Tascam 388 Transport Trouble

Damn. I didn't mean to come across like you were testing my patience or anything. You're not.

So do you have a multimeter?

No worries, I just didn't want to appear like I was pushing away any help offered.


I do have a multimeter, which I used to measure the fuses earlier.

Thanks
 
Okay. Page 4-9 of the service manual has the schematic for the MOTHER 2 PCB. For starters set your meter to DC volts and, with the unit powered, measure between pins 1 and 4 of P5. It might take a little sleuthing to determine which connector is P5, and also to locate pin 1 (and then pin 4), but if you remove the power supply card and look down at its connectors on the motherboard you should see labels for each connector, and you should be able to find P5. Then look on the power supply card at each connector. There should be a "1" embossed on the connector body to locate pin 1.

Measure for DC volts, and then also measure for AC volts between the same two pins.

Report back.

HTH

P.S. What make/model is your multimeter?
 
Flip the cardbay cover upside down, take a picture of it and post it. I think those are the spacers that should be press-fit into the cover for each of the 6 mounting screws.
Yes I think you are right. These appear to be missing from the middle of the card bay cover. The other 4 corners have the same spacers still. I bet these came loose because one of those screws was stripped and I had to use a bit of force to remove it.

I'm guessing these would have to be epoxied back on?

IMG_3742.JPG
 
Yes I think you are right. These appear to be missing from the middle of the card bay cover. The other 4 corners have the same spacers still. I bet these came loose because one of those screws was stripped and I had to use a bit of force to remove it.

I'm guessing these would have to be epoxied back on?

View attachment 99416

Yeah epoxy or maybe something like JB Weld.
 
I have watched the one video and it looks like there is no take up on the reel motors. This can be due to failed hold voltage applied due to a burned out diode or tensions set way off. People who do not understand these things seem to always jump to conclusions that are wrong as in fooling with the brakes. The brake if they release are fine until you start to stop a tape and that is after you get the motors working. Like other servo tension decks, the center reference voltages must be set and then the tension amounts using a Tentelometer. Those people that think they set them without the Tentelometer are wasting time as it never works. I worked on these so long ago that I do not remember much about them other than they are big and heavy and too large to work on in my shop.
Open reel decks in general though have common design parts. The X1000R and X2000R deck also have servo problems and a new symptom can happen right after a tape is snapped which is what one of the post said was done. This upset a mechanical voltage reference that MUST be put back or no adjustment is going to do it.
 
Okay. Page 4-9 of the service manual has the schematic for the MOTHER 2 PCB. For starters set your meter to DC volts and, with the unit powered, measure between pins 1 and 4 of P5. It might take a little sleuthing to determine which connector is P5, and also to locate pin 1 (and then pin 4), but if you remove the power supply card and look down at its connectors on the motherboard you should see labels for each connector, and you should be able to find P5. Then look on the power supply card at each connector. There should be a "1" embossed on the connector body to locate pin 1.

Measure for DC volts, and then also measure for AC volts between the same two pins.

Report back.

HTH

P.S. What make/model is your multimeter?

Do those measurements make any sense?
 
I have watched the one video and it looks like there is no take up on the reel motors. This can be due to failed hold voltage applied due to a burned out diode or tensions set way off. People who do not understand these things seem to always jump to conclusions that are wrong as in fooling with the brakes. The brake if they release are fine until you start to stop a tape and that is after you get the motors working. Like other servo tension decks, the center reference voltages must be set and then the tension amounts using a Tentelometer. Those people that think they set them without the Tentelometer are wasting time as it never works. I worked on these so long ago that I do not remember much about them other than they are big and heavy and too large to work on in my shop.
Open reel decks in general though have common design parts. The X1000R and X2000R deck also have servo problems and a new symptom can happen right after a tape is snapped which is what one of the post said was done. This upset a mechanical voltage reference that MUST be put back or no adjustment is going to do it.


Did you watch the first or second video? This is the second video: https://m.youtube.com/watch?v=xNCx06Viyyw&feature=youtu.be
 
Assuming you are confident you were measuring the correct pins, the DC should be about 15V, and the AC should be zero or very very close to zero...like only a couple-three millivolts. With no DC output and over 8V AC I suspect that supply rail has one or more component failures. It's still possible something downstream of the supply is the root cause.

You probably shouldn't put your good power supply in that machine.

The next thing is to power the supply unplugged from the motherboard so you can test the outputs with it isolated from everything downstream. To do this you have to make a set of extender cables so you can have the card only connected to the outputs of the main transformer, or have to have a way of powering the card on the workbench completely disconnected from the machine. This gets complicated. This is the next step because it is the only reasonable way to determine if something downstream has failed and is jacking the power supply, or if the power supply has failed (and what failed), or if it is both.

The fuses are all good and it's not blowing any fuses when you power it up, right?
 
Assuming you are confident you were measuring the correct pins, the DC should be about 15V, and the AC should be zero or very very close to zero...like only a couple-three millivolts. With no DC output and over 8V AC I suspect that supply rail has one or more component failures. It's still possible something downstream of the supply is the root cause.

You probably shouldn't put your good power supply in that machine.

The next thing is to power the supply unplugged from the motherboard so you can test the outputs with it isolated from everything downstream. To do this you have to make a set of extender cables so you can have the card only connected to the outputs of the main transformer, or have to have a way of powering the card on the workbench completely disconnected from the machine. This gets complicated. This is the next step because it is the only reasonable way to determine if something downstream has failed and is jacking the power supply, or if the power supply has failed (and what failed), or if it is both.

The fuses are all good and it's not blowing any fuses when you power it up, right?

Thanks.

I measured all the fuses and they were fine. They are brand new. When I got the machine, it had old fuses, which all appeared okay (did not measure those yet).

I feel confident that I measured the correct pins, and I did double check already.

As far as the next step, that is a bit out of my comfort zone, but I will try to discuss it with a tech I know (not a reel to reel tech, but he's done some odd stuff for me before).
 
Upon further review it looks like the 15V transport supply doesn't live on the power supply board. I'll have to look further. There is a fairly good sized filter cap for that rail on the power supply board C116, but I don't see where the AC is rectified to DC upstream of that filter, nor do I see any regulation...maybe it's unregulated which is fine but there still should be rectification.
 
Upon further review it looks like the 15V transport supply doesn't live on the power supply board. I'll have to look further. There is a fairly good sized filter cap for that rail on the power supply board C116, but I don't see where the AC is rectified to DC upstream of that filter, nor do I see any regulation...maybe it's unregulated which is fine but there still should be rectification.

Thanks, I appreciate you looking into it.
 
Upon further review it looks like the 15V transport supply doesn't live on the power supply board. I'll have to look further. There is a fairly good sized filter cap for that rail on the power supply board C116, but I don't see where the AC is rectified to DC upstream of that filter, nor do I see any regulation...maybe it's unregulated which is fine but there still should be rectification.

Any further thoughts on what I can check out? Will otherwise probably dump it at a tech in the next couple of weeks.
 
I haven't had time to look. Sorry. A veritable truckload of competing priorities on my end at the moment.
 
I'm going up north tomorrow to drop it off with a real tech. Thanks for all the tips and such everybody, just getting above my pay grade. Will post back when I know more..
 
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