Vintage Roberts Vu Meters Bad?

[buildafriend]

Hello,

I scooped up a small lot of Roberts series 990 Vu meters from the Akai M6 off of eBay. Upon hooking them up I don't see any needle action and I'm wondering if it's possible that the first 3 of 8 are bad ( which would imply that all or most may be bad ) or if I am not hooking them up properly. I've tried what the picture shows and I've tried flipping it. I've also tried hooking the leads to where I think the lamp power connects up top. Other meters I have sitting around seem to work perfectly this way. Is there something special about these that might be causing my failure or would you guess these are no bueno? I'm just asking to see what you guys think before I ask for a refund.

All the best,

 

[radardoug]

Have you tried them with d.c.?

 

[envelope]

Not sure is M6 Vu wiring is same as M8, but attached here is the schematic for M8 showing the  Vu meter wired between TR2 and the Output jack, so you can see exactly how it is integrated.

 

[buildafriend]

thanks radardoug, no I havent yet but I'll give it a shot to see if they move.

envelope, interesting that the resistor comes from ground to the meter in the M8.  I have only seen meters hooked up the opposite way, but I tried it that way by flipping my wiring

 

[API]

Do you know if they have an internal rectifier?