Hi,
I was recently playing with IV conversion in my CD460.
I have added a D1 inspired IV conversion. I liked the sound very much. Then I started playing with a separate power supply for SAA7220. There something went wrong. The player does not recognize CDs. I removed the regulator (but left a bigger cap at leg 24 (VDD) of the SAA7220) It does not spin when I close the drawer. You cannot spin the CDs by hand either. It looks like some magnetic force keeps it in its position.
I have the service manual but do not have an osciloscope. Is there anything I can do using just a multimeter? The VDD of the SAA7220 is at 4.85V. This looks ok to me.
I do not have any formal electronic education. Just some common sense.
I would love to get this machine going as the sound was very good.
Any help will be very much appreciated.
Greg
I was recently playing with IV conversion in my CD460.
I have added a D1 inspired IV conversion. I liked the sound very much. Then I started playing with a separate power supply for SAA7220. There something went wrong. The player does not recognize CDs. I removed the regulator (but left a bigger cap at leg 24 (VDD) of the SAA7220) It does not spin when I close the drawer. You cannot spin the CDs by hand either. It looks like some magnetic force keeps it in its position.
I have the service manual but do not have an osciloscope. Is there anything I can do using just a multimeter? The VDD of the SAA7220 is at 4.85V. This looks ok to me.
I do not have any formal electronic education. Just some common sense.
I would love to get this machine going as the sound was very good.
Any help will be very much appreciated.
Greg
If the CD will not turn by hand and the power is OFF then there is a major mechanical issue. If it is more a case of very hard to turn (but only when the power is on) then it could be something as simple as a missing rail (I'm assuming it uses the Hall Effect type motor and not a simple DC type.)
Hi Mooly,
I can turn it easily, when the power is off. It is difficult to turn it with the power on. Will check the rails.
Greg
I can turn it easily, when the power is off. It is difficult to turn it with the power on. Will check the rails.
Greg
Look out for fusible resistors too, Philips often sprinkled these around the boards. One could be open circuit.
Mooly,
Looks like -11V is missing. I guess BC818 (which I believe provides some sort of regulation) is dead. I have some -13V on the emitter. The base resistor (which goes to the ground) is ok. The collector should be at -11V but is 0. I will google bc818 and if I have anything similar I will put it in. Meanwhile will order smd bc818 as the original.
Greg
Looks like -11V is missing. I guess BC818 (which I believe provides some sort of regulation) is dead. I have some -13V on the emitter. The base resistor (which goes to the ground) is ok. The collector should be at -11V but is 0. I will google bc818 and if I have anything similar I will put it in. Meanwhile will order smd bc818 as the original.
Greg
I see that I have BC818-25 as muting transistors on the same board. I guess they could jump in for BC818-16. I am bypassing muting transistors anyway...
Greg
Greg
Sounds promising. The BC818 is a general purpose NPN (800ma current rating). The "16" is one of the lower hfe groups so should be fine to swap for a higher one.
Hi Mooly,
Yes I am also positive now. Will try tonight (if time allows - kids new to be brought to/from a choir practice). Otherwise tomorrow! Fingers crossed.
Greg
Yes I am also positive now. Will try tonight (if time allows - kids new to be brought to/from a choir practice). Otherwise tomorrow! Fingers crossed.
Greg
Caution
A word of caution re: working on any electronic equipment.
From many years of experience, I have learned to give ample time but at least 30 minutes after switching off equipment for the power supply reservoir capacitors to discharge or decay.
It is very common through eagerness, to put something on the bench and begin working on it before the supplies have decayed.
THIS IS ESPECIALLY IMPORTANT ON ANYTHING THAT CONTAINS SWITCHED MODE POWER SUPPLIES..!!!!
When you bring solder or desoldering braid into close proximity to any circuit board that has recently been powered, the risk of shorting reserve stored energy to other parts or tracks is massive and usually ends in tears. Likewise, when you remove electrolytic capacitors from a board, have some carbon loaded foam nearby and 'plug' them into the foam to slowly discharge them for a few hours before using them again. They can hold significant residual charge for a long time unless they are helped to decay slowly. NEVER short them to discharge them as this can cause significant internal damage.
A word of caution re: working on any electronic equipment.
From many years of experience, I have learned to give ample time but at least 30 minutes after switching off equipment for the power supply reservoir capacitors to discharge or decay.
