altruistica
Member
Hi Guys,
Well progress on the mixer front....kind of two steps forward, one step back.
Delving deeper into the mixer, there are some things that are great (the quasi modular construction) and some things that are a PITA (the design of the MASTER section seems 'Ad Hoc'....as if the design team were running out of time). I presume lots of the restrictions were down to designing two mixers in the footprint of one. There is a large hole in the top right of the mixer where the automation facilities of the M3700 must sit.. My gripes with the MASTER section is that it seems like an accident waiting to happen with all its separate wiring and necessitating the removal of lots of small wires to investigate any problems that might occur. I suppose, these things are all built to a price, but I think the design could have been improved by the use of ribbon cables which would terminate further down the rear of the desk to branch out then to the rear connectors. As it is, it is a bunch of spaghetti with no markings on the boards themselves as to which connectors go where (this would of cost practically nothing).
I am of course trying to excuse my own stupidity as I connected a two pin wire that was carrying the +8v and ground, to the Group 8 fader out, a thing that you would think hard to do. Not when you see the layout of the boards and see that some Group outs are (1-6) are hard wired onto three separate boards, Group7 out is at the front of another board and Group8 is at the rear of another board. The +8V lead from the rear of the mixer (a separate wire by itself) fits an inch way from the Group 8 fader (on a separate board with no markings on either cable or board to show its a power supply and not an audio connector). When you're having to hold the whole module in one hand, while re-plugging the leads (mainly audio outputs at the rear, about 20 of them and the 10 fader cables at the front) making sure you don't damage the three buss connectors with the whole master panel having to be manoeuvred (maneuvered) to enable the leads to be fitted.....as I said, it's a PITA.
Griping over, where am I?
Well, I think the initial problem I had (the outputs suddenly disappearing and replaced by hiss) may have been down to power supply. I've recapped it and it seems to be providing steady power now (I don't know how to check what you said Cory....scope the rails?...could you elaborate?). I replaced a ton of caps in the eight master boards....some so low you wonder how anything still worked. I re-soldered all the tiny fader boards that act as connectors between the Master Panel and the Output faders as some were loose. I re-soldered the headphone out and lead as it had been wired incorrectly.
I've re-connected things and now I have the following.
The SIP (Solo-in-Place) facility works as it should with PFL and SIP available. The AUXES all seem ok. The biggest thing to sort out now is that I have no signal either metering on the GROUP2 and GROUP3 busses and the MASTER R. I've checked it's not an insert problem, but I'm at a bit of a loss on how to check other things. I did have the Control Panel connected just with the three buss ribbons and the baseplate. This allowed you to put just one of the eight boards on the baseplate, power on the mixer and check various things. I did check the ICs of the MASTER stage (JRC4580Ds if memory serves me right). I found voltage at the correct pin but I think I'm mis-interpreting the diagrams. Maybe a day off the mixer will allow my brain time for all this gunk to make sense.
As it is, I think I might have tried fixing twenty years of neglect in two weeks.........I'm now thinking a longer time-span to sort out what I want to sort out. After I get the Master Panel sorted, I'm going to tackle re-capping the INPUT modules 25-32 which house the GROUP submixes to the Master L/R as GROUP1 fader on CH25 still gurgles and bubbles. No doubt the others will benefit too.
On the MIC pre, on one of the malfunctioning channels, I noticed a 470uF cap that was well under spec. This was a 'non-polar' cap (470uF N.P). I read that it should only be replaced with the same non polar........is that true?
I think that's it for now....sorry about the long post.
Al
Well progress on the mixer front....kind of two steps forward, one step back.
Delving deeper into the mixer, there are some things that are great (the quasi modular construction) and some things that are a PITA (the design of the MASTER section seems 'Ad Hoc'....as if the design team were running out of time). I presume lots of the restrictions were down to designing two mixers in the footprint of one. There is a large hole in the top right of the mixer where the automation facilities of the M3700 must sit.. My gripes with the MASTER section is that it seems like an accident waiting to happen with all its separate wiring and necessitating the removal of lots of small wires to investigate any problems that might occur. I suppose, these things are all built to a price, but I think the design could have been improved by the use of ribbon cables which would terminate further down the rear of the desk to branch out then to the rear connectors. As it is, it is a bunch of spaghetti with no markings on the boards themselves as to which connectors go where (this would of cost practically nothing).
I am of course trying to excuse my own stupidity as I connected a two pin wire that was carrying the +8v and ground, to the Group 8 fader out, a thing that you would think hard to do. Not when you see the layout of the boards and see that some Group outs are (1-6) are hard wired onto three separate boards, Group7 out is at the front of another board and Group8 is at the rear of another board. The +8V lead from the rear of the mixer (a separate wire by itself) fits an inch way from the Group 8 fader (on a separate board with no markings on either cable or board to show its a power supply and not an audio connector). When you're having to hold the whole module in one hand, while re-plugging the leads (mainly audio outputs at the rear, about 20 of them and the 10 fader cables at the front) making sure you don't damage the three buss connectors with the whole master panel having to be manoeuvred (maneuvered) to enable the leads to be fitted.....as I said, it's a PITA.
Griping over, where am I?
Well, I think the initial problem I had (the outputs suddenly disappearing and replaced by hiss) may have been down to power supply. I've recapped it and it seems to be providing steady power now (I don't know how to check what you said Cory....scope the rails?...could you elaborate?). I replaced a ton of caps in the eight master boards....some so low you wonder how anything still worked. I re-soldered all the tiny fader boards that act as connectors between the Master Panel and the Output faders as some were loose. I re-soldered the headphone out and lead as it had been wired incorrectly.
I've re-connected things and now I have the following.
The SIP (Solo-in-Place) facility works as it should with PFL and SIP available. The AUXES all seem ok. The biggest thing to sort out now is that I have no signal either metering on the GROUP2 and GROUP3 busses and the MASTER R. I've checked it's not an insert problem, but I'm at a bit of a loss on how to check other things. I did have the Control Panel connected just with the three buss ribbons and the baseplate. This allowed you to put just one of the eight boards on the baseplate, power on the mixer and check various things. I did check the ICs of the MASTER stage (JRC4580Ds if memory serves me right). I found voltage at the correct pin but I think I'm mis-interpreting the diagrams. Maybe a day off the mixer will allow my brain time for all this gunk to make sense.
As it is, I think I might have tried fixing twenty years of neglect in two weeks.........I'm now thinking a longer time-span to sort out what I want to sort out. After I get the Master Panel sorted, I'm going to tackle re-capping the INPUT modules 25-32 which house the GROUP submixes to the Master L/R as GROUP1 fader on CH25 still gurgles and bubbles. No doubt the others will benefit too.
On the MIC pre, on one of the malfunctioning channels, I noticed a 470uF cap that was well under spec. This was a 'non-polar' cap (470uF N.P). I read that it should only be replaced with the same non polar........is that true?
I think that's it for now....sorry about the long post.
Al