Hello pioneer buffs, wondering if anyone has even seen a Pioneer SA-9800 fluorescent display fail? If so what are the common causes for this? Hoping someone out there has some insight to this unusual and rare problem??
Pioneer SA-9800 fluorescent display failure?
- Thread starter quadmatrix82
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Hi there, thanks for the reply! i'll have a read 
I have a SA-9800 and the display doesn't work, wasn't sure where to start in terms of diagnosing the problem...never heard of them failing before, maybe its a dry joint somewhere??
I have a SA-9800 and the display doesn't work, wasn't sure where to start in terms of diagnosing the problem...never heard of them failing before, maybe its a dry joint somewhere??At JVC, we used to see the solder joints on the filament connections crack, all the time. I've seen this in other products as well. I would resolder the tube first, and go from there.
sa-9800 sa9800 display troubleshooting
Here's the "from there":
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.
Here's the "from there":
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.
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Backlight
Active Member
I also have an issue with the display of my SA-9800. I started another thread for that. I didn't notice this thread... Markthefixer responded and pointed me here.
My display is not "off", but lost it's brightness about a week ago.
I measured all voltages and it is ok. The display heater receives 3.6 volts AC when in bright position and a bit less when in dim position. The voltage to the filament however, reads 48/49 volts DC when in bright position and 53 in dim position. On my SA-7800 the filament receives 43 Volts DC. I assume this indicates something is wrong in the filament circuit or the filament itself such as an increased resistance of the filament resulting in higher voltage on PIN 10 of the indicator board. I measured all resistors in the circuit and they are according specs.
A previous owner has replaced the zener diode (soldered on the wrong side of the board:scratch2 indicating there might have been an issue in the past.
Reading this thread I understand cracks in the solder joints to the filament do occur. Could it be causing a problem in this situation? "Ticking" the indicator PCB does not cause any brightness flickering.
I started recapping a little over week ago the PSU, Protection and Indicator PCB. A couple of days later the display lost it's brightness. Today I finished recapping PA-L/R, TC and filter boards. It sounds absolutely beautiful! Cosmetically the amp is "as new" too! But the joy is ruined by a very dimmed display... I want to have this amp in absolute top condition...
Anything I can try? Please help.
My display is not "off", but lost it's brightness about a week ago.
I measured all voltages and it is ok. The display heater receives 3.6 volts AC when in bright position and a bit less when in dim position. The voltage to the filament however, reads 48/49 volts DC when in bright position and 53 in dim position. On my SA-7800 the filament receives 43 Volts DC. I assume this indicates something is wrong in the filament circuit or the filament itself such as an increased resistance of the filament resulting in higher voltage on PIN 10 of the indicator board. I measured all resistors in the circuit and they are according specs.
A previous owner has replaced the zener diode (soldered on the wrong side of the board:scratch2
indicating there might have been an issue in the past.Reading this thread I understand cracks in the solder joints to the filament do occur. Could it be causing a problem in this situation? "Ticking" the indicator PCB does not cause any brightness flickering.
I started recapping a little over week ago the PSU, Protection and Indicator PCB. A couple of days later the display lost it's brightness. Today I finished recapping PA-L/R, TC and filter boards. It sounds absolutely beautiful! Cosmetically the amp is "as new" too! But the joy is ruined by a very dimmed display... I want to have this amp in absolute top condition...
Anything I can try? Please help.
You're splitting the troubleshooting between two threads. :nono:
The heater voltage is measured ACROSS the two heater terminals, and the DC bias voltage is measured at pin 26, the center tap of the transformer feeding pins 25 & 27.
While examining the sa-7800 schematic shows that the center tap of the filament transformer, IN THIS MODEL IS GROUNDED. Zero volts...
Thus the statements that :
makes absolutely no sense at all and points to some sort of instrument or technique problem. The difference between 43 and 48 volts is a blind alley.
The heater voltage is measured ACROSS the two heater terminals, and the DC bias voltage is measured at pin 26, the center tap of the transformer feeding pins 25 & 27.
While examining the sa-7800 schematic shows that the center tap of the filament transformer, IN THIS MODEL IS GROUNDED. Zero volts...
Thus the statements that :
makes absolutely no sense at all and points to some sort of instrument or technique problem. The difference between 43 and 48 volts is a blind alley.
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Backlight
Active Member
You're correct. anybody who wishes to follow this troubleshooting please go to http://www.audiokarma.org/forums/showthread.php?t=277855
allhartfidelity
More gear than sense
Yes, old thred but relevant info. Checked all on the list here, and still no display (of any kind) Any new info to be had?
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
did you go through that thread?
then there is this one - and all the associated threads.
http://audiokarma.org/forums/index.php?threads/yet-another-sa-9800-dimmed-display.695078
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allhartfidelity
More gear than sense
Fairly sure ive been through them all, wanted to do so before i asked for assistance. I will check again to be sure. I do have all the voltages you outlined (and ohms) within 1 volt. I will have a look again at the threads, thank you for your reply and link.
