Today I ordered 2 CXA1372S from an Asian ebay vendor just in case I don't find one among my parts machines:
2 PCS SONY CXA1372S RFSignal Processing Servo Amplifier | eBay
$8 USD for 2 of them. Free shipping. This seller has a 99.5% rating. For many years I've frequently bought parts from highly rated Asian ebay vendors. So far I've had no bad experiences. Note: Shipping does take 2-4 weeks.
For those who are in a hurry or who prefer US vendors there is a highly rated USA ebay vendor who sells the CXA1372S for $15 USD with free shipping.
CXA1372S Original New Sony Integrated Circuit 5052406127855 | eBay
-EB
2 PCS SONY CXA1372S RFSignal Processing Servo Amplifier | eBay
$8 USD for 2 of them. Free shipping. This seller has a 99.5% rating. For many years I've frequently bought parts from highly rated Asian ebay vendors. So far I've had no bad experiences. Note: Shipping does take 2-4 weeks.
For those who are in a hurry or who prefer US vendors there is a highly rated USA ebay vendor who sells the CXA1372S for $15 USD with free shipping.
CXA1372S Original New Sony Integrated Circuit 5052406127855 | eBay
-EB
lets hope its an easy fix.Following up with my Sony CDP-491 and CDP-591 single-disc CD players:
- I have 3 of these units (2x CDP-491, one CDP-591).
- All 3 are now in working condition.
- Two currently contain brand-new generic KSS-240A pickups.
- One still has its original KSS-240A.
- All 3 machines exhibit similar RF signals and eye patterns.
- RF amplitude for all 3 units is 1.0-1.2V P-P.
Because I now have 3 nearly identical machines which are all functional I’m thinking of some “diy experiments:”
The CXD2500 digital decoder IC has several logic outputs which indicate disc errors of varying severity. I plan to re-read the IC datasheet in order to refresh my memory of how these error detector outputs operate. If I connect them to my logic analyzer then I will able to measure both the quantity and type of errors for a given disc or for a given track on a disc.
Questions I wish to answer:
1) What is the total “error count” for playing the same CD on each machine?
2) Would careful adjustment of focus balance and E-F tracking balance improve the performance of the vintage original KSS-240A?
3) What is the resonant frequency of each focus and tracking actuator?
4) How much does this differ between original vs. generic KSS-240A?
5) How much does platter height affect performance? I’m thinking that having the platter height adjusted correctly (+/-0.25mm) might improve the performance of the optical pickup.
6) What is the best method for adjusting platter height? Is it possible to use the average DC voltage going into the focus actuator coil as an indicator of the correct platter height?
7) Is the optical alignment of a vintage pickup degraded by warping/ageing of the plastic “hinges” which support the tracking actuator and lens? If so, is there any possible way to improve this? (other than total replacement of the optical pickup).
…And: I’m more than happy to receive questions and suggestions from diyAudio members which relate to KSS-240A optical pickups.
-EB
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1) No idea tbh.
2) Quite possibly. Also tracking and focus gain adjustment can make quite a difference to 'playability' and shock resistance. Tracking gain can be got very close by looking for the very low frequency fundamental waveform (that will appear in the tracking error waveform ) as you turn the gain up. Back off the gain from the point the LF fundamental just begins to show.
3) Again no idea... but I do remember us doing Bode plots of the servos and coils and treating them as a combined electro/mechanical system on a three day residential Sony course. It was hard going with lots of number crunching. After all that we were told 'but you don't need any of that for servicing and repair although it helps with the general understanding'.
4) I suspect old lens suspension assemblies will possibly have changed their characteristics over the years. Particularly true of those using a little squidgy neoprene do-dah as a means of controlling the lens. The lens is free on its spigot but is restrained by this little 'elastic band' at the back pulling it down. Sony D50 discmans with the KSS110? (original version) were like that.
5) Platter height makes more of a difference on some models than others. You don't want it that high that the focus offset needs to be massive to move the lens up enough, on the other hand it must be able to allow the full focus range for initially finding a disc. Perhaps you could look at an average DC value on the scope for all three and get a feel for where it should be set.
7) This carries on from '4'. They can get saggy and the lens resting at the lowest position but as long the flexibility remains similar then they should be OK. That is the big question though. Has the plastic hardened and deteriorated. If it has then its new pickup time.
