Tascam M-___ Story...

[sweetbeats]

Just a drive-by posting...

I was looking at a listing for an M-50 on eBay...I've been billing the M-___ as a prototype M-500 but I think it may be more accurate to consider it an M-50 protoype. Yes the M-50 and the M-512 are very similar, but I noticed the M-50 only has only two balanced outs and a bunch of level switches like the M-___ (as opposed to the 8 channel balance amp of the M-512/520)...see pic of M-50 master jack panel also below...sorry its blurry...its all I could find).

Now, lookit the M-___ fader trim strip here:

And now lookit the fader trim strip on the M-50 in the pic below...verrrry M-___'ish. The M-50 was an early M-512 which preceded the M-520 IIRC...so maybe there are some more evolutionary steps there.

 

[Richard King]

If I remember my time sequence correctly, the M-50 came out before the M-512 (and M-520), so it would make sense that the M-____ would have been before the M-50. BUT, I don't think it was a prototype (other than color scheme) for anything that ever hit the market. I would guess that it was one of two things, first, a prototype of a product that was totally abandoned or, second, a completely custom built to order (and spec) for someone. The reason that it is not a prototype for any existing product is that the signal flow resembles nothing that I am aware of that Tascam ever brought to market. Up to that time all their mixers were of a split design, the M-___ is an inline design, totally foreign to Tascam at the time. Companies build up prototypes that are abandoned for one reason or another all the time, so it's not at all uncommon. I remember going to a satellite convention years ago and seeing a prototype Dish Network satellite receiver with a built in DVD player. This was before DVD players dropped to the $100 and under range. It was a viable product at the time, but became unviable by the time it was ready for prime time and was abandoned. It could be that they decided it was not viable as a totally modular design and that got them thinking in the direction of the M-50 with it's modular in four channel groupings only and their customary split design.

 

[sweetbeats]

If I remember my time sequence correctly, the M-50 came out before the M-512 (and M-520), so it would make sense that the M-____ would have been before the M-50. BUT, I don't think it was a prototype (other than color scheme) for anything that ever hit the market. I would guess that it was one of two things, first, a prototype of a product that was totally abandoned or, second, a completely custom built to order (and spec) for someone. The reason that it is not a prototype for any existing product is that the signal flow resembles nothing that I am aware of that Tascam ever brought to market. Up to that time all their mixers were of a split design, the M-___ is an inline design, totally foreign to Tascam at the time. Companies build up prototypes that are abandoned for one reason or another all the time, so it's not at all uncommon. I remember going to a satellite convention years ago and seeing a prototype Dish Network satellite receiver with a built in DVD player. This was before DVD players dropped to the $100 and under range. It was a viable product at the time, but became unviable by the time it was ready for prime time and was abandoned. It could be that they decided it was not viable as a totally modular design and that got them thinking in the direction of the M-50 with it's modular in four channel groupings only and their customary split design.

Yes. That is exactly what I've thought as well. It never made it to market.

I don't believe it to be a made-to-order mixer either...Teac, AFAIK didn't get into that like boutique manufacturers of the day.

I think it was a venture into tackling the modular inline market but it was likely determined that it wasn't a marketable idea...Teac had built such a strong base (and continue to do so today) building products with the right features for the right price and that's how they captured their market base, even defining a new market. The M-___ was either an exploratory test bed for new products (for instance the eq section is nearly identical function-wise to the PE-40 rack-mount para-eq) or sort of an in-house R&D "show car" to explore a new direction and was then scrapped because it would be too expensive to build and market, effectively pricing out of Teac's primary market base. I'm thinking the latter and they used bits and pieces from it to develop other products, and the design was then scaled down to be within Teac's market base (ala M-50) The M-50 would've been much cheaper to build, and all I'm saying is I see more and more evolutionary links between the M-50 and the M-___.

