newbie tascam 388 questions

i suppose it does't really matter i might as well just replace it. It is quite a lot more effort test the power supply I'm assuming?
 
The test I had you do works for any diode. If you had your black probe plugged into the black COM jack and the red probe connected to the red volts/ohm jack on the right, and the meter set to the 200 ohms range on the dial you should get something less than 1 when measuring the diode one way, and open circuit (no continuity) the other direction. You measured open circuit both ways. That = toast.

Jaycar had all three in stock?
 
I think the original diode is bad and yes you should replace it.

Testing the power supply is more involved and requires an oscilloscope and ideally some custom extender cables so you can isolate the power supply from the systems it powers.
 
ah testing the power supply is out then, I'm working on a desk in my bedroom here btw. Ill get the smaller part and hopefully it works.

edit: the new diode give the same results in the continuity test, 1. in both ways. Surely this diode is not toast as well?
 
I've got a smaller diode, I'm going to put that in now. Not sure what's up with the meter either.

I went and picked up my Tascam 122mk2 (2 track cassette) from the Tascam tech in the area (he refuses to fix my 388 because i put the belt on it in the first place, but now we're kind of becoming friends, it's a long story...) and he got out his service manual for the 388 and seems to think that transistors Q141 Q142 Q143 on the reel servo PCB and also C3 and C4 on the TR PCB assembly could be bad. This was his tip for me. This guy really knows his stuff, only works on Tascam gear and has done so for the past 40 years.
Anyway, not sure if this makes any sense to you SB but thought i'd better let you know.
 
no luck with the new diode at D141 unfortunately, i guess ill test the other resistors the tech mentioned and get back to you. Thanks for help thus far!!!


edit: Q143 seems to be gone, which is the one he was saying was most likely
 
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Q141, Q142 and Q143 were on my list of possible casualties.

Those aren't resistors. Those are transistors. Do you have a transistor tester on your multimeter?

How did you determine Q143 is "gone"?
 
maybe this isn't the best way but it OLs no matter how I test it. The other transistors on the board which are exactly the same don't do this.
 
Actually forget that, I'm going to test out of the PCB, maybe that was affecting things. He did say one would blown and the other not as they are of the same value. I think the pin out of my replacement transistor is different to the original also.

http://www.jaycar.com.au/medias/sys_master/images/h08/hfe/8832608174110/ZT2115-dataSheetMain.pdf

I was given this transistor as a replacement but I'm not to confident in the advice they have given re. this at Jaycar. What do you think?

Here is the datasheet for the orginal: 2SC2320 Datasheet. 2SC2320 Equivalent. Transistor PDF DataSheet. BJT, POWER MOSFET, IGBT, IC, TRIACS CATALOG
 
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now that i've pulled them out of the board they are testing the same re continuity. they both read 820. Not sure why my meter in the diode/continuity/beep mode doesn't give a voltage drop? Google states:

Set your meter to the continuity / diode "bleep" test. Connect the red meter lead to the base of the transistor. Connect the black meter lead to the emitter. A good NPN transistor will read a junction drop voltage of between 0.45v and 0.9v.
 
Transistors have to be tested out of circuit.

drrats I'm sorry to say but I'm having a really hard time following what you are doing, not to mention what you might be doing wrong. You have to slow down and be methodical with your efforts, and understand what you are doing before you do it. I can't help you if you are going to rush ahead and not fully explain what you are doing.

I have at least a dozen questions from your last posts about what you are doing and meaning, and all manner of things you aren't teasing out before lurching ahead. I'm at a loss as to how to help you. I think this is how you arrived in this predicament in the first place.

I don't know if you are using your meter correctly, I don't know what you are testing...I don't even know if you are aware the pin assignment on your new part is reverse of the original part.

My advice to you is to take the unit to a technician before you further compound the problem(s).

I apologize if this seems harsh...I don't mean to offend.
 
No offence taken whatsoever SB.

I am definitely trying to get this done asap (and yes the carelessness at the beginning did result in the short, which I have learnt from, and if there's one thing I can take away from all this it's that i'm kind of alright at soldering now). I think this is probably where we differ in that I don't actually enjoy restoring old tape machines, I just really want to get this 388 going so that I can put some music down lol.

In post #92 you'll see that I am aware of the pin-out differences. After removing the transistors from the board they all seemed to measure the same continuity, which leaves me at a dead end. Maybe Q143 has been toasted. I wouldn't know because I don't have anyone to show me how to use my multimeter and so can't be sure I'm actually using it correctly. I think if this wasn't a problem perhaps things would be different, this is where the breakdown largely happening imo. Im unsure if I'm testing things correctly, which in the case of the diode at D141 resulted in, 'put the new diode in, test the machine'.

I'm going to call the other tech who worked on the machine to begin with (and who advise me to put the take up reel in myself) and tell him what I've done. There is also the issue with channel 2 not working that's probably going to be a headache also. At the end of the day, if it's taking me a week to diagnose whether a diode is toasted (and we never actually came to a conclusion on that of course), then perhaps a tech who can tell the difference in 5 mins is worth paying $130/ph for. Especially as I'm not repairing this stuff for fun.

When you originally told me to check the diode at D141, I thought we might be onto something simple, unfortunately things didn't turn out this way. I'm extremely appreciative of everything you've helped me with so far but I think we've reached the point in which my lack of knowledge makes this undertaking perhaps not such a good idea in hindsight. Sorry that eagerness to get this going has resulted in you having to say I cant help you anymore, but I think we've both reached the same conclusions at the same time tbh!

Anyway, thanks again for help. I really do appreciate it as you were obviously never obligated to help from the beginning. I'll be sure the keep you in the loop and let you know how things pan out :)
 
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