It is very common through eagerness, to put something on the bench and begin working on it before the supplies have decayed.
THIS IS ESPECIALLY IMPORTANT ON ANYTHING THAT CONTAINS SWITCHED MODE POWER SUPPLIES..!!!!
When you bring solder or desoldering braid into close proximity to any circuit board that has recently been powered, the risk of shorting reserve stored energy to other parts or tracks is massive and usually ends in tears. Likewise, when you remove electrolytic capacitors from a board, have some carbon loaded foam nearby and 'plug' them into the foam to slowly discharge them for a few hours before using them again. They can hold significant residual charge for a long time unless they are helped to decay slowly. NEVER short them to discharge them as this can cause significant internal damage.
Hi guys,
I have transplanted a muting transistor to the negative PS line. It is alive again! I connected D1 again and rock'n'roll! Thank you all very much.
The remaining part is the display. Now it is completely dead. Before there were a least a few segments. I am not sure yet how worried I should be. The keyboard works so the uP seems to be ok. As for the display the MM5450 has already arrived. I need to order the new led segments. Or is there anything else which needs to be looked at before /i blow something up again?
@db0360:
Thank you for your advise! I have been a bit too hasty I'm afraid. I have respect for tube amps PS caps and I discharge them through a resistor. But I have to admit that I am too relaxed about low voltage stuff.
I have transplanted a muting transistor to the negative PS line. It is alive again! I connected D1 again and rock'n'roll! Thank you all very much.
The remaining part is the display. Now it is completely dead. Before there were a least a few segments. I am not sure yet how worried I should be. The keyboard works so the uP seems to be ok. As for the display the MM5450 has already arrived. I need to order the new led segments. Or is there anything else which needs to be looked at before /i blow something up again?
@db0360:
Thank you for your advise! I have been a bit too hasty I'm afraid. I have respect for tube amps PS caps and I discharge them through a resistor. But I have to admit that I am too relaxed about low voltage stuff.
Excellent 🙂
(the display looks like one of these ? which were very prone to segments failing. The driver uP was a monolithic type incorporated onto the LED PCB. I've no idea where you might get one from now)
http://www.diyaudio.com/forums/digi...cd-readout-broken-bad-joints.html#post1598355
(the display looks like one of these ? which were very prone to segments failing. The driver uP was a monolithic type incorporated onto the LED PCB. I've no idea where you might get one from now)
http://www.diyaudio.com/forums/digi...cd-readout-broken-bad-joints.html#post1598355
I have a broken CD 460 coming that I intend to butcher for the DAC chip...
I could try to carefully rescue the display (it is working from the description on Ebay) and send it out to you...
I could try to carefully rescue the display (it is working from the description on Ebay) and send it out to you...
Mooly, the display is NSM4202A. Yes, it is known for segment failing.
It is possible to buy a substitute on e-bay but the prices are outrageous.
On the other hand it is also possible to use Micrel MM5450 with 4 single 7 segment LEDs instead. There is some documentation on the net about this. It will be functionally the same (btw the new substitutes - not NOS - use the same Micrel chip (smd)).
I have the bigger version. So I guess I will go on with it.
Stixx, thank you for your kind offer. Is it a lot of work for you? Let me know. I have to admit that building my own using Micrel isounds also interesting.
It is possible to buy a substitute on e-bay but the prices are outrageous.
On the other hand it is also possible to use Micrel MM5450 with 4 single 7 segment LEDs instead. There is some documentation on the net about this. It will be functionally the same (btw the new substitutes - not NOS - use the same Micrel chip (smd)).
I have the bigger version. So I guess I will go on with it.
Stixx, thank you for your kind offer. Is it a lot of work for you? Let me know. I have to admit that building my own using Micrel isounds also interesting.
Yes, they were a common failure item. Only you know which route you want to go down but keeping it all original has a certain appeal 🙂
What is actually failing in these displays? The control unit or the LEDs themselves? Or both?
If it is the control unit I cound keep the original LED panel and rewire it to the new driver.
If it is the control unit I cound keep the original LED panel and rewire it to the new driver.
I have to take it apart anyway, so no big deal 😉
You can have the display for the cost of shipping to your location.
I will PM you once I have received the player...
I really don't know...never investigated one. We just replaced them and binned the duff ones back in the day.
- Status
- Not open for further replies.