Tascam M3700 Story...

sr71rules

Member
Well, here goes!

I've recently acquired a broken Tascam M3700 which I had planned to use as spares for my (mostly) working Tascam M3500 but, with some urging from the the board here, I'm instead going to try and repair the M3700 to it's full glory. Feel free to read up on how I got here: Refurb M3500 into an M3700, or M3700 into an M3500....?

For the sake of completeness, here is the back story on the board as I know it:

I bought the board from a guy in western Massachusetts, here in the states. He advertised on Craigslist that he was closing his studio and that he wanted to get rid of the M3700. The price was set at $200 and he said in the posting that the board was not working properly. I contacted him and found out that the board was blowing a specific fuse over and over again. He mentioned that he had done some troubleshooting and discovered that when module 22 and/or module 32 was plugged in the fuse would pop immediately. He then said that even with those two modules unplugged the fuse was still popping after some delay.

I already have an M3500 which I am slowly giving a spit and polish for installation in my new studio. To that end I was ordering spare parts when I could and days earlier had ordered a few spare 4 channel groups for the board at a total shipped cost of well over $200. When I saw the board listed on Craigslist I considered it a good deal even if only for spares. I could see it had the full meter bridge, which my M3500 lacked so I committed to buy it and made the three hour trip out with my dad and his big red van from the late 80s. It's harrowing, but I think worth it :)

With the board back at my house I began to poke around and see what I could make of it. A few things of note:

1.) The board has the balancing kit providing 16 balanced 'Tape Ins' on DB25 connectors and a mirrored pair of the 8 Group Outs, also on DB25s. (Without the balancing kit the Group Outs are also doubled on the board to make it easier to feed 16 tracks without needing to patch and unpatch.)

2.) The M3700 is the automated version of the M3500 but this M3700 has the optional JL Cooper 'M3700 Pro' automation addon. This will no doubt lead to a series of posts all on it's own.

3.) The seller had both the original Tascam manual in it's binder as well as the JL Cooper manual for the expanded Automation System.

4.) The Expanded automation system seems to be focused around a Mac application and as luck would have it the 3.5" floppy disk containing that application was tucked away inside the binder as well.

5.) The owner before the owner I bought it from had the first 16 channels modded with Burr Brown 2604 opamps. All 5 of the opamps on those channels have been replaced.

The fuse in question feeds the input section of the board so none of the I/O work but everything else seems fine. The on board automation system seems to work and all the lights and meters are working as well. I can save and load snapshots but with out audio it all seems little silly...

More to come!
 
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Troubleshooting - Step 1

With the board home it was time to start to narrow down what the issues are.

I stopped off and picked up a heap of the fuses that kept blowing, 5A slowblow, and cracked open the power supply. I swapped in a new fuse, wired the board to the PSU and pressed the power button. Everything lights up, audio passes and the fuse lights up like a light bulb and pops.

The expected result.

From there I pull open the board and unplugged module 32 and module 22 which the previous owner said were the problems. I dropped in a new fuse pressed power and watched as the fuse lit up and popped.

Now I started to pull whole chunks out. The board is setup in groups of 4 channels. Two screws at the top, two at the bottom, and a lot of cables. The channels are all separate from each other and have a half dozen or so wires per strip for bussing, faders, meters, power, ect. I totally pulled out modules 29-32 and 21-24. I put in a new 5A fuse, powered up the board and watched it blow. I then pulled out 25-28, new fuse.. same result.

Ok. Perhaps it's not the channels...

I have the M3500 which is quite similar. The power supplies are different in a few ways but the core parts remain the same. The voltage rails are the same but the M3500 draws less power and is thus less powerful but since I had my 32 channel board down to 20 channels I thought it perhaps not crazy to try the M3500 power supply instead.

I opened it up and found a 4A fuse in the place the other power supply has a 5A fuse so I didn't see any danger in trying it out. Worst that happens is the board draws too much power and pops the same fuse as the other supply. I should point out here that I have never done anything like this before and was certainly in over my head. Try this at your own risk!

With the M3700 loaded with only 20 channels and the M3500 power supply hooked up I pressed the power button.

The board lit up as per normal.

