Question about screw threads on an unusual Mark I head...

[sushiboy]

Hi Everyone. My first posting. And what a dull one it is. I'm based in London. A while ago I bought a Mark I head from a very well-connected friend (former guitar tech with probably the most famous rock band in the world). The head is apparently unusual in that it has no reverb or graphic EQ, and, according to my friend, was built as part of a matched pair for one of the guys from a band called Foreigner - from whom he bought both. The head was fitted into a rack-mount unit but I was also given the original casing. Since my studio is increasingly free of rack mounted gear I've been trying to fit it back into the case, but am having problems finding four correct corner screws to hold it in place. They certainly aren't metric, like we have over here, but can anyone tell exactly what I need to be looking for? I guess the amp would be dated late 1970s? Again, sorry for the most boring debut post in history of this forum! Terry in London.

 

[DaveP]

The older late seventies Mark I chassis took 10/32 screw size. The later Mark series chassis starting around the Mark IIb used the 8/32 dimensions.
They are typically about 1 1/4 inch long. How that helps and welcome to the forum.

 

[igfraso]

Sushiboy,
you probably know this already but... just in case.
Mark I and Mark IIA cabinets and shells can only accept Mark I and IIA chassis.
The distance between the screws is different for newer Mark cabinets and shells. Starting with the Mark IIB, all Mark cabinets/shells and chassis are compatible among themselves.

Welcome to the forum.
Regards

 

[sushiboy]

Gosh, what a helpful forum this is! Thanks so much! My understanding is that it was the guy Ian (from Foreigner - I just Wiki'd them... really had no idea they were so *massively* popular in the US... or that I'd been using a celebrity amp!) had the pair of heads racked up by his tech, so I'm imagining that the case I was given is the original one. I'll try to find the screw thread you suggested. Much love from a rather cold London! T xxx

 

[gts]

If you can't find any let me know.
I have some that I could send you. (you cover shipping/ mailing cost which unfortunately isn't cheap).

 

[JOEY B.]

The screw size for the early Mark I chassis mount is 10-24 . It is a standard thread size rather than a metric, and I'm not sure how common it will be in Europe.