[GreenKeys] Dovetron mfg error (was Model 15 question)

[Jim Haynes]

The note is:  If you have the Binary Bit Processor BBP-100 Mark II as 
shown on drawing 75349 then inspect the bottom side of the PC board to see 
if there is an extraneous trace connecting the top ends of R21 and R22. 
By top ends I mean the ends that are on top if you hold the drawing 
vertically so it reads right side up.  The bottom ends are supposed to be 
connected together and to pin 6 of U11. The top ends are not supposed to 
be connected together.  If they are the threshold voltage will stay at
0 volts so the threshold correction circuit is inoperative.

Then look at resistors R24 and R25.  These are supposed to be 10K
resistors.  You may find they are 100K, because 1% resistors have
an extra digit in the value.  If the colors are brown-black-black-orange
you have 100K resistors and the unit will hardly work at all after the
extraneous PC trace is cut.  Replace with 10K resistors, and they
probably don't need to be 1%.

This error may explain why some Dovetron demodulators get poor
performance reports.  I guess it didn't get detected at the factory
because the units with the errors do work with good signals, but
not with weak and fading and noisy signals.

Jim W6JVE
 	---

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