My iPod's audio, wired into tape inputs, could be see registering on the channel meters and the stereo bus VUs were dancing. I looked at the M3500 power supply, at the fuse that kept blowing on the M3700's power supply. It's not lighting up, it's not getting hot and it's not deforming. I quickly switched it off.

I called a friend who is an electrical engineer and told him what I had done... still worried I may have done damage with the wrong power supply. He seemed Ok with it and I powered it back up to see if it would run a little longer. I left it on for increasing amounts of time with no ill effect. Obviously, the power rail to the automation system was not present so that didn't light up but otherwise things looked good.

The problem is in a small part of the power supply and perhaps not with the whole board! I've ordered my first multimeter and, with the help of a friend, will begin to test parts of the bad section of the PSU next weekend. Since I have such complete documentation and a nearly identical second board I'm feeling confident things are going to work out just fine. Here's hoping that's not hubris...

Tomorrow night I'll try loading in, one at a time, the 4 channel sections I pulled out tonight and see if that has any effect. I'd like to find out if any channels are an issue or if it's purely a power supply problem. I don't want to over tax the M3500 power supply though.

I have a lot of information to discuss with the JL Cooper Automation addon but I'll save that for writing up during lunch tomorrow. I'm pretty excited about the M3700 at this point and I can't wait to get some more testing done. If I can solve this power supply problem using this board will be ideal since it's in otherwise better condition than my M3500. Might be able to finish the clean up on the M3500 and sell it forward...

Robert
 
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You *should* be able to run the M-3700 at idle with the M-3500 PSU. In fact, I would bet the M-3500 supply would run the M-3700 to a degree as long as the supply rails are the same, and assuming Tascam overbuilt the M-3500 supply like they did with the likes of the M-520 PSU...evm1024 figured the main transformer in the PS-520 was good for about 4x the draw of the mixer.

I don't have any M-3x00 documentation, but if you put up a scan of the PSU schematic I can help hunt down the culprit.
 
Arg... closed the wrong window. Here goes again!

The two power supplies are nearly identical. The M3700 and the M3500 share the same PCB. The M3500 is missing the top row of Caps and all the electronics attached to F6, which is the rail for the automation computer. In addition, F1 and F2 are rated 4A, instead of 5A. Everything else is the same.

P001 and P002 at the bottom are feeds from the transformer. Top right hand P012 and P013 are feeds to the umbilical.

Above F1 and F2 is a connector that feeds a bridge rectifier mounted to the rear of the PSU, the heat sinks. P006 and P007 are transistors also mounted to the heat sink. They might be voltage regulators.. I'll double check when I get home.

The PCB looks good aside from darkening around the fuse that keeps popping. The larger caps appear to be glued to the PCB and don't look blown to me.

M3700 PSU Schem.jpg
(let me know if you'd like the higher res version, the forum seems to have shrunk it quite a bit.)

My problem is F2 keeps blowing its 5A fuse. Hell, it blows 8A fuses too! My multimeter arrives on Monday which should allow me to poke around a bit I guess and check that things are working. Uncharted territory for me...

I have the whole of the M3500 manual scanned as well as the JL Cooper automation addon manual but not the M3700 manual yet. The M3500 manual was purchased from a guy on Ebay since Tascam didn't have it but it's not too bad. I'll start scanning the M3700 manual this weekend, I hope.

Robert
 
JL Cooper PRO3700 Automation Addon

As mentioned above, my M3700 has the optional JL Cooper Automation addon. JL Cooper was the maker of the automation system installed on the board when you bought it from the factory but JL Cooper also sold an addon module that could be plugged into the console.

As I understand it, when you bought the M3700 from Tascam the board came with a piece of software that was able to show you what was happening on the board but didn't allow you to make any changes. It was basically just a way to view the positions of the VCA faders, since they are not motorized.

With JL Cooper's PRO3700 addon and a Mac computer you get "moving fader graphics, automatic disk archiving, and a large easy to read time code display" in real time as the mix was happening. You could then also 'edit' a mix offline where you can copy and paste bits of the automation and manually enter changes for the mix using timecode as a reference. It also allowed more flexibility in terms of choosing how you group things such as VCA groups and mute groups.

When you consider that the only interconnect between board and Mac is Midi it becomes clear that they have simply built a custom GUI around what it basically a Midi editor. Pretty cool use of existing tech!