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allhartfidelity
More gear than sense
Yes, thank you. i just thought to inquire as all my voltages are within 1v AND my display is, and always was dead. Not dim, just dead. Thank you for the efforts.
allhartfidelity
More gear than sense
Thank you Mark. Having gone through your :from here" again, pin 3 and is 69.2v instead of 52. Ive lifted the board on its side and repaird some loose joints, and have a magnifier. (To see the board clearly) What i originally thought was a dead display, is actually just very very dim. If looking at lack of burn marks on the PS is any indication of use, i would say the unit does not have many total hours on it. (Perhaps display then does not) Would this overvoltage be problematic?
Also, maybe a different topic...the light for the power switch from pins 14/16 show 50v AC. The light does not work. Being an 8v lamp(verified working) though it strange. Doubt its connected, but thought to mention.
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Just to be sure, you did verify the several volts (no manual rt now to get exact number) of AC to the heater filament? Pins 14 and 15 of the AWV-002 indicator assembly.
Fed from pins 23 and 25 (from T3) of the AWR-191 power supply.
T3 is fed a SMALL amount of secondary AC from FU4 (green wire off of transformer), THROUGH a substantial 330 ohms of resistance R23 at 1/4 watt.
T3's secondary center tap goes to part of the brightness switch:
in BRIGHT, it is directly GROUNDED to pin 11 of the protection board.
in DIM it's a 470 ohm resistor, with a (D5) 8.1 volt zener diode bypassing it, connected to the PROTECTION board (pin 11) GROUND.
IF the pin 11 ground isn't grounded (chassis) all kinds of mischief will ensue.
look at the display in a darkened room, it's not dead is it? Just REALLY dim?
I am specifically asking if you have read the thread(s) where txturbo recovered a display using procedures similar to old syle CRT filament rejuvenation?
Lastly, the lamp "discrepancy" - they run the 8v lamp with a HUGE pair of series resistors: R21 470 ohms 5 watts and R22 560 ohms 5 watts to drop the power down
to a manageable level. This originating voltage is the exact same place (FU4, green wire) that T3 is fed, also with series resistances.
Using a 10 meg impedance voltmeter, should one of those two resistors increase in resistance (burn up) enough to considerably dim the bulb, the meter will still read the voltage IF the lamp isn't part of the circuit. Use an ohmmeter function to check the two resistors.
errata: you really should branch this off into your very own thread in the forum.
Fed from pins 23 and 25 (from T3) of the AWR-191 power supply.
T3 is fed a SMALL amount of secondary AC from FU4 (green wire off of transformer), THROUGH a substantial 330 ohms of resistance R23 at 1/4 watt.
T3's secondary center tap goes to part of the brightness switch:
in BRIGHT, it is directly GROUNDED to pin 11 of the protection board.
in DIM it's a 470 ohm resistor, with a (D5) 8.1 volt zener diode bypassing it, connected to the PROTECTION board (pin 11) GROUND.
IF the pin 11 ground isn't grounded (chassis) all kinds of mischief will ensue.
look at the display in a darkened room, it's not dead is it? Just REALLY dim?
I am specifically asking if you have read the thread(s) where txturbo recovered a display using procedures similar to old syle CRT filament rejuvenation?
Lastly, the lamp "discrepancy" - they run the 8v lamp with a HUGE pair of series resistors: R21 470 ohms 5 watts and R22 560 ohms 5 watts to drop the power down
to a manageable level. This originating voltage is the exact same place (FU4, green wire) that T3 is fed, also with series resistances.
Using a 10 meg impedance voltmeter, should one of those two resistors increase in resistance (burn up) enough to considerably dim the bulb, the meter will still read the voltage IF the lamp isn't part of the circuit. Use an ohmmeter function to check the two resistors.
errata: you really should branch this off into your very own thread in the forum.
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allhartfidelity
More gear than sense
I will go back through it all again when i get back in the country, and do so very slowly.
No, i did not read in great detail the thread on rejuvenation by txturbo, as i thought it was not a weak wore out tube given lack of use the unit has had. I did browse that section however, and will pay closer attention to it then.
Yes, the meter in a pitch dark room does function, which i had not notice before thinking it was dead. I will print all info and suggestions and go over it bit by bit as to not leave anything out. Thank you immensely for your time on this, i greatly appreciate all you have done. Ive gleaned much info through the years with your selfless postings.
No, i did not read in great detail the thread on rejuvenation by txturbo, as i thought it was not a weak wore out tube given lack of use the unit has had. I did browse that section however, and will pay closer attention to it then.
Yes, the meter in a pitch dark room does function, which i had not notice before thinking it was dead. I will print all info and suggestions and go over it bit by bit as to not leave anything out. Thank you immensely for your time on this, i greatly appreciate all you have done. Ive gleaned much info through the years with your selfless postings.