ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi everyone... I tried reading up on the common issues on these machines before posting, but I'm stuck on a couple issues. So, I have two of these on the bench right now. One is a customer's and one is mine someone gave me a few years ago.
I'll start with the issues on my machine and what I have done to it:
1. Original problem when plugged in was No power.
2. Located and replaced open 400mA fuse in power supply and two shorted diodes for -25v unregulated supply location 6458 and 6467 according to service manual I have.
3. Also found -6v regulator was at -2v and -18v regulator was at -14v. Didn't have them in stock so I fed the appropriate -6 and -18v DC supplies into the board with regulators' output pins disconnected.
4. At that point the machine would spin the disc for about 4-5 seconds then stop and give the infamous ? on the display.
5. Performed the griplet repair on both the servo and decoder boards, still has the same problem reading discs.
6. I also checked all caps in power supply, decoder board and servo board. No leaky or high ESR caps were found. I guess I could just change them all, but I've got a lot of time in it already at this point and I think it might be something else.
7. Anyone have any thoughts on this issue?
Now for the second one which is my customer's unit:
1. Original symptom was that it would play fine for about 5 tracks, then start skipping / struggling to track the disc. Same issue on any disc I tried.
2. Opened it up and found that someone had already done the griplet repair.
3. Cleaned and lubricated the laser arm and mechanism and cleaned the lens.
4. Disassembled the disc motor, cleaned and lubricated the shaft, brushes, etc.
5. Reassembled and started up at track 5. To my pleasure it played fine through tracks 5, 6, 7, etc. then it started failing again towards the end of the disc, tracks 10 and 11. I'm not sure if it was a coincidence or the improvement was related to the cleaning and lubrication I did.
6. Any ideas on this one?
Thanks for any help and sorry to post two issues in one thread, I just thought it might be easier to show what I've done and learned about these machines and hoping a CDX expert might chime in with some suggestions.
I hope you are well!
Greg
Hi, Hope everyone is doing well! I'm just wondering if anyone has any thoughts on these issues before I give up on them?
Thanks,
Don't give up on a CDX sir!!
In both your cases,the laser seems to be functioning as the disc wouldn't turn if it had failed.
Both cases seem to be due to the same thing-corrupted data from the disc,so the decoder is "dancing in the dark"?
The notorious griplets become oxidised within the solder,so I alway's drill through them,then wire through too,to make sure that the connection is good.
It's worth replacing the blue Philips(use the same type BC/Vishay)capacitors(33uf) on the little U shaped laser servo pcb mounted next to the laser assembly.Don't touch the presets there though!!!
If the capacitors on the decoder pcb are Nichicons,they will almost certainly still be ok,but if they are Philips,change them(22uf).
That lot should keep you busy?
Wonderful machines,well worth some tlc!
Keep us posted,
Nick
Hi Nick, thank you for the reply. I agree that these CDX machines do sound wonderful! I did de-solder and feed thin wires through the griplet points and confirmed continuity from top to bottom of the boards so I don't think that's the issue. I'll check the capacitors and report back.
Ok, so I replaced the caps on the u-shaped laser servo PC boards (even though they checked OK) and still have the same problem with both units. As mentioned in my original post, the first unit spins the disc but won't read it and then gets the "?" error on the display. The second unit plays fine for about 5 tracks, then starts skipping and having tracking issues. Any more ideas?
Thanks,Greg
It could be an alignment issue with the door switch. I had a CDX that would not read and play when I loaded a CD and pressed play. I finally learned that I could gently press down on the glass door (on the left side) when it closed to help the switch engage and then the laser would read and recognize the disc. I don't know if that problem relates to you but it is something to check. Also, when you are test playing the disc is the CDX still apart or do you have it reassembled? I had another CDX that wasn't loading and playing when I tested it all opened up but when the cabinet was all put back together it played great.
They are cool little CD players but a little quirky.
-sonavor
The machine that is misstracking towards the centre of the disc,may need alignment of the disc motor lower bearing?This affect's the height of the turntable and so the focal length of the laser.It's quite a critical adjustment,but explained in the manual.
You don't mention the decoder capacitors I suggested for investigation?Are they Nichicons or Philips?
The power supply work that you carried out,might be significant?Are you confident now that all supply voltages are correct?
Sonavor, Thanks for the reply. I'm working with them apart, but I'm pretty sure the door switches are engaged otherwise it wouldn't attempt to play a disc. I'll double-check them though.
Hi Nick, thanks for the reply....I'll check the disc motor bearing alignment in the manual and see if it helps. It does seem like a disc motor issue as this is usually the cause of CD players that don't track well towards the end of the disc. Not sure why it would be out of adjustment, but we'll see.
As far as the capacitors on the U-shaped board... they were all Nichicon 33uf/16v expect the axial C2124 was a Philips 33uf/16v. I replaced them all with good Nichicons and no difference on either unit. I even swapped the U-shaped boards from unit to unit with no difference on either machine. I was surprised the one that plays until track 5 tracked with the different board, but it did.
In terms of the unit with the power supply work, I haven't bothered to order the -18v and -6v regulators yet because I was frustrated and didn't want to keep spending money and time if I wasn't able to get it to play discs. But, during tests, I'm feeding a stable -6v and -18v into the circuit board with the output pin of the regulators disconnected. I'm monitoring the voltage as it tries to play and it's not dipping down, so I was thinking that part is OK. But, maybe I just need to bite the bullet and order the correct regulators. All the other power supply voltages are good. To be honest, I was surprised one unit could have so many different failures (open fuse, two defective regulators and disc reading problems).... I mean, this thing must have been working at one point before it lost power, right?
In the meantime, I'll try the disc motor adjustments and maybe play around with swapping power supplies and CD mechanisms from one unit to the other to see if I can narrow down the issues.
Thanks again,Greg
Ok Gregg.
Well,it seems as though you have two machines that have been "got at" by persons unknown?
Something we all dread,as this tends to confuse the issue.
I think that you will need to return the machines to as original as much as possible?
I'm puzzled eg by the fact that you have Nichicon caps on the laser pcb 02.These are usually Philips axials.There is much discussion about the particular characteristics of the Philips caps,and they do seem to work best here.Polarity is crucial with some of the caps too,as there are both positive and negative supplies involved
You still don't mention the cap's on the decoder pcb 05.If they are Nichicons,fine,but if Philips,they are suspect.
Confused?
The fact that both machines spin the disc,and one indeed plays a few tracks too,makes me think that there is not a major failing.
You need to remember that these cd players employ three (later machines 4!)servo systems,that all must work in concert for the disc to play.The most crucial time is at start up,so any psu problems will have a bearing then!
I have the original training course notes somewhere,I'll see if I can find and scan them for you,if it will help?
Nick, so the caps on the Laser PCB 02 were all Nichicon radials except one Philips axial. I replaced them all with good quality Nichicons. I may have misunderstood your previous post. I thought you said if they were Philips to change them. I didn't notice any difference after replacing them. One of the Philips axials measured low so I was hoping it would help to resolve one of the units. The Nichicons all measured OK, but I changed them anyway.
I think I also missed the part in your post about the caps on the Decoder PCB 05. I know I measured them all in circuit previously and they measured OK, but I'll have to double-check them next week to see what type they are. If Philips I will change them.
As far as the power supply, I agree that these regulated voltages are critical. I will try to locate and replace the -18v and -6v regulators with the proper type to eliminate that as an issue.
I don't have the test disc and laser simulator discussed in the service manual for making alignments, but I'll try to check what I can (motor, RF eye pattern, etc.)
Thanks again for all your help....I'm really looking forward to getting these fixed as one belongs to an important customer and the other is mine... I would love to add it to my system as the sound quality is amazing from what I've heard so far!
And, if you happen to find the training course that would be great!
Best,
A scan of the training course would make a nice addition to the Beoworld service manual library :-).
Just to clarify Gregg,the caps on the laser pcb 02,are usually Philips axials (33uf)
I like to replace them with new BC/Vishay types as they are the same spec.Nothing wrong with the Nichicons per se,but the Philips/BC/Vishay ones just seem to work better here.It's a mystery?
As to decoder pcb05,this board is crucial as it's where all the clever stuff is carried out.It's usually populated with either Nichicons(22uf radial) or Philips caps.
As mentioned,the Nichicons are fine here,and very rarely have they suffered any age related deterioration,but it can happen.The Philips radial ones,if employed here are usually suspect.
I usually change them all anyway,but I should get out more(not at all at the moment sadly!)
It's worth going the pcb for any dry joints too,particularly around the large ERCO chip SAA7020.In addition to the notorious griplets,there are some other wire link through's too.
Rest assued that when you get these machines working fully,you will be impressed.
I used to have five of them,mad or what?
I've copied the notes John,but I can't work out how to upload them to the site?
Did I send you the BG4000 training notes btw?
Hi Nick,
I didn't receive the Beogram 4000 notes but would love to have them. I guess we will need to ask Keith. You may have to send them to him for posting in the service library.
John
Hi Nick, I'll check out the caps and solder connections on the decoder board and report back. I appreciate your time and passion for this stuff! I'm the same way!
Take care,
Hey Nick, Well, I seem to have made some progress! I checked the caps on the Decoder Board 05 and while they are Philips, they all checked OK in circuit. So I moved on to the Servo Board 04 and found that the Philips axial 33uf 16v and 40v caps were all checking higher than normal on my ESR meter so I swapped them all out on the CDX unit that played but would skip after track 5 or so. After cap replacement, I was able to play all the way through a disc twice that previously failed on the later tracks. So, I'm pretty sure that one is fixed! Yay! Still need to test further, but I'm feeling pretty good about that one.
I then took the power supply board out of the working unit and put it in the other one that I still need the regulator IC's, and it still failed in the same way... disc spins for a few seconds, then the "?" on display. So, I checked the caps on the Decoder board (also Philips) and they checked good. The Servo board caps checked better than the other machine, so I just swapped the servo board from the working machine to this one and it also played perfectly! I also immediately noticed that the disc motor sounded quieter (I think the disc motor is struggling to come up to correct speed maybe with its original servo board). So, I recapped the original Servo board and put it back in this player. Now the disc just spins and spins and spins forever and never stops or goes to the "?". But, it still doesn't track the CD and play. I also noticed the motor doesn't sound as quiet as it did with the other board.
So, I seem to still have an issue on the Servo board. Unless it's some kind of intermittent that just happened to work after disassembly and reassembly. I called it a night instead of swapping the "good" servo board back in the non-working unit to confirm my findings. I've done the griplets and the caps on the Servo board and checked for solder issues. Didn't see anything else obvious. I'll try to get back into it, but just wondering if you have any thoughts that might save me some time and lead me in the right direction? The hours are piling up on this one, but I feel like I'm oh so close!
Progress indeed Greg!
I'd be inclined to put all the good bit's into one machine,so at least you have one working and a sense of achievement too?You can use it for comparison too of course.
You've identified the one faulty servo board,and it seems as though something is awry there since re-capping,as it now behaves differently?Prap's one of the cap's fitted in reverse,or a solder blob across the print somewhere?
I would replace the Philips decoder caps too anyway, based on experience.We've all be fooled by components(particularly cap's)testing ok in and out of circuit,but not performing well under voltage.
It's tedious on the decoder board,as there are so many of them,but worth the effort usually.
As you can see from the course notes,the integrity of the data through the decoder is crucial for correct operation,so anything like noisy supply lines can upset it.
Label the known to be good boards,so you don't get them mixed up,and have another good look at that dodgy recapped servo board?
Thanks Nick, yes I've thought of many of those things, I just didn't spend any more time on it after the 2nd one failed.... got frustrated and went home, LOL! I agree that caps can check good in circuit and still be bad and was planning on recapping the decoder boards eventually anyway.... but I figured since I think I've narrowed it down to the Servo board I would continue with that one. I also thought about putting my customer's unit back together to use for comparison, but I'm gonna have to order the correct -18V and -6v regulators for the other one's power supply so I can know that board is working correctly without having to feed voltages into it. So, that might have to be my next step.
I'll double-check my work on the 2nd unit's Servo board, although as I was recapping it I wasn't too confident it would fix it because only one cap checked slightly off and the rest checked good compared to the other board where the caps were obviously bad. But yes, it would be nice to use the other unit for comparison measurements at this point.
Have you seen anything else beside electrolytics fail on the Servo boards such as IC's, transistors, film capacitors, etc.?
And I hear ya on labeling the known good boards... already done!
Thanks again... I appreciate your time and responses! Will report back soon (hopefully with good news!)
UPDATE - This morning I tested it and it was back to the original symptom of playing for a few seconds then the "?". So, I pulled the servo board and put the working board back into it and it plays perfectly. I double-checked all my work on the servo board, checked the caps, diodes, transistors, everything seems fine. Made comparisons to the working board and couldn't find anything different. Put the defective board back in and noticed that sometimes it spins and spins and sometimes it spins then stops and gives the "?". So, I don't think anything happened during my repair of the servo board. Maybe an IC is failing? Voltages to the motor board seem good, Have my + and - 12v and the motor is getting like -4.5- 5.0v while spinning. I'm kinda stuck at this point.
Well,it's narrowed down to that dodgy servo pcb now Greg.Apart from the two notorious griplets,there are numerous wire link's between tracks,and more links between the two sides of the board where component wires go through too!
If it's an intermittent connection somewhere,I would expect that flexing the board or gently tugging on the loom wires at the plug in connections,would throw up some indication?
The loom connectors can act up,but it's where the wire connects into the plug,rather that the connector itself.Again though,you should be able to "provoke it" if this is the culprit,by waggling the loom to see if the fault state alters..
I did have one odd problem that turned out to be due to oxidation of the connections for the servo upc,which of course controls the board.6201(servo upc) sit's in a raised socket,and in my case,it had been secured with blob's of glue.On investigation,both the pins of the chip and the socket connectors were quite black with oxidation.I had to replace the socket,but the chip pins cleaned up ok.
Might be worth checking that out too?
I don't remember having to replace any other componets on this pcb except of course the caps!
I haven't really found that it is intermittent in the sense that it will sometimes play a cd with the defective board. Only that sometimes it plays for a few seconds and the "?" on the display and sometimes it just spins and spins, but still never tracks a cd. As soon as I plug the working board in there it works every time. I checked and cleaned the IC pins and sockets and even swapped IC's from the working board. No luck. So, I may just have to wait for the power supply regulators to arrive so I can have both machines side by side to make comparisons with.... Or I might just get frustrated and throw it off the bench!!! LOL! I am glad I got my customer's unit working at least!
Thanks again for your help!