Sugden CD21SE strange logic problem. Design fault ?

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:up: good to know its working OK

The LPC (laser power control) feature is standard on all CD/DVD/SACD players and relies on a photodiode mounted on the same die as the laser diode itself. So the photodiode receives a true and direct representation of the emitted light.

The circuit itself is just a simple feedback arrangement around an opamp with the circuit altering the laser diode current to maintain the light level at some preset value... as set by the trimmer pot. Its absolutely necessary due to the characteristic of the diode which is extremely temperature sensitive. A constant current drive would give a light output that varied enormously over the operating range of the player.

It might just be worth replacing the transistor that drives the laser diode... never had one fail on these but they can fail as a generalisation. Not often, I've probably had two or three over the years across various players.

No argument from me there. But how do you monitor the feedback if it's disabled? They've tied that particular input to the VDD rail. And there is nothing in the datasheet that advocates that...

The transistor on the optical block itself? There aren't any others. The 1300 does the rest as far as I can tell.
 
Posted together ;)

So it was the chip after all on that board ?

Nope. Your magic mod seems to be sorting everything so far... I put the same old 1300 back. Just prettied it up a bit first. As I said, it took quite a beating getting it off.

The mod (12k to 22k) is in the focus circuit as far as I can see. Unfortunately I don't have a circuit diagram for either the servo board or the rest of the set.

Anyone know of one? I see Daisy were involved with the board. They don't seem to be around anymore. French outfit, weren't they? I did correspond with one of their boffs years ago, very helpful chap.
 
Is that what we are looking at there, the two scuffed electrolytics ? If so then I've never seen anything like that before.

Yep. Have a close look at the connector bodies too. The wire link I added is to replace a track almost completely sanded away.

At first I thought the customer had attacked it. Sadly, many customers have a dark side that fills me (and many innocent audio products) with terror. One of these Sugden players had been badly mauled too. Suspension rubbers destroyed, wiring destroyed. Melted plastic everywhere. It took at least an hour to clean up the mess.
 
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Daisy actually appears at the bottom of the pdf as well. They are long gone as a company these days.

If the power control is disabled on the chip then the VAM pickup must include something similar on the PCB on the pickup. The CDM12.1 was like that wheras the CD12.4 had the chip actually mounted on the pickup.

No idea where you would get a circuit from tbh, lol and no idea on the scuffing either. That is just weird.
 
The one machine, recipient of the only reliable servo board I referred to in post 4, was already packed up and ready to be returned to its owner.

So I took it all apart again, brand new 22k resistor clutched in my hand....and guess what? This board has already been modded. And at the factory too. No wonder it was the only reliable board!

So thanks again Mooly. I'm 'cautiously optimistic' this ugly saga is finally at an end. I will definitely follow up.

One last thing, and I know this will appeal to the tweakers :)

I see the SPDIF feed is taken directly off the SAA7327H. Pins 44 (gnd) and 51 (data). Absolutely nothing between there and the RCA socket. No buffer of any kind. So if you have such a chip and no SPDIF, here's a way to do it.
 
:) it happens that way sometimes. Lets hope the machines are OK now.

Alas this is not to be :mad:

All three machines are dotted around the workshop with the covers off, plugged in, and ready to go. This afternoon, went to the closest one, flipped the power switch at the back and off it went, spinning the CD backwards, a series of dashes flashing on the display and completely non-responsive to the front panel switches.

Power cycling it with the front standby switch did restore order though and it worked fine after that.

The other two powered up perfectly.

Later in the afternoon, one of the 'good' sets did the same thing. Spins the CD backwards and gets stuck in flashing dashed line mode.

So very very disappointed. The only light in the tunnel is the possibility that if the unit remain powered up (rear switch on), but in standby, operation will be normal. It could take days to prove though...

We are back at the original thread title. Design Fault? It would seem so, but whose? The servo board could be the problem....or it could be the interface with the front panel programmable chip. Who takes credit for that? Did Daisy supply that too?

Much reading last night and somewhere I read (but I forget where) the product, either the servo board - or maybe it was a laser mechanism; it required two DC supplies, 5v and one other (higher I think, maybe 9 or 12). With the express instruction that 5v must be applied first, and removed last.

Now this Daisy board has both 5v and 9v supply requirements. Possibly cold starting from the back panel cause the wrong voltage to arrive first?

Anyone have any experience with this? Servo board is HECD-019A / DN24A533. tiefbassuebertr refers to it also in some posts he made years ago. Apparently it was used in some quite good players. He lists some of them. Mooly, I think yours is listed too.
 
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