Very old Mark I in for repair

I love my job....

This was bought off ebay last week for a steal. Turns out to be an original 74' Mark I. Oldest I've had the pleasure of working on so far. Glad I got the call. Client called and said, "I bought a Mecca Boogie and it don't work"....

Looks like Mike did a cap job in 91' and put in a new filter cap board as well. Almost everything else is original except for some rewiring of the filament strand which I'll put back to spec. Came with a crappy Celestion. Gonna get an Altec in it and some STR415's and it'll be good as new.

All pots date 73', All tranny's date 73' except for the OT which is 606-4-02. So I'm calling it a 74'.

Check it out:

very cool! love the shots. I'd love to find one like that with the wood cab too.

Wow! With one of the beautiful, dovetailed hardwood cabinets. There is some good, vintage gear out there if you know what you are looking for and are patient. Great find. Did you tell the customer how lucky they were?

Very cool. You mentioned it came with a Celestion, but the pics from the auction show an Altec.

lockbody said:

Very cool. You mentioned it came with a Celestion, but the pics from the auction show an Altec.

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Well, the auction also says it was checked out by a tech and works great... :roll:

Never seen one where the wicker has aged so much! Grill on my '77 15" is clean as a whistle, that amp must've had some life.

Strange to think looking at those internals that it was the absolute bleeding-edge hyper amp of it's day. Great Boogie!

zebpedersen said:

Never seen one where the wicker has aged so much! Grill on my '77 15" is clean as a whistle, that amp must've had some life.

Strange to think looking at those internals that it was the absolute bleeding-edge hyper amp of it's day. Great Boogie!

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Yeah, it ended up being a sweet playing amp. Pure original Boogie tone. From a tech point of view it's simply a blackface Fender with a rewired preamp. The power section is note for note blackface fender circuit with the exception of the power tube grid resistors(2.2k instead of 1.5k) and the coupling cap between the preamp and power amp(.002uf instead of .001uf).

I documented this amp very closely and am finishing up a hand drawn schematic shortly.

The reverb by the way on this amp is the deepest I've ever heard on a Boogie. Very lush and musical with no excessive sproingy sound...

jonarobb said:

The reverb by the way on this amp is the deepest I've ever heard on a Boogie. Very lush and musical with no excessive sproingy sound...

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Yeah I must admit that the reverb is probably the weakest part of my MK1, I guess on the even earlier ones they kept that from the Fender which can only be a good thing.

Interesting seeing the control layout and what you say about the internal design - I'm not sure if these were options at this stage or they hadn't been introduced yet or what, but no pull-boosts, no 60/100W switch... I had no idea actually how similar these things were to the Fender amps they were based on! Maybe they became less Fender and more Boogie as the earliest production years went on?

Very cool!

What is the "Normal/Boost" switch doing? Never seen that one before!

FillmoreEast said:

Very cool!

What is the "Normal/Boost" switch doing? Never seen that one before!

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Unlike later Mark I's where the Boost was tied directly to the tone stack, the Normal/Boost feature on this amp is really just a 100w/60w switch. It's tied directly to the cathodes of the center pair of power tubes. Normal is 60w and Boost is 100w.

jonarobb said:

FillmoreEast said:

Very cool!

What is the "Normal/Boost" switch doing? Never seen that one before!

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Unlike later Mark I's where the Boost was tied directly to the tone stack, the Normal/Boost feature on this amp is really just a 100w/60w switch. It's tied directly to the cathodes of the center pair of power tubes. Normal is 60w and Boost is 100w.

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Allright! Cause I know a guy who owned two 15" Mark I's in the '70s and they had four switches.
I thinking that maybe they both had 60/100 switch, and some kind of Gain-Boost switch?

My bud has a 1980 IIb 15in and the four switches are:
Eq in/out, 60/100 watts, standby and power.

But his amps didn't have EQ

Some of these Mark I's have a graphic EQ.
My '77 has also a front switch for EQ in and EQ out.
Mike Bendinelli mod the placement of the graphic EQ in the circuit. He says that placing it after the master makes it much more usable (I guess Keith Richards also had his Mark I modded this way).

The gain boost and the EQ can be accessed also with a stereo footswitch (check the jack under the chassis).
Regards

igfraso said:

The gain boost and the EQ can be accessed also with a stereo footswitch (check the jack under the chassis).
Regards

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This is not consistent and therefore not good information. The earliest Mark I's didn't have a jack under the chassis. The jacks started appearing as custom orders and were wired according to the customer request. I've seen the jack under the chassis wired for the following uses:

Pre-Amp Out
Pre-Amp Out/Power Amp In
Power Amp In
Reverb On/Off
EQ On/Off
Boost On/Off

Or any combination of these features.

Unless you know how your 1/4 jack under the chassis is wired it's not a good idea to just go plugging cables into it.