Resurrection of a Philips CD555 Sound Machine

Does anybody have some pointers into repairing the CD part of this unit?
It is a TDA-1540-based machine, with a CD-2 vertical unit. Currently, the CD does not read TOC.
The lens seems to focus fine in factory test modes, but tracking does not function (hence the TOC read failure). Motor seems to spin properly.

I am currently working my way through the cassette unit, I printed a new gear that was rot, and installed a new belt. Everything else seems to work fine (radio, amplifier, speakers).

Thanks,
Virgil

 

Hi, Hugo

Yes, I know, sorry about the mishap. Here's my experience on it.
It was extremely frustrating yesterday - when trying to reply to another thread (http://www.stereo2go.com/forums/threads/bought-this-deck-cheap-for-dolby-s.744) - I kept getting a message that I can't post to that thread because I didn't start a conversation (though I had resurrected and migrated my old login from the old site).

I then spent 20 or so minutes trying to find a simple button that said "start a new thread", which I failed to find on the new site design.
So I posted this one (which I actually do want to post as a new thread) so I can reply to the other thread...

I hope that makes sense.

Thanks,
Virgil

 

When resurrecting Discmans, it was playing with Tracking Balance pot which saved the day. Once it was a weak/dying laser, and once it was a cracked flex board (Kaosun at kaosuncd.com fixed that Philips for me)

 

Hi,

Just some quick updates on the machine:
I've completed the repair of the cassette part; after several 3D prototypes and some printer mishaps, I got a pretty good gear printed and installed.
The following videos show the transport in action in testing and also mounted back in the machine.
I've completely disassembled the transport because it required cleaning, degreasing and re-greasing. I've used Bayer high-friction grease for the cassette door and lithium-based for the three ball bearings moving the head transport up and down.
I've done some recordings as well, and it sounds fantastic - for a machine with no manual controls it records superbly.
The Dolby system is used for both playback and recording, and the machine has automatic bias calibration for Type I, Type II and Type IV.

Transport tests:


Tape playback tests:


Back in the face panel:


Printed gears:


The CD part is next.
No capacitors were damaged in the making of these videos

 

Congratulations! You are almost there... Any signs of life from CD player?
How did you manage to print gears?

 

Hi, Jorge

Thanks for the kind words.

For the cassette:
I designed and printed the gear myself. My 3D printer decided to act up after about 1/2 year of storage, and it took about a week to "convince" it to behave again.
I used the orange / yellow TPU filament (which is flexible), not the blue PLA filament (which is hard); the TPU makes less noise and is closer to the original gear's material.
Here's a link for the yellow filament I ended up using:
https://www.amazon.com/dp/B01J23VHPW

For the CD:
Unfortunately no signs of life from the CD player, I'll have to dig deeper. It's hard to get by another transport like this - including the servo PCB where I think the issue is. Mine is a CDM-2/29 0301. I need to compile a list of possible model donors just in case™.

 

Virgil,
I see that you are an expert yourself but I would like to share my experience with one of my CD players. Thanks to @Jorge , i found out about Kaosuncd and this guy repaired my diskman nicely.

 

You can read my (horror) story of Philips RCD2 laser mech here: Philips AZ-6892
Once I recognized the trouble, I bought three (!) more Discmans with the same laser, and all three had corroded lasers. Sent all four lasers to Kaosun and he managed to resurrect two!!! If you take a look at this you realize why I consider him a Magician:


Your CD555 has CDM-2, lucky you! My list shows quite a few players with this mechanism. Hopefully it is just bad electrolytic or drifted tracking/focus pots

 

Hi, Jorge,

Thanks for sharing; I read the story about your Philips AZ-6892 some weeks ago and I'm very happy to hear he came through with reviving two units. He is a good magician, then.

Yes, while the CDM-2 is quite common, there are at least /10 and /29 versions I know of and each has eight different PCB's (0000, 0001, 0003, 0300, 0301, 0303, 0008, 0307) with different connectors and signal paths.
Would you mind sharing the list with me? I'm aware of only one other unit matching this transport identically and even that has to be within certain revisions, because of a design/unit change later in fabrication.

Oh, if life would be so easy no, all capacitors tested out fine, and the only varistor is for focus, which checks out fine. This is going to take some time...

 

Hi, Boodokhan,

This model has a special place in my heart; it's unfortunate I ended up with one that was so neglected.
I hunted for one for more than a year until this one showed up. There was sand and rust inside - yet nothing corroded on the PCBs - and clearly this sat outdoors.
After taking a bubble bath the main unit is almost spotless; I had to reglue the speakers' cabinets joints (they're made of wood) and clean the drivers as well. Now that all that is out of the way and in good shape, I hope I can revive this transport without a donor.