2) Quite possibly. Also tracking and focus gain adjustment can make quite a difference to 'playability' and shock resistance. Tracking gain can be got very close by looking for the very low frequency fundamental waveform (that will appear in the tracking error waveform ) as you turn the gain up. Back off the gain from the point the LF fundamental just begins to show.
3) Again no idea... but I do remember us doing Bode plots of the servos and coils and treating them as a combined electro/mechanical system on a three day residential Sony course. It was hard going with lots of number crunching. After all that we were told 'but you don't need any of that for servicing and repair although it helps with the general understanding'.
4) I suspect old lens suspension assemblies will possibly have changed their characteristics over the years. Particularly true of those using a little squidgy neoprene do-dah as a means of controlling the lens. The lens is free on its spigot but is restrained by this little 'elastic band' at the back pulling it down. Sony D50 discmans with the KSS110? (original version) were like that.
5) Platter height makes more of a difference on some models than others. You don't want it that high that the focus offset needs to be massive to move the lens up enough, on the other hand it must be able to allow the full focus range for initially finding a disc. Perhaps you could look at an average DC value on the scope for all three and get a feel for where it should be set.
7) This carries on from '4'. They can get saggy and the lens resting at the lowest position but as long the flexibility remains similar then they should be OK. That is the big question though. Has the plastic hardened and deteriorated. If it has then its new pickup time.
Table height is critical.
Adjustment of the servos will greatly improve the error rate.
No clue, I bet they are different.
Find the specs on the suspension exactly as you would with a speaker. You can use the same equipment in fact.
Best way to set turntable height is with a jig, or gauge block. I have several for different machines I bought when doing warranty service.
Sagging of the suspension will degrade performance. I don't think anything will fix that beyond hanging the head upside down for the same number of years. When setting the gains, we used to use a lissajous pattern. You could easily see non-linearity and suspension defects.
Mechanical alignment makes a massive difference in performance.
-Chris
Adjustment of the servos will greatly improve the error rate.
No clue, I bet they are different.
Find the specs on the suspension exactly as you would with a speaker. You can use the same equipment in fact.
Best way to set turntable height is with a jig, or gauge block. I have several for different machines I bought when doing warranty service.
Sagging of the suspension will degrade performance. I don't think anything will fix that beyond hanging the head upside down for the same number of years. When setting the gains, we used to use a lissajous pattern. You could easily see non-linearity and suspension defects.
Mechanical alignment makes a massive difference in performance.
-Chris
I confirmed the Onkyo DX-C120 multi-disc changer contains the KSS-240A optical pickup.
It has the version with the small servo PC board mounted directly underneath the disc transport. This is quite similar to my Sony CDP-491 & CDP-591 single-disk CD players.
By now I have played 20-30 discs in each of my 3 single-disc KSS-240A CD players (Sony CDP-491 & CDP-591).
Interestingly the 2 units where I installed current-production generic KSS-240A pickups are much less likely to skip when I tap on the case of the CD player.
However I haven't attempted any adjustment of the "skippy" machine which still contains its original Sony factory KSS-240A. It does play all of my discs and it has proper RF level (1.0V P-P). It also has a good looking eye pattern. However it remains very sensitive to skipping when I tap lightly on the CD player. I haven't checked the height of its disc platter. I do know that someone (not me) changed its spindle motor. So it's possible that its disc platter is too high or too low.
Like I said above, my next KSS-240A restoration project will be inspecting and testing the 2 multi-disc machines (Sony CDP-201, Onkyo DX-C120).
-EB
Might be worth doing as I suggested earlier and trying to get an average DC value for the focus coil when playing. You could maybe rig up a R/C network to connect across the coil and measure an average voltage.
If you could do that on some original players then that should give a good representation of the voltage needed for a correctly set platter height.
If you could do that on some original players then that should give a good representation of the voltage needed for a correctly set platter height.
This is exactly what I plan to do.
Interesting observation:
The Denon DCM-320 focus and tracking actuator driver stages have discrete output transistors operating from +/-8V DC rails.
The focus driver output transistor for one power supply rail is much larger.
The other 3 transistors are much smaller (one of these is for the other polarity of focus drive. Both polarities of tracking drive transistors are small).
To me this implies a substantial continuous DC current flows through this one focus drive transistor while playing a disc.
My assumption is this raises the lens from its "power-off" resting position up to the correct position for focusing on the disc.
I also intend to record and analyze the "focus search" waveform. I'm thinking that a well-adjusted transport should detect focus when the focus coil voltage is equally between the starting and ending voltages of the focus ramp signal. The lens can only move (at most) about 1mm up or down. It seems to me that the correct platter height should position the lens (for playing a disc) halfway between its upper and lower movement limits.
-EB
Use calipers and measure the top of the laser head to the top of the disc table. This will be the same for every machine using that head. It will never change.
Do not mess with the pots on the KSS-240A. They are (not in order) Laser power, Focus offset, E-F Balance. If you have a clear eye pattern, they are fine.
Do not mess with the pots on the KSS-240A. They are (not in order) Laser power, Focus offset, E-F Balance. If you have a clear eye pattern, they are fine.
Chris's method sounds good if you can do an accurate measurement. I guess you could even fabricate your own spacer/gauge to suit those pickups.
It would be good to compare both methods actually. I'm thinking would a weakened lens suspension alter the DC value needed... I think it must but would not like to say by how much.
It would be good to compare both methods actually. I'm thinking would a weakened lens suspension alter the DC value needed... I think it must but would not like to say by how much.
The problem with a sagging suspension is that if you adjust to read initially, there will be excessive power dissipated in the focus coil - depending on how much sag there is. This is exactly the problem in early Philips transports. Or it will lock to the disc, but not read or maybe play it once the servos are closed.
You are better off setting the correct table height and replacing defective heads. These heads are pretty cheap after all.
You are better off setting the correct table height and replacing defective heads. These heads are pretty cheap after all.
Excellent point.
I recall at least one CD player from years ago where a focus/tracking actuator driver IC ran so hot that it darkened the PC board and eventually failed. IIRC that was an unusual low-end Marantz model with a 4-digit model number. I think it was called the “Legacy series.” It’s transport was made by Sanyo. Maybe the entire machine was made by Sanyo.
I’m measuring average voltage & current for the focus actuator coil while playing a disc. I’ll also measure DC resistance of the actuator coils too. I expect the results should be nearly identical for every KSS-240A optical pickup.
I currently have six CD players which contain KSS-240A optical pickups. All are able to play a disc at this time. To me six units is a big enough sample size to obtain credible data for KSS-240A pickups.
So far I’m quite happy with the performance of these current-production generic KSS-240A pickups. They outperform my expectation for an item which cost only USD $11 each.
Note: None of them have sintered bronze slider bushings. However their plastic bushings all have a perfectly smooth and precise fit to the existing steel guide rods.
And although their 3 trimpots aren’t sealed with drops of white paint like original Sony KSS-240A pickups, all of them (so far) display good clean eye patterns & correct RF levels (1.0-1.2V P-P) right out of the box.
-EB
Well I went slightly off-track with my KSS-240A restoration project when this item showed up on my doorstep:
Denon DCD-1500II
This was an ebay purchase.
USD $50 with free shipping.
Advertised condition: "For parts or not working."
Shipping alone would typically be >$25 USD, considering how much a Denon DCD-1500II weighs (more on that later in another thread).
Although I'm attempting to reduce the size of my vintage CD player collection, I could not resist this opportunity.
For many years I've admired the Denon DCD-1500II but (until now) never owned one.
I was also eager to check out a CD player which contains the legendary KSS-151A optical pickup.
The unit arrived with a zip lock bag taped to its top cover containing random sheet-metal screws, most of them not original hardware. But the player itself was relatively unmolested with the exception of its tray drive assembly. This machine uses 2 different sizes of square cross-section rubber drive belts. Neither appeared to be the correct size, although both looked new. Oddly there was white "plastic lubricant grease" on both the belts themselves and all over the pulleys. Of course the tray would not open. I'm thinking someone obtained a "belt replacement kit" from ebay but didn't understand how to install it. So they gave up and sold off the CD player.
After thorough cleaning and installation of proper size belts the tray began to move very smoothly.
The only remaining problem is with the clamper arm.
The rotating clamper itself rubs on the arm which holds it.
This prevents the CD from rotating.
This player uses a magnetic clamper but the arm which holds it is rather long and the mechanism which raises and lowers it is a bit ungainly. There are no places where its height can be adjusted easily. I temporarily added paper shims to reposition the clamper arm so that the disc can rotate freely.
Voila! It plays!
RF level is slightly >1.0V P-P with a nice looking eye pattern.
