sweetbeats
Reel deep thoughts...
Been doing a number of things past few days...got into the power supply mods, tore apart the power supply umbilical I made in preparation for a corrected/improved version, rewiring the frame for proper grounding, and doing some minor structural improvements on the frame.
Ask me how painful this is to pull apart the original power supply umbilical I made...necessary but it sucks.
Random comment from a friend of mine who's developed mixing products for at least three well known companies...upon seeing pictures of the module boards and the control surface features on the Tascam M-__: "It looks like they let the designers work with both hands this time."
Ask me how painful this is to pull apart the original power supply umbilical I made...necessary but it sucks.
Random comment from a friend of mine who's developed mixing products for at least three well known companies...upon seeing pictures of the module boards and the control surface features on the Tascam M-__: "It looks like they let the designers work with both hands this time."
sweetbeats
Reel deep thoughts...
Power supply mods...
I've done all of this stuff so far except for the last thing:
Here's the PCB done and ready to go back in...the new +/-15V regulators are there to the right wired and ready to mount. The yellow blobs are tantalum caps to keep the regulators from oscillating since they will be further away from their filter caps:
Here is a shot of the backplane. Most of that stuff was already there. The new +/-15V bridge is there to the right. The +/-15V regulators can be seen to the left (look for the yellow blobs). They were originally just mounted to the PCB with no heat dissipation and they were discolored. The heatsink has a bunch of threaded hole mounting points so why not relocate 'em and keep 'em cool?
Here is the PCB back in the chassis:
And here is the little heatsink I added to the +6V regulator...Cute...raided a handful of these TO-220 heatsinks from a PC mainboard awhile ago that was going to scrap:
Anyway, don't know if the changes will bring any audible results, but it will make the PSU more robust. The most important changes really are around the changes to the ground scheme.
I've done all of this stuff so far except for the last thing:
- Isolate 0V references for the +/-15V, +/-35V, +6V and +48V rails (and tie together in the mixer frame)
- Improve PCB jumper connections for better conductivity of select paths
- Increase value of +/-15V and +/-35V rail primary filter caps from 4,700uF to 10,000uF
- Increase voltage rating of +/-35V primary filter caps from 35V to 50V
- Replace +/-35V secondary filter caps with proper value (22uF was installed, should be 47uF)
- Replace +/-15V and +/-35V HF bypass caps with new XR7 parts
- Replace +/-15V rail bridge rectifier
- Replace +/-15V rail regulator ICs with lower noise higher PSRR parts
- Relocate +/-15V rail regulator ICs to backplane heatsink for better heat dissipation
- Add mini heatsink to +6V regulator IC
- Revise PSU chassis ground scheme
Here's the PCB done and ready to go back in...the new +/-15V regulators are there to the right wired and ready to mount. The yellow blobs are tantalum caps to keep the regulators from oscillating since they will be further away from their filter caps:
Here is a shot of the backplane. Most of that stuff was already there. The new +/-15V bridge is there to the right. The +/-15V regulators can be seen to the left (look for the yellow blobs). They were originally just mounted to the PCB with no heat dissipation and they were discolored. The heatsink has a bunch of threaded hole mounting points so why not relocate 'em and keep 'em cool?
Here is the PCB back in the chassis:
And here is the little heatsink I added to the +6V regulator...Cute...raided a handful of these TO-220 heatsinks from a PC mainboard awhile ago that was going to scrap:
Anyway, don't know if the changes will bring any audible results, but it will make the PSU more robust. The most important changes really are around the changes to the ground scheme.
T
The Ghost of FM
Banned
I'm sure that brought a smile to your face, reading that!
But, one of things that made TASCAM the success it was, is due largely to the fact that they made recording technology affordable to the masses, which requires a bit of cost cutting into the designs. No shame in that objective.
Cheers!
sweetbeats
Reel deep thoughts...
