Good evening all.
I have a Pioneer SX-D7000 that has a power supply problem I could use some help on. The unit powers up and displays the normal operation lights but the radio (display) does not light up and the final amplifier does not engage. All functions seem to work like switching inputs and such, even the radio memory banks seem to switch and work as they should. This unit has two displays, one for the radio and one for the volume level. Volume display works fine.
Probing around I found the that power supply's negative supply doesn't seem to be working. As such, it seems it is the bias supply for the radio's vacuum tube display. I'm sure it supplies other things preventing the final amplifier from getting the "green light" and powering up.
Below is the schematic of the power supply with my voltage samples in red.
Everything on the supply looks good except for the negative supply. I show -84V (should be -70) going in, and then the next sample is +10V.
I took a chance and replaced the three transistors in between:
but this delivered no change.
I am much more a vacuum tube guy so I'm a bit stumped on this one and am not sure what else to target from here. Could one of you SS techs please take a look and advise? It is much appreciated.
73's,
I have a Pioneer SX-D7000 that has a power supply problem I could use some help on. The unit powers up and displays the normal operation lights but the radio (display) does not light up and the final amplifier does not engage. All functions seem to work like switching inputs and such, even the radio memory banks seem to switch and work as they should. This unit has two displays, one for the radio and one for the volume level. Volume display works fine.
Probing around I found the that power supply's negative supply doesn't seem to be working. As such, it seems it is the bias supply for the radio's vacuum tube display. I'm sure it supplies other things preventing the final amplifier from getting the "green light" and powering up.
Below is the schematic of the power supply with my voltage samples in red.
An externally hosted image should be here but it was not working when we last tested it.
Everything on the supply looks good except for the negative supply. I show -84V (should be -70) going in, and then the next sample is +10V.
I took a chance and replaced the three transistors in between:
- Q2 - 2SK34 replaced with NTE312
- Q5 - 2SA912 replaced with NTE288
- Q6 - 2SB507P replaced with NTE153
but this delivered no change.
I am much more a vacuum tube guy so I'm a bit stumped on this one and am not sure what else to target from here. Could one of you SS techs please take a look and advise? It is much appreciated.
73's,
Forget the complicated bits and think about the -30volt rail. This supplies the florescent display. Check the voltage on Q6 emitter. Should be near to -50v. If it is check the next in line, Q8 collector. Should be about the same. If it is check Q8 emitter for about -30volts.
You state you have a positive voltage on the -30v rail, that is because one of the feed resistors is open circuit. Probably R5.
Replacing transistors for types that you think may be OK is not the way to fault find!
You state you have a positive voltage on the -30v rail, that is because one of the feed resistors is open circuit. Probably R5.
Replacing transistors for types that you think may be OK is not the way to fault find!
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