af KlausM » tirs 4. jun 2013 13:26
Lækker forstærker, til lykke med den. forpladen ser pæn ud på billedet, pøj pøj med displayet; kan det være en eller nogle lamper, der belyser displayet bagfra, der er gået? Sådan var en Sansui B2102 forstærker, jeg engang havde, konstrueret.
ellers er der lidt råd her fra en AK tråd:
sa-9800 sa9800 display troubleshooting
Check the power supply DC voltages on the awr-194 power supply board (power on, be CAREFUL)
referenced from a bare metal chassis ground(black probe):
to (red probe, insulate all but the very tip of the red probe, for when you slip - so no shorts):
pin 13 +68v important for a lot of things, but this feeds the display tube's grid through the bright/dim switch
pins 3&4 +52v
pins 5&6 +32v
pin 7 +18v *** important for display, no +18, no display!! ****
pins 10&11 -32v
pins 1&2 -52v
and between pins 25(red probe) & 27(black probe)about 3 volts AC
Then pin 26 should show zero ohms (power off!!) to ground with the bright / dim switch set to bright (when dim it's 470 ohms to ground, bypassed with a 8.1v zener diode). If it isn't.... no display.....
for general information, these pins 26,26 & 27 are fed by a transformer on the power supply board, that has a 330 ohm resistor in series with it's primary - which if the 330 ohm resistor dies - no 3 volts AC and no display....
also
1. pin 13 +68v for the display goes through the bright dim switch (bright 1600 ohms, dim 1200 ohms) to pin 10 on the avw-002 indicator board.
2. Thus with power off, pin 13 of the awr-194 power supply board shhould show with the bright switch bright 1600 ohms to pin 10 on the avw-002 indicator board.
3. And also with power off, pin 13 of the awr-194 power supply board shhould show with the bright switch dim 1200 ohms to pin 10 on the avw-002 indicator board.
as an aside, all those little function indicator labels on the fluroscan tube, are grounded when dark and at +18v when lit. This is also the "signal" that is switched on and off for the bar segments in the display.
Mvh Klaus
Acoustic Research AR-3a Improved, AR-10Pi, AR-11, AR-9
Sansui AU-11000A, TU-9900, SR-929
Hafler DH-220 XL-280 DH-500, XL-600
BeoGram 3000 med STAX UA-7 CF arm + Empire EDR-9