I'll look in again tommorow. Check that cap. Pin 66 seems to be clamped by an internal "zener" at -18 volts. Sometimes quoted voltages like that are not always correct in service manuals, they should be but aren't. 10 volts dropped across R3847 (100 ohm) sounds a bit high, is it a 1 watt resistor or more ?
If you are careful you could try varying pin 66 voltage but see what you find first with the caps.
If you are careful you could try varying pin 66 voltage but see what you find first with the caps.
Hi Tony,
I have the same dull display on a CD5000 that I just acquired. I'll have a look at this cap and see if it fixes mine.
I noticed you showed some relevant schematics on an earlier post, you don't have other schematics for this machine available do you? I'm planning to make some modifications in the DAC area and it would be useful to have the full schematics or service manual.
Regards
Pete
What modifications are you planning? I'm going to keep mine fairly simple to start with.
Upgrade 4 diodes on the +5v supply to schottkys.
Larger cap (8200uF) on the +5v pre reg.
Seperate 317 regs for the 3 DAC +5v feeds
Upgrade the caps around the dac feeds
Take the dac output direct to RCAs (bypass the seperate opamp)
Then I'll have a listen and see if it's worthwhile doing anything else
Regards
Pete
Maybe not entirely appropriate in this thread but I find tube displays often to be very dirty between the actual display and glass/screen. Separating the PCB from the frontcover and careful cleaning is often a remedy providing that the electronics are OK.
I recently bought a mint Kenwood DP-5050 that did not have a scratch but the display was unreadable from dust/debri buildup on the display itself and on the backside of the front cover screen. Sometimes it is necessary to use isopropyl alcohol to remove the stuff.
Use a soft cloth !
I recently bought a mint Kenwood DP-5050 that did not have a scratch but the display was unreadable from dust/debri buildup on the display itself and on the backside of the front cover screen. Sometimes it is necessary to use isopropyl alcohol to remove the stuff.
Use a soft cloth !
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Made the changes outlined above, the players strting to sing a bit now. Quite a nice, detailed sound for fairly small cost.
On the downside, replacing the cap didn't help with the display brightness. I rempoved the display to clean the glass on both sides. Something went wrong so now I have no display at all. As I couldn't see it before from more than a foot away it's not a big loss and it's still playing ok.
The odd thing with this player is that that the on-off switch on the front of the player only seems to work on the display pcb. The tx, loader and audio pcb seem to be permanently powered.
Regards
Pete
On the downside, replacing the cap didn't help with the display brightness. I rempoved the display to clean the glass on both sides. Something went wrong so now I have no display at all. As I couldn't see it before from more than a foot away it's not a big loss and it's still playing ok.
The odd thing with this player is that that the on-off switch on the front of the player only seems to work on the display pcb. The tx, loader and audio pcb seem to be permanently powered.
Regards
Pete
In my case it didn't solve the problem either. My initial thoughts were that it had - but after reassembling it, I realised that although it was ever so slightly better, it still wasn't at maximum brightness. So I'm guessing the VFD is well and truly knackered.
I had this great plan of trying to interface some other display to the electronics, but I just don't have the time (and I don't think it's worth the effort!).
So I have a nice gold CD5000 with a dull display.. (and now it's resident on a shelf..)
Tony.
It is not so technical that "something went wrong" without knowing what. Just find out what went wrong. It can't be a very serious problem if you acted carefully. My guess is that one of the pins of the display has a dry or broken joint. So resoldering the display could be a solution.
Regarding the player being powered continuously: this happens a lot since companies found out that real mains switches cost more than push buttons. Bad for the VFD, bad for the power bill ( if you add up all gear that can't be switched off ), bad for the environment ...
Yes, when I have some quiet time I have to get the meter out and do some further analysis. At the moment it's not a priority as it's still playing and honestly, if I only restore the display to it's previous brightness it's pretty much useless anyway. I'm hopeful that some component that was suffering (and causing the lack of brighness) finally gave up the ghost 
Pete
Pete
Hi,
That was the page that convinced me to but one as well but I doubt I'll go down the tube route, just the snip-it.
Incidentally, how is the display on yours, can you see it from more than a meter away? Interested to know if this poor display is really a fault or standard with this model.
Regards
Pete
That was the page that convinced me to but one as well but I doubt I'll go down the tube route, just the snip-it.
Incidentally, how is the display on yours, can you see it from more than a meter away? Interested to know if this poor display is really a fault or standard with this model.
Regards
Pete
Hi,
Got the display working again, fault was with a transistor (7250) providing power to the contoller chip in the display pcb.
Still very dim though. The supply to the dot matrix seems to be 5v ac which is stepped down though a couple or resistors to about 3.7v ac. I bridged one of the resistors to bump the voltage up a bit but it didn't have any effect on the brightness. I'm coming to the conclusion that this isn't an error, just lousy displays on these players.
Regards
Pete
Got the display working again, fault was with a transistor (7250) providing power to the contoller chip in the display pcb.
Still very dim though. The supply to the dot matrix seems to be 5v ac which is stepped down though a couple or resistors to about 3.7v ac. I bridged one of the resistors to bump the voltage up a bit but it didn't have any effect on the brightness. I'm coming to the conclusion that this isn't an error, just lousy displays on these players.
Regards
Pete
If it's the same as the circuit at the start of this thread then the negative 28 volts determines the "brightness" to a large extent, but make sure the zener and the two resistors that ties the heaters to this supply is OK.
If all the voltages are OK... and you have to be very sure and use a scope to see no excessive ripple is present etc then the display is faulty. The DC relationship between all the supplies is critical, particularly the heater.
If all the voltages are OK... and you have to be very sure and use a scope to see no excessive ripple is present etc then the display is faulty. The DC relationship between all the supplies is critical, particularly the heater.
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