Here is some more logical thinking that would explain the venture into a modular inline design...yes all Teac had brought to market were split designs but many of their mixers were modular (single strip modules) even all the way back to their first, the Series 10...the Model 15 and Model 16 strips load into the frame the same way as the M-___ and the jack panels are very similar in construction and appearance...even the motherboards on the Model 15 look like the M-___. So I think maybe they were trying to figure out where to go next and maybe they were modeling after the look of the MCI consoles with the stacked meter bridge, continuing on the modular design of the Model 15 and 16 but going inline...so that supports that it was in-house, and that idea is further supported by the way the PSU connects on that Molex connector...now, nothing against Molex connectors but that is not as slick a way to have an outboard PSU connect like Teac had been doing it for years using Hirose connectors. Why not use the Hirose connector on the M-___? I'm thinking it has something to do with connecting to a bench supply. I think it was an in-house prototype for a new direction and it got too spendy so they scaled it down and the 12 channel M-___ became the 12_channel M-50. Jimmy at Tascam says they always crushed their prototypes and that somehow the M-___ must have made out the door either by legitemate or illegitemate means. Judging by the wear on the pots, switches and faders both internally and externally it seems to me it was used little and that would support it being away from the only PSU configured to run it which was on the bench at Teac. The only stumper is that the memo strips have stuff written on them like "bass", "vocal"...that totally scraps my theory...that and the fact that the guy who was running the garage sale from which shoulderpain picked up the M-___ said it belonged to Jerry Garcia.

One more comment: it is really interesting to me that the larger pushbutton caps with the color inset didn't make it to the M-50 (and subsequently the M-500 mixers) but showed up on the 300 series mixers...those button caps appeared on the 122 cassette decks as well and other products...they would have been too big for the M-50/M-500 mixers but maybe there were comments that the smaller switches were too cramped so they pulled out what they did on the M-___ for the M-300 mixers...

Okay. Enough for now, but it is just fun to try and place this thing chronologically as well as logically in the development history of Teac. Too bad nobody there is interested in it.

 

[Richard King]

said it belonged to Jerry Garcia.

Time to dig up the body and do a DNA test. Then again, you've cleaned that thing up so well there's probably not a chance.

 

[sweetbeats]

No-no...I swabbed it first and I'm waiting for the lab to follow up.

Kidding.

Sheesh...that's kinda kreepy...

 

[sweetbeats]

So how cool is Tascam...They stock parts for the M-___!!!!

Yep! Button caps! Okay...they're actually for the 300-series mixers...but its fun to be able to order parts for the M-___ even though they think the parts are for something else.

So this is what you do when you are nervous about trying to get your Tascam 58 basket-case back together: you play with the button color scheme on your M-___ for the second time. I have a parts 388 now so I have enough red button caps to do all the mutes red. So my color scheme has changed a little again for the channel strips since I have the ideal parts on-hand now, and also since Tascam stocks two of the other colors I need, the blue and green. So now the color scheme is settled:

• Source = orange
• Routing assign = putty
• Enable/on = blue
• Anything related to the MONItor buss: green
• Mute = red

Here is channel strip #1 with the new scheme next to channel 3 which is the old scheme. Hey...easy...this is purely therapeutic for an OCD-er...

 

[lo.fi.love]

Cory: My girlfriend is getting her Masters in Occupational Therapy. I think she could design a therapy program for you, based on something similar to this, if in old age you end up suffering from dementia. I'll seal it in a time capsule and I'll give you its coordinates, OK?

Just kidding... you're doing a great job. I REALLY get a big kick out of reading these threads, and I've learned a great deal from you here. I've already put some of what I've learned to use.

 

[sweetbeats]

Jeff! LOL! Seriously...THAT was funny.

The best part is that I'm a nursing home administrator...have been for about 12 years and often times we ponder what we will be like when we reach a very seasoned age. Just put a mixer in front of me and likely I'll be peachy...I'll probably stop trying to steal my neighbor's dessert too...

I'll soon be pulling the caps and select opamps off of module #2. The knob and switch caps are already cleaned up as well as the dress panel. I also think it will be pretty important to figure out why the STEREO buss is lacking the right channel. I suspect it is a bad wiring connection which means pulling the master module out and poking around but every time I do that something seems to go wrong...its pretty fragile in a number of ways but that right channel has to work...pretty crippled without it.

 

[sweetbeats]

I'm going batty...

Trying to get a lock on how to hook everything up to the M-___ in the studio...I'm doing this because I need to make changes to my patchbays and I want to figure out what in my collection of cables I don't need, and what else I need to obtain...what gets permanently patched to what and what goes to a patchbay. This is a real exercise for my brain.