But here's the thing I've said time and again: Teac was exceptionally smart about how they managed the drivers of a product's price point. There were certain things they did not compromise. I have had the opportunity to completely tear apart and repair/refurbish professional audio products from a number of manufacturers, and a good selection of Teac products. My comments and impressions are specific to Teac/Tascam professional audio products from the 80s because that's my scope of experience, with the exception of my BR-20T halftrack. With that caviat in mind, my adventures have brought many facets to light for me about Teac professional audio products of that era. For instance, where other manufacturers have been want to select capacitor values of a more strict "corporate value" (to reduce costs by procuring a specific value of cap in much greater quantity), Teac selected values more appropriate to the circuit and application...the engineering and design speaks for itself on the PCBs. Just one example, but as I became aware of things like that it became glaringly obvious. And the quality of the components selected is often a grade above competitors. So it's what's inside on top of a loooong list of industry steering innovations. I know much of the snob set turn up their nose, but Teac deserves credit for performance and feature-focused engineering and design and consumer-driven (not *market*) product development within their respective markets. I feel, if one looks at a reasonable cross-section of products from other companies, he/she will find Teac as a unique standout.
So the fact I have made upgrades to the modified PS-520 power supply utilized to power the M-__ mixer should NOT imply it was poorly designed. It was overkill to power the M-520 by a factor of at least 3 or maybe 4. It's just the M-__ has a good number more active components to drive, and there are ground-scheme best-practices I've learned and adopted that are still not consistently followed today. It's a controversial subject and always has been. I just know I used them and they worked like crazy on my Soundtracs MX32 and my environment is a real RFI challenge.
So the fact I have made upgrades to the modified PS-520 power supply utilized to power the M-__ mixer should NOT imply it was poorly designed. It was overkill to power the M-520 by a factor of at least 3 or maybe 4. It's just the M-__ has a good number more active components to drive, and there are ground-scheme best-practices I've learned and adopted that are still not consistently followed today. It's a controversial subject and always has been. I just know I used them and they worked like crazy on my Soundtracs MX32 and my environment is a real RFI challenge.
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sweetbeats
Reel deep thoughts...
Mixer frame mods...
Grounding is the big one.
The best practice I learned for a mixer with an external power supply is the power supply chassis should be positively strapped to the "building ground", and the power supply chassis and mixer frame chassis should be positively bonded through the power supply umbilical shield (ideally good quality cable with braided shield). The 0V references for the power rails should stay isolated from the chassis until the conductors reach the mixer frame chassis, at which point they should be bonded together with the mixer frame as close as reasonably possible to where the conductors enter the mixer frame. The point here is for any RFI picked up on the way up to the mixer frame to be shunted to ground as soon as possible upon entering the mixer frame. Then all metal sections of the mixer frame should be bonded together for safety and so any metal part of the mixer chassis can be a point of ground reference for the boards or circuits within the frame...a veritable ocean of noise shunting opportunity. That way ground wire runs within the mixer can be made as short as possible.
So when I looked at the ground wires in the mixer frame my memory was refreshed that the wires go from the back side of the umbilical connector to central points on the main motherboard. After re-pinning the connector to align with the pin assignment in the power supply (in preparation for the new cable), I simply picked a good mounting point, clipped those wires, and then put on some heat shrink and crimped and soldered on a ring connector...remove an existing sheet metal screw, drill the hole out and then go get some hardware including star washers to make sure there's a good conductive bite between the ground conductor and the frame...I like to use conductive grease too. Still need to bolt it up but here is where it stands at present:
So then I tipped up the M-__ and lovingly gave the unnecessarily long ground runs for the +/-15V rails a haircut.
Here is the underside of the frame. I'm holding on to three wires that used to carry the 0V reference for the +/-15V rails...the wires traveled a couple feet from the back of the frame where the umbilical connects:
Clip those wires off, pull the insulation off them to twist them into a fat wire...
And then as with the ground wires coming out of the back side of the power connector I put on some heat shrink and crimped and soldered on a ring connector...removed an existing sheet metal screw, drilled the hole out, yada-yada. Again, still need to bolt it up but here is where it stands at present:
Same thing with 0V conductor for the +/-35V rails...white wire that traveled all the way from the back of the mixer. Clip it and bond it to the chassis. And remember the whole chassis is now an effective ground reference for everything because that white wire and the three wires from underneath for the +/-15V ground are now bonded to the chassis near the entry point into the mixer frame:
I also found 12 screws missing that attach the card edge connectors to the plate for the motherboards...I don't know why they left them off. I got some screws to fill those mounting points.
