help with Grampian/Gotham wiring

[marchingband]

Just resumed work on my lathe (presto 8DG, Gotham amp, Hrampian typeD cutterhead) after a year off ... having trouble remembering how to wire the cutterhead to the amp.

gotham amp has 7 options at the input, Im using:
5 : hot
7 : ground

and 7 at the output, Im using:
1 : FB hot
2 : FB shield
4 : (to cutterhead) hot
5 : (to cutterhead) shield

the connections on the cutterhead are
FB 'S' (I have it going to output 2 on amp)
FB 'F' (I have it going to output 1 on amp)
M 'S' (I have it attached to output 5 on amp (looks like ground on schematics))
M 'F' (I have it attached to output 4 on amp)

The tubes all heat up, and I can her the program VERY faintly coming from the cutterhead, but the VU doesn't move, it just hovers at 5mv after warming up and doesnt budge, no matter how I adjust the program or the gain on the amp.

anyone know what could be going on? The amp did get jostled a little during transport since I last used it ...

[marchingband]

ps. Also had head overhauled (incl. new coil) by Len Horowitz since last use.

[Kris D]

Hi - If you are referencing the meter on the front of the amp for VU stop!!
It is not a VU meter, it is used to set the bias adjust for the power tubes. I have a PDF of the manual and will look for it tonight. Until you are sure what is going on with the amp I would suggest testing it with a speaker instead of the cutterhead. There is an octal jumper plug on the back of the amp that can be changed to allow for non feedback operation and testing.

Feel free to PM me for more info.

Best - Kris

PS- Don't risk blowing your cutterhead and take it one step at a time!

[downtown]

Please explain how to alter the octal jumper to test the amp with a speaker?
Nick Stevens
Downtown Recording