I put up a related thread here, but no bites. Not trying to be duplicative, just hoping to get some input...anything...even just questions...anything that will help me think through this and at least create dialogue because I think that will help me formulate a plan.

The main issue I'm grappling with right now is how to utilize the AUX sends (1~4), the MONItor buss, and the STUDIO switchrack and outputs.

AUX busses: I'd say if the M-___ is short on anything its AUX sends, but that really goes for any Teac board of the day compared to contemporary mixers. One pair of AUX sends, AUXes 1-2, are configured as a stereo pair (since the controls on the strip are PAN and LEVEL...can be used as two mono send as well of course by panning hard R and hard L). The other pair is configured as two mono sends. Each is switcheable PRE/POST, can source whatever is selected as the INPUT on the channel strip or can independently source the LINE2 input -OR- you can source whatever is sourced in the MONItor buss on that strip. So the AUX sends are pretty flexible, but there aren't enough. That's being whinny, I know. So many of you are happy as clams with far less.

I want to run the RS-20B stereo spring reverb in a stereo send effect loop...so that would naturally connect up to the AUX 1-2 buss...then I have a digital effects processor which can accomodate two mono inputs that route to two stereo effects engines...so that would be AUXes 3-4. Cue feeds? Arg. No AUXes left. That leaves the MONITOR buss and the STUDIO feed.

MONITOR buss: Buckle up..."thinking" out load...Now, I'm thinking the MONITOR buss is typically supposed to be used for the engineer since it can pretty much source anything in a bunch of ways: per strip LEVEL and PAN controls and source selection of either the selected INPUT of the strip, the LINE1 or LINE2 input or the BUSS IN jack OR the REMOTE mix which allows quick switching between banks of sources (i.e. if you were to set some or all the MONITOR switchracks to source the REMOTE mix then you can switch all those between their respective MIC, LINE1 or LINE2 inputs with the push of a single button, and then furthermore there are two banks of REMOTE mixes so you can setup bank A to source the MIC input on any strip with the MONITOR switchrack set to REMOTE, and bank B could be set to, say, LINE1 and then you can source bank A or B at the strip...so basically you can run two remote mixes simultaneously utilizing up to 12 different sources between the two and be able to switch the source of each of those banks with the push of a single button rather than having to hit the source button in each strip. The MONITOR buss goes to either its own master control OR it can be dumped to the STEREO buss...not sure yet if when doing that (which is controlled at each strip...yeah...that's right...you can mix and match which of the 12 MONITOR mix sections go to the MONITOR MASTER and/or to the STEREO buss...you can setup a REMOTE mix bank A on, say, 4 channels and route that to the STEREO buss, have another REMOTE mix bank B setup on let's say another 4 channels to route normal to the MONITOR buss and then the last 4 channels could have the MONITOR switchracks set to something other than the REMOTE mixes like INPUT, LINE1, LINE2 or BUSS and sent to the MONITOR master or the STEREO buss...)...anyway, not sure if when dumping MONITOR switchracks to the STEREO buss it mutes anything else routed to the STEREO buss on that channel or mixes in with it...hoping it is the latter...that would be like a 2 x 2 summing mixer on each channel strip...then lastly there is a MONITOR switchrack on the master module to source INPUT, LINE1, LINE2 or BUSS...I'm not sure about that yet. I'm thinking that allows you two quick-switch the source of the MONITOR master buss from whatever is sourced at each channel strip to 1 of those 4 groups...probably pre-fade pre-eq. Dunno. Each channel strip has a MONITOR MUTE control too and IIRC that is post switchrack but pre master so you can still source whatever is sourced in the MONITOR switchrack by either pair of AUX busses on that strip making the MONITOR buss on that strip a powerful tool for getting all kinds of sources to the AUX buss if the MONITOR buss is muted on that strip...Bottom line is as I type this I'm thinking that the MONITOR buss is WAYYY to complex a tool for using as a cue feed...must be an engineer's friend...

