newbie tascam 388 questions

the PCB seems to be fine now. I've re-soldered everything and made new tracers. Unfortunately, it didn't fix my problem so i guess i've fried something other than the PCB.
 
whenever i use the transport the take up reel moves about and inch and then stops. perhaps i should test to see if i've burnt out this new reel motor somehow?

To come so close to having this going and then to have done something as dumb as this has made me so upset. I've been trying to fix this for months, if I call the repair tech and say we may be back where we started i'm not sure he's going to be very happy. If I could at least diagnose which parts i've burnt out then I could order them from the states and give them to him when i take it back to his shop.
 
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I don't think you've killed your replacement motor.

Don't beat yourself up.

But don't forget this either.

I learned a terrible lesson years ago when I fried my mint Tascam 58 with a careless tiny mistake.

I can't underscore enough for readers of this how important it is to be slow, careful and methodical with work like this...and ALSO be prepared that if you are moving into uncharted territory, working outside of your skill-set, realize you could jack your unit up for good. You could also kill yourself...milliamperes can stop your heart.

But...truly, don't beat yourself up...it does you no good at all...won't fix anything. You've got what you've got now and you should be realistic it may be tough to fix so accept that and let's move forward okay?

When you powered it up with solder lands 19 & 20 bridged on the MECH JOINT PCB, what did you see/smell/hear? Where did smoke come from etc?

Let me look at the schematics for the JOINT PCB and see if I can point us in the right direction.

You've learned a lesson. Use it for good moving forward. Get some better light. :D

BTW "tracer" should just be "trace". Solder traces connect solder "lands" or "pads" where the components or wires are mounted.
 
of the five fuses it is listed on the pcb as a 4A fuse(what the manual states and what is on my actual fuse PCB seem to be different). the one on the very side closest the reels (front of the 388).

When i turned it on it was on it's side. I turned it off and looked at the back and there was smoke but hard to tell if it was coming from the mecha PCB or the motor or just something in the area. given that the traces on the mecha pcb have blackened i think that's what got smoky. but there could have been something else that i cant see easily of course.

Thanks for setting me straight re trace etc. you can probably tell how green I am about this stuff just from my terminology.

I really should have used a lamp yes, i even thought so at the time just before it happened. I guess this is why I was so upset with myself! It could have all been so easy, but yes i've learned my lesson, time to move on.

And thanks for the help sweetbeats and everyone else. It's so great that 388 people can help each other out here!! Hopefully I'll learn something and be able to and pass it on to other 388 owners in the future.
 
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Terminals 19 & 20 on the mechanical joint PCB are the ground and + power for the reel motor. You shorted them which creates a momentary heavy load on that power supply and high current flow on the components in the pathway before the fuse does its job and blows.

I would pull the power supply and reel servo PCBs and look for zorched components or solder traces. I would also test rectifier diode D141 on the reel servo PCB.

The next step, even if you find and replace that which looks zorched, is to test the power supply. Often times the zorch is not visible to the naked eye. To test the power supply you have to isolate it from its various loads which, on the 388, requires a set of custom extender cables. You want the power supply only connected to that which feeds it (the main transformer through the fuse PCB), and then test each DC supply for AC components (they shouldn't be there...if they are the rectifier is in question), and voltage stability and amplitude (testing the regulator) using an oscilloscope.
 
Well first pull the power supply and reel servo cards out of the cardbay and look for charred stuff. Those are the two cards to the far right of the cardbay.

Do you have a multimeter?
 
okay ill have a look at those cards when I get home. I do have a multimeter but I've never really used it so you'll have to bare with me.

Edit: there seems to be no damage to any of the PCB cards in the far right section of the 388
 
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yep found it! D141 is slight burnt looking actually! also looking burnt are all the pads associated with J101 which are connected to one of the D141 ends as you know.
 
yes all pad are scorched and the trace between D141 and J101 (you wrote j104, typo?) is also scorched. I have removed D141 from the board already
IMG_9845.jpg
 
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I said J104 because the other end of the diode is connected to J104.

I wouldn't call that scorched (J101 solder lands). Yes it looks like they got warm, but that could even happen in normal operation. Scorched is burned lacquer, blackened PCB material, traces lifted from the board due to burning, etc.

Can you post a pic of the diode D141?

Then set your multimeter to DC volts, get a battery, and connect everything up like in the picture below. Hopefully it makes sense. Make note of the voltage reading, then flip the diode backwards and check as in and make note of the voltage reading.

Dang...it would let me upload the photo...says it is t a valid format but it's a jpeg. Anybody else having this issue uploading from an iOS device using Safari?
 
I had this problem when posting from my computer. my iphone took the photos as.JPG and seemed they wouldn't upload. I renamed the photo .jpg using lowercase and then no problems. Not sure if what I did helped because i didn't do that with the first photo I posted! Also not sure you can rename files in such a way on your ios device anyway..
 
IMG_9848.jpg

Here's the diode. Also changing to lower case didn't work that time for me. I had a few attempts at uploading the picture, closing and opening the insert image box each time. On the third time it went through, which is strange. I've pm'ed you my email though to send it through if that helps. Cheers!
 
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