I also discovered the sheet metal screws that attach the sides of the frame to the wrist-rest were pretty much stripped out of the L-brackets. They wrist-rest is a fairly heavy-gauge piece of square tubing and really provides the vast majority of the torsional structure at the front of the frame. Not good. Went and got some machine screws, washers, nylock nuts and am drilling the holes out and will fasten it all together with the machine screws...better than original.
And the original underpan for this thing was a couple completely chewed-up pieces of cheap fiber board. I'm looking into having some aluminum perforated panel sheared and formed on a break to make a fitted vented panel for the bottom.
Grounding is the big one.
The best practice I learned for a mixer with an external power supply is the power supply chassis should be positively strapped to the "building ground", and the power supply chassis and mixer frame chassis should be positively bonded through the power supply umbilical shield (ideally good quality cable with braided shield). The 0V references for the power rails should stay isolated from the chassis until the conductors reach the mixer frame chassis, at which point they should be bonded together with the mixer frame as close as reasonably possible to where the conductors enter the mixer frame. The point here is for any RFI picked up on the way up to the mixer frame to be shunted to ground as soon as possible upon entering the mixer frame. Then all metal sections of the mixer frame should be bonded together for safety and so any metal part of the mixer chassis can be a point of ground reference for the boards or circuits within the frame...a veritable ocean of noise shunting opportunity. That way ground wire runs within the mixer can be made as short as possible.
So when I looked at the ground wires in the mixer frame my memory was refreshed that the wires go from the back side of the umbilical connector to central points on the main motherboard. After re-pinning the connector to align with the pin assignment in the power supply (in preparation for the new cable), I simply picked a good mounting point, clipped those wires, and then put on some heat shrink and crimped and soldered on a ring connector...remove an existing sheet metal screw, drill the hole out and then go get some hardware including star washers to make sure there's a good conductive bite between the ground conductor and the frame...I like to use conductive grease too. Still need to bolt it up but here is where it stands at present:
So then I tipped up the M-__ and lovingly gave the unnecessarily long ground runs for the +/-15V rails a haircut.
Here is the underside of the frame. I'm holding on to three wires that used to carry the 0V reference for the +/-15V rails...the wires traveled a couple feet from the back of the frame where the umbilical connects:
Clip those wires off, pull the insulation off them to twist them into a fat wire...
And then as with the ground wires coming out of the back side of the power connector I put on some heat shrink and crimped and soldered on a ring connector...removed an existing sheet metal screw, drilled the hole out, yada-yada. Again, still need to bolt it up but here is where it stands at present:
Same thing with 0V conductor for the +/-35V rails...white wire that traveled all the way from the back of the mixer. Clip it and bond it to the chassis. And remember the whole chassis is now an effective ground reference for everything because that white wire and the three wires from underneath for the +/-15V ground are now bonded to the chassis near the entry point into the mixer frame:
I also found 12 screws missing that attach the card edge connectors to the plate for the motherboards...I don't know why they left them off. I got some screws to fill those mounting points.
I also discovered the sheet metal screws that attach the sides of the frame to the wrist-rest were pretty much stripped out of the L-brackets. They wrist-rest is a fairly heavy-gauge piece of square tubing and really provides the vast majority of the torsional structure at the front of the frame. Not good. Went and got some machine screws, washers, nylock nuts and am drilling the holes out and will fasten it all together with the machine screws...better than original.
And the original underpan for this thing was a couple completely chewed-up pieces of cheap fiber board. I'm looking into having some aluminum perforated panel sheared and formed on a break to make a fitted vented panel for the bottom.
T
The Ghost of FM
Banned
I totally agree with you.
What I was more thinking of in the way they cut costs was to not do massive die-cast transport plates like your 3M deuce has and opt for plastic knobs in place of machined aluminum ones. Those sorts of things.
Cheers!
sweetbeats
Reel deep thoughts...
Right...I gotcha.
Yes there *definitely* is a very distinct difference in the *massive* over-engineering both physically and electronically of machines like my 3M halftrack and My Ampex multitrack, or my MCI mixing desk as compared to Teac (and lots of other brand's) products.
But generally speaking I can see the distinct thought process behind HOW Teac managed price point and it is inspiring. They really did remarkably well...so many areas I've seen companies take hold of typical excuses whereas Teac said something like (as evidences by what I see in their products) "this is our standard and we'll not drop below it.