STUDIO feed: So that leaves the STUDIO feed as the only cue mix unless I am just settled with not having simultaneous access to effects sends and use an AUX buss or two as (a) cue feed(s). The STUDIO feed might work and I know it is typically designed to drive an amp and speakers in the recording room for playback and communication. The talkback mic on the M-___ can be routed to the STUDIO feed as well as the AUX 1-2 or AUX 3-4 buss (or the SLATE), so that reinforces the STUDIO feed as a cue mix path, BUT the only controls for the STUDIO feed are a MASTER LEVEL control, and a source switchrack of either the STEREO buss, MONITOR buss, EXT1 and EXT2 inputs (stereo return paths...likely for 2-track playback decks I assume) or mirroring the CONTROL ROOM feed...so that seems limiting to me because I'm planning on using the STEREO buss as the two-track feed to the BR-20T, not as a cue feed.

As an aside the M-___ will sort of be doing double-duty as far as multitracking: I'll have either the Tascam 58 or the Ampex 440-8 hooked up to it via the PGM GROUP 1 ~ 8 outputs and LINE2 1 ~ 8 inputs. I am then planning on using the channel DIRECT OUTs 1 ~ 12 as mono feeds for the DAW, and then the LINE1 1 ~ 12 inputs as DAW returns so I can use the M-___ as a 12-channel analog summing mixer for digital multitrack projects.

So there's got to be a way to make this work and I'm just wondering if I am missing something in how one would normally use an analog mixer and its busses during the different stages of recording...maybe the STEREO buss would make a nice stereo cue feed during tracking and overdubbing and then it gets used as the two-track send during mixdown?

That's the kind of thing I need help with...I think maybe I'm trying to figure out how everything in every step of the process can be handled by a dedicated function on the board and maybe there is more sharing if functions depending on the different stages of the process...I'm still too digitally-minded regarding the process being able to setup everything you need rather than having it be a morphing process as far as the purpose of the different pieces of gear in the chain.

AND WHERE TO RETURN EFFECTS?? Seems like a basic question but because of how I want to use the line inputs there are only two left out of the 24 (8-track takes up 8, DAW returns take up 12, BR-20T takes up 2)...There is also the EXT1 input (I was planning on using the EXT2 input as a quick monitor path for the BR-20T and have that folded back to the LINE2 inputs on channels 11-12...), but that can only be routed to the STUDIO or CONTROL ROOM switchracks...There is also the ECHO RETURN 1 & 2...those each have a LEVEL and PAN control and can be routed to any of the 8 PGM GROUPS, the STEREO buss or the MONITOR buss...those might work then as a L-R pair of inputs for returning the reverb an being able to route that to the STEREO buss if that was being used as a comprehensive cue feed during tracking and overdubbing...then maybe the digital effects unit can be returned to the last pair of LINE2 inputs...maybe I'm just using a single mono effect on that and AUX 3 is a mono effect send and AUX 4 is an additional cue feed...

See whay I'm getting dizzy over this???

I need help.

 

[sweetbeats]

I'll have to post more detail later, but I realized that before I decide how to patch things together in the studio, I really need to get to the bottom of the specifics of all the functions on the M-___. So I did that last night and made some exciting (for me) discoveries...I now know how everything works and its cooler than I thought (keep in mind I get excited over the green color of Nichicon bipolar MUSE caps...)...

 

[sweetbeats]

Man!

More discoveries lead to more questions...seems silly that I haven't really sat down and gone through the sleuthing to really know what each button/function/jack/pot does on this thing, but amidst life and other projects it just hasn't happened yet...until now. I had made some assumptions about certain things too so it wasn't a priority to confirm, but now that I'm doing that it makes me appreciate even more what Teac did with this thing...again, more detail later, but several times now in the last 24 hours the dialogue in my head has been "Hmm...okay...I need to see then if 'X' does 'Y'...it'd be really cool/smart if it did because then it could be used to do _________ [sweetbeats sits down at the M-___ to test 'X' function for 'Y' result and...] Oh my goodness! It does do 'Y'! That's so cool! So...wait...if 'X' does 'Y', does 'Y' then do 'Z' and then does (a similar section) do that same thing??" I had a half-page of hand-written notes and questions to which I worked out answers last night...now I have 1.5 pages of more questions. Its been a little tough to confirm a couple things since the right channel of the STEREO buss is out (and BTW several things seem to be touchy in the master module which I can get to work intermittently by pressing on the card frame over the connector on the motherboard...maybe some of my trouble is just connector-related), but I've been able to come up with work-arounds for now...

