good evening
i recently obtained a Technics sl-p2 cd player. the first problem is it would not load a cd but i fixed this simply by replacing the drive belt.
secondly this is the one that is confusing me when the unit is turned on, as it warms up there is a bad digital distortion that is more or less depending on the volume of the recording if that makes sense. but would disappear when the unit heated up. But when it heated up the psu really gets hot. when i say hot i mean so hot you cant touch the transformer and the heat sink for the 3 regulators also gets hot.
figuring there was a bad component or bad fuses (fuses where fine) i noticed pin 3 (+9.5v) was reading 16v pin 4 (-9.5v) was reading -16v (both pins 3 and 4 refer to the cn410 output refer to schematic) pin 7 (-19v) was reading -25v. also when the psu is disconnected from the unit, the voltages dont change and also it does not get hot.
any suggestions? any help would be greatly appreciated as you have no idea how long i have spent looking and troubleshooting this circuit.
attached is the schematic.
Thankyou in advance
i recently obtained a Technics sl-p2 cd player. the first problem is it would not load a cd but i fixed this simply by replacing the drive belt.
secondly this is the one that is confusing me when the unit is turned on, as it warms up there is a bad digital distortion that is more or less depending on the volume of the recording if that makes sense. but would disappear when the unit heated up. But when it heated up the psu really gets hot. when i say hot i mean so hot you cant touch the transformer and the heat sink for the 3 regulators also gets hot.
figuring there was a bad component or bad fuses (fuses where fine) i noticed pin 3 (+9.5v) was reading 16v pin 4 (-9.5v) was reading -16v (both pins 3 and 4 refer to the cn410 output refer to schematic) pin 7 (-19v) was reading -25v. also when the psu is disconnected from the unit, the voltages dont change and also it does not get hot.
any suggestions? any help would be greatly appreciated as you have no idea how long i have spent looking and troubleshooting this circuit.
attached is the schematic.
Thankyou in advance
Attachments
Yes, measure it on resistance range across live and neutral as I mention above. The 240 volt setting is the one that gives highest primary resistance.
The 167 ohms will be the 240 volt setting but something isn't right here.
Do you see the two AC voltages from the tranny marked as 1.8 volts AC. They will go to the filaments of the display.
1) Are those two voltages correct ?
2) In a dark room, do the filaments of the display stand out as being bright ? too bright. They should be a dull (barely visible) glow.
Service manuals can be wrong in voltages given... its a well recognised hazard.
Running out of time just now... so check the above anyway. Also, if you look at the transformer primary windings then the two windings should end up in series for 240 volts AC. Does it all look original ? Not been worked on or got at before.
Up to now your DC voltages are sky high compared to the circuit. See what those two AC voltages measure and importantly, are the filaments too bright. That could be as good a guide as any.
Do you see the two AC voltages from the tranny marked as 1.8 volts AC. They will go to the filaments of the display.
1) Are those two voltages correct ?
2) In a dark room, do the filaments of the display stand out as being bright ? too bright. They should be a dull (barely visible) glow.
Service manuals can be wrong in voltages given... its a well recognised hazard.
Running out of time just now... so check the above anyway. Also, if you look at the transformer primary windings then the two windings should end up in series for 240 volts AC. Does it all look original ? Not been worked on or got at before.
Up to now your DC voltages are sky high compared to the circuit. See what those two AC voltages measure and importantly, are the filaments too bright. That could be as good a guide as any.
Quick example of incorrect voltages... manual shows approx 37 vac across the top winding. Rectified and smoothed that is 52 volts DC. The two voltages given only add up to 45. A basic error.
On balance I suspect this could be OK and you are looking for a genuine player problem. Make sure the regulated rails do not alter when the fault develops. Any reg that sizzles indicates a problem. If you can touch them for 4 or 5 seconds before burning yourself then they could well be OK.
On balance I suspect this could be OK and you are looking for a genuine player problem. Make sure the regulated rails do not alter when the fault develops. Any reg that sizzles indicates a problem. If you can touch them for 4 or 5 seconds before burning yourself then they could well be OK.
This could be right.
Each of the 110/120Vac windings has a resistance of ~82ohms.
In parallel for 110/120Vac mains, the combined resistance is ~41ohms.
In series for 220/240Vac mains, the combined resistance is ~164ohms.
To confirm again, the higher primary resistance is the correct setting for the higher 220/240Vac mains supply.
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I think on balance that this is going to be OK and that you are looking for a "real" fault in the player itself. I see from your location that you have temperatures in the mid 30's so that is going to be a big factor too in how hot it all gets.
As to the fault... hard to say but I would suggest checking the RF signal from the pickup and looking at amplitude and quality. If its marginal it can give the kind of effect you describe. That has to be a first step along with confirming any adjustments for focus bias and E-F offset (if it has such adjustments) are optimal. It may be a failing pickup too.
You need to do more tests on it all now.
As to the fault... hard to say but I would suggest checking the RF signal from the pickup and looking at amplitude and quality. If its marginal it can give the kind of effect you describe. That has to be a first step along with confirming any adjustments for focus bias and E-F offset (if it has such adjustments) are optimal. It may be a failing pickup too.
You need to do more tests on it all now.
I think we have to say yes to that one. Those particular rails are unregulated and again the numbers don't agree with the info in the manual with 16.7 volts ac showing as giving 9.1 and -11.1, so 20 volts total. The actual mains voltage will also alter the readings. Its shown as suitable for 220v to 240v (presumably catering for the tolerances those supplies can legally have) so there is a wide range there.
also, you cant laugh at my diagnostic techniques but during the distortion phases i put my finger on the chip marked technics MN6615 and the distortion would stop. it also felt rather warm. and when i touched the top of the capacitors in the psu it would cause very slight distortion for a second. but im scared of how hot the transformer gets thats my real worry as the distortion dissapears where as the transformer keeps getting hot.
Fingers are good at finding faults 
Particularly high voltages... when you think they are missing but find they are not
DRAM ? Does this chip look anything like this (the way its connected and the fact it has no components hung off it)
http://www.diyaudio.com/forums/digital-source/171326-cd-player-distortion-laser-5.html#post2268053
DRAM failure (and that was the issue with the player in the link) was one fault that many early players suffered from and the symptom is distortion. I'm not convinced your issue is the same as this but the fact you touch the chip and it alters the fault... worth investigating. If you have no freezer spray then try an ice cube wrapped in plastic and just touch the chip to cool it. If the symptom changes then that is a good sign the chip is duff.
Particularly high voltages... when you think they are missing but find they are not DRAM ? Does this chip look anything like this (the way its connected and the fact it has no components hung off it)
http://www.diyaudio.com/forums/digital-source/171326-cd-player-distortion-laser-5.html#post2268053
DRAM failure (and that was the issue with the player in the link) was one fault that many early players suffered from and the symptom is distortion. I'm not convinced your issue is the same as this but the fact you touch the chip and it alters the fault... worth investigating. If you have no freezer spray then try an ice cube wrapped in plastic and just touch the chip to cool it. If the symptom changes then that is a good sign the chip is duff.
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