Tascam 788 Portastudio disassembly

Unfortunately, it's a dead link. I was searching images for Tascam Tactile Switch and that popped up. When I clicked on it, it just went to Full Compass' web site but the switch wasn't showing. I snapped the photo because it had what appeared to be a part number in the photo.

I don't know if DIgikey or Mouser would have a similar switch. I wonder if you have a 2488 service manual if it would have a part number. Also, it anyone has a 2488, they could measure the switch to see if it's the same size.
 
TalismanRich said:
I found this on Digikey. https://www.digikey.com/en/products/detail/te-connectivity-alcoswitch-switches/1825955-2/1632531

There are multiple switches with the ground leg, with differing height buttons, and different configurations. Once someone determines the configuration and size, then you should be able to narrow down the choices.
Click to expand...
Yes, that’s essentially what I was saying in my previous post. Digikey or Mouser should have the part. I’m going to reach out to Tascam too on the off-chance they have the part or have information about the part.
 
iamsetsetiam said:
Thanks much for responding. I have a multimeter that buzzes when there is continuity, but I am not sure where I would place the multimeter probes, which also might be too big for this as well. Ya, I was wondering about that key cap to switch issue as well - what is the "easier" fix for that. The 788 in these pictures is the one I bought for parts and not the one I need to fix - on this for parts 788 those switches worked fine before I disassembled it.
Click to expand...
Here are some pictures of mu Korg D16XD key switches:
D16XD Buttons.jpg
You can see the plastic buttons on the top panel, which have legs to space them off the pcb.
Also on the pcb are the through-hole mounted switches with black plastic storks.
You can see red and green LEDs adjacent to some of the switches, and nearby are transistors to drive those LEDs.

D16XD Switches (Top).png
Here is a close-up of the switches. Those black areas on the body of the switches are where the connections go through the pcb.

D16XD Switches (Solder side).png
Here is the solder-side of the pcb. Those arrangements of 4 solder points, both at the left and the right are where button switches are located.
It is your equivalent of these 4 solder points that you should be buzzing with a multi-meter.
Mine have both make and break contacts, but are not both used.
You can also see some white plastic tabs poking through rectangular holes in the pcb, which are part of the button keytops assembly.

If your product had been previously disassembled, but not screwed back together tightly enough, that could lead
to the buttons not plunging down far enough to depress the actual switches properly. The button would appear to be faulty,
even though the actual switch was perfectly good.
Before thinking about replacing a switch, you should verify that it is faulty by buzzing it.
Perhaps you can operate your recorder opened up, and pressing the actual switches, rather than the normal buttons.
I did this on mine, and discovered that the switches were actually good.
 
Slouching Raymond said:
Here are some pictures of mu Korg D16XD key switches:
View attachment 128616
You can see the plastic buttons on the top panel, which have legs to space them off the pcb.
Also on the pcb are the through-hole mounted switches with black plastic storks.
You can see red and green LEDs adjacent to some of the switches, and nearby are transistors to drive those LEDs.

View attachment 128619
Here is a close-up of the switches. Those black areas on the body of the switches are where the connections go through the pcb.

View attachment 128622
Here is the solder-side of the pcb. Those arrangements of 4 solder points, both at the left and the right are where button switches are located.
It is your equivalent of these 4 solder points that you should be buzzing with a multi-meter.
Mine have both make and break contacts, but are not both used.
You can also see some white plastic tabs poking through rectangular holes in the pcb, which are part of the button keytops assembly.

If your product had been previously disassembled, but not screwed back together tightly enough, that could lead
to the buttons not plunging down far enough to depress the actual switches properly. The button would appear to be faulty,
even though the actual switch was perfectly good.
Before thinking about replacing a switch, you should verify that it is faulty by buzzing it.
Perhaps you can operate your recorder opened up, and pressing the actual switches, rather than the normal buttons.
I did this on mine, and discovered that the switches were actually good.
Click to expand...
Just to be clear, the 788 does not use tactile switches with four contacts, rather two contacts and a ground lug for the body of the switch.
 