 

[sweetbeats]

Its coming...

The 1-year anniversary of my acquisition of the M-___ is coming...It was actually loaded in my car in Burbank California in the early AM of October 3rd, like just after midnight, so that's the date I'm formally acknowledging is the date it came into my possession.

I was reviewing the early parts of this thread to reference a couple things and I think in honor of the anniversary I want to update the videos found in this post. So much has been learned since a year ago (especially with the work I've done in the last day or so answering my own questions), and even though I feel like the thing is still a basket-case (because the master section is still partially non-functional and only one channel strip has been gone through) when I look back a lot has actually been accomplished.

I honestly don't know if anybody is interested in video chapters covering the functions of the different sections of the mixer now that I am putting my own questions and unknowns to rest, but I'm going to do it and put them up here. I need to shoot the videos for myself honestly...When I had my M-520 I was always referencing a couple sections of the manual because I'd forget a particular routing source or function and it was nice to have the flow diagram handy...It would take too much time for me to draw a flow diagram for the M-___ so I'm just going to shoot video and that way when I forget I can refresh by watching the tutorial. Some of the stuff get's pretty complicated because most of the channel inputs can be sourced about 8 different ways and each channel has 3 main and 2 sub inputs and there are important particulars in there about pre and post mutes and levels in the routing...I don't do enough work with my mixers to have it become second-nature at least not the more complex ones like the M-520 and the M-___.

BTW, I think if the M-___ had an actual model number it wouldn't be three-digit number like I've assumed all along. I really think the M-___ was an exploratory prototype for the M-50 which led to the M-500 mixers. Again, the M-50 is very similar to the M-512 but there are a couple distinct differences between the two (the M-50 lacks the 8-channel balance amp section and just has balanced outputs for the STEREO buss like the M-___ with switcheable output level, and the orange on the fader trim strip). I think the model number would have been two-digit...there was a long history of two-digit model numbers (i.e. M-30, M-35, Model 15, Model 16...and then the M-50). with the advent of the M-500 mixers Tascam switched to three digits for the 500 and then the 100, 200 and 300 series as well as the M-600 and then from there to four-digit numbers (i.e. 1500, 2500, 1600, 2600, 3500, 3700, 5000 and was there a 7000??), but the M-___ clearly predates the M-500 series and I'm pretty sure it predates the M-50 for which I believe it was a prototypical stage...so I think it should be the M-__ with TWO underscore marks for two unknown digits...I wish I knew what Teac called it in-house. Prototypes always have a project number...I've wanted to get a nameplate from a 30 or 50-series atr and modify it to put on the M-__...maybe even just mod it so it lacks a model number and just says "TASCAM" on it with the orange and brown...

 

[sweetbeats]

I'm stoked...

Okay...more questions answered last night...more detail later...one teaser though: each channel strip can also function as a line level stereo channel...isn't that crazy? Its a little funky how you have to do it but because you can source the channel strip to either of the line inputs (LINE1 or LINE2), and you can also independently source the MONI section on that strip to either LINE1 or LINE2, you can source the strip to one, and the MONI section to the other, pan the strip hard one way, and pan the MONI section hard the other, and then using the "MONI TO STEREO" switch dump the source of the MONI section to the STEREO buss along with the source of the strip. The MONI TO STEREO switch dumps the MONI section into the STEREO buss post fader, pan and mute so the channel strip controls don't effect the panning and level of the MONI section that has been dumped into the STEREO buss...true stereo line mixing out of one channel strip. The funky part is that this only works for routing to the STEREO buss, the eq section can only effect the channel strip source -OR- the MONI section, and the MONI level is on a rotary pot and of course the channel strip level is on a slide fader. BUT...its still cool. This would make it possible to return 4 stereo effects units into the mix when mixing down to 2-track from 8-track for instance as the STEREO buss is the natural buss to send to the mixdown deck, channels 1 ~ 8 would be returns from the 8-track, channels 9 ~ 12 would be stereo effects returns, and then auxes 1 ~ 4 could be used as effects sends. I don't have a need to return 4 stereo effects units...I'm just stating a real-world scenario.

