I have a Mission PCM II, owned since new.
Problems started a few months ago, the display would go on or off at random, but still played fine.
Then it got random about whether it would play or not - but once working it continued as long as it remained powered up.
Now the trasnport drawer will open, but won't close using the open/close or play buttons - it will close using a light finger push - and won't respond to any other buttons.
I have unplugged and checked all the internal connectors - all were clean and shiney. Also visually checked the boards for poor joints or corrosion but can't see anything obvious.
The PCB under one voltage regulator is blackened - could this be a result of the component failing? There are other signs of heating around many components, but none are black like this.
Could this failure cause the symptoms I described? Any other suggestions as to what else I should check?
I can email higher res pictures if this would help.
Thanks in advance,
Andy
Problems started a few months ago, the display would go on or off at random, but still played fine.
Then it got random about whether it would play or not - but once working it continued as long as it remained powered up.
Now the trasnport drawer will open, but won't close using the open/close or play buttons - it will close using a light finger push - and won't respond to any other buttons.
I have unplugged and checked all the internal connectors - all were clean and shiney. Also visually checked the boards for poor joints or corrosion but can't see anything obvious.
The PCB under one voltage regulator is blackened - could this be a result of the component failing? There are other signs of heating around many components, but none are black like this.
Could this failure cause the symptoms I described? Any other suggestions as to what else I should check?
I can email higher res pictures if this would help.
Thanks in advance,
Andy
Attachments
Andy. Have you checked the voltage going to the regulator ? Check the others and see if you can see the type eg 7805 =5v, 7815 =15v 7812 =12v etc. (negative regs are - 7805 etc)
If you don't get any reading or an odd reading for the bleckened one then it will need replacing. You should check to see if any caps in the chain are shot.
For testing purposes the regs 3 legs (viewed from the front) is In, Gnd, Out.
Higher res pics would be of help.
If you don't get any reading or an odd reading for the bleckened one then it will need replacing. You should check to see if any caps in the chain are shot.
For testing purposes the regs 3 legs (viewed from the front) is In, Gnd, Out.
Higher res pics would be of help.
Please post photos of the supply area.
I'm trying to remember what Philips model this is based on. Anyone?
Andy
I'm trying to remember what Philips model this is based on. Anyone?
Andy
Great response already, thanks!
The regulator is a MC7906CT.
Searching old threads suggests the PCM II is based on the Philips CD660 - uses a TDA1541A S1 and SAA7220P/B.
Here is a close-up of the regulator.
I'm a newbie when it comes to checking components - I've replaced 'memory' caps in 2 tuners and replaced a timer IC and LCD driver IC on a speed display board, but that's my limit so far. I have a digital multimeter, and willing to learn, so please excuse any dumb questions!
The regulator is a MC7906CT.
Searching old threads suggests the PCM II is based on the Philips CD660 - uses a TDA1541A S1 and SAA7220P/B.
Here is a close-up of the regulator.
I'm a newbie when it comes to checking components - I've replaced 'memory' caps in 2 tuners and replaced a timer IC and LCD driver IC on a speed display board, but that's my limit so far. I have a digital multimeter, and willing to learn, so please excuse any dumb questions!
Attachments
Here is the back end of the board - the regulator is just hidden under the loose grey/black 5-pin connector (sorry - took the pic before finding the black bits).
Hopefully you can also see the brown discolouration around quite a few of the resistors. Is this normal for old boards, or does it suggest that everything has been getting hotter than it should?
Hopefully you can also see the brown discolouration around quite a few of the resistors. Is this normal for old boards, or does it suggest that everything has been getting hotter than it should?
Attachments
That regulator is a -6v.
It looks hot enough to have melted the solder and also the pcb trach looks to be cracked. It could be the photo angle.
Scrape off the black stuff.
Andy
It looks hot enough to have melted the solder and also the pcb trach looks to be cracked. It could be the photo angle.
Scrape off the black stuff.
Andy
PC at home crashed yesterday so had to spend the evening trying to fix that .....
Local shop had every other type of 79xx regulator in stock except a 7906 - they'll have one for me later this week, so I will replace it anyway and see what happens.
I'll keep you posted.
Thanks again.
Andy
Local shop had every other type of 79xx regulator in stock except a 7906 - they'll have one for me later this week, so I will replace it anyway and see what happens.
I'll keep you posted.
Thanks again.
Andy
Finally found time to look further.
A meter across the regulator (7906) shows Vin = 13V, Vout=7V
Data sheet says it should be 8-21 V input and 5.7 to 6.3 V out.
Local shop still hasn't managed to get a replacement - any ideas of where to get one without a huge carriage cost?
I also checked the tracks and get typically 0.1 to 0.2 ohm from the regulator solder 'blob' to the next component along the track (without scraping the connection clean).
The 47uF caps across the regulator appear to charge (using a continuity check across the regulator, I get a reading then it stops).
Any more ideas? The controller chip on this board is an MAB8461P/W127.
Andy
A meter across the regulator (7906) shows Vin = 13V, Vout=7V
Data sheet says it should be 8-21 V input and 5.7 to 6.3 V out.
Local shop still hasn't managed to get a replacement - any ideas of where to get one without a huge carriage cost?
I also checked the tracks and get typically 0.1 to 0.2 ohm from the regulator solder 'blob' to the next component along the track (without scraping the connection clean).
