Chicago, IL
Seems like most was done already,next try a Jumper at W10 if sound is normal then speech module,Ribbon cable?
check for cracked or shorted resistors also.
(Topic ID: 246154)
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Sorcerer
Williams, 1985
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Quoted from Crispin:Thanks PINTEC, just saw this before going to bed but will try W10 again tomorrow. I tried it while isolating the speech board by unplugging the ribbon cable and jumping W10 and the sounds were the same, there but very low. I'll also bust out the dmm again and probe for shorted resistors.
I believe the speech module is ok, suggest: keep the speech board off and jumper W10 connected until the low sound problem is remedied. then the final test will be re connecting the module.
Quoted from Crispin:Please ignore the R71 and R73 posts. My friend Dennis who has a Sorcerer was kind enough to check his R71 and R73, gave me his readings of 1.6 and 2.8 and pointed out I had my dmm set on continuity. Once probed properly I have the same readings. After reading note 5 in the manual for the cpu all of the bypass B capicitors before the IC chips are .01 mfd. I have 2 of these that have no resistance the one before U18 and one before U51.
change the PIA it talks directly to the DA chip and a failed DA would cause low sounds however it was replaced so a failed PIA could simulate a bad DA chip
some cases the PIA will be able to do the math correctly however one line may be faulty, now pointing back to the replaced DA converter a faulty DA does exactly that low faint sound and speech ok
next confirm the replaced DA converter wasn't defective with another DA converter or recheck traces going in and out of DA make sure they arrive at all paths and no shorts to adjacent pins.
Quoted from Crispin:Installed a new socket and 6821 at U13 and still the same result.
everything else is doing what its supposed to do cpu/ram/software/decoders because we can hear the produced sounds.
the problem is surrounding the DA faulty resistors could display a good value with a meter but when under load is when they cannot do their job.
put another 3904 in at 51 if it was changed before the old DA was
change 1 resistor at a time surrounding the DA followed by Caps
aside from pin 3 there is -12 going into R77 that power resistor may have failed
IMG_20190725_215757718 (resized).jpgQuoted from PINTEC:everything else is doing what its supposed to do cpu/ram/software/decoders because we can hear the produced sounds.
the problem is surrounding the DA faulty resistors could display a good value with a meter but when under load is when they cannot do their job.
put another 3904 in at 51 if it was changed before the old DA was
change 1 resistor at a time surrounding the DA followed by Caps
aside from pin 3 there is -12 going into R77 that power resistor may have failed
[quoted image]
Quoted from Crispin:PINTECH YOU DA MAN! I removed the board and checked the address lines for the U48 D/A converter adn all were ok and not shorted to each other, The R77 has -13V on the top end and 1. on the other. I then moved to Q51 and swapped in a new 2N3904 NPN transistor and that did the trick. I put the board in fired her up and thanked the Lord for the guy in Chicago!! Thanks so much for taking the time to walk me through it!
Thanks!
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