Circumpunct
New Member
New chip's in, but result on the scope (pin1) is the same.
Troubleshooting CD Players
- Thread starter dr*audio
- Start date
dr*audio
Fish fingers and custard!
Measure the dc voltages on pins 1, 2, 3, 4 and 8 of the IC.
Circumpunct
New Member
Without motor:
1. -157mV
2. 2.52V
3. 2.52V
4. -5.1V
8. 5.06V
With motor:
1. ~100mV positive, jumping around
2. 2.56V
3. 2.53V
4. -5.1V
8. 5.03V
dr*audio
Fish fingers and custard!
DC voltages are ok. Something else is going on.
Circumpunct
New Member
Wish i could add something to the discussion. The PDO trace - was that normal?
dr*audio
Fish fingers and custard!
It is consistent with the motor speed varying. I think we have to break the loop. I need to think on this a bit.
dr*audio
Fish fingers and custard!
Ok, try this.
1. Remove R964.
2. Jumper the pad from R964 that connects to D913 to ground with as short a wire as possible.
This should make the VCO ( IC906 pin 8) run at a fixed frequency, and the PDO should stop moving around and the motor should run at a fixed speed.
1. Remove R964.
2. Jumper the pad from R964 that connects to D913 to ground with as short a wire as possible.
This should make the VCO ( IC906 pin 8) run at a fixed frequency, and the PDO should stop moving around and the motor should run at a fixed speed.
Circumpunct
New Member
Ok thanks, will do that later.
I said earlier there was no ripple on any of the rails to the cd board. That was rubbish. The plus and minus 5v rails to ic903 in fact have 80mV pk-pk of high frequency ripple on them:
That's at 1mS sweep rate. 50mV / div.
Measuring the ripple at the entry point to the cd board i get only 30mV pk-pk.
Circumpunct
New Member
Thought i'd measure esr of all the caps on this board. 11 out of 25 'failed'. The following went one notch into the red on my meter:
C943, 942, 920, 949, 955, 956, 953.
These went two notches into the red:
C950, 921, 944 and 909.
Did as you said with r964. Fired it up and no difference - motor speed random just as before.
C943, 942, 920, 949, 955, 956, 953.
These went two notches into the red:
C950, 921, 944 and 909.
Did as you said with r964. Fired it up and no difference - motor speed random just as before.
dr*audio
Fish fingers and custard!
So, with R964 removed, check the the VCO ( IC906 pin 8) and PDO signals. Are they constant?
Circumpunct
New Member
VCO (probed at R969)
0.5uS 1V/div The voltage here is constant-ish. Every second or so the sled moves the laser out a bit and the speed wobbles accompanied by a dip wobble on the pk-pk voltage shown.
PDO
Same description applies to this trace.
dr*audio
Fish fingers and custard!
It's looking like IC906 is bad. Do you have a variable bench supply? If not you can use a battery. What I want to do is Apply a constant voltage to the motor drive IC, verify that the disc motor spins at a constant rate, and then see what the control voltages (MDP and MDS) are doing. But don't do anything yet. I need to look at the training manual and see how the CLV (constant linear velocity) servo works.
dr*audio
Fish fingers and custard!
I am pretty cure IC906 is bad. You can try doing the PLL adjustment but it doesn't appear that affects the motor speed. You can try the following but I am not sure which signal does what. I thought I still have the training manual for the CD repair course but I don't.
I think if you remove R952 and connect a wire to the pad of R952 that connects to IC904 Pin 5, or just clip a lead on pin 5, you can connect your power supply there and ground and set it to 1V. The spindle motor should now spin at a constant speed. then you can look at R956, the side that connects to IC906 pin 3 and see if it is stable. If it's moving all over the place I think IC906 is bad, but it could still be moving if the IC is trying to control the motor speed. I'm just not sure. I would hate to order that IC and be wrong because it's expensive. Also it's a surface mount part; are you equipped to safely remove and solder a new one in? I think it's time to throw in the towel on this.
Circumpunct
New Member
Thanks again for all your help with this one. It's been educational if nothing else, and good practise. Close to giving up too. I wonder if, when the negative rails failed in the power supply, they put out a spike before shorting, that semi fried the chip. I only have a standard iron and solder wick, but i'm sure i've watched videos where they solder all the pins in a blob and then wick away afterwards. So no, i'm not equipped! I don't like giving up though, so i think i'll make the company who sell that ic an offer. Then again, all those borderline caps....this unit's had a ton of use i reckon, the PSU was a mess.
Off to play with the PLL - nothing to lose...
Circumpunct
New Member
Oh look what i found...cheap enough and in my neck of the woods.
CX23035 SONY DECODER INTEGRATED CIRCUIT QFP ''UK COMPANY SINCE1983 NIKKO'' | eBay UK
CX23035 SONY DECODER INTEGRATED CIRCUIT QFP A message to our customers in ITALY, Please read before purchasing: Please be advised, due to delays with post to Italy, and in some instances parcels going missing, we can no longer send parcels by standard airmail. If you decide to purchase, we have...
www.ebay.co.uk
dr*audio
Fish fingers and custard!