I played several discs all the way through.
I was immediately impressed with the "musicality" of its sound, even though I'm only using modest bench-shelf monitor speakers.
Compared to my recent stack of Sony "pulse DAC" CD player restorations (which sound pretty good in their own right), there is "something special" about the way this DCD-1500II sounds.
I can't wait to hear it in my upstairs audio system. I'm envisioning a 3-way comparison between the Denon DCD-1500II and two other CD players which I recently restored: Mission PCM4000, Sony DVP-NS999ES. I'll soon start a thread about this.
-EB
Denon DCD-1500II
This was an ebay purchase.
USD $50 with free shipping.
Advertised condition: "For parts or not working."
Shipping alone would typically be >$25 USD, considering how much a Denon DCD-1500II weighs (more on that later in another thread).
Although I'm attempting to reduce the size of my vintage CD player collection, I could not resist this opportunity.
For many years I've admired the Denon DCD-1500II but (until now) never owned one.
I was also eager to check out a CD player which contains the legendary KSS-151A optical pickup.
The unit arrived with a zip lock bag taped to its top cover containing random sheet-metal screws, most of them not original hardware. But the player itself was relatively unmolested with the exception of its tray drive assembly. This machine uses 2 different sizes of square cross-section rubber drive belts. Neither appeared to be the correct size, although both looked new. Oddly there was white "plastic lubricant grease" on both the belts themselves and all over the pulleys. Of course the tray would not open. I'm thinking someone obtained a "belt replacement kit" from ebay but didn't understand how to install it. So they gave up and sold off the CD player.
After thorough cleaning and installation of proper size belts the tray began to move very smoothly.
The only remaining problem is with the clamper arm.
The rotating clamper itself rubs on the arm which holds it.
This prevents the CD from rotating.
This player uses a magnetic clamper but the arm which holds it is rather long and the mechanism which raises and lowers it is a bit ungainly. There are no places where its height can be adjusted easily. I temporarily added paper shims to reposition the clamper arm so that the disc can rotate freely.
Voila! It plays!
RF level is slightly >1.0V P-P with a nice looking eye pattern.
I played several discs all the way through.
I was immediately impressed with the "musicality" of its sound, even though I'm only using modest bench-shelf monitor speakers.
Compared to my recent stack of Sony "pulse DAC" CD player restorations (which sound pretty good in their own right), there is "something special" about the way this DCD-1500II sounds.
I can't wait to hear it in my upstairs audio system. I'm envisioning a 3-way comparison between the Denon DCD-1500II and two other CD players which I recently restored: Mission PCM4000, Sony DVP-NS999ES. I'll soon start a thread about this.
-EB
Cool 
The Denon's are nice machines.
I bought a DCD1500 (the original first version) back in the day to upgrade my Sony CDP101 and I kept the Denon several years before going to a Micromega. The Denon sounded noticeably more musical than the 1st generation Sony. The mkii like yours should be better still.
I regret in many ways parting with the old players I have had, it would be good to revisit them and see how they stand up to the later models.
The Denon's are nice machines.I bought a DCD1500 (the original first version) back in the day to upgrade my Sony CDP101 and I kept the Denon several years before going to a Micromega. The Denon sounded noticeably more musical than the 1st generation Sony. The mkii like yours should be better still.
I regret in many ways parting with the old players I have had, it would be good to revisit them and see how they stand up to the later models.
Today I'm looking at more CD players which use the KSS-240A optical pickup.
Today's victim is a Sony CDP-C201 5-disc changer. This is a rather "basic" unit. It's been sitting around forever in a back corner of my workshop. I don't recall what its original fault was.
First tests:
I'm beginning to suspect the clear epoxy IC which contains the ABCD E-F optical detectors, the RF preamp, & the laser diode APC circuit. I have another faulty KSS-240A where the RF level changes intermittently and randomly. I suspect its fault is also located inside the clear epoxy IC.
Modern generic KSS-240A pickups don't use that clear epoxy IC. Instead they have a standard black SOIC IC mounted on the side PC board which acts as the RF preamp and APC controller. This is why the clear epoxy chip on the underside of the generic KSS-240A has fewer pins. This smaller clear epoxy IC chip contains only the ABCD E-F optical detectors.
No other active circuitry.
I think I'll order more generic KSS-240A for USD $11 each.
