No heart to bin it can anyone help

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My 30 year old Technics Tape Deck Model RS-M02 has given up the Ghost.
Until recently I had never looked inside but am amazed at the wonder of engineering it is.....pure quality.
It will simply no longer do anything FF REW PLAY etc.......the amp and mechanics are OK so I deduced that it must be in the "controller circuit" and referring to the schematic diagram I was given with it when I bought it (would you get that today?) this is IC no. 401 a technics component AN 6251.
The problem is that we are in Spain and I have no hope of finding much about where to buy a spare.
Can an anyone help with it? I have a broad knowledge of circuits, a soldering iron, multimeter, solder sucker and hammer!
I would be very grateful.
Thanks
 
thanks john

attached the schematic I have been in contact with the German site and they say they will supply one for €50? I find that a little high but will try and get other quotes.
Many thanks for your help. john
 
My old databook reference it as a 24-pin IC for "recorder-control", possibly a custom IC made just for that very purpose.

There is no description or pinout data.

Sorry that's all the info I have got.
 
eblc1388 said:
My old databook reference it as a 24-pin IC for "recorder-control", possibly a custom IC made just for that very purpose.

There is no description or pinout data.

Sorry that's all the info I have got.
Click to expand...

Any ideas as where I migt be able to buy one?

thanks john
 
That schematic is about as helpful as a modern one with a microcontroller in it. Maybe Technics/Panasonic was way ahead of its time?

Here is a wild guess. Maybe it will be so off base that the discussion it generates will be helpful. The IC has switch inputs, what look like pull-ups, and outputs many of which go to inverters. Can you test the standing voltage on the outputs? Do the switches do anything to that voltage? What happens if you put a logic-level signal or ground an output, such as FF or REW? If the function works, then you have more assurance where the problem is. Since you appear to know trouble-shooting, you may already have done that and I apologize, if it is redundant.

Edit: What I mean is the chip may just be acting as a debouncer for the most part.

The asking price for the obsolete chip is high, but not a big surprise compared to what I have seen seen in my locale. I have seen typical $4 chips with asking prices ten times that. Of course, they only have to sell one to keep the store open another week. At 50 euro, I would try to find another tape deck. Are tape decks they still made? Good luck. John
 
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You have got a schematic and you can at least troubleshoot the IC pin voltage using a voltmeter.

Make up a checklist. Record all pin voltages with no key press. Press one button at a time and check if any pin of the AN6251 change states. Record them on the list.

Then confirm all parts external to the AN6251 is good before shelling out a large sum of money to get the replacement chip. Simply put, the chip replacement has to be the last resort and the tape deck should then work after you replace the IC.
 
It's a cassette tape deck, I had a Nakamichi deck that I sold ages ago when CDs came out. Even the CD is becoming a dinosaur now that solid state music is common. I suppose they're are a couple of reel to reel owners out there somewhere that refuse to let go. Can you even buy cassette tapes anymore?

On the other hand you can probably find an identical unit at the local pawn shop or on eBay. Gut it for parts.
 

Thanks again.............I have measured the voltages on in and outputs......the inputs give 4.8v and fall at touching the button to zero and instantly return to 4.8v.......the outputs are 4.8v and fall to zero on touching the button to return to 4.8v 4 seconds later.
All functions are the same.
All other voltages appear to be good.
I can not get the function to work by grounding the output?
I wish I could find another tape deck! it seems these are as rare as rokinhorse ****! I don't realy know what I am looking for in the CI pins but logic will be that the common component to all the functions is the chip?
I am still looking for a chip but no luck except at 50€!
Anybody know if Technics have a service department that might help with Vintage equipment? they migh have some! wishfull thinking.
Anyway thanks guys for your help.
 
While it could still be the chip, the fact that bypassing it still leaves the unit dead raises my suspicion that the real problem may be somewhere else. At least, I wouldn't go swapping 50-euro parts to find out.

I would call it dead and try to find a way to get my favorite tapes transferred to digital. As they say, I feel your pain. I had a favorite recording of Horowitz playing Scarlatti on vinyl. I will probably never get to listen to it again. For those who know the recording, the digital version is different...particularly the ending on vinyl when he plays Stars and Stripes Forever. John
 


Hi John
well if its easy its not worth doing!? I think you are right the chip is working! how and why I don't know but it is not dead and does somthing!
so I now have pushed the "pinch plunger" by hand and pressed the FF button and it works but for only 4 seconds and the plunger drops out! infact if I push the "head plunger" and the PLAY it works for 4 secs too................so now my attention is on the part Q428-433........what does that do? and do you think it might be relavent? I hope its just a capacitor gone down? what would you do?
Hope I'm not boring you yet?
 
Can't you reverse engineer at least part of the schematic?

If the IC is a simple digital IC you might be able to program a PIC to emulate it?
 

Now, let's find a source for the short time-out problem that would be common to both functions. There is a switch labeled "timer." What does that do? I would also check the power pin to the AN6251 to see if it is dropping out at the same time as the function stops.

BTW, I am old and can barely read part, but not all of the schematic. I assume you scanned it at a higher resolution, but reduced it to post here. Can you PM me a higher resolution version? Thanks.

John
 
Hero999 said:
Can't you reverse engineer at least part of the schematic?

If the IC is a simple digital IC you might be able to program a PIC to emulate it?
Click to expand...

Thanks, I would love to! if I knew what you are talking about.....but it sounds like a super project.
 

Glad to see that there are some "older types" on this forum! I thought they were all "whiz kids" LOL. The diagram is in Green and will not copy well. I have sent you a PM for your e-mail and will send what I have got here.
The "timer" is not well described and I have never used it which makes me laugh as that was what I was doing thirty years ago for some side money......we used to copywrite and proof read the early hand books for Sony and other Japanese companies........great fun I should have done more with it........infact that's how I got the M02!
 
helo friends

"My 30 year old Technics Tape Deck Model RS-M02 has given up the Ghost.
Until recently I had never looked inside but am amazed at the wonder of engineering it is.....pure quality.
It will simply no longer do anything FF REW PLAY etc.......the amp and mechanics are OK so I deduced that it must be in the "controller circuit" and referring to the schematic diagram I was given with it when I bought it (would you get that today?) this is IC no. 401 a technics component AN 6251."

I had the same problem, in my SanYo plus serie D65, I doubted on the IC An6251 and must searching blindly (because I could not find a service manual), and after check many transistors, capacitors, diodes, replacing 8 IC .. finally found the main culprit .. IC 4001 is fault.And my Sanyo d65 now work again ic 4001 on position on my board With code ic304
 

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