/diy/ - Do It Yourself » Thread #891970

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Anonymous Thu 22 Oct 2015 22:20:34 No.891970 View Reply Report Delete

Quoted By: >>891971 >>891979

I'm trying to fix a JH-110 reel to reel tape machine and I don't know anything about circuitry. Based on my troubleshooting, reading online and reading the manual I think the problem I'm having with it is related to the ICs. Replacing them might be the fix, but I'm unsure about what kind I need exactly to replace them.

one of the ICs says DCAJK4M with UA741CP under it.

This one on amazon says UA741CP,
http://www.amazon.com/TEXAS-INSTRUMENTS-UA741CP-OP-AMP-pieces/dp/B00LQQ56K6/ref=sr_1_3?ie=UTF8&qid=1445563088&sr=8-3&keywords=ua741

Is that exact enough or do I need to find one with the other serial number as well? Or is the other serial number just some sort of manufacturer's serial number I have the manual with all the schematics if anyone needs to take a look at it to answer my question.

Anonymous

Anonymous Thu 22 Oct 2015 22:23:12 No.891971 Report Delete

Quoted By:

>>891970
>manufacturer's serial number I have the manual
manufacturer's serial number? I have the manual*

Anonymous

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Anonymous Thu 22 Oct 2015 23:06:59 No.891979 Report Delete

Quoted By: >>891992

>>891970
Chips tend not degrade over time, that wouldn't be my first guess as to the problem.

Electrolytic capacitors are usually the first to go, check for any bulging ones. Next check for any corroded or cracked traces on the PCBs.

Can you describe the symptoms better? IE is it doing absolutely nothing, or is one aspect of it broken. Do you know anything about how it broke? Was it dropped, just stopped working one day, etc.

Anonymous

Anonymous Thu 22 Oct 2015 23:49:32 No.891992 Report Delete

Quoted By: >>891996

>>891979
>can you describe the symptoms better?
The reels spin 4-5x faster than they should when in play mode, and the switch that changes the tape speed doesn't work. Earlier the transport (the section of the tape machine that controls play, stop, fast forward etc) didn't work correctly, but I fixed that by pushing in some loose and improperly placed ICs. One of them was stretched so that only the left 4 pins were in the left of the socket and the right four were outside of the socket. Putting those back in fixed the transport problem.

I figure the speed of the reels is probably related to the tape speed knob that isn't working, and according to the manual those ICs also affect that knob. Based on that, and this guy's similar experience,
https://www.gearslutz.com/board/so-much-gear-so-little-time/344325-tape-machine-mci-jh110-problem-help.html

I figure it might be the ICs. It could also be the red sockets that the ICs are placed in:
http://analogrules.com/MCIred.html

They're generally considered shitty and are commonly replaced. I'm inexperienced with soldering and it's not my tape machine, so that's too big of a project for me to unsolder all those and solder on all the new ones. But yeah when I get back to the studio I'll take a closer look at the capacitors. Even if I can't fix it, I'll at least know what the problem is.

Anonymous

Anonymous Fri 23 Oct 2015 00:06:40 No.891996 Report Delete

Quoted By: >>891997

>>891992
Are you sure it's not the switch itself? Try touching the wires it's supposed to control together.

Anonymous

Anonymous Fri 23 Oct 2015 00:12:13 No.891997 Report Delete

Quoted By: >>892001

>>891996
I'm not entirely sure, but it's controlled by the same chip board as the transport and the transports problems were fixed by fixing the ICs so it seems possible. I can try touching the wires tomorrow when I'm at the studio, but for now do you know the answer to my question in the OP?

Anonymous

Anonymous Fri 23 Oct 2015 00:23:37 No.892001 Report Delete

Quoted By: >>892002

>>891997
You are correct in that the first number is just a manufacturing thing. UA741CP is the correct op amp. Since it is just an op amp, you could easily test it with a +-5v to 15v power supply and a volt meter.

Switches do get dirty and they can be a source of problems. The people in your thread that you linked to also mentioned that the red sockets on your board are problematic.

Anonymous

Anonymous Fri 23 Oct 2015 00:28:52 No.892002 Report Delete

Quoted By:

>>892001
>http://analogrules.com/MCIred.html

Ok, I just read this. Now it makes sense when you said that one of the ICs was hanging out. That never usually happens. The sockets are probably a good bet

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