-EB
Today's victim is a Sony CDP-C201 5-disc changer. This is a rather "basic" unit. It's been sitting around forever in a back corner of my workshop. I don't recall what its original fault was.
First tests:
- There's 2 belts in the tray and roulette wheel assembly. Fortunately both belts are in good shape.
- Tray and roulette wheel work correctly.
- Couldn't get it to initialize a disc most of the time.
- Finally it did initialize and played about 1/2 of a disc before stopping.
- Since then I haven't gotten it to initialize any disc.
- I think it fails to detect "focus OK."
- I subbed a different KSS-240A optical pickup.
- Immediate success!
I'm beginning to suspect the clear epoxy IC which contains the ABCD E-F optical detectors, the RF preamp, & the laser diode APC circuit. I have another faulty KSS-240A where the RF level changes intermittently and randomly. I suspect its fault is also located inside the clear epoxy IC.
Modern generic KSS-240A pickups don't use that clear epoxy IC. Instead they have a standard black SOIC IC mounted on the side PC board which acts as the RF preamp and APC controller. This is why the clear epoxy chip on the underside of the generic KSS-240A has fewer pins. This smaller clear epoxy IC chip contains only the ABCD E-F optical detectors.
No other active circuitry.
I think I'll order more generic KSS-240A for USD $11 each.
-EB
Stock up while the going is good you mean. Just think how much these will be worth in another 50 years.I’ll need to test several more of these generic KSS-240A optical pickups before recommending them to other diyAudio members. Things I still wish to learn about them:
1) How many companies are manufacturing these CD optical pickups today?
I’ve seen the name “Smartech Electronics and Machinery Manufacturing Co., LTD.”
In fact this company publishes a 14-page detailed data sheet for their KSS-213C:
View attachment Generic KSS-213 optical pickup specs 1944121.pdf
I don’t yet have a data sheet for their KSS-240A however.
2) What percent are fully functional when received? (100% for me so far)
3) Do they perform as well as original Sony optical pickups?
4) How long will they last? (This won’t be easy to answer quickly)
5) What is the best way to select a reliable vendor when buying from eBay or alibaba?
6) Can they simply be dropped into a CD player without needing any additional adjustments?
My Sony CDP-C201 played one disc all night long on repeat and is still playing today.
Today I will reassemble it fully so that I can load 5 discs and play them all in sequence over a lengthy test period.
I don’t suspect any other issues.
Although this machine is 30 years old it has been stored on a shelf for most of the past 20 years. Its motors and other mechanical parts may have very few hours of use.
I suspect it was retired because it would only work occasionally.
That issue appears to have been fixed by changing out the KSS-240A.
-EB
Different head, but a nice machine. KSS-151A
I just got a Denon DCD-2560. The dampers had to go since they were solid. I need to figure something out for these, foam would work. I have replacement output coupling caps coming, op amps have been replaced and that allowed me to adjust the LSD for minimum distortion. I am thinking of upgrading the DACs at this point, but there are 4 of them. Performance is now limited by the DAC chips and not the analogue stage like it was.
The laser current is 4% high. Magnetic clamp (GREAT!!) and spindle motor is coming for it. Aligning the tracking offset and removing the dampers made a huge difference in tracking. No surprises there.
Very happy overall.
-Chris
I just got a Denon DCD-2560. The dampers had to go since they were solid. I need to figure something out for these, foam would work. I have replacement output coupling caps coming, op amps have been replaced and that allowed me to adjust the LSD for minimum distortion. I am thinking of upgrading the DACs at this point, but there are 4 of them. Performance is now limited by the DAC chips and not the analogue stage like it was.
The laser current is 4% high. Magnetic clamp (GREAT!!) and spindle motor is coming for it. Aligning the tracking offset and removing the dampers made a huge difference in tracking. No surprises there.
Very happy overall.
-Chris
I've no idea where these replacements are made tbh but it is good to hear you have had a positive experience from them all up to now. Again, no idea on ebay suppliers and the like. You take a chance.
The KSS240 was always considered 'plug and play' as far as I remember because all the adjustments are on the head itself and not within the player circuitry. Altering focus bias to see if the RF pattern is optimum can't hurt though if you have a decent scope.
The KSS240 was always considered 'plug and play' as far as I remember because all the adjustments are on the head itself and not within the player circuitry. Altering focus bias to see if the RF pattern is optimum can't hurt though if you have a decent scope.