I recently acquired a Philips Cd 204 I'm in the process of restoring to full working conditions. So far I have fixed the tray (gear and belt broken), replaced all caps in the PSU (actually old Nichicon's were perfectly fine), replaced all low quality Philips caps in all boards but the CDM-1.
I have one last problem to fix, the headphone amplifier: if I connect it to the other boards, RCA output is distorted and headphone output is severely distorted; if I unplug it, RCA output is perfectly fine.
Schematic is attached, it is a simple 1x buffer feeded directly by the RCA output; I checked the cable and it is fine, voltages are fine, caps are new and resistors are not shorted. Only remaining option is a faulty op-amp: it is actually a NJM4560 not a NJM4556, but anyway it appears to be a pretty standard headphone amplifier of those days. Is it a common failure ? Do you have any suggestion for a modern replacement ?
I do not plan to use it (fixed volume is useless) but anyway I would like to fix it.
Thanks
I have one last problem to fix, the headphone amplifier: if I connect it to the other boards, RCA output is distorted and headphone output is severely distorted; if I unplug it, RCA output is perfectly fine.
Schematic is attached, it is a simple 1x buffer feeded directly by the RCA output; I checked the cable and it is fine, voltages are fine, caps are new and resistors are not shorted. Only remaining option is a faulty op-amp: it is actually a NJM4560 not a NJM4556, but anyway it appears to be a pretty standard headphone amplifier of those days. Is it a common failure ? Do you have any suggestion for a modern replacement ?
I do not plan to use it (fixed volume is useless) but anyway I would like to fix it.
Thanks
Attachments
Unfortunately, the cables are too short and I cannot measures voltages with everything connected. I did test voltages on the other side of the cable: +/- 12 V is ok, signal inputs are at 0 V versus ground (pin 3 and 5). I also tested the cable and it is ok; I cannot test any further.
One hint I have is that when the headphone is plugged into the socket, I can hear a click and that suggest me the output is not at 0 V. 90% is faulty op-amp.
One hint I have is that when the headphone is plugged into the socket, I can hear a click and that suggest me the output is not at 0 V. 90% is faulty op-amp.
What I'm worried about is the output load handling capabilities: the original NJM4560 is rated for 400 ohm load, while most of similar op-amp's are rated for higher load. The ideal replacement is the BA4580, but I cannot find it in DIP 8 package. The NE5532 is available (and indeed used on the CD204 for the output filter/buffer) and I have also found the LM4562.
The new op-amp arrived but that did not fix the problems.
Even with the new op-amp there are still 8V on the headphone output; while trying to measure voltages, one wire in the cable connecting the headphone amp to the main audio board detached from the plug so the cable has to crimped back ...
I'm giving up, it is really just a race with myself, there is no point in fixing the headphone output, with fixed volume is plain useless.
I have removed the cable and the CD player works beautifully, albeit with one dead headphone socket in the front
Even with the new op-amp there are still 8V on the headphone output; while trying to measure voltages, one wire in the cable connecting the headphone amp to the main audio board detached from the plug so the cable has to crimped back ...
I'm giving up, it is really just a race with myself, there is no point in fixing the headphone output, with fixed volume is plain useless.
I have removed the cable and the CD player works beautifully, albeit with one dead headphone socket in the front
It has to be an easy fix and more to the point I would want to know why connecting this board causes the other issues you mention.
I'm not even going to second guess anything like this but would suggest you check that the board is really plugging in to where it is supposed to and not some other unused connector somewhere. Maybe someone has unsoldered the leads to the board and reconnected them in the wrong positions.
Ultimately there is nothing really on that board and so it is an easy fix... and fun to track down
I'm not even going to second guess anything like this but would suggest you check that the board is really plugging in to where it is supposed to and not some other unused connector somewhere. Maybe someone has unsoldered the leads to the board and reconnected them in the wrong positions.
Ultimately there is nothing really on that board and so it is an easy fix... and fun to track down
That is exactly my point, it is such a simple board it should not be difficult to find what is wrong.
I actually had checked the cable unplugged and it measured ok, but the moment I was trying to check it plugged-in it started breaking. Now I have to crimp it back before doing any further test.
The sockets look fine to me there is no evidence of any miscabling or foul play. But I guess it has to do with the power supplies as yesterday while I was trying to stick the multimeter probes on the boards and the cable was pulled, the CD started acting strangely, opening the tray un-commanded and showing weird number on the display.
And another aspect is that the moment the headphone works, I will surely disconnect it and leave it off as I do not use it and it is connected directly to the RCA outputs.
