1992 Mark IV, circuit questions

[kenkamm]

Hi all,

I have a Mark IV built in 1992. I am not the first owner. I am converting from combo to head, so I removed the amp and took a look inside. As I looked around in there I found a couple of things that didn't look like the pictures I'd seen in the big Mark IV thread, so I was wondering if my amp has been modified. If anyone can shed some light on this, it would be great. The amp seems to work fine, but I don't have another Mark IV to compare to.

Here are the pics from the Mark IV thread:

And here are a couple of pics of mine. I circled the areas of concern in red. In the first picture, it looks like a couple of resistors may have been substituted on the outer poweramp tubes. In the second picture, it looks like a component was added, and stuck in place with some glue. The circuit board looks like it was reworked in the area where the leads of the component connect.

Thanks,
Ken

 

[Boogiebabies]

The small black resistors on the power amp are just smaller 2.7K 3 watt. They look just like the ones used on later IV's.
The brown box cap looks like it's either a mod or correction to the recording out circuit as it's in the GEQ/Recording Out section near the inductor.

 

[kenkamm]

Wow. I guess that sure sums it up! Thanks for your help, I guess I'm good to go. I'm not too worried about the recording circuit.

Thanks,
Ken

 

[Shep]

Hey you have revision G mk IV i have a revision F. Whats you serial number??

 

[kenkamm]

My serial number is 5446. What's yours?

 

[Shep]

My serial number is 5446. What's yours?

#2263 Hmm wonder how many others are out there??

 

[kenkamm]

Others of what? Mark IVs in general? Lots.

 

[Boogiebabies]

Revisions to the circuit board.

 

[kenkamm]

Ah. Gotcha.

 

[Shep]

wonder what the differnce's are. It would be cool to find out.