It goes far beyond skin deep.
Yes there *definitely* is a very distinct difference in the *massive* over-engineering both physically and electronically of machines like my 3M halftrack and My Ampex multitrack, or my MCI mixing desk as compared to Teac (and lots of other brand's) products.
But generally speaking I can see the distinct thought process behind HOW Teac managed price point and it is inspiring. They really did remarkably well...so many areas I've seen companies take hold of typical excuses whereas Teac said something like (as evidences by what I see in their products) "this is our standard and we'll not drop below it.
It goes far beyond skin deep.
sweetbeats
Reel deep thoughts...
Got the power supply finished tonight which entailed a little soldering on the power supply connector, and making the new chassis ground lug to bond the power supply chassis to the mixer frame chassis.
Also got half the new power supply umbilical soldered up...I'm waiting for new parts for the mixer end of it...new gold-plated brass Molex pins and sockets and a new set of housings.
Anyway, here's the guts of the mixer end of the cable and then a shot with the hood installed. Not my prettiest work but that's where the hood comes in.
The mixer frame chassis reinforcements are all done as well.
Also got half the new power supply umbilical soldered up...I'm waiting for new parts for the mixer end of it...new gold-plated brass Molex pins and sockets and a new set of housings.
Anyway, here's the guts of the mixer end of the cable and then a shot with the hood installed. Not my prettiest work but that's where the hood comes in.
The mixer frame chassis reinforcements are all done as well.
A Reel Person
It's Too Funky in Here!!!
!!!
Incredible reworking & attention to detail!
This thing will be better than new!!!
Incredible reworking & attention to detail!
This thing will be better than new!!!
XploZiveToyz
All American Un-American
You're a damn nut! In a good kind of way! LOL!
sweetbeats
Reel deep thoughts...
Hah!
Not everybody would agree with you...but I'll take what I can get.
Actually spent quite a bit of time on the M-__ today...can't finish it up yet since I'm still waiting for parts, but I *did* satiate some things that were gnawing at my mind regarding structural matters. I said I was done. I couldn't let it go. There are dozens of sheet metal screws that hold the frame sections together. I don't like sheet metal screws...I much prefer machine screws and nuts. Now I didn't go through and replace all the sheet metal screws because they actually do handle quite a bit of torque, and the frame seems pretty solid, but I added internal tooth star washers to all of them...I want them to bite tight and stay that way. Plus this will help ensure good electrical continuity between the sections. I had also checked to see that the frame was square...it was off 1/8". I loosened up most of the screws, at least the ones that pertained to what needed to move...the frame is more stout than I thought. I had to tip the thing up on a back corner (so it was sitting like a diamond) and jump and drop my chest on the top corner to get it to budge that 1/8". Its square now. The meter bridge wasn't straight either...closer to the front of the mixer on the left by 1/32"...that's fixed...and higher on the right...fixed that too. So the frame is all straight, tight, and back together.
Juuuuust waiting for parts so I can finish wiring the frame and finish the power umbilical. Then it will be testing time.
There are other grounding mods I could do, but I'm going to wait and see if they're necessary. They would involve the ground conductor of all the jacks on the backplane getting grounded as close as possible to the respective module chassis at the jack, rather than going all the way through the module and getting grounded at the motherboard. Not that complicated, but if things are quiet as they are, no sense in making the changes.
Making some inquiries into having a bottom panel made up out of perforated panel.
Then I'm sure there will be niggling things to take care of...headphone circuit has a little bit-o-sputnik sounds going on...the low frequency on the oscillator isn't working again...I'll have to look back and refresh my memory as to what evm1024 did to fix that...it had to do with a delicate capacitance issue.
BUT...
Wow...
Its getting really close to truly being "done", folks.
Not everybody would agree with you...but I'll take what I can get.
