off
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Paul Honeycutt


From:
Colorado, USA
Post Posted 27 Aug 2017 11:03 am     Reply with quote

That has to be an early Boogie, having no mid control. They were originally hot rodded Princetons, which had no Middle control, so that's it's linage.

I have a reissue hardwood cab MK I with no pull pots or graphic EQ, but has a "Tweed" setting on the power switch. I have a vintage Altec in it. It's a bit different, but pretty close in sound to the originals with some simple mods.

Glad to see that you're restoring that Boogie!
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Paul Honeycutt


From:
Colorado, USA
Post Posted 27 Aug 2017 11:05 am     Reply with quote

A quick question. Once you get it done, is there any noise at idle? My RI has a lot of hissy noise, but once you play you don't notice it, but I'm trying to figure out if it's tubes, drifting resistors or filter caps as I'm selling it.
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Ken Fox


From:
Nashville, GA USA
Post Posted 27 Aug 2017 11:48 am     Reply with quote

Amp is very quiet at idle
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Paul Honeycutt


From:
Colorado, USA
Post Posted 30 Aug 2017 2:15 pm     Reply with quote

Thanks, Ken. I think my plate resistors are the culprit, but I'm going to start with tube replacements.
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