Tascam 388 - problem no rewind and no fast forward, smoke comes out !

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Julien D

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Hi ;)

I just bought a TASCAM 388 in good condition but full of dusts on the outside and inside. I cleaned everything and it is now perfectly clean. Heads are currently in good condition. I cleaned them with isopropyl alcohol 99.9% and I can record all tracks easily. I bought a new tape (RMG LPR 35 1/4) and the mixing part works well. The capstan belt is good.

When I tested it the first time, I could not use the functions play, rewind and fast forward so I checked the fuses and one was burnt. I changed all the fuses. It worked better but I still had transportation problems. I then adjusted the tension of rollers on the reel servo pcb (R112, R212, etc ..) and it finally works !!! I then tested the recording of all tracks. Everything worked.

But then I noticed that the tape counter remained at zero when the tape was running. So I verified the tach (counter) roller and the sensors and everything was ok ...

So I decided to unplug the connectors on PCB boards (capstan servo pcb) in case. When I turned on the machine after that, I saw smoke coming out (between pcb power supply and reel servo pcb I think) and I immediately switch off. :facepalm:


A fuse has burned out ... I changed and I reconnected the connectors on the PCB board. I switched the machine and the same fuse burnt again if I remember correctly.
I changed again and I tested the play functions, rewind and fast forward. Nothing worked properly. I still set the tension of rollers (R112 and R212) and I can now use again play function but I can not rewind and fast forward ...

I made a video to show you my problem:

https://www.youtube.com/watch?v=EC5mqNMwYKQ&feature=youtu.be

I feel that the roller pitch engages in all cases when it should be engage just when I push the play button, right?

Thank you for your help! :wtf:

Julien

PS: the tape counter is working now ... I just missed to put a washer under the roller counter ...
 
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Given the circumstances & watching the video, I'd suspect a power regulator or other power related component on the power regulator board. Smoke is never good. If there's smoke, you can often ID the burned component visually.

I think when you press a button a higher voltage spikes momentarily to "pick" the solenoid and start the motors, then settles almost immediately into a slightly lesser voltage. To me, it looks like the initial burst of energy is delivered, but no voltage follows it to sustain the motors or closed solenoid.

There's initial motion and tension is sustained, so I'd suspect the overall power regulator board/section, as opposed to a bit more out on the "branch" of power transistors that drive the individual components.

That's an amateur opinion & I'm shooting a bit from the hip. A technician should take a look.

Good luck.
:spank::eek:;)
 
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Quite different than the first video!

The new video shows what I'd suspect is more of a motor drive transistor problem. The drive transistors for the motors are stacked in pairs and are located/attached to the rear heat sink assembly. I had a similar looking problem several years ago. You'll need to consult the manual and do a bit of component level troubleshooting, but (after thoroughly checking the basics) I think best to focus in the transistor deck area.

:spank::eek:;)
 
Do you mean this transistors (link below) ? They look fine. I have a multimeter, I can check if they are good. And what do you think of the roller pitch problem ? As you can see in the video, it engages even when I push the fast forward and rewind button, is it normal ?

Thank you for your quick answer ! :thumbs up:

http://imageshack.com/a/img540/8662/kfUauR.jpg
 
Having read both A Reel Persons post and the OP's, and remembering my conversations with our in-house tech where I used to work, it sounds like a problem with a capacitor, or maybe a resistor. But capacitor seems most likely because you have one area smoking. That may mean while everything else is working around it, that one capacitor could not contain the voltage surge that A Reel Person talked about. It may also be a transitor did not change the current to the proper functions, causing it to overload the capacitor which now has had an amplified current from the transistor remain contained within the capacitor. Without a resistor to regulate what goes in to the capacitor from that transistor, I assume that would seriously heat up whatever components are in that area if left sitting while powered on.

Basically somewhere in the machine, the Dam has been made to hold back to much water, and it broke.

The only electronic education I have is from listening to Bill for a year. Please tell me if this theory is absolutely wrong.

EDIT: Considering the same fuse is sacrificing itself repeatedly, I would say that it has to be a capacitor, it can't contained the voltage, thus engaging the fuse to blow so that the rest of the machine/circuit are saved from a power surge.
 
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Hi Roozter !