There's more of course, but that is just about the coolest discovery. The nearest competitor in coolness is the whole REMOTE bussing. I've got that totally figured out. More later...

All of this is completely pointless if only half the STEREO buss works though, but I did some dinking around last night. At first it was depressing because not only was the right channel still down in the STEREO buss, but now there was no PFL coming through, and the stereo SOLO buss was missing a channel too (the left)...plus things were now panning backwards (i.e. with the right channel down in the STEREO buss you'd expect that if you panned a channel right you'd hear nothing...well, it was passing signal when panned right, and not left). It was making me dizzy. I was starting to feel like things were sort of coming apart.

I pulled the master section to look at it some more and reseat connections...I didn't want to take it all apart...it makes me a little nervous because some of the connections are definitely fragile (case in point one more wire came loose from one of the little bridge PCB's that goes between two of the section PCB's...I'll have to repair that...ultimately I need to just replace all 10 wires that go to that little bridge PCB but I'm being lazy...). I was totally figuring that I'd need to tear it all apart again though...figured it was a failed component in the master section and not connections from the channel strips to the master section through the motherboard because I had tested the motherboard and it was good.

Well, I couldn't see anything obvious in looking at the master section except of course for the new loose wire. I decided to call it a night and put the module back in the frame and turned it on because I wanted to see if the bad right channel issue existed in all outputs as well, or just the headphones. So I was getting signal out of both channels from the CONTROL ROOM, STUDIO, and STEREO outs when sourced to the STEREO buss...things were even panning correctly. There was a terrible hum though...turned out to be my Behringer headphone amp...that thing has been trouble unfortunately...anyway, so output on both channels nice and clean. SOLO buss was still only one side though, but the PFL worked (only one channel...its mono but of course outputs to both channels). So now I was thinking that both the headphone amp was a problem and something with the connections in the SOLO buss globally. Then I realized that the master meters were both deflecting with signal whereas before only the left channel deflected reflecting the bad STEREO buss issue. I plugged into the headphone jack on the M-__ and the setereo performance matched what I experienced at the various output jacks. SO...something was now working that was not before, and it was not a headphone amp problem. I stopped there for the night. Thinking about it I was both encouraged and discouraged. I was thinking that some connection I had reseated had fixed things, but I haven't mapped the connections for the master section. That would have been good to do at some point and I 'm sure I will someday, but it is going to be time consuming. So I was encouraged that it was looking more like it wasn't a component failure, but rather a flaky connection...much less like it was coming apart and more like typical old mixer stuff to fix...but discouraged not knowing where the problem was, and unable at this point to identify what all the connections do...I wondered if it could be the connection from the motherboard to the PCB...the connections look clean and appear visually to be making good contact. I have not applied DeoxIT to them though nor have I flexed contacts to make sure there is good contact. This morning I tested the theory and at this point it does indeed appear that it is just an issue with the connectors between the motherboard and the PCB. I was able to put my tweaker on effected connection points, apply pressure and make and break signal. I was able to get everything to work, so needless to say its time to flex contacts in the socket on the motherboard and apply DeoxIT and do some reseating. This would be awesome. And it gets better...

Remember how I've been ruminating over the DIM control that hasn't been working? At least I thought it wasn't working...IT IS! I don't know what I did wrong before...I can't remember my testing methodology from before, but the MUTE and DIM controls are, of course, in the CONTROL ROOM switchrack...they allow the board operator to quickly MUTE the output to the monitors or diminish (DIM) the output (probably by, like, -20 or something) so you can still hear the program but hold a conversation to discuss something, and in both cases make no changes to the CONTROL ROOM MASTER level pot...so those functions should only effect the signal at the CONTROL ROOM OUT jacks. They both work...I must have had things connected to the wrong jacks or something or been monitoring in the wrong way...its easy to do (for me) since the master section has so many monitoring, sourcing and routing options...

