During calibration on one M-board all of the sudden the pitch went down while adjusting, resulting in a slow beating coming out of the speaker. The frequency counter showed an oscillation of only about 3Hz whenever I triggered that board. It turned out that the TA7504M OpAmp (IC3 on M-Board) has gone bad.
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| Original TA7504M |
With help from a friend a substitute (UA741) has been found which perfectly acts as an equivalent. After I have replaced the faulty one, the board started playing the notes in the correct pitch again. Problem solved.
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| Replacement UA741CH |
Of course the original part is also floating around, but it's around 15€ for each and I have read a few articles that many of those old parts are faked substitutes anyway - they are just relabelled. The equivalent is also NOS, but I found them on Ebay for about 1€ for each.
Reviewed by MFox
on
10:00 AM
Rating:
