Has someone had some experience with this old , but good sounding, player?
Service note says to look for the following (no disc in):
1. The optical pick-up move to outside and then move to inside.
2. Laser beam emits spreadingly.
3. The objective lens perform up-and-down three times.
I have 2. and 3. but not 1. But player starts to play, for about 50 seconds, but then jumps back for about 20 sec. and keep repeating it. Focus coil transistors are getting very hot; I replaced them with new (stronger BD139/140), still the same. Could it be shorted coil?
I would like to fix it if possible as I want to replace audio section with discrete op amps - the player itself does actually sound surprisingly good, and is good base for mods.
Service note says to look for the following (no disc in):
1. The optical pick-up move to outside and then move to inside.
2. Laser beam emits spreadingly.
3. The objective lens perform up-and-down three times.
I have 2. and 3. but not 1. But player starts to play, for about 50 seconds, but then jumps back for about 20 sec. and keep repeating it. Focus coil transistors are getting very hot; I replaced them with new (stronger BD139/140), still the same. Could it be shorted coil?
I would like to fix it if possible as I want to replace audio section with discrete op amps - the player itself does actually sound surprisingly good, and is good base for mods.
This morning I dismantled optical assembly - took sliding bars out, cleaned them and bushes. Lubricated with a bit of fine machine oil (didn't have white silicone grease but may get it later) and put it back together. Sled seam to be free and easy moving when pushing worm gear by finger. Still, transistors (focus coil) are getting hot again and it would jump back a bit after about 60 sec. of playing. I measured coils (focus and tracking), they are about 7 Ohms each - seams about right to me...
The pick-up mechanism is KSS-152A .
The pick-up mechanism is KSS-152A .
Hard to say. I wouldn't expect the focus amp to very hot yet it doesn't sound like a focus problem.
Its worth connecting your meter across the sled motor and watch the voltage in play mode. The sled motor should have minimal voltage across it as the sled inches along. Perhaps as low as a few 10's/100's of millivolts.If the voltage starts to suddenly rise it indicates a problem with friction. When the voltage and motor power overcomes the friction the sled jerks causing the jumping.
Worth checking if only to eliminate it.
Its worth connecting your meter across the sled motor and watch the voltage in play mode. The sled motor should have minimal voltage across it as the sled inches along. Perhaps as low as a few 10's/100's of millivolts.If the voltage starts to suddenly rise it indicates a problem with friction. When the voltage and motor power overcomes the friction the sled jerks causing the jumping.
Worth checking if only to eliminate it.
Ok, I did what you said; initially voltage was around 20mV. As CD start playing, voltage started rising - it vent up to 4V in about 30 sec. and it stopped rising there, but CD kept playing for another 20 sec. or so and then jumped back.
I will open it up again. Interesting problem, as it did feel free to move when I was moving it by hand (finger)...
I will open it up again. Interesting problem, as it did feel free to move when I was moving it by hand (finger)...
Check the gears for burrs and for "tropicalised" grease (grease thats gone hard and "sugary). Also of course the sled motor could be faulty. Many sleds will often run end to end with just the "power" and voltage a DVM can provide on its diode range (just) but it give an idea of how it should be. Try a 1.5 battery and series resistor to whizz it up and down.
If the motor is suspect/faulty then discconect it (electrically and the gears) and apply 9 volts each way to see if it frees it up and cleans the commutator.
If the motor is suspect/faulty then discconect it (electrically and the gears) and apply 9 volts each way to see if it frees it up and cleans the commutator.
I checked motor as per your suggestion - it would not run on DWM power, but did run happily on 1.5V and 9V...
Gears were all clean, and then I inspected bushes again, they are holes cut in plastic. To the naked eye everything seamed to be ok and clean. Then I used 10x magnifying glass and then I saw them: tiny layers, scattered here and there on the walls of bushes, of "tropicalised" grease. So I used suitable size drill bit and gently passed it through the holes few times and that cleared them. I assembled everything back together, using a bit of lithium grease, turned it on - and it works.
Though transistors on focus coil are still getting hot (PNP one more than NPN ?). That, I think , is just a design problem ( or a feature of the design). I will install small heat sink on them, just to help them out a little bit.
Thanks Mooly, and Happy New Year; and to every one else too...
Gears were all clean, and then I inspected bushes again, they are holes cut in plastic. To the naked eye everything seamed to be ok and clean. Then I used 10x magnifying glass and then I saw them: tiny layers, scattered here and there on the walls of bushes, of "tropicalised" grease. So I used suitable size drill bit and gently passed it through the holes few times and that cleared them. I assembled everything back together, using a bit of lithium grease, turned it on - and it works.