I looked at the pcb card and I find a big green transistor which look suspect on the reel servo pcb card ( http://imageshack.com/a/img537/5093/lKjN8Q.jpg ).

What do you think about that ? All the resistors and the capacitors look good visually. I test them with my multimeter and it's seem ok.
 
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Julien D said:
Hi Roozter !

I looked at the pcb card and I find a big green transistor which look suspect on the reel servo pcb card ( http://imageshack.com/a/img537/5093/lKjN8Q.jpg ).

What do you think about that ? All the resistors and the capacitors look good visually. I test them with my multimeter and it's seem ok.
Click to expand...

I'm no expert, but I know that a transistor amplifies the voltage before it sends it off. If the current can't pass through it I would assume it would just retain the current, causing it to heat. Now, why it can't continue the circuit is beyond me. Your fuse is probably blowing due to what's happening with that transistor though. I either think you have a bad capacitor, it my look fine but may not be functioning properly and the voltage is too much for the transistor to deal with. Or, something is not accepting the current from the transistor. Or the transistor may be amplifying but not passing the current itself. Maybe replace said transistor, and if that does not work, replace any capacitors or... Inductors, I believe is what they may be, that are in the nearest part of the circuit that contains that transistor.
 
Ok, definitely not normal!

Given that there was smoke and a fuse keeps blowing, all bets are off for normal operation until you get that sorted.

I'd start at the basics & determine if all your voltages are present from the power supply section, then use the schematics to find which circuit that specific fuse supports & focus in there. Remember, you said you originally disconnected the Capstan board when the problem started, so I'd look carefully at the schematics to see if there is any relationship there to the symptoms. For the pinch roller to activate during FF mode is entirely abnormal.

Think about something like mis-placed connectors. What about it causes the pinch roller solenoid to "pick" when you're actually looking for the right reel motor to turn? Inversely, the right motor does not turn at all. To me, that hints at a possible mix/match of the connectors, which in certain cases look the same with the same # of pins.

I mismatched a head/load & capstan motor connector once a long time ago on a cassette 234, and it behaved similarly to this, where it cycled the heads up and down instead of driving the tape forward. There's nothing iron clad about that, but more of a suggestion to think out of the box. That, and none of this started until you moved the connectors. Time to retrace your footsteps.

:spank::eek:;)

PS: a fuse blows most often to protect whatever circuit it's installed in from overload, not necessarily that a bad component is causing the fuse to blow. However, it can go either way. The fact that the fuse blows is probably preventing more smoke from leaving the machine. Aside from the operational problem, the fuse blowing is your most stark and tangible symptom & I'd focus on that very closely.
 
The servo system of the 388 is complex. No more complex than any other period machines, but the interconnections are more complex on the 388; it is much harder to isolate systems and boards on the 388...I don't recommend just unplugging certain boards to try and isolate them because the boards are more interdependent.

Given the symptoms (servo system malfunction and logic malfunction) and given you did take certain boards out of the system by unplugging them, and there was smoke, I think your 388 needs some serious tech involvement well beyond me. Sorry to share this discouraging opinion, but I know if I had a machine behaving such as your in my stable it would be given "parts machine" status.
 
sweetbeats said:
The servo system of the 388 is complex. No more complex than any other period machines, but the interconnections are more complex on the 388; it is much harder to isolate systems and boards on the 388...I don't recommend just unplugging certain boards to try and isolate them because the boards are more interdependent.

Given the symptoms (servo system malfunction and logic malfunction) and given you did take certain boards out of the system by unplugging them, and there was smoke, I think your 388 needs some serious tech involvement well beyond me. Sorry to share this discouraging opinion, but I know if I had a machine behaving such as your in my stable it would be given "parts machine" status.
Click to expand...

Hi Sweatbeats !

I've got some news.

I took my tascam repaired but they failed to solve the transport problem...they have found some bad componant on the reel servo pcb card and on the cap servo PCB card and they changed it. The problem now is that the pinch roller doesn't engaged (It try...).

The tension roller work fine and I can use ff and rw fonction but I can't use the play function because of the pinch roller...

The teck guy was not a specialist of this machine and didn't want to spend more time on it...

You can see what happens in this video. Maybe the problem comes from the PCB control card? What do you think about that ?

:wtf:

https://www.youtube.com/watch?v=owno8yOSImU&feature=youtu.be
 
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