ARC VT100 driver adjustment

[kenneth]

Has anyone experience on how to install and adjust the driver tubes on my Audio Research Vt100 MkI. I dont find the junction between R7,8 and R11,12. The instructions and schematic seems to belong to a MkII. Shouldnt the MkI and II be identical in this regard.

Thanks,

Kenneth

 

[kevinkr]

Unfortunately, not necessarily. You might try contacting ARC directly, and their site archive might even have the schematics for the VT-100. I long ago quit servicing ARC gear so I can't help you further.

 

[HollowState]

I think you will find the VT-100 schematic below.
http://www.arcdb.ws/VT100/VT100.html

 

[kevinkr]

The schematic listed on arcdb is for a VT100 MKII which differs in some ways from the MKI although I do not know the specifics.

Contacting ARC for a service manual and schematics is probably the best bet.

 

[HollowState]

The schematic listed on arcdb is for a VT100 MKII...

Ok, now you have me scratching my head. The diagram is listed under the VT-100 heading. Not the MK-II or III heading. The schematic clearly says VT100 in the lower left corner. Are you saying the website is just wrong? Below the VT100 designation is "AUDIO REV11" (eleven, not II) whatever that means.

I do know that at some point in time, AR stopped putting componet values on their diagrams in the instruction manuals and only referenced parts as R1 and C2 etc. Because values are given I would suspect this to be an older schematic. Just wondering. Can you shed some light?

 

[kevinkr]

True, and it appears erroneously to me perhaps that rev 11 is rev II in adobe 8 linux version so I am not really sure. It could be the MKI schematic, but rev 11 seems odd for a design that lasted just two years before being replaced by the MKII version, and the MKII was made for a long time. The MKIII uses 6H30 so it is not hard to tell them apart..

 

[Cobra2]

VT100 MkII; what jfets are used?
I,m trying to repair one, and the fets are painted...

Arne K