I actually had checked the cable unplugged and it measured ok, but the moment I was trying to check it plugged-in it started breaking. Now I have to crimp it back before doing any further test.
The sockets look fine to me there is no evidence of any miscabling or foul play. But I guess it has to do with the power supplies as yesterday while I was trying to stick the multimeter probes on the boards and the cable was pulled, the CD started acting strangely, opening the tray un-commanded and showing weird number on the display.
And another aspect is that the moment the headphone works, I will surely disconnect it and leave it off as I do not use it and it is connected directly to the RCA outputs.
Thanks for reopening the thread.
Today I finished repairing a Portable CD Player (Philips D6800) and it's working well now. I changed the pickup gear and resoldered the power connector. Very easy. BUT there's something that I would love to solve (or improve, better said).
When connected from Line output to a HiFi system, it sounds GREAT. Well,.... it's a portable player so it's not heaven, but it sounds good.
But when hearing to headphones output, well.... it sounds ok but with a little distortion and probably an inverted V curve on the frequencies. Mids are a little bit high. For example, claps sounds like destroying your brain. But in general it's not a bad sound considering it's a 1989 player.
So the question here is what is making this "bad" sound on the headphone output. Obviously the "fault" is in the headphone circuit. It has a little caps and the opamp. I don't think the caps are the culprit, well maybe yes, but I think it's the opamp who is generating this sound.
Maybe changing the opamp to another high quality opamp will improve?
The actual opamp is NJM3415M.
Thanks!!
Today I finished repairing a Portable CD Player (Philips D6800) and it's working well now. I changed the pickup gear and resoldered the power connector. Very easy. BUT there's something that I would love to solve (or improve, better said).
When connected from Line output to a HiFi system, it sounds GREAT. Well,.... it's a portable player so it's not heaven, but it sounds good.
But when hearing to headphones output, well.... it sounds ok but with a little distortion and probably an inverted V curve on the frequencies. Mids are a little bit high. For example, claps sounds like destroying your brain. But in general it's not a bad sound considering it's a 1989 player.
So the question here is what is making this "bad" sound on the headphone output. Obviously the "fault" is in the headphone circuit. It has a little caps and the opamp. I don't think the caps are the culprit, well maybe yes, but I think it's the opamp who is generating this sound.
Maybe changing the opamp to another high quality opamp will improve?
The actual opamp is NJM3415M.
Thanks!!
It needs an objective measurement to see if anything is going on and that means a using a scope to look at the signal (using a test CD with sine tones) and seeing if anything is going on. You should also look at the signal amplitude across the actual headphones in use and see if it varies with frequency using 20 to 20kHz sweep.
Have you tried different headphones?
Have you tried different headphones?
Yes, I used other headphones.
I have another model (AZ6801) that is different on the outside but the internals are the same. And it sounds like D6800: very good using line, and ok but with a little distortion and explosive mids using headphones. Its just like listening an old walkman.
I deduced that this is the normal sound on this kind of machines, but I dont know if I can improve it by changing the opamp. Maybe Philips reduced costs with this model using a crap opamp.
I have another model (AZ6801) that is different on the outside but the internals are the same. And it sounds like D6800: very good using line, and ok but with a little distortion and explosive mids using headphones. Its just like listening an old walkman.
I deduced that this is the normal sound on this kind of machines, but I dont know if I can improve it by changing the opamp. Maybe Philips reduced costs with this model using a crap opamp.
I don't think changing the opamp will make any difference tbh, it really is the best part for the job and able to deliver relatively high current (70ma I think) while swinging close to the rails. An 'M' version is the surface mount outline... RC4560IPWR might be a possible swap if you are determined to try.
Fair enough, the 4560IPWR is a TSSOP outline, I guess yours is a regular SOP outline.
I would still scope the output under load and see if anything shows up but given you have two players the same it sounds as if its going to be normal. No switches for 'audio enhancements' on the headphone output?
I would still scope the output under load and see if anything shows up but given you have two players the same it sounds as if its going to be normal. No switches for 'audio enhancements' on the headphone output?
Nope.
Do you mean that I have to measure the signal in the jack itself while headphones connected?
I can burn a test cd to play different freqs.
Once I thought about recapping. The man on my local electronics store said that I’ll found no improvement by recapping because the caps he sell are so basic and probably worse quality than the originals.
Do you mean that I have to measure the signal in the jack itself while headphones connected?
I can burn a test cd to play different freqs.
Once I thought about recapping. The man on my local electronics store said that I’ll found no improvement by recapping because the caps he sell are so basic and probably worse quality than the originals.
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