Actually spent quite a bit of time on the M-__ today...can't finish it up yet since I'm still waiting for parts, but I *did* satiate some things that were gnawing at my mind regarding structural matters. I said I was done. I couldn't let it go. There are dozens of sheet metal screws that hold the frame sections together. I don't like sheet metal screws...I much prefer machine screws and nuts. Now I didn't go through and replace all the sheet metal screws because they actually do handle quite a bit of torque, and the frame seems pretty solid, but I added internal tooth star washers to all of them...I want them to bite tight and stay that way. Plus this will help ensure good electrical continuity between the sections. I had also checked to see that the frame was square...it was off 1/8". I loosened up most of the screws, at least the ones that pertained to what needed to move...the frame is more stout than I thought. I had to tip the thing up on a back corner (so it was sitting like a diamond) and jump and drop my chest on the top corner to get it to budge that 1/8". Its square now. The meter bridge wasn't straight either...closer to the front of the mixer on the left by 1/32"...that's fixed...and higher on the right...fixed that too. So the frame is all straight, tight, and back together.
Juuuuust waiting for parts so I can finish wiring the frame and finish the power umbilical. Then it will be testing time.
There are other grounding mods I could do, but I'm going to wait and see if they're necessary. They would involve the ground conductor of all the jacks on the backplane getting grounded as close as possible to the respective module chassis at the jack, rather than going all the way through the module and getting grounded at the motherboard. Not that complicated, but if things are quiet as they are, no sense in making the changes.
Making some inquiries into having a bottom panel made up out of perforated panel.
Then I'm sure there will be niggling things to take care of...headphone circuit has a little bit-o-sputnik sounds going on...the low frequency on the oscillator isn't working again...I'll have to look back and refresh my memory as to what evm1024 did to fix that...it had to do with a delicate capacitance issue.
BUT...
Wow...
Its getting really close to truly being "done", folks.
sweetbeats
Reel deep thoughts...
Parts came today...
sweetbeats
Reel deep thoughts...
Parts!
XploZiveToyz
All American Un-American
It's does my heart good to see people passionate about something. We all need a labor of love!
sweetbeats
Reel deep thoughts...
Me and my electronics friends... 
I brought the rest of the modules back to my place. This is kind of a cool shot, the modules all stacked up next to the M-512:
Moving in a little closer...I'm happy with the new color scheme:
By contrast you can kind of see how it used to be with this shot taken before I even came into possession of the console...lots of putty color, both with the knob caps and also with the switch caps:
These are the putty switch caps that used to be installed on the I/O modules...48 of them:
Another little bit of subtle color management I worked in is with the fader caps...modules 1~8 also have the PGM BUSS 1~8 master controls, while modules 9~12 have the master controls for AUX busses 1~4. So just to help visually break up those differential purposes between those two groups of modules I used different color fader caps:
Okay. Time to heat up the soldering iron.
I brought the rest of the modules back to my place. This is kind of a cool shot, the modules all stacked up next to the M-512:
Moving in a little closer...I'm happy with the new color scheme:
By contrast you can kind of see how it used to be with this shot taken before I even came into possession of the console...lots of putty color, both with the knob caps and also with the switch caps:
These are the putty switch caps that used to be installed on the I/O modules...48 of them:
Another little bit of subtle color management I worked in is with the fader caps...modules 1~8 also have the PGM BUSS 1~8 master controls, while modules 9~12 have the master controls for AUX busses 1~4. So just to help visually break up those differential purposes between those two groups of modules I used different color fader caps:
Okay. Time to heat up the soldering iron.
T
The Ghost of FM
Banned
New color scheme looks great!
Of course, this also means new wallpaper shots will need to be done!
Cheers!
ps: got the new 234 shots, so I'll get to work on those over the next couple of days.
Of course, this also means new wallpaper shots will need to be done!
Cheers!
ps: got the new 234 shots, so I'll get to work on those over the next couple of days.
sweetbeats
Reel deep thoughts...
Dang, Jeff...didn't even give me a chance to send you a PM!
I *hope* there's something usable in there...tricky to get a good shot with the iPhone...shallow depth of field was an issue with the perspective shots...tried really hard to get good flat lighting without reflections in the meter lenses or cassette bay door. Anyway, hope there's something usable.
I *hope* there's something usable in there...tricky to get a good shot with the iPhone...shallow depth of field was an issue with the perspective shots...tried really hard to get good flat lighting without reflections in the meter lenses or cassette bay door. Anyway, hope there's something usable.
sweetbeats
Reel deep thoughts...
Old beat-up mixer frame power connector housing on the left, new one on the right:
Pretty...new gold-plated brass pins, crimped and, for good measure, soldered up:
Pretty...new gold-plated brass pins, crimped and, for good measure, soldered up:
