Need help repairing CDTV’s CD-ROM control board.

[ChefDeadpool]

So I spent this evening part-swapping at my friend’s house with his working CDTV. We were able to narrow the problem down (it will play Audio CDs but not data discs) to the control board on the CD-ROM drive.

I’m thinking my first step is to buy all the capacitors on the board and replace them. It’s a weird two-layer board that has through-hole components on one side and surface mount on the other, though, so I’ma bit leery to do anything with it.

Does anyone else have any additional suggestions as to repairing this board?

[alexh]

Originally Posted by ChefDeadpool

We were able to narrow the problem down to the control board on the CD-ROM drive.

So your drive with his control board reads data discs in your CDTV?

I believe that there is very little difference / no difference between Audio CD's and Data CD's in terms of laser pickup etc. So if you can read audio disks then a GOOD amount of the controller board is working.

However the paths the digital data coming off the disc take when they leave the laser pickup are completely different. One goes to a DAC and then the analog audio to a mixer where it is combined with Paula Audio. The other goes via a DATA bus into DRAM.

I may be wrong but I would imagine that the command/control interface is the same as the data interface. So if you can play/stop/skip tracks etc. then you should be able to read data... very strange

[alexh]

http://www.a1k.org/forum/showthread.php?t=57039

[ChefDeadpool]

Thanks for that link. I'm ordering all the parts now, save that I had to substitute a 100uF 16v cap of the same dimensions as the 100uF 6.3v, as the lead time on that part as 18 weeks

Here's my saved project if anyone else wants to re-cap their CDTV's CD-ROM:

https://www.mouser.com/ProjectManage...sID=7990586464

[ChefDeadpool]

So, changing the caps didn’t change the condition of the board at all. It still has the same problems.

At this point, i’m starting to suspect that the DAC or another major support chip on the board is faulty.

Here’s a list of all the chips on the board. Maybe someone with more experience with these chips can point to something that stands out?

The only thing I have on hand for replacement is the 64kbit RAM chip.

TOP - Thru Hole

Loc     P/N + Other markings	    Brand	    Description
IC4 	mn4164a-08 457 [m]	        Panasonic   NMOS 65536x1 bit dynamic ram
IC307 	AN3824NK 	8.8	            Panasonic   VCR Capstan Direct Drive Motor Circuit
IC202	Technics AN8377N	16.7	Panasonic	3-channel linear driver for DC motors
IC306	AN7809R			            Panasonic   Positive Output Voltage Regulators with Reset pin (1A/500mA Type)
				
BOTTOM - SMT				
				
IC1	    MN188161REB1 0D.4  [m]  	Panasonic   8-bit 1-Chip Microcomputer
IC2	    MN53010KZB	0*D3 [m]        Panasonic   CMOS Gate Array
IC3	    M50422P	A 44108	            Mitsubishi	DAC
IC5	    LC8951 A248 09149	        Sanyo       Real Time Error Correction and Host Interface Processor
IC6	    4464S-08LL 0D355 [m]    	Samsung     SRAM
IC7     74LS245	14B	                TI	        Octal Bus Transciever
IC8	    74LS244 04C	                TI	        Buffer/Line Driver
IC9	    74LS541 06X		            TI          Octal Buffer + Line Driver with 3-state output
IC10    74LS244 04C		            TI	        Octal Buffer + Line Driver with 3-state output
IC13	74HC00A	91 17 H	[t]         ??          Quad 2-input NAND gate
IC101	M51598FP		            Mitsubishi	Preamplifier for Optical Pickup
IC102	3771 9107 M53			    ??          ??
IC103	XRA10339F 045 496	        Rohm        ??	
IC201	M51564P 043005		        Mitsubishi  Optical Pickup for Servo Control
IC203	XRU4066BF 049 120			Rohm        ??
IC301	XRU4066BF 049 120			Rohm        ??
IC302	XRA10324F 042 375			Rohm        ??
IC303	XRU4066BF 049 120			Rohm        ??
IC304	AN6554NS [M] 0D.6		    Panasonic   DC Quadruple Operational Amplifier
IC305	10393 XRKJ                  ??          ??

Photos of both sides of the board:

Top:

Bottom:

[ChefDeadpool]

Does anyone else think the soldering on the 40-pin interface port looks questionable?

[ChefDeadpool]

Resoldering the 40-pin connector didn't help. I was hoping for a cold solder joint.

[ChefDeadpool]

Going to try reflowing the solder on the LC8951 after checking it live with a logic probe. I found this thread as the only one referencing a failed 8951; I'm going to see if mine has similar symptoms:

http://www.sega-16.com/forum/archive...22027-p-3.html

[ChefDeadpool]

The logic probe seems to indicate I have whatever the same problem is that this guy with the Sega CD is having, and I contacted him on Skype. He was unable to find an answer to his problem. I'm going to go ahead with buying the chip and replacing it. This seems to be something that affects the first revision (LC8951 and not LC89510, LC89515, etc) chips. Later revs claim to be pin and software compatible with the 8951, so actually using one of the later versions might be desirable.

I also found a thread from another CDTV owner with this problem. I'm trying to go through some effort to contact him as well to see if he made any progress:

http://www.amibay.com/showthread.php...ght=cdtv+audio

[ChefDeadpool]

I should update that replacing the LC8951 did not fix the issue. I am suspicious that the SRAM could be the culprit, so I’m going to head to utsource to see if I can track down another part.

[xArtx]

The DAC and it’s clock is required for CD audio, but not for data.

[ChefDeadpool]

Replacing the SRAM did not fix this. Is it possible there is program code on one of these chips that tells it how to talk to the Amiga, and that code has been corrupted? I'm just shooting in the dark here. Does anyone have any idea which chip might contain the firmware?

Note: I did some additional research on what the board chips are and was able to come up with a few more answers. I added the descriptions to the parts list above.