It's cheap enough. To remove the IC you really need a hot air de-soldering tool.Oh look what i found...cheap enough and in my neck of the woods.
CX23035 SONY DECODER INTEGRATED CIRCUIT QFP ''UK COMPANY SINCE1983 NIKKO'' | eBay UK
CX23035 SONY DECODER INTEGRATED CIRCUIT QFP A message to our customers in ITALY, Please read before purchasing: Please be advised, due to delays with post to Italy, and in some instances parcels going missing, we can no longer send parcels by standard airmail. If you decide to purchase, we have...www.ebay.co.uk
Without this you will tear the pads and then all is lost.
Circumpunct
New Member
That looks nice. Me want.
I was planning to slice thru all the legs with a knife, then push all the half legs off the pads with the nose of my iron. Would that not work?
dr*audio
Fish fingers and custard!
No, the pads are very delicate.
Before I got the hot air tool I used to wick all the solder off I could, then slide a .010" guitar string under the leads at the component body, then gently slide the string outward while heating the leads with my iron. It worked but I ended up tearing pads even after I got experienced at it. It's tricky and takes practice, so unless you have some junk boards to try it on, I advise against it.
Circumpunct
New Member
Yes, i just found out the hard way after going at the legs with my Knipex. Not torn any but some have been um nibbled back somewhat. Think i redefined 'torn' there...
Some of those are unused pins anyway, so i might just get away with it.
Nice tip. Can only lay my hands on nylon charango strings - what could possibly go wrong?
Retired FL
New Member
CD player only focuses and starts playing upside down !
Hello, I am starting repairing a nice Denon DCD-7.5 CD player with the Sony KSS-240A laser. 1991 vintage, cosmetically in great shape, unknown usage. Upon disk loading you can hear the laser hunting, but it does not apparently focus, and thus not spin. Picking up and turning the whole player physically upside down while loading a disk, carefully between the CD being held as part of the loading and the focus hunting, will get it running nicely !. Then, even turning the machine back the right way up, it plays great, till the disk is ejected (and thus presumably has to refocus next time). CD seems to be held secure, but with the disk out the spindle motor table seems to have vertical play of 1mm or so.
The KSS-240A to the left of the easy to see 3 pots has what looks like 6 vertical test points - can one of those be used for the RF eye signal instead of taking the drive out and soldering a wire to the RF test point ?. I could not find a layout/detailed schematic for the KSS-240A itself.
Have some CD experience though not seen this before, done some research, wondering if the fault is :
A) Worn bushing on the spindle motor ? thus the disk table is ~1mm too low (explaining why it can focus upside down ?), and I should raise the table carefully ? so like 2mm above the laser.
B) Maybe some spring ? that raises the laser assembly upon disk insertion has grown weak or sagging ? (so laser closer to the disk when turned upside down), and how do you adjust for that ?.
C) Sled rail ware ? (unlikely ?) - how fix/compensate ?.
D) Maybe the lens suspension has given up ? but the lens does bounce a bit when carefully pushed, and it's light weight, and rather not get a modern KSS-240A copy if the original, though 32 years old, is OK.
E) Or do I just go ahead and try increasing the laser current a bit ? (with the risk of burning out a good original lazer).
I have cleaned the lens & table, otherwise not taken apart yet. Sounds like a mechanical issue, thus would like to fix mechanically, appreciate ideas, thanks
Hello, I am starting repairing a nice Denon DCD-7.5 CD player with the Sony KSS-240A laser. 1991 vintage, cosmetically in great shape, unknown usage. Upon disk loading you can hear the laser hunting, but it does not apparently focus, and thus not spin. Picking up and turning the whole player physically upside down while loading a disk, carefully between the CD being held as part of the loading and the focus hunting, will get it running nicely !. Then, even turning the machine back the right way up, it plays great, till the disk is ejected (and thus presumably has to refocus next time). CD seems to be held secure, but with the disk out the spindle motor table seems to have vertical play of 1mm or so.
The KSS-240A to the left of the easy to see 3 pots has what looks like 6 vertical test points - can one of those be used for the RF eye signal instead of taking the drive out and soldering a wire to the RF test point ?. I could not find a layout/detailed schematic for the KSS-240A itself.
Have some CD experience though not seen this before, done some research, wondering if the fault is :
A) Worn bushing on the spindle motor ? thus the disk table is ~1mm too low (explaining why it can focus upside down ?), and I should raise the table carefully ? so like 2mm above the laser.
B) Maybe some spring ? that raises the laser assembly upon disk insertion has grown weak or sagging ? (so laser closer to the disk when turned upside down), and how do you adjust for that ?.
C) Sled rail ware ? (unlikely ?) - how fix/compensate ?.
D) Maybe the lens suspension has given up ? but the lens does bounce a bit when carefully pushed, and it's light weight, and rather not get a modern KSS-240A copy if the original, though 32 years old, is OK.
E) Or do I just go ahead and try increasing the laser current a bit ? (with the risk of burning out a good original lazer).
I have cleaned the lens & table, otherwise not taken apart yet. Sounds like a mechanical issue, thus would like to fix mechanically, appreciate ideas, thanks