Telefunken v676a - Strange Problem

[ralfw]

Hello everyone,

as I’m working on a Rack full of seven v672s I added a v676a, which is working fine in this Rack until I slide any of the v672s in. Then only the v676a start to pulsating. The Pre does still work than, but generate this strange pulsating noise. Does anyone have experience with this kind of problem and can help?

As a PSU I’m using a TAB N324.

Kind regards Ralf

 

[Rob Flinn]

Look up the total current draw of the modules compared to the PSU delivery capability.

 

[ralfw]

Look up the total current draw of the modules compared to the PSU delivery capability.

Hello and thank you Rob, the PSU delivers a maximum of 5,5 A +- 10%. From the service manuals I read that all of the v672s and the one v676a using a maximum of 0,7 A. That‘s why I’m pretty sure it shouldn’t be a problem.

 

[Rob Flinn]

Has the psu been serviced ?

 

[rock soderstrom]

Hello everyone,

as I’m working on a Rack full of seven v672s I added a v676a, which is working fine in this Rack until I slide any of the v672s in. Then only the v676a start to pulsating. The Pre does still work than, but generate this strange pulsating noise. Does anyone have experience with this kind of problem and can help?

As a PSU I’m using a TAB N324.

Kind regards Ralf

Maybe the pinout of the modules is slightly different and thus the modules do not like it to be connected to the same backplane?

 

[rock soderstrom]

I can not find a V672s, does it match to this model?
Last one is for the V676a

 

[ralfw]

I'v only measured the output of the PSU. Because it looked fine to me and that fact that all seven v672s ar working fine, I thought the PSU should be fine. But I probably have to give the PSU a service to make sure it's definatly working fine. Thanks for the hint.

 

[ralfw]

I can not find a V672s, does it match to this model?
View attachment 144046View attachment 144045Last one is for the V676a

Wow. Thanks for your effort. Because I have a Rack full of seven "different" v672 Amps, I put a "s" at the end. So we're talking about four v672, two v672/1 and one v672/2. I already have the schematics, but thanks again, Buddy.

To make it clear. All seven v672 Amps are working 100%, noiseless and without any hum or pulsating. The v676a is working as well when only the v676a is connected to the Rack. But only aslong as none of the v672 Amps are connected to the Rack. It doesn't make a difference if I connect only one, two, three or all of the v672 Amps to the Rack. From the moment I'm adding one of them to the Rack, the v676a starts to generate some pulsating noise. It's rediculous. That's why I'm asking here. I'll check the PSU a little deeper. Maybe there is something causing the problem which doesn't harm the v672 Amps but could be a problem for the v676a.

 

[ralfw]

So here's a quick shot of my Rack.

 

[rock soderstrom]

View attachment 144127
So here's a quick shot of my Rack.

Yes, a PSU check is not a mistake but I would pay attention to the external wiring of the modules. Your rack is wired for a specific type of module, this could be the problem once the V672 hits the V676, note the pinouts, things like grounding and where the external feedback resistors are connected. Good luck.

 

[ralfw]

Yes, a PSU check is not a mistake but I would pay attention to the external wiring of the modules. Your rack is wired for a specific type of module, this could be the problem once the V672 hits the V676, note the pinouts, things like grounding and where the external feedback resistors are connected. Good luck.

Thank you. I'm back at my lab now, so I'm going to check all the connections again.