Just to clarify, the disassembled 788 is one I bought very cheap that was listed "as is" with no power supply etc. and I bought it to perhaps be able to get parts for my 788 and to practice the disassembly since I am such a newbie at this stuff. When I got it, I did hook up the power supply from my 788 to the "for parts" one and it started up just fine. It is a very early firmware version of the 788 which essentially can't be upgraded which greatly limits its capablilites. Also a couple of the sliders were severly bent, stuff like that. But I did test the operation of the rewind and stop buttons which seemed to work fine. So, theoretically, should it come to it, I should be able to use working switches from this disassembled one on my 788 - there are many of these kind of switches to potentially "harvest". And I do have some significant doubts that my meager soldering skills (and equiptment) plus old eyes and less than steady (to say the least) hands are sufficient to remove/install these tiny (to me) switches. Also, in terms of doing the continuity test (and thanks for clarifying which pins to probe, Sweetbeats) what kind of probes do you use? Mine are just the relatively large standard multimeter probes with collars that mostly get in the way and have no way of attaching to the pins - in some cases there just seem to be little blobs of solder on the pcb and not even any pin sticking though/out. So finding a way to do that continuity check is very tricky for me. I did eventually find a way to sort of hold the two probes with one hand in a way so that the tips of the probe were about the proper spacing apart to match the spacing of the switch pins and then reach around and press the switch on the other side with my other had - very awkward/inprecise/unreliable to say the least. I looked around online, and didn't see anything probe-wise that would seem to be able to grab those little pins or even globs of solder and stay in place securely while you depress the switch etc.
 
Slouching Raymond said:
Here are some pictures of mu Korg D16XD key switches:
View attachment 128616
You can see the plastic buttons on the top panel, which have legs to space them off the pcb.
Also on the pcb are the through-hole mounted switches with black plastic storks.
You can see red and green LEDs adjacent to some of the switches, and nearby are transistors to drive those LEDs.

View attachment 128619
Here is a close-up of the switches. Those black areas on the body of the switches are where the connections go through the pcb.

View attachment 128622
Here is the solder-side of the pcb. Those arrangements of 4 solder points, both at the left and the right are where button switches are located.
It is your equivalent of these 4 solder points that you should be buzzing with a multi-meter.
Mine have both make and break contacts, but are not both used.
You can also see some white plastic tabs poking through rectangular holes in the pcb, which are part of the button keytops assembly.

If your product had been previously disassembled, but not screwed back together tightly enough, that could lead
to the buttons not plunging down far enough to depress the actual switches properly. The button would appear to be faulty,
even though the actual switch was perfectly good.
Before thinking about replacing a switch, you should verify that it is faulty by buzzing it.
Perhaps you can operate your recorder opened up, and pressing the actual switches, rather than the normal buttons.
I did this on mine, and discovered that the switches were actually good.
Click to expand...
Thanks for posting those pictures and sharing your thoughts. What exactly did you do to improve the functionality of those plastic buttons, which do look very similiar to the 788, once you discovered that your switches themselves were fine?
 
iamsetsetiam said:
Just to clarify, the disassembled 788 is one I bought very cheap that was listed "as is" with no power supply etc. and I bought it to perhaps be able to get parts for my 788 and to practice the disassembly since I am such a newbie at this stuff. When I got it, I did hook up the power supply from my 788 to the "for parts" one and it started up just fine. It is a very early firmware version of the 788 which essentially can't be upgraded which greatly limits its capablilites. Also a couple of the sliders were severly bent, stuff like that. But I did test the operation of the rewind and stop buttons which seemed to work fine. So, theoretically, should it come to it, I should be able to use working switches from this disassembled one on my 788 - there are many of these kind of switches to potentially "harvest". And I do have some significant doubts that my meager soldering skills (and equiptment) plus old eyes and less than steady (to say the least) hands are sufficient to remove/install these tiny (to me) switches. Also, in terms of doing the continuity test (and thanks for clarifying which pins to probe, Sweetbeats) what kind of probes do you use? Mine are just the relatively large standard multimeter probes with collars that mostly get in the way and have no way of attaching to the pins - in some cases there just seem to be little blobs of solder on the pcb and not even any pin sticking though/out. So finding a way to do that continuity check is very tricky for me. I did eventually find a way to sort of hold the two probes with one hand in a way so that the tips of the probe were about the proper spacing apart to match the spacing of the switch pins and then reach around and press the switch on the other side with my other had - very awkward/inprecise/unreliable to say the least. I looked around online, and didn't see anything probe-wise that would seem to be able to grab those little pins or even globs of solder and stay in place securely while you depress the switch etc.
Click to expand...
Holding the two probes With one hand chopstick style on the two solder lands and pushing the button with the other is how I would do it…you’re not risking damaging anything electrically if one slips because you’re doing this with no power applied to the PCB. The other thing you could do is set the button actuator on something so you can hold one probe in each hand and actuate the button by pushing on the probes if that makes sense.