So if doctoring the motherboard connections fixes my channel issues in the master section, the last conquest is to investigate the output level switching issues in the master section. The CONTROL ROOM, STUDIO and MONITOR OUT jacks all have switchable nominal output level capability, -10dBv or +4dBu unbalanced. IIRC 1 or 2 seemed to work, and 1 or 2 did not...not a deal breaker, but you know me...I want everything to work and I'm getting reinforcement here that, even though it is a prototype mixer, everything on it seems to be functional. So I'm hoping that since I bungled the testing of the DIM function I had something connected or switched wrong when I was testing the output levels. If they don't all work I'm going to leave that one alone at this point. Its not critical. If the other stuff is working (and another big thanks to evm1024 for his help with the oscillator ), then it is time to put the dress panel and knob and switch caps back on the master module and call it "done"!

To be continued...

 

[sweetbeats]

Everything works...

Output level select switches etc.

Now, the dodgey STEREO buss channel and SOLO buss channel is still an issue...MONITOR buss too. I'm not so confident that it has to do with the socket on the motherboard. So that's kind of a so-so result, but at least I know it isn't a component on one of the PCB's because at this point it is a gentle press in a certain spot right over the PCB that has the connection terminals to the motherboard on it and everything works.

All my investigative work to figure out the details of what does what/where it goes/etc. has been a really good exercise and its kind of fun because whereas I used to get muddled pretty quickly trying to figure out what button needs pressed or why I'm hearing what I'm not expecting to hear or the opposite, now I feel like I can manage the board and I more intuitively know how to control and route signal without having to stare at it for 5 minutes...and I'm getting a little more dexterity...with the two rows of controls on each strip its hard to hop from strip to strip hitting a certain control because its like there's a wall of pots in between but I'm getting better at it.

Here's a question: there's all these SOLO options right? Like 5 SOLO sources including the PFL circuit. Okay...so one of them is labeled PGM and basically it soloes the input of the group routing switches...so you can solo what is available to route to the PGM groups...seems silly. Can anybody think of a reason why that would be handy?? Its basically like soloing what is headed to the STEREO buss on that same channel since that's the source of the groups, but there's also a ST SOLO (stereo solo) button...seems redundant.

 

[sweetbeats]

I can't let it go...

I diving in and replacing all those bussing wires in the master section. I'm pretty sure that those are the source of my problems.

As I've said before the master section is less refined/more kludgey/more prototype-ish than the channel modules. I have a feeling the bussing wires were soldered more than once in the R&D department and the wires were never long enough so anytime you have to remove those small PCB bridges the solder joints get strained. The other thing I noticed is that all the bussing wires on the channel modules are heavier guage...I have a feeling that if this mixer had ever gone to production they would have used the heavier guage wires in master section. Fortunately, I have a bunch of those wires as remains from the Tascam 48 I parted out. The solder pads are pretty toasted on both of the briding PCB's so I'm going to have to get crafty in how I weld them to the board...the traces are relatively skinny. I think I'm going to try to solder them to the backside of the contact pins.

Might make more sense in this picture...I'm holding the two small PCB's that need help...you can see where they attach to the TEST OSC PCB (the main PCB in the master section that plugs into the motherboard) in the background...some of the wires I'll use to replace the old wiring are coiled to the right of my hand:

So, more on that later, but I really think I need to take care of that and do it right to hopefully fix the connection issue for good or at the very least prevent it from becoming a weaker link than it already is.

 

[sweetbeats]

The trim panels are somewhere in that pile...

Hybid black and english walnut lumber milled from an old tree we felled in our field last year...

Trying to decide if I should make the panels the same thickness and dimensions as the panels that were on the M-__ when I got it (except no end caps for the meter bridge were present...gonna have to speculate on that one...), or make them thicker ala Model 15/M-16...

 

[sweetbeats]

a tangent

Related thread regarding info on the M-16 mixer here.

The M-16 has sort snuck under my radar, but in my effort to learn as much as I can about the M-__ I think it is valuable to learn about products that did make it to market.

 

[sweetbeats]

Dress and Jack Panel Scans

I've been wanting to do this for awhile now. Below are scans of the jack panels and dress panels for the channel modules ("I/O Module") and the master section ("Control Module"). I'll be able to use these for documenting functions of each and also I can use them as cue sheets.

I/O Module Dress Panel & Jack Panel:

Control Module Dress Panel & Jack Panel:

 

[cjacek]

OMG, this is a completely PRO function board.

 

[sweetbeats]

Sweet!!

The master module is completely reassembled for the first time since taking it apart almost a year ago. That means it is totally functional to my satisfaction meaning: absolutely 100% fully functional and reliable.

