Dead VUs on a 4k

[tko]

Hi Everyone,

I am all the way down here in New Zealand and I'm having trouble with techs.

I have some VU's that are down and my on my 4k, as well as the Left VU on the 2 buss.

Is there someone who could help me out with any tips, direction on how to fix this?

I have some tech experience I have build compressors and recapped a few things.

Thanks in advance TKO - STL Audio.

[sintech]

Hi, I doubt it's a mechanical problem, the meter cards have protection diodes in place, and the meters are British made Sifam's with tank like quality.

I'd trouble shoot like this:

You can diode test with your multimeter, across the + and - of the VU meter, and see the needle move to rule out mechanical failure.

Re-seating the Ribbon cable to the meter, is the first thing to do, secondly, if you get the Right hand Ribbon (which we know is ok) and try it in the left hand meter, and like wise the left hand Ribbon in the Right hand meter.

From what works or not you'll know now if it's the card on the VU meter, or the meter distribution card. (the other end of the ribbon)

If it's the buffered type, the VU cards will have an TL072 op-amp, you could switch that for a known good one.

In the past, I've had to gently tighten the brass nuts, this has brought more VU's back to life than you know!

[tko]

Thanks Sintech,

I chased the ribbon back to the distribution card, mounted underneath the producer panel? and what do you know... 3 plugs had worked loose. Plugged them in and all 6 faulty VUs are back in action! g

Even tho it was easy I feel very proud of myself!

Thanks TKO.

[sintech]

 

[walrus]

Meter weirdness that I've experienced is the nuts being too tight!
Loosening them just a tad makes them work again, and if you then tighten them again, the meter stops working. 

Eventually, I took the meters totally to pieces and cleaned up all the contact surfaces. This proved a definitive cure, but I couldn't work out why a tight nut caused failure......