That's all wonderful but the system has a huge, huge caveat when you try to get it running these days.. they support exactly 10 models of Mac computer. These machines range in sales dates between 1986 and 1993. Yikes! Considering the software was released in 1992, that's not bad but it sure makes things harder for me today! Basically, they support most of those all in one units with the tiny black and white screen and a couple desktop type machines.

Since I have the floppy disk with the software I prepped one of my older Macs with the oldest OS it would run (System 8.6) and tried to launch the software. It fails with the error that I need to put the mac in '2 grey or 2 color mode'. Not an option I have available in the OS. Perhaps someone out there has a way to trick a Mac into such an old display mode. The lowest I could choose was 256 grays...

The onboard automation system in the M3700 is quite powerful though I'd be happy to use it as is but considering the PRO3700 automation addon is basically enabling the machine to slave the automation system to Midi input, I suspect I can play a few tricks and use that, albeit without the spiffy interface. Since the M3700's automation system seems to always be spitting out the midi data for changes made I should be able to record that midi stream into my DAW, or a secondary DAW, and then setup the board to listen for that midi information and play the mix back.

The onboard automation is configured via a set of 4 dip switches. The stock M3700 uses every permutation of those switches to parse the incoming time code (MTC, Midi Beat, SMPTE 30, SMPTE DF, ect) for proper sync or to put the console into snapshot mode, with one exception. With all four dip switches in the 'up' or on position the board makes use of the JL Cooper addon. This is not mentioned in the M3700 manual or on the board but it explained in the JL Cooper manual. I assume it just does nothing in that setting if you don't have the addon.

The only problem is that when you choose the PRO3700 I don't believe the console itself makes any attempt to record the automation changes and when you switch the console into the mode where it will slave to the incoming midi.. you have to reset the onboard computer and thus loose any automation you've written. It should be possible though to playback the mix while recording the midi output, reset the automation computer, and then play it back.

Why do any of this you ask? If this works I can save my mixes as midi files and not have to worry about maintaining a large pile of 3.5" disks which I don't trust at all. When I want to go back to a mix I just load up the midi file and play it back in sync.

I'm going to keep my eyes peeled for a desktop style compatible Mac but the only way I can justify all the work of getting that to work (and building a pile of spares) would be if I can get the unit on a network and store the mix files elsewhere for archiving. Even still, I'll prob keep the midi files around as a more dependable way to maintain the old mixes going forward.

Also.. I'm a geek and I want to see what the computer interface can do!

And yes, I know this is crazy and I know it can be done easier and perhaps more reliably with my DAW but I'm so impressed with this board and I really want to see it do what it was made to do. It's tool cool not try at least!

Robert
 
Quick side question...

Do either of your boards have any stereo input channels? Looking at your pics of the 3700, that one doesn't appear to...but what about the 3500?

Anyway...I've been on the hunt for some of those, and any time someone parts out a 3500, I'm always checking if any of the input channels are stereo.
That was the other thing I wished I had gotten when I purchased mine...at least one of the modules worth (4 stereo channels) would have done me fine for the few stereo pairs I occasionally track. Just makes the mixdown easier and saves some channels.
 
I think you're only about the second person I've ever heard of who has the JLCooper kit. I thought I was the only one. You can pick up an old Mac on ebay and an opcode interface to get your Cooper stuff happening. System 6 or 7 works fine. The Mac list on the JlCooper manual is based on the 68030 processor era. I've used as late as a 90's era PowerPc Performa with the Cooper software. A cheap Mac Plus or Performa 200 etc will also work. Make sure that once you have a Mac with system 6 or 7 based floppy drive, make a zillion copies of the JL Cooper floppy. Without those, you're lost. And the Cooper floppy is the old old single side type, which is only readable on a handful of old Macs. Burn copies as fast as you can if you want to transfer to the later day larger capacity floppies that Apple used or to cd !!!!!!!