The 47uF caps across the regulator appear to charge (using a continuity check across the regulator, I get a reading then it stops).
Any more ideas? The controller chip on this board is an MAB8461P/W127.
Andy
Available from EBAY.
http://cgi.ebay.co.uk/Voltage-Regul...oryZ4663QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Buy a couple !!
Andy
http://cgi.ebay.co.uk/Voltage-Regul...oryZ4663QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Buy a couple !!
Andy
Use a 7905 with i diod i series with the gnd pin to get 5.7V - if that voltage is ok!? (or use two diodes for 6.4V)
/R
/R
poynton said:
I did, thanks for the link - fitted one, and now have correct -6V on that track.
Problem is still there though.
I have a work colleague who might be able to help me out understanding how to check the MAB8461 controller - but any other help is welcomed!
Andy
MAB8461P W127 for PCM II
Dear Andy,
Nice to contact you, I probably have the same problem in my CD player(Mission Cyrus PCM II).
And a professional craftman said that the controller IC MAB8461P W127 seems to be dead as you posted in the bulletin.
Have you successfully solve this problem?
Where is it available to find the part(MAB8461P W127)?
I hope to receive good news soon.
Tanks in advance!
CHAE
Dear Andy,
Nice to contact you, I probably have the same problem in my CD player(Mission Cyrus PCM II).
And a professional craftman said that the controller IC MAB8461P W127 seems to be dead as you posted in the bulletin.
Have you successfully solve this problem?
Where is it available to find the part(MAB8461P W127)?
I hope to receive good news soon.
Tanks in advance!
CHAE
Hi Chae,
Sorry, can't give you any good news. I cannot find anywhere that has the controller with the W127 program.
I have tried a 'wanted' advertisement on here to see if I could get either a chip or a complete machine, but no luck there either.
If anyone has a machine / board / chip that they want to sell or loan so that I can get my colleague to decode a working chip, please contact me.
Andy
Sorry, can't give you any good news. I cannot find anywhere that has the controller with the W127 program.
I have tried a 'wanted' advertisement on here to see if I could get either a chip or a complete machine, but no luck there either.
If anyone has a machine / board / chip that they want to sell or loan so that I can get my colleague to decode a working chip, please contact me.
Andy
Thanks for kind information
Hi Andy,
Thanks for the kind answer.
Hope to keep correspondance....
Good luck!
Hi Andy,
Thanks for the kind answer.
Hope to keep correspondance....
Good luck!
Sorry, this isn't particularly helpful, but are you sure it's a Mission PCM II? The insides of yours don't look like the insides of mine. The insides of the PCM II look like the picture in post #23 of this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=60144&perpage=25&pagenumber=1
Yours looks more like the PCM 7000, the insides of which are shown in post #1 of the same thread.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=60144&perpage=25&pagenumber=1
Yours looks more like the PCM 7000, the insides of which are shown in post #1 of the same thread.
Definitely a PCM II
We have the same machines - in my picture, the top 2 boards (i.e. the 2 big green boards in your picture on post #23) are removed to expose the lower boards.
The PCM 7000 has 2 lower boards on the RHS (as viewed from the front of the player), whereas the PCM II has only one (white) which carries the controller chip.
Andy
We have the same machines - in my picture, the top 2 boards (i.e. the 2 big green boards in your picture on post #23) are removed to expose the lower boards.
The PCM 7000 has 2 lower boards on the RHS (as viewed from the front of the player), whereas the PCM II has only one (white) which carries the controller chip.
Andy
rwtompkins - just read through the other thread - I assume you did finally get your boards out successfully?
I've had mine apart several times, so PM me if you need any advice on doing that.
Andy
I've had mine apart several times, so PM me if you need any advice on doing that.
Andy
Re: Definitely a PCM II
Doh! What an idiot I am. So sorry, Andy - was only trying to clarify things a bit.
Yes, I did get the boards out in the end. Sure enough, the chip was a TDA1541A but I've since acquired another PCM II which turned out to have a TDA1541A S1 (single crown). What a find! However, the player itself isn't in very good condition - one of the big caps is leaking, for starters, and the CD tray misbehaves - it keeps closing as soon as you open it, before you have time to insert/remove a CD. Anyone got any idea what this could be?
I'm thinking of amalgamating the two machines, in which case I might have parts left over that would help you, but it's all a bit iffy at this stage.
I would lend you one of my machines but I'm in London and I don't really want to post it, even if it were affordable. However, if you're ever passing...
I love these machines - wonderful sound for next to nothing second-hand, and how could anyone resist that fantastic display?
AndrewB said:
Doh! What an idiot I am. So sorry, Andy - was only trying to clarify things a bit.
Yes, I did get the boards out in the end. Sure enough, the chip was a TDA1541A but I've since acquired another PCM II which turned out to have a TDA1541A S1 (single crown). What a find! However, the player itself isn't in very good condition - one of the big caps is leaking, for starters, and the CD tray misbehaves - it keeps closing as soon as you open it, before you have time to insert/remove a CD. Anyone got any idea what this could be?
I'm thinking of amalgamating the two machines, in which case I might have parts left over that would help you, but it's all a bit iffy at this stage.
I would lend you one of my machines but I'm in London and I don't really want to post it, even if it were affordable. However, if you're ever passing...
I love these machines - wonderful sound for next to nothing second-hand, and how could anyone resist that fantastic display?