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Gregory "Mark X" - Schematic Needed


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5/5/2005 2:33 PM
Paul Marossy
Gregory "Mark X" - Schematic Needed
I just picked up this amp mostly out of curiousity. It's not a bad sounding amp, I think it's from the mid 60's, but I am not real sure about that. Anyhow, I am looking for a schematic for it. There's one in the bottom of the enclosure, but it has significant water damage, rendering most of it illegible. Anyone ever heard of one of these amps or know of a source for a schematic? I've come up empty doing a search on the web...
 
5/9/2005 8:57 AM
Paul Marossy

From what I can tell, it is an almost exact copy of a Vox Pacemaker except with a single tone control. It would be nice to confirm that. I am kinda leary of trying to draw up a schematic on it - hard to follow the wiring as installed...
 
5/11/2005 3:29 PM
Tim Gagan

A Gregory Apollo 800 was the fodder for the first amp I built: I stripped it out and built a different circuit into. I've poked around a bit for information, but the only thing I've ever been able to find out about Gregory amps is that they have a reputation for being about the worst amps ever made among the few people that have heard of them. Mine does sound great, now, though (5F6-A preamp, Marshall 18-watt power amp...)
 
5/11/2005 3:44 PM
Paul Marossy

I must agree that they are the cheapest things that I ever did see! This little Mark X amp sounds great, though. I have a partially completed schematic here: http://www.diyguitarist.com/PDF_Files/MarkX-Schem.pdf  
 
I made out what I could from the schematic glued on the bottom of the enclosure. I just have to fill in some missing values - the schematic in the amp itself only shows about half of the component values!  
 
Here is a page on my Mark X and what it has become: http://www.diyguitarist.com/GuitarAmps/MarkX.htm
 
5/12/2005 9:27 AM
Paul Marossy

OK, I drew up a schematic last night. Here it is: http://www.diyguitarist.com/PDF_Files/MarkXSchemR1.pdf  
 
I feel pretty good about it except for a couple of things: I forgot to verify the plate resistor on V2A. Would it normally be the same value as the cathode resistor in this configuration? Also, I forgot to write down where the wire from the wiper of the "strength" pot goes. IIRC, it was to Pin 1 of V2B...
 
5/13/2005 5:20 PM
Tim Gagan

Hi Paul,  
Thanks for drawing & sharing the schematic. Judging by the tube complement and what I remember of mine, it looks like the Gregory Mark X and the Gregory Apollo 800 were about the same amp. Your cabinet looks alot like mine, too, but the Apollo 800 chassis has an angled front and just an odd shape. Same handle!
 
5/13/2005 9:28 PM
Paul Marossy

Hmm... interesting. Yeah, those handles are unique, that's for sure. I updated the schematic tonight - added cathode voltages on the power tubes and made a couple of small corrections in a couple of places. :)
 

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