Philips CD820 CDM4/19 reads TOC, nothing else

[mag2211]

Hello everybody !!! It is my first post at this forum. Forgive me my bad English. I tried to find some help at many Polish audio forums, but without any luck. I am not an electronics engineer, but I`m doing my best trying to mod my CDP

I bought recently Philips CD player Cd618 (CDM4/19 SAA7310). Unfortunately the laser was already dying and it burned while I was trying to rise laser current, measuring voltage at 4k7 resistor. But what is even worse, laser burned also the main chip.

After that I bought CD820 (CDM4/19 SAA7310 SAA7220).
It was working fine untill i decided to replace all old elektrolite capacitors.

Now CD do not want to read cd`s. It displays TOC, I can jump to any track, but track following do not work. Cd spins but the time is not displayed while playing and after few seconds CDP returns to TOC and an "Error" appears.

In service mod a get Error 07 - Subcode error, no valid subcode within 3 sec.

Funny thing is, that if I jump staigth to track 4 (or higher) after TOC appears the CD plays correctly. I can jump between tracks (but cant skip between 3-4 tracks at once - only track by track using "forward" and "backward" buttons). The time is then displayed correctly, CDP plays absolutely normal.

My question is: is there any capacitor near laser supply and control chips able to control current or voltage ??

I had the same problem while modding other CDP. I changed then Zener diodes, other diodes in radial drive circuit (I think in radial... near laser supply), turned pots left and right and CDP started to read normally.

Now I tried the same trick at my new CD820 but it did not work.

Any constructive suggestion is welcome.

Regards
Mateusz from Poland

[amc184]

Before delving into the myriad of electrical problems that could cause this, I'd look for a couple of physical ones:
- Are any of the new electrolytic capacitors under the laser mechanism fouling the swingarm? If your replacements are bigger, this can easily happen. Check the the swingarm moves very freely.
- Did you crack a PCB trace while replacing the capacitors?

[dtm1962]

Changed out all my electrolytic capacitors and I can't even get to the TOC. It will spin for 5 seconds or so and show Error on display.

I picked up another 855 that was dead. The 5V regulator had failed. Now I replaced the regulator and it is fine.

So I swapped out complete transport drive and put the 2nd unit in the 1st unit and I have exactly the same problem.
Put the 1st transport into 2nd player and it works fine. so this eliminates the transport and the main board is determined to be at fault.

Firstly in Service Mode and press Play, I get Error 7 which state "HF /subcode missing"

So put it in Service Mode again and (Pause/Repeat/FF) to get the "P105" service mode. I press Forward Track 3 times to get the player to try to play music.
It will play music 1-2% of the time and the rest sounds like chopped/sliced bits of music completely distorted and unrecognizable. It sounds like ch-ch-ch-ch at the same speed as the music....

I resoldered every connection on the board and checked for solder bridges as well. Any ideas?

Let me know.

[mag2211]

Originally Posted by amc184

Before delving into the myriad of electrical problems that could cause this, I'd look for a couple of physical ones:
- Are any of the new electrolytic capacitors under the laser mechanism fouling the swingarm? If your replacements are bigger, this can easily happen. Check the the swingarm moves very freely.
- Did you crack a PCB trace while replacing the capacitors?

Answers are no. I was very careful while soldering. I thing that if I had cracked any trace, CDP would not play at all.
Swing arm moves freely.
I managed even to play track 1, but I had to start from track 4 and then go backward. CDP even jumped from track 15 to track 1 !!!
The only problem is that CDP cant find track 1 at start.

[lor.e.s]

Hello

You could check pin 28 (Re2) on TDA8809. It´s the input pin for amplified currents from photo-diodes D3 and D4. I read somewhere that on some units there´s insufficient contact between pin28 and the pcb trace. You could try resoldering.

I don´t know the symptoms related to this fault.

Regards

[poynton]

Originally Posted by mag2211

....................
It was working fine untill i decided to replace all old elektrolite capacitors.

...............

Unfortunately, this highlights a common problem.
When doing mods, only one at a time !!!


Andy


.

[amc184]

I've had a problem like this before, when a player wouldn't track well at one end of the CD. I think it turned out to be a problem with the Radial Drive circuit. Check PSU voltages, cap values etc. around this area.

I think that if I had cracked any trace, CDP would not play at all

Nope, a cracked trace can cause all kinds of faults, and it is easy to crack a trace on these cheap single sided Philips boards. Have a careful check, especially around the area I mentioned above.

@ dtm1962

Changed out all my electrolytic capacitors ........

Best to post only in your own thread, I'll respond there.

[mag2211]

I have found bastard !!! It was elektrolite capacitor number 2604 2,2uF 16V connected to pin 29 of SAA7310. Now CDP starsts reading 1st track without grumble. I placed there 10uf which was too much.
I hope nothing else is gonna come up.
Thanks all.

[dtm1962]

Originally Posted by mag2211

I have found bastard !!! It was elektrolite capacitor number 2604 2,2uF 16V connected to pin 29 of SAA7310. Now CDP starsts reading 1st track without grumble. I placed there 10uf which was too much.
I hope nothing else is gonna come up.
Thanks all.

Voila I did the same problem as I put a 47uF 25V cap on the Pin 22 on Rotel 855 player!!

I put back the 2.2uF cpa and it works like a CHARM!

Thanks mag2211 and AMC (Anton)!!!!!!

[mag2211]

I`m glad I could help.