Though transistors on focus coil are still getting hot (PNP one more than NPN ?). That, I think , is just a design problem ( or a feature of the design). I will install small heat sink on them, just to help them out a little bit.
Thanks Mooly, and Happy New Year; and to every one else too...
Excellent work, pleased to hear you were able to fix it. Can't say for sure without seeing the circuit but remember the focus drive transistors and coil are often just like a speaker coil and amp on a split supply, The focus coil has to be driven "upward" (the equivalent of a DC offset) and that means one transistor in the pair is doing more work and will get hotter. I'm sure its normal and OK.
I have attached diagram with 8 transistors shown, just to confirm. I think it is the same problem as used to be with first generation of Sony CDPs, like 101 and 501...Their original driver STK6922 was getting terribly hot in operation driving focus coil, and would not last long. But that one could have been directly replaced it with Sony BX1201 and it was running cool. But I do not know what made the difference between two...
In your circuit one transistor (say the NPN) is conducting to put (say) 1 volt DC across the focus coil so the transistor heats up. That means the PNP is non conducting so runs cold. However in practice the PNP acts as an active "pull down" on the coil although its work is minimal because the coil needs a positive voltage to bias it mechanically away from the rest position. So the heating of just one device is normal.
The BX1201 was a metal encapsulated package. I seem to remember there were some other components R's and C's to change the value of too.
But yours is fine
The BX1201 was a metal encapsulated package. I seem to remember there were some other components R's and C's to change the value of too.
But yours is fine
There is no normal condition where the focus coil drive transistors should be getting hot in this player. In stop mode, the output voltage of the drive pair should be 0VDC, + or - 100mV, so neither xstor should be warm. In play mode, unless the platter height is way off, the mean average voltage should be under 1V, so should run no more than a little warm. If no abnormal voltages seen, remotely possible it could be a leaky npn xstor in the pair. If only hot in play, with normal voltages, it may be the focus gain is turned way too high(causing loud hissing from pickup) or the focus coil is partially shorted(never seen that on a kss152).
As for the STK6922/BX1201 thing, that was an IC failure issue that would cause the focus coil to melt down, not vice versa, and only seen on the very early players.
Must add that this whole generation of Alpine-Luxman players were pretty darned crappy and unreliable. I would not invest much time or money into this one.
As for the STK6922/BX1201 thing, that was an IC failure issue that would cause the focus coil to melt down, not vice versa, and only seen on the very early players.
Must add that this whole generation of Alpine-Luxman players were pretty darned crappy and unreliable. I would not invest much time or money into this one.
Thanks for input stephensank.
I guess that you may be right - I compared voltages from manual to the ones I measured (ah, I should have done it earlier!) and got the following:
Manual specs.: Q1302 (NPN) My measerement
B= 1V B= -0.6V
C= 11V C= 12V
E= 0V E= -0.03V
Q1301 (PNP)
B= 1V B= -0.6V
C= -11V C= -12V
E= 0V E= -0.03V
There is obviously a problem! It seams that you have been working on these units; does it mean that Servo processor is at fault (pin 11, FE0)? As I mentioned before, I replaced all 8 transistors with new ones.
I guess that you may be right - I compared voltages from manual to the ones I measured (ah, I should have done it earlier!) and got the following:
Manual specs.: Q1302 (NPN) My measerement
B= 1V B= -0.6V
C= 11V C= 12V
E= 0V E= -0.03V
Q1301 (PNP)
B= 1V B= -0.6V
C= -11V C= -12V
E= 0V E= -0.03V
There is obviously a problem! It seams that you have been working on these units; does it mean that Servo processor is at fault (pin 11, FE0)? As I mentioned before, I replaced all 8 transistors with new ones.
I honestly think you are imagining a problem where one doesn't exist.
How hot are they really ? Can you hold a finger on them for 10 seconds. Does the solder of the transistor leads sizzle water ? I know its difficult gauging temperatures but if it passes those "tests" I would say it was OK. If its as hot as a domestic radiator on full then thats not over hot for a transistor.
Look at your figures and theirs.
The manual says there is 1 volt across the base emitter junction of the NPN. That's not possible as a DC reading because the base emitter junction appears as a diode and limits the drop to 0.7 "ish" as a maximum.
The emitter voltage is really the voltage that appears across the coil. You measure 30 millivolts. That gives a DC current of 4 milliamps into 7 ohm. The transistor would be cold at that. Was that in stop mode ?
Unfortunately service manuals often give hugely inaccurate or just plain wrong information sometimes.
I honestly think your chasing something that doesn't exist
How hot are they really ? Can you hold a finger on them for 10 seconds. Does the solder of the transistor leads sizzle water ? I know its difficult gauging temperatures but if it passes those "tests" I would say it was OK. If its as hot as a domestic radiator on full then thats not over hot for a transistor.
