M-600 Master Section Problem

  • Thread starter Thread starter ron-e-g
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ron-e-g

ron-e-g

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Hello, I've been occupied with calibrating my MS-16. So I put the console on the back burner. Now I'm ready to start troubleshooting a problem with the master section.
Basically, I don't get audio out of the right channel through the tape returns or channel inputs. I bought a spare console for parts, So I changed out the Master module with the other board's and it didn't effect this problem.

When I patch in to the stereo input, a CD player or R/R or even a Cassette player they output through the board fine. Both Master meters register fine. But not from the recorder outputs. That is left only.

Can anyone help to shed some light on this, or suggest what or where might be the problem?

Ron
 
Have you checked the patch-bay and cabling associated with it for signal continuity? All it takes is one bad patch cable/connector there to gum up the works.

Cheers! :)
 
Honestly..not sure where to start on that. I have checked that the input/outputs (all balanced) are correct from/to recorder. These balanced D-sub and bantam (TT) jacks are giving me fits!
This may be a mute point but I even have this problem when I insert direct to a channel input via XLR microphone cable.

Hint..maybe. When I got the board some previous owner had installed a double fader in the left master location. That was then patched over to the right fader input.

Another thing I noticed only after inspecting the parts console. The meters have been modified to run at 6v. I think you might recall the fiasco I had trying to replace only one.

But thing of it is. When changing the Master module I noticed some wiring that goes to the D-sub jacks (in several locations) on the back,looks as though it has been soldered. It's soldered approx. 1/8 of an inch back from where it inters it's respective jack or plug. It don't look factory. But it don't seem to make sense either. The parts board don't look like this one (in that respect).
 
If stuff looks modded, it's probably best to speak to the person who did the mods and ask them why they felt the need to do what they did and also explain your current signal flow issues with them.

All I can do is make basic logical suggestions as I've never used an M600, much less a modded one.

Cheers! :)
 
Schematics are going to be a must to sort through an issue like this.
 
Well thats a start, but it gets crappy real quick with "mods" as they are rarely documented. It takes a good working knowledge to get through the schematics on an unmolested piece of gear, but a whole different skill set to determine what the mods are.

By chance can you post the schematic(s) for the master section? I tried a cursory search online but didnt get any hits. We might be able to help, but schematics are almost a must.
 
Stereo Master.webpStereo Master2.webpSANY0400.webpSANY0401.webp
Notice the black wires.
 
There should be more schematics for the master module, notice the call outs on the far left of the schematic " to master module" and "from master module" Need to see what feeds P101.
 
My first guess is the normaling contacts on the stereo send rcv on the rear panel.

Easiest way to check that is insert a TRS to TRS cable: one end in Stereo "send" L and the other end in Stereo "rcv" or "return" L.

Report back please.
 
mdainsd said:
Easiest way to check that is insert a TRS to TRS cable: one end in Stereo "send" L and the other end in Stereo "rcv" or "return" L.

Report back please.
Click to expand...

All d-sub on the back. Everything goes to Dsub/Bantam patchbays. Patchbay Layout.webp
 
patch bay 5: cable inserted into 1st and 3rd jacks from the left, top row.
 
??? Im trying to help you with your stated problem, no left channel output from any of the input strips. Put the jumper cable where I instructed, then test a channel strip for left output using either a mic in or a line in.
 
Oh..OK but it's the right that has no output to phones or monitor speakers or the right master meter. From the channel inputs, and tape returns.

I patched the R/stereo out to the R/stereo in. I do have both R/L now. Although the right seems somewhat weaker signal on the Master meter.
 
Last edited:
sorry, lol. second and forth jacks from the left, top row patch bay 5. put a jumper cable between those two points and try.
 
great! The confirmed that the biggest part pf the problem is the normalling contacts inside the jacks of the patchbay.

You did use a TRS to TRS cable as opposed to a TS to TS cable?

I just went through a large format console for my studio and every channel strip in mine had this problem in the channel send jacks.
 
Yes. The patch cable I used was Tip/ring/sleeve. I thought all of mine were. But after closer inspection, I see some are not.
 
You might try wiggling or spinning the jumper connectors in the two jacks you are plugged into in an effort to see if poor electrical contact in one or both of those jacks is causing the reduced level in the right channel. There are actually cleaning plugs for the bantam style patch bays. You insert them and they have a hole that you can then spray contact cleaned into and the plug directs it inside the jack. I prefer DeOxit as my cleaner of choice.

I dont know about your board but as I said mine had problems on all of the jacks that had switching functions built in (normalling). y theory is that mine was installed in a studio for years. All those send and return jacks were populated with plugs that took the signals to a patch bay. When a plug is instaslled in one of those jacks it holds the two normaling switch contacts in the open position. Then apply years of Engineers, Producers and talent chain smoking in the the studio control room, and all that nasty crap yets into the electronics. In this case is coats the open contacts. Then when it was de-commissioned, the plugs were all removed and all those switch contacts should have closed the circuit, but they dont because of all the tar and crap on the contacts.
 
What's got me stumped, is the fact that with no patches the recorder's signal only comes through in the left on the master meter and through the headphones.. I have the console and recorder connected as per diagram shown earlier. That's the suggested by the manual. The only difference is the MTR out was set-up at the right side set of 16 jacks. meaning where the diagram shows it as 17 it's actually 1. The fold-back cable from the MTR outs on PB 1 is also at this location. I was told these two fold-back cables should go to PB 3 left side (MTR out) above the tape returns. But there is a note in the manual that this should not happen. It suggest assign them to tape returns only. I don't completely understand that and if indeed it is patched correctly. I don't understand the fold-back.
File.webp
 
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