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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 24th Apr 2015, 3:51 pm   #1
hsbhachu3d
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Default AA072 AA072D IC replacement.

I have a pair of these that need replacement. Any idea of how to go around it as I have not found any replacements anywhere?
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Old 24th Apr 2015, 4:33 pm   #2
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Default Re: AA072 AA072D IC replacement.

Any maker's logo, or any clues from where they're used?

David
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Old 24th Apr 2015, 7:00 pm   #3
Nickthedentist
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Default Re: AA072 AA072D IC replacement.

They wouldn't be the same as TL072, would they?

https://www.st-andrews.ac.uk/~www_pa...pamps/071.html
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Old 25th Apr 2015, 12:29 am   #4
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Default Re: AA072 AA072D IC replacement.

The IC is made by TAIYO AA072 and is 8 pin upright made of bright orange plastic. There is a grey greenish colour one which is the AA072D. Also 8 pin.

They were made for Akai Reel to reels like the X-2000SD, X-200D, X-250D and the M-10.

There are no details online wherever about them but I managed to get hold of a schematic on the akai M-10 that shows where its installed. Also, Someone online posted of a workaround schematic on a russian website. I couldn't read so I've just assumed. I will post pictures here and you guys can judge
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Old 25th Apr 2015, 12:38 am   #5
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Default Re: AA072 AA072D IC replacement.

Hi,
These are IC's that were used in early 1970's audio gear such as Akai M-10 reel to reel decks. Unobtainable these days unless you can find a parts deck. It is possible to construct a replacement using discrete components.

See this previous thread,
https://www.vintage-radio.net/forum/...ad.php?t=41131

Regards
David
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Old 25th Apr 2015, 2:54 am   #6
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Default Re: AA072 AA072D IC replacement.

What is the Value of C1? 22pF or uF?
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Old 25th Apr 2015, 8:14 am   #7
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Default Re: AA072 AA072D IC replacement.

Very certainly pF.

With a source impedance of 92k for the first stage, the capacitor on the second stage will make it an integrator, so the second transistor gain will be throttled-back to unity at about 0.1 Hz, and will drop further proportional to frequency, so its gain at 1kHz will be very low.

With 22pF, there is a high frequency roll-off, but the frequencies will be about a million times higher.

One way round this one is to get some tiny PCBs made and load them with surface mount components. It sounds like there could be a ready market for them. BC109 equivalents or MMBT3904 or any of a large number of different transistor types would do nicely. Someone's already opened one and sussed out the circuit, which is the hard part.

David
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Old 25th Apr 2015, 8:35 am   #8
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Default Re: AA072 AA072D IC replacement.

The (2S)C458 transistors shown in the circuit diagram are a common low noise Japanese transistor of the period. Similar to a BC109 but plastic cased.
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Old 25th Apr 2015, 10:44 am   #9
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Default Re: AA072 AA072D IC replacement.

Looking at the values and assuming that the resistors in the original part were either Ruthenium Oxide or else Tantalum Nitride, then if you fdo build an SMT replacement, choosing metal film resistors ought to give a worthwhile reduction in noise.

David
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