Look at your figures and theirs.
The manual says there is 1 volt across the base emitter junction of the NPN. That's not possible as a DC reading because the base emitter junction appears as a diode and limits the drop to 0.7 "ish" as a maximum.
The emitter voltage is really the voltage that appears across the coil. You measure 30 millivolts. That gives a DC current of 4 milliamps into 7 ohm. The transistor would be cold at that. Was that in stop mode ?
Unfortunately service manuals often give hugely inaccurate or just plain wrong information sometimes.
I honestly think your chasing something that doesn't exist
I would describe my knowledge of electronics as "basic". I measured about 30 millivolts, that was in STOP mode. In PLAY mode it climbed up to 4 Volts.
I just try temperature test; both transistors have metal tab on the back (BD139/140). The one that is not as hot I can hold finger on, and I measured about 60 deg.C
The other one I could not hold finger on for more then a second, and I measured temperature of 110 deg.C (using multimeter and K type probe).
I just try temperature test; both transistors have metal tab on the back (BD139/140). The one that is not as hot I can hold finger on, and I measured about 60 deg.C
The other one I could not hold finger on for more then a second, and I measured temperature of 110 deg.C (using multimeter and K type probe).
That does sound hot I must admit. Well it is hot, too hot really although such things do occur in commercial gear.
Have you had the player from new or might it have some history ?
It obviously all works OK... and 110 degrees is still technically OK for a silicon device but at those temperatures other effects may be noticed. Has the board discoloured around the transistor or its leads ? That would indicate long term running at high temperature which may suggest its normal.
Just to be sure on the info The focus drive showed 4 volts on the emitter of the driver pair of transistors ? That sounds high enough to be driving the pickup out of the block (and yet its all working) and would also pull nearly half an amp through the coil. I wonder if you are getting a true reading on the meter because the presence of high frequency AC (the focus error waveform) might be confusing the DVM.
After its been playing for a few minutes is the pickup (the top of it) hot ?
Have you tried as Stephen suggested and turned the focus gain down ? It's not a hugely critical adjustment. Note the position of the pot first. Be sure it is focus gain and not focus bias or offset you adjust (assuming it has those adjustments)
Have you had the player from new or might it have some history ?
It obviously all works OK... and 110 degrees is still technically OK for a silicon device but at those temperatures other effects may be noticed. Has the board discoloured around the transistor or its leads ? That would indicate long term running at high temperature which may suggest its normal.
Just to be sure on the info
The focus drive showed 4 volts on the emitter of the driver pair of transistors ? That sounds high enough to be driving the pickup out of the block (and yet its all working) and would also pull nearly half an amp through the coil. I wonder if you are getting a true reading on the meter because the presence of high frequency AC (the focus error waveform) might be confusing the DVM.After its been playing for a few minutes is the pickup (the top of it) hot ?
Have you tried as Stephen suggested and turned the focus gain down ? It's not a hugely critical adjustment. Note the position of the pot first. Be sure it is focus gain and not focus bias or offset you adjust (assuming it has those adjustments)
There is no signs of discolouration or burns on the board. And the top of pick-up does not get hot?!
What precaution should I take if high frequency AC is suspect to confuse the DVM? As transistor is getting so hot, I think reading may be close to correct.
I have attached two pages of adjustment procedure that can be done, and I will do it when I get test CD (is it possible to copy such CD from somewhere - it will cost me $50 to buy). Step No. 4 is not exactly clear to me; it requires CD and Oscilator as input, what is monitor, and I do not have 2 pointer AC voltmeter (or I don't know what it is...).
The player does have a history , I know just a part of it. I bought it from a guy on eBay for $10, and I think he got it on some kind of market or so, he said he didn't know how to fix skipping problem (which we managed to do) so he was selling it as it is.
I haven't try Stephen suggestion yet, as I said I would like to do it properly, not just by "feel" so I would prefer to have that test CD...
What precaution should I take if high frequency AC is suspect to confuse the DVM? As transistor is getting so hot, I think reading may be close to correct.
I have attached two pages of adjustment procedure that can be done, and I will do it when I get test CD (is it possible to copy such CD from somewhere - it will cost me $50 to buy). Step No. 4 is not exactly clear to me; it requires CD and Oscilator as input, what is monitor, and I do not have 2 pointer AC voltmeter (or I don't know what it is...).
The player does have a history , I know just a part of it. I bought it from a guy on eBay for $10, and I think he got it on some kind of market or so, he said he didn't know how to fix skipping problem (which we managed to do) so he was selling it as it is.
I haven't try Stephen suggestion yet, as I said I would like to do it properly, not just by "feel" so I would prefer to have that test CD...
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