STUDER A764; difference between 1.726.350.00 and 1.726.350.81?

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Hello STUDER experts:

Recently I bought an used A764 with RDS and MPX amp board. Tuner works fine. I download the service manual and found that it only has circuit diagram for FM tuner board 1.726.350.81. This .00 to .81 upgrade replaced 18 pin IC TEA 6000 by 20 pin IC TEA 6100. However, the printed circuit board of 1.726.350.81 was still 1.726.320.11, Search the picture of A764 I found that there was a little adaptor board convert 20 pin TEA 6100 to 18 pin TEA 6000.

What is the main purpose for this upgrade? Circuit diagram 5/26 also shown block diagram of TEA 6000 and SAA 1057, but nothing on the adaptor board. Data sheet reveals that TEA6000 feathured 3-stage IF limiter while it was 4-stage symmetrical IF for TEA6100. Since .81 revision still use the same PC board it would be possible to do this upgrade by replacing components.

Anyone has gone through this process before? Do we have to re-align the tuner after the components change?

By the way, which components are responsible for 50us/75us change of 1.726.352?

Thank you for your input.

Best Regards,

Yeun-Jung Wu

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Block diagram of TEA6000 and TEA6100; little adaptor board.

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Compare 5/28 of A764 manual and 101 of B260 manual reveal the corresponding pin of TEA6100 and TEA6000:


TEA6100 TEA6000

18 ---------------18
16 -------------- 15
17 -------------- 17
19 -------------- 16
9 ---------------- 8
10 -------------- 9
7 ---------------- 1
8 ---------------- 2
1 --------------- 12
20 --------------10

6 --------------- 3
-------------------------------------

On TEA6100 site: pin 20 connect to pin 2

On TEA6000 site: pin 6, 7, 11, 13, 5, 4 no longer used


On circuit board R171 (68k), C133 (33p) are short, R118 (10k) was replaced by 1k resistor.

[R169, R166, R168, R164 could be eliminated.]

Is it corret?

Best Regards,

Yeun-Jung Wu

[b0190]

More pictures of this adaptor board: it seems that comparison of schematic diagrams of A764 and B260 is on the right track. .00 ti ,81 upgrade was also found in ReVox B260S.