I replaced all the buss wiring that goes from the TEST OSC PCB in master section which, again, is the one that actually interfaces with the motherboard. This was a bit of a painstaking task because as I mentioned earlier the solder pads were in fair to poor condition and I'm guessing it is from multiple solderings when in development. So there were 14 wires to replace, hot and shield connections at the TEST OSC PCB and hot connections on the little bridging PCB's...they bring signals from those buss connections to and from the PCB's in the master section (from the STEREO, SOLO and MONITOR busses and to the PGM group outs). I actually found a decent way to twist and wrap the hot connections at the briding PCB's around the backside of the multipin posts. This is what took so much time, but in the end it aviods having to deal with solder pads at all...the wires are connected direct to the backside of the first set of pins on each PCB (after first removing the original solder), and then that is all soldered together for each circuit. The proximity was tight but I was able to do it and clean and triple check the gap in between each connection. Below are two pictures...the first is of the first PCB that needed work that carries the SOLO and MONITOR busses, and the second is of the PCB that carries the PGM groups and STEREO busses. You can see I used a small zip tie on each to add additional strain relief to the solder joints, and you can also see I made sure that there is enough slack in the new wiring so I don't have to grit my teeth when taking this thing apart...also a reminder that the wiring itself is heavier guage than when was put in at the factory so it should last...And the result? Rock-solid connections...no flakiness at all. A small victory.

I tested 100% of every function/jack/switch/pot/etc. and everything works awesome. With that I finally felt comfortable putting the dress panel, knobs and switch caps back on and loading it in the frame hopefully for the last time in awhile. Here is a photo montage of how it looks. You can really see the contrast between the condition/cleanliness between the master section and the channel strip next to it which has not received the sweetbeats treatment yet...

Its such a huge burden lifted having the master section fully functional and back in...it makes it feel like I'm over the hump even though there are still 11 channel strips to go through, an armreast to redo and trim panels to fabricate...I guess having the master section done means that the mixer is basically fully functional whereas without it it is obviously crippled. As far as the operator is concerned that master section is the heart of the console. Since all the channel strips work with the exception of a couple funky things on channel 12 and a few noisy pots, I now have a mixer that can actually be used reliably in a tracking situation.

An overview of the last year as far as repair tasks accomplished on the M-__:

• cleaned, repainted and repaired the frame (excepting the armrest that needs to be recovered again)
• tested and conducted minor repairs on the motherboard
• modified and recapped a PS-520 power supply to power the mixer (kudos to evm1024 for his help with this)
• fabricated the PSU umbilical to mate the modded PS-520 to the mixer frame
• cleaned, painted and recapped the meter bridge
• cleaned, socketed select IC's and recapped channel 1
• cleaned, repaired and recapped the master section (again, kudos to evm1024 for diagnosing and repairing the oscillator)

Channel 2 is partially disassembled at this time getting ready for the same treatment channel 1 received.

Rough-cut walnut lumber is onsite to fab the trim panels.

All capacitors to recap the rest of the channels are on-hand.

Who knows where this project will be this time next year???

OMG, this is a completely PRO function board.

Well I'd tend to agree...strange then that much of the "pro" world doesn't see mixers like this as pro...I think it hinges on the fact that it is an "unbalanced -10dBv" board utilizing RCA pin jacks, though this one (like many of Tascam's mixers) features a number of outputs with switcheable nominal level -10/+4...but it is still unbalanced and so certain folks see it as semi-pro...oh just another small format unbalanced "piece of junk" from Tascam. Whatever. I can see that Teac was thinking about that issue in some capacity with this board because of the punch-outs on the channel jack frames for multiple XLR jacks, and quite a lot of unpopulated locations on some of the channel PCB's, namely the BUSS PCB (the one with all the group routing switches and such)...betcha with time I might be able to figure out how to setup balanced outs on this thing, though I really have no reason to do so.

This is clearly a prototype mixer. It never made it to market, and yet the channel strips are very refined, everything is functional...if Teac took this much attention to detail with a prototype, and were capable of putting together a mixer of this level of function that IMHO sounds great, what else does it say of the company and its products of that era? I'm still resting my case and care less what others think.