With the Cooper stuff going and your rig synchronized to incoming smpte from tape or daw, you basically never use the 3700 floppy drive again unless you reset the dip switches. I've never used snapshot mode as that would really only be for cues in live plays etc. Dynamic mode is the norm/ 30ndf. Saving to the Mac hard drive is so much faster, especially if you create lots of different mix versions to save. At least back when I used the 3700 more often for actual mixing. Daws are so far superior now. A later era Mac with an external cd burner/toast/and-or a network connection is one additional way to save your mixes. Other than for installing the program, the floppy drive on your old Mac won't be used.

Drawing in updates on the Mac is also faster than doing update passes on the console with the vcas in update mode. So , all is much faster with the Cooper setup. Not like a daw ... but fantastic for its day .

Controlling daw faders with the 3700 is fun , although then sort of leaves the entire Cooper equation out. Unless you're piping your daw audio outputs to the 3700 for mix time . In a mix scenario though, you're faced with whether you want to use your Cooper system ... or the far superior automation in your daw. Decisions decisions.

The Tascam floppy you mentiioned was called Faderview. I have bunches of those. Cool at the time to see the dancing faders on attached Macs, but the idea was to get you drooling to buy the JLCooper package.

The JLCooper manual is a hoot for its time. The unlimited grouping chapter can be useful as well as the auto fadeout pages. I'd make a pdf of the binder pages as I have referenced that thing more than I thought over the past 20 years.

I have also explored using Basilink etc as a possible someday way to get off the old Macs, but that's not been a big priority. There are some midi roadblocks with that approach.
 
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Miroslav, I didn't know they existed until now! I'll be keeping my eyes out for them as well.. though I suspect automatable modules will be quite rare indeed...

BRDTS, Thanks for all the info! I have copied the program from the floppy to my storage server which is backed up offsite. Not going to lose that! Same with the manuals. I'm scanning them all and making them text searchable. Can't be too careful!

In terms of the automation software on the Mac, anything I can do to never have to use a floppy disk is worth it for me. If I can get a mac that will work for the PRO3700 software and onto a network I'll be a very happy guy. Should make an interesting project...

Do you have a copy of the Faderview software? I would like to archive that as well.

I too have been considering emulating an old Mac with Sheepshaver or Basilisk but I can't imagine getting MIDI to work in the environment is a very high probability and stability would be questionable as well...

I'm really looking forward to getting the board back into tip top shape!

Robert
 
Quick Update:

I have reloaded all the M3700 modules back into the console and still no fuse popping issues on the M3500 power supply. That being said the board is misbehaving quite a bit on that power supply. I'm not going to worry too much about it until the M3700 PSU is in good condition again. Lots of little things like audio showing up on meters it shouldn't be and levels being way out of whack, at least on the meters. Could be a million reasons for that, not least of which the board being driven hundreds of miles, not being calibrated and then run with an underspec'd power supply. It's a little hard to describe. Things like the Group Out meters show audio when nothing is routed to them. When you do route audio the meter jumps way past it's max and then, if you switch over to the 'tape in' meter bank.. the Group out audio starts to creep up on those meters too. That's how it looks anyway... Not going to mess with it until it's powered properly.

The only one that is troubling me is that with audio passing through the board, showing up on all the right meters, I can't hear anything on the headphones. Maybe I'll do a quick test with some speakers on the main stereo out tomorrow. I've yet to pull apart the master section though so it could be just the headphone jack is unplugged internally. I would have expected some noise or distorted sound.. but nothing at all.

Lots to think about.. tomorrow.

Robert
 
BRDTS, are you suggesting any 68030 Mac will work? The App seems to run even on my Powermac Blue and White G3 but gives me the '2 color or 2 grey' error. I thought perhaps the trick would be to make a Mac reduce it's display way.. way down. Even under OS9 the app starts. Perhaps it's more flexible on those old systems?

It's a bit of a head scratcher and I don't want to start another gear collection if I can avoid it...

Robert
 
Interesting Modifications...

More work on the board...

I'm growing increasingly hesitant of powering the board on both with the troublesome PSU and the M3500 PSU. None more of that until the proper supply is working. I needed to get some troubleshooting done, which I did, now it's time for patience.

I've opened up the last remaining parts of the board to look for obvious problems and check connectors and general cleanliness. The inside of the console is quite clean and it looks like perhaps when the modded the board they gave the console a full refurbishment and spit shine.