You should try the cleaning procedure linked in the video in @TalismanRich ‘s post. If that doesn’t work you can send the boards to me and I can swap parts (PM me if you want me to do this), find any local electronics shop and have them do it, they may even be able to identify new parts and order them, or go back to my original Al instructions to get all the details about your switches and call Mouser or Digikey. Options. It’s totally fixable.
 
I am forever resorting to the one-handed 'chopstics' method, as the other hand is needed to hold up the circuit board.
One of my meters has sharper points than the others, which allows them to slightly dig into the solder blobs, and not slide off.
The same technique goes for oscilloscope probes, remove the sprung claw part to reveal a little spike, for digging into solder.
I use a jewelers eye-glass to check out tiddly components.
Looking at your photos again, sweetbeats appears right about your switches having 2 soldered legs, plus a mechanically strong soldered leg.
Right next to each switch is an orange diode, with 2 legs. You can see in your first of 6 photos that each switch/diode pair have solder points in the shape of a diamond, on the pcb solder side. It should be easy to identify the switch connections. You don't have to clamp on to a component leg, as the solder blob and hidden leg should be all one.

iamsetsetiam said:
What exactly did you do to improve the functionality of those plastic buttons, which do look very similiar to the 788, once you discovered that your switches themselves were fine?
Click to expand...
First, ensure that the button has full travel to reach the switch properly, by fully tightening any case screws. This worked for me.
If it still doesn't quite reach, I'd look at somehow placing a shim over the switch to increase its height.
 
So I am hearing from the pros that this "chopstick" thing that I was attempting to do is actually the right way - who knew?! And rigging up some way to have the switch button depressed thus freeing up both hands also is worth exploring. Thanks for the ideas!
 
Slouching Raymond said:
I am forever resorting to the one-handed 'chopstics' method, as the other hand is needed to hold up the circuit board.
One of my meters has sharper points than the others, which allows them to slightly dig into the solder blobs, and not slide off.
The same technique goes for oscilloscope probes, remove the sprung claw part to reveal a little spike, for digging into solder.
I use a jewelers eye-glass to check out tiddly components.
Looking at your photos again, sweetbeats appears right about your switches having 2 soldered legs, plus a mechanically strong soldered leg.
Right next to each switch is an orange diode, with 2 legs. You can see in your first of 6 photos that each switch/diode pair have solder points in the shape of a diamond, on the pcb solder side. It should be easy to identify the switch connections. You don't have to clamp on to a component leg, as the solder blob and hidden leg should be all one.


First, ensure that the button has full travel to reach the switch properly, by fully tightening any case screws. This worked for me.
If it still doesn't quite reach, I'd look at somehow placing a shim over the switch to increase its height.
Click to expand...
The button properly engaging/hitting the switch indeed appears to have been the problem with my 788. After testing those switches when directly pressed for continuity, all good, (so the switches themselves are fine) and and then directly pressing them with power on to see if they did what they should do in terms of the 788's operation, which they did do, it seemed like that button to switch contact was indeed likely the culprit. So I especially tightened the pcb to the front case (that holds the plastic buttons) screws in the vicinity of the problem switches, and then did the same with the screws attaching the two halves of the 788 together - end result those switches are working well, tho not perfectly, but more than good enough for now at least. Perhaps another solution, similiar to something you mentioned, would be to somehow build up the portion of the plastic buttons where they hit the switch so as to broaden and extend the 'sweet spot' - dunno. Thanks again. Set
 
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