I have a CD player with a 4 digit 7 segment vintage LED display. Like these: https://en.wikipedia.org/wiki/Seven-segment_display
One of the segments (segment G) is intermittent. It goes in and out. I understand that if segment G was out in all 4 digits, then it could possibly be a driver transistor, controller, diode, etc. But it's only out in one of the digits. The other three digits are not affected. And on top of that it's intermittent.
I could not seen any suspect traces, or bad solder joints anywhere.
Any ideas of what may be causing this? Thanks for all of the help!
Edit: The model number is NSM4202A.
One of the segments (segment G) is intermittent. It goes in and out. I understand that if segment G was out in all 4 digits, then it could possibly be a driver transistor, controller, diode, etc. But it's only out in one of the digits. The other three digits are not affected. And on top of that it's intermittent.
I could not seen any suspect traces, or bad solder joints anywhere.
Any ideas of what may be causing this? Thanks for all of the help!
Edit: The model number is NSM4202A.
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Check if resoldering solves, if not...
Loose connection inside the display module. Live with it or change the module.
Gajanan Phadte
Loose connection inside the display module. Live with it or change the module.
Gajanan Phadte
As I understand, the display itself is probably epoxy potted from the back. But can the LEDs be accessed from the front if the black mask is peeled off?
Which CD player ?
Some are notorious for having failing displays.
Early displays are unobtainium !!!
Andy
Old Micromega from 1992. The segment LED is manufactured by National Semiconductor. I don't have the model number handy at the moment, but I wasn't able to find any references online earlier. It looks just like this: http://farm3.static.flickr.com/2255/2264283210_7b88b582a3.jpg
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If its a MM 'Stage' or derivative then the display is actually in a socket. Just pull it out and test on a DVM to see if its common cathode or common anode.
It should still be possible to test if its CC or CA in circuit. Pin outs are pretty standard for these type of displays. Testing it like this would also confirm whether its a faulty LED or a problem elsewhere.
This will give you an idea what's available generally. You need to measure the dimensions of the package for a start. (if the link doesn't work then enter 'led 7 segment' as a search term and then click on LED displays. Other sites no doubt list far more)
LED Displays | CPC UK
This will give you an idea what's available generally. You need to measure the dimensions of the package for a start. (if the link doesn't work then enter 'led 7 segment' as a search term and then click on LED displays. Other sites no doubt list far more)
LED Displays | CPC UK
This one is the closest that I could find, size, color, etc.: http://www.digikey.com/product-detail/en/TDCG1050M/TDCG1050M-ND/4074705
But that would really suck if I replaced it and the segment was still out.
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So get the pinouts by confirming what type of display it is (CC or CA), do a static diode test to see if they all light (if ones dead then that's conclusive). If a diode test isn't 100% definitive then measure the voltage applied to, and the voltage across the suspect segment for confirmation. A dead segment will typically be open circuit and so have the full 5 volts (typically) voltage across it and not be lit. Or more rarely it might be short or low resistance in which case you would still see the 5 volts applied to any series limiting resistor for that segment.
To me this display looks like the standard philips display of the time (mid to late 80ies, e.g. Philips CD460). These displays were very prone to this type of failure and IIRC the failure was not caused by the display but by the controler/driver chip and/or bad contacts (bonded wires to the chip or vias on the display board).
These are the Philips type,
http://www.diyaudio.com/forums/digi...cd-readout-broken-bad-joints.html#post1598355
http://www.diyaudio.com/forums/digi...cd-readout-broken-bad-joints.html#post1598355
The model number is NSM4202A. It's an old part used in Philips/Sony players. I believe they were made by National Semi (NS?).
I took it completely apart and put it back together again. Re-soldered all of the joints. I opened the plastic hood, the actual LEDs are bare/open, just tiny little microscopic filament wires.
I'm guessing segment G has become faulty. I don't think I can repair it. After putting it together, it does the same thing. Flickers in and out every 5-10 minutes.
I put a request in a t the parts section of this forum. Thanks for all of the help guys, but this will be hard to source 🙁
Philips CD303 DISPLAY philips cd 202 NSM 4202 & MERIDIAN CD | eBay
Not quite unobtainable but very expensive !!!!
Andy
Not quite unobtainable but very expensive !!!!
Andy
Yep, that's one of the display + monolithic driver all encapsulated onto the board. Not repairable. You'll be very very lucky to get a good one this far down the line.
Looks like I spoke to soon 😉
Expensive but worth it for a treasured player. I seem to recall there was a resistor to change (that sets the LED current) on some of these. There was a printed sheet in the packet detailing values. If replacing a display I would err on the low current side... and try it first on the old one to see the effect.
Expensive but worth it for a treasured player. I seem to recall there was a resistor to change (that sets the LED current) on some of these. There was a printed sheet in the packet detailing values. If replacing a display I would err on the low current side... and try it first on the old one to see the effect.
Unfortunately that one has completely different pin layout. It has to be the model with A, NSM4202A.
Looks like I'll be building this: http://www.diyaudio.com/forums/digi...-replacement-philips-sony-cdm-transports.html
Placed an order for the PCB (3 of them) boards. Seems easy enough. Since I'll be getting three boards, is there anyone else who may be interested in one?
Placed an order for the PCB (3 of them) boards. Seems easy enough. Since I'll be getting three boards, is there anyone else who may be interested in one?
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