Some of the faders feel a bit wonky though and I'm going to see what I can do about that. Tim Kroeger did a great job documenting his refurb project on his (excellent) website [tubegeek] but he has an M3500 which means his faders are quite different from mine. I'll pull a section out and take a look. I don't know if they are scratchy or sending out bad data to the automation system but I can at least look them over.

Something that did catch my eye though as I took apart the last section of the board:

Tascam_M3700_01.jpg

Tascam_M3700_03.jpg

Any one have any idea what that might be? My first thought is perhaps a grounding mod? The wires start on the PCBs for the master section, the top picture, and then run through the board to a long strip of metal under the lower section of the channel strips. Having just reassembled that section of board.. I will now disassemble it again to see what the deal there is. I'll post more pics if I see anything interesting. The wires quickly disappear under a metal channel so it's not obvious that they are there under the channel stips. On the M3x00 boards a strip of metal on the top of the console about 3 inches wide separates the master section from the channel strips and it's within that gap that I shot the second image.

Robert
 
Arg... closed the wrong window. Here goes again!

The two power supplies are nearly identical. The M3700 and the M3500 share the same PCB. The M3500 is missing the top row of Caps and all the electronics attached to F6, which is the rail for the automation computer. In addition, F1 and F2 are rated 4A, instead of 5A. Everything else is the same.

P001 and P002 at the bottom are feeds from the transformer. Top right hand P012 and P013 are feeds to the umbilical.

Above F1 and F2 is a connector that feeds a bridge rectifier mounted to the rear of the PSU, the heat sinks. P006 and P007 are transistors also mounted to the heat sink. They might be voltage regulators.. I'll double check when I get home.

The PCB looks good aside from darkening around the fuse that keeps popping. The larger caps appear to be glued to the PCB and don't look blown to me.

View attachment 64275
(let me know if you'd like the higher res version, the forum seems to have shrunk it quite a bit.)

My problem is F2 keeps blowing its 5A fuse. Hell, it blows 8A fuses too! My multimeter arrives on Monday which should allow me to poke around a bit I guess and check that things are working. Uncharted territory for me...

I have the whole of the M3500 manual scanned as well as the JL Cooper automation addon manual but not the M3700 manual yet. The M3500 manual was purchased from a guy on Ebay since Tascam didn't have it but it's not too bad. I'll start scanning the M3700 manual this weekend, I hope.

Robert

I need the schematic, not the PCB layout. Can you scan the M-3700 PSU schematic? PM me and I can give you an email address.
 
I'm a n00b...

When I said this was my first refurb project.. I wasn't kidding! :)

I've attached the Schematic to this post but who knows what the forum software will do to it! Happy to email it along.

M3700 PSU.jpg
 
It was not long ago that somebody said the same thing to me when I posted up an image of a PCB layout ("no...I need the schematic..." heheh)
 
Hey don't sweat it sr71, I'm just finishing up my first refurb project myself (an MCI tape machine) then I may well be looking at recapping the PSU for my 3700 (that'll be another first for me!). You'll learn a lot and the guys here are GREAT! Good luck with the project, I look forward to seeing your progress. If your manual is missing pages or has some bad prints or something, give me a holler, I can probably provide scans from mine.
 
I've been really enjoy the boards here and it'll take a lot more to embarrass me than posting the wrong doc :)

I have the full Tascam M3700 manual in it's binder and have scanned all the 8.5x11 pages and am thinking about getting an 11x17 scanner to handle the rest... 'Cause, obviously, there is space in my life for more electronics...
 
The price was set at $200
:eek::eek::eek::eek::eek: HOLY MOLY!! Really? And here I thought I got a steal at $1k with NO JL Cooper!:(


The M3700 is the automated version of the M3500 but this M3700 has the optional JL Cooper 'M3700 Pro' automation addon. This will no doubt lead to a series of posts all on it's own.

Oh my god, am I jealous. I even contacted JL Cooper to see if they had any of these laying around. I could feel their eyes roll and hear the laughter as I sent my email.

I think you're only about the second person I've ever heard of who has the JLCooper kit.

Me too. And YOU were the first a few years back. Did I mention I'm jealous.


Controlling daw faders with the 3700 is fun , although then sort of leaves the entire Cooper equation out.