 

List of laser mechs is the second worksheet of my Excel table here: PCDPs
Initially downloaded from somewhere, there are few sites with this list. Frankly, I never compared if they are the same, just transferred one into Excel. If DCM-2 modifications are not interchangeable then your "fun" shall continue
Just in case my five cents help: when resurrecting Marantz CD-63 (Philips clone), ALL Philips-branded electrolytics were "at least" 30-40% off

 

Hi, Jorge

Thanks much for the list! I've identified a couple more players, besides the CD150 which I knew about. I want to limit myself to TDA-1540-based machines, since those are cheaper, though from what I've seen, they still go for a pretty penny on eBay.

Its current symptoms are that the arm moves all the way to the exterior of the disc upon power-on; no TOC is read and the spindle motor speed seems to be off. Some time ago I measured all electrolytic capacitors on this PCB and found (only) one that was off, the 100uF which I replaced with a generic black one I had.

I am slowly working my way through the various testing procedures of the CDM-2/29 service manual; insofar the MAB-8441P/T012 microprocessor seems to be OK - I performed its self-test procedure. I hope I can debug this without the need to purchase a donor unit.

I've attached a photo of my mechanism and its logic board.

 

Unless its a typo, when you press Play it should swing to the center of the disc, then lock onto CD, then read TOC. If arm moves to the exterior instead, thats the problem.

 

Nope, not a typo, that's what it presently does, the arm moves to the edge and not the center; currently there's no try to focus either (lens coils don't get actuated).

 

Unless laser moves to the center, the sequence of "laser On, focus On, lock onto CD, read TOC" wont even start. So, the servo board might be OK, at least it does what it should in this situation... by playing dead.
There are 4 or 5 axial caps on the laser mech itself, "internet wisdom" says that once they get busted (old age plus they r under a lot of stress with swing-arm mechanisms) then laser positioning goes awry. Erratic swinging is not exactly what you have here, if it was a linear mech I would say that the previous fix attempt flipped the polarity of sled motor. Check all connections to be on the safe side. If all look solid, then I would spend $20 on a set of new Vishay caps for the swing-arm.

 

I have a small update; unfortunately, fixing this CD proves to be a bit challenging.
I purchased a CD150 in working condition. The mechanism inside it is a CDM2/10. Its servo PCB is identical to my CDM2/29.
Its motor spindle CD mount is different since this mechanism uses a regular clamp because it's mounted horizontally as opposed to the 70CD555 which is vertical and magnetic. So, out of the two mechanisms and servos, I made an appropriate one. The resulting mechanism works great in the CD150, just like its original one.

When I connected this new, Frankensteined CDM2/29 to the 70CD555, it didn't do squat, symptoms pretty much like above.
So I started suspecting the uP responsible for the buttons input and display (another MAB8441P, but -TC18, not -T012 like on the servo). As expected, the CD150 had an identical one on its display PCB.
After a quick swap, we now get:
1) Put CD in door, close door
2) Display goes --:-- (which means "read CD TOC")
3) CD starts spinning, lens focuses, CD motor applies break
4) Display goes ERROR
5) Pressing "PLAY" on the keypad shows "1" on the display, CD spins and then displays ERROR
6) Pressing "NEXT" or "PREV" on the keypad shows "1", "2", ... on the display, CD spins and then displays ERROR.

I tried to enter service mode on the CDM2/29 with the following procedure:
a) Press and hold Previous, Next and Time/Track and Power On the unit.
b) Display should read "0" and the servo + uP should enter "test standby mode".
c) From there one can navigate into service positions 1, 2, 3 by using Next.
None of these happen. Step a) above is completely ignored, as the unit tries to read the CD and displays ERROR per 1) - 4) above; it's like it ignores my keypresses, yet those very same keys work perfect (see 5 - 6 above).

I double-checked all voltages entering the servo PCB and the uP PCB from the 70CD555's power supply board: they are OK, a fairly clean set of +5, -5, +12, -11.8V, etc.

At this point I'm going to ask a friend for a MHz oscilloscope and see if there's any I2C protocol exchange between the two MAB8441P's: the servo - MAB8441P-T012 and the uP PCB - MAB8441P-TC18.
My cute Tektronix doesn't go that high :-(

 

You did not mention: does laser emits light?
Before going into deep search for a busted chip or SMD piece, set all Focus/Tracking pots in their neutral/center positions. Since you reset TT platter, there is a good chance that it is not within +/- 0.1mm of the original specs

 

Hi, Jorge

Yes, the laser emits light (see: lens focuses - above). I've set the focus pot in the middle (it was almost in the middle anyway) and it still shows --:--. I verified that my frankensteined servo (with the modified TT) works by testing it in the CD150 donor. No issues there. My theory is there is something in the logic path that prevents the data to go from the servo to the uP (via I2C as mentioned).

The more important thing here is it doesn't enter service mode. In service mode 1 one adjusts the focus pot to get proper focusing of the lens. The CDM2 service manual describes the procedure in detail.

Thanks much,
Virgil

 

While I am thinking, post all your findings at kaosuncd.com: Kaosun resurrected hundreds or even thousands of CD players. When he decides to help, his advises are spot on!
I have the same problem with Philips Discman, but since its laser got fixed by Kaosun, I am not asking for his help else he decides I held him responsible for my incompetence. Will get back once I think of something...