Theory: My Mark I might be a Mark II???

[kdove]

I have a '78 original Mark I ... I love this amp. My theory is that it must have been on the work bench as the Mark II was born. The reason I say that is ... I've only worked on this amp twice:

1st time-I was beginning to hear funny noises last year and had never re-tubed the amp. So, as I was taking out the pre-amp tubes I found this funny device in V1. I eventually tracked it down as a FETRON. Boogiebabies helped guide me through rewiring this amp ... replacing it with the 12ax7 wiring. I noticed then that the Mark II schematic had a lot of the fetron adjustments.

2nd time-Currently, I'm in a live discussion about changing my filter caps (this may actually be the real problem from last year by-the-way). Most of my filter caps are different from what's represented on my original Mark I schematic. After taking the chassis out and spending a great deal of time discovering what WAS really in my amp, I take a look at the Mark II schematic ... bingo my Mark I amp has the exactly filter caps in the original Mark II schematic.

Bottom line: I wonder if I've got either a mix of the two Marks OR a Mark II before they decided to relabel it. I might need to trace everything in this amp to the Mark II schematic and see what I find. Interested in opinions.

 

[sundaypunch]

I can't speak for Boogie but Fender was notorious for making changes on the fly. Many of their amps from the 1960's have a hybrid of circuits. Maybe Boogie started changing some of their components prior to an "official" change in model?

 

[kdove]

Well it ws definitely a mom & pop operation when mine was built. Randall Smith signed the chassis and his wife sent me the order paperwork ... so I think it's possible.

 

[Boogiebabies]

It seems like a MK I preamp with a MK IIA power supply. From memory, I don't remember seeing a relay or 5 preamp tubes. The pre was pure MK I with Fetrons. I would not put it past a rolling revolution or intermediate change between series.

 

[kdove]

It seems like a MK I preamp with a MK IIA power supply. From memory, I don't remember seeing a relay or 5 preamp tubes. The pre was pure MK I with Fetrons. I would not put it past a rolling revolution or intermediate change between series.

MK1 pre-amp with MK2 power supply ... with the fetron on both MK1 & MK2 ... yep that's probably a couple of rolling changes.

So the plan ... anytime in the future that I find myself stumped on the Mark 1 ... the first thing I.m going to do is check that Mark 2 schematic.

Thanks

I think I'm going to order the F&T (2) and Sprague (3) filter caps from thetubestore and change them myself ... now that I know those are the right values.