I've never owned a Mac, but ok, ebay here we come!!:D


Unless you're piping your daw audio outputs to the 3700 for mix time .

:confused:Ummm, on second thought.... I have an Maudio 10/10lt out to my M3700. Although, with 2 synched MSR's..who needs a ...well, you know what I mean.:laughings:

The Tascam floppy you mentiioned was called Faderview. I have bunches of those. Cool at the time to see the dancing faders on attached Macs, but the idea was to get you drooling to buy the JLCooper package.
:eek:(note to self...time to read the Manual again:rolleyes::D)Faderview huh? Ummm, on second thought again.. I WANT TO SEE THOSE DANCIN FADERS!!!




hey, any chance getting one of those floppy's?

YEA!!, me too! Me too!:D

(note to self..must rationalize latest purchase of new i7/975 computer to wife..for new purchase of old Mac...hmm, I sense a blistering "cold war" ahead)
 
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Don't be too jealous (yet) Rick. You need special (Read: Epically old) hardware to make it work. None of the Macs I have kicking around are able to run the software. I broke down and ordered a 'Macintosh LC' from ebay which, according to the Manual, will run it. I then had to find some Opcode Midi interfaces, which I never would have known without BRDTS's tip. They are fairly common on ebay and not too expensive. I bought two, one was less then $5 and the other (way too much) at about $20. Then, I had to find and buy an ethernet card for the Macintosh LC which should allow me to save my mix files to my network, probably via FTP. Did I mention the Macintosh LC will only run 50 pin SCSI hardware and doesn't have a CD-ROM drive? I'm going to somehow have to find a source of working small capacity (less then 500MB) SCSI drives to serve as backups or convert the LC to boot and run from floppy disks...

I've done all this and the PSU isn't even fixed yet...

I am way way too excited about this board and am forcing myself to slow down. What happens if the PSU problem is only the gateway to a world of hurt? What damage has the previous owner done trying to fix the issue? If the M3700 doesn't work properly and I can't rely on it.. I'll have a pile of over priced useless Mac hardware who's novelty will soon wear off...

That being said.. if it does work... YAAA HOOOOO!!!! :)
 
Wow, were you quick. I didn't even get my "edit" done before you replied.:D

Opcode Midi interfaces, which I never would have known without BRDTS's tip.
Hmmm, me too. Kinda wierd, but I've owned an Opcode Studio 128 for YEARS...and never used the damn thing.:rolleyes: Same with a Lexicon Core 32. Geezus..where have the years gone.:(;)

I've done all this and the PSU isn't even fixed yet...
Yea, that's a tough one. The last time I turned mine on, about 10 minutes later, all the lights on the mixer flashed and the meters all pegged for about 2 or 3 seconds...:eek::eek: YIKES! I wondered if the PSU was giving out. But then again, there was a big ole Oregon storm going on, and I think it was due to our electrical voltage dropping. Who knows though. I still worry about the age of my unit. Where I live, there ain't NO techs of any kind. :(


That being said.. if it does work... YAAA HOOOOO!!!!
You betcha!
LONG LIVE ANALOG!! Good luck to ya. These old workhorses are fantastic as far as I'm concerned. I wouldn't trade mine for ANYTHING...well, within reason.:D I've even got a new i7 PC and still haven't integrated it in my system yet. Just not that interested in digital.
 
Did I mention how excited I was :) Anything M3700 related gets my complete attention.. when I see the emails notifying me of new post.. I dash over to the site.

The Macintosh LC arrives Monday and I should have an Opcode interface by then as well. Even on a Mac from 1995 I can't run the M3700 Pro software. It complains that I need to be in a 2 color, or 2 grey display mode and I can't manage to force the Mac to do it. All of the ones I've tried will only go down to 256 greys. Crazy.

I'd be interested to see what it looks like under your automation control panel Rick. I think I know which part of my board is the addon but I'm not sure. Under the automation display and control panel is a stack of 4 PCBs and on top of the highest one, in the lower left corner, is a small PCB with some chips on it that say JL Cooper so I suspect that's the addon. From reading the two manuals I'm reasonably sure...

I've been getting some great PSU help from Sweetbeats and I have a friend coming up this weekend to help me out. Hopefully I'll have a pathway to a working PSU soon!
 
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