Repairs to a CPC464.

[Bryce]

What have you measured so far? I'd check with a scope whether you are getting a signal at pin 6 of the Op-amp - IC302 - LM6324 and that you are getting the signal back out on pin 8. That will at least confirm that the read head and the amplification stages are working. If you're getting nothing on pin 8, then the problem has at least been narrowed down to a handful of parts.

Bryce.

[Audronic]

@Bryce


I have done nothing at the moment i just discovered that it would not load.


What is the best practical way to do tape repairs ?
Remove the Tape player from Keyboard assembly 
Or leave it there with a long (Homemade) Connection Cable. for Power, Control and Data after removing the wires for the LED. ?


Thanks    Ray

[Audronic]

The saga continues :-


Yes the second half of the LA6324 is Unwell.
Can I use an LM 324 in place of the LA6324 ?? The specs look similar .
I decided to remove the Cassette player from the Keyboard as it makes the job a little easier .
I have disconnected the Data out wire (Green) and also measured there to eliminate the loading back from the 8255.


What an interesting Project.


Ray 

[Bryce]

The saga continues :-


Yes the second half of the LA6324 is Unwell.
Can I use an LM 324 in place of the LA624 ?? The specs look similar .
I decided to remove the Cassette player from the Keyboard as it makes the job a little easier .
I have disconnected the Data out wire (Green) and also measured there to eliminate the loading back from the 8255.

What an interesting Project.

Ray

The LM324 has completely different characteristics. It would work, but you'd have to swap lots of other parts on the PCB to tweak the values back to where they should be. A lot of work for nothing and the LA6324 is still easily available so why go to all the bother?

Bryce.

[Audronic]

Oops the first search of EBay for the LA6324 came up with Nothing.
After your comments i had another look and have ordered some  from China.
Project on hold for 3 weeks.


Thanks     Ray

[pelrun]

Check the big online electronics part retailers (farnell/rs/digikey), they're usually a lot better than China/ebay for a lot of things.


Edit: heh, couldn't find them there myself, nevermind

[Audronic]

@pelrun


Thanks for the contacts.
I have already ordered from China  LM324 10 for $1.90 AU  La6324 10 for $19.00 . The specs look almost exactly the same as the LM324s
I will go to Radio Parts in Melbourne Monday and pickup a couple of LM324's (about $2.00 each) and see how they go.


Off topic My Boss had a callsign VK3?WB his initials (Not sure about the question mark Might have been AWB).
Well done in getting the VK4CPC (Queensland ??).


Ray

[pelrun]

Yeah, I'm in Brisbane. Wanted VK4PEL, but that's only for standard licenses (I'm advanced), so CPC was it.


Got it over a year ago, probably should update my sig...

[Bryce]

LA 6324: Op-amp, DIL-14 bei reichelt elektronik

Don't know how good the Aussi suppliers are, but in Europe it's a very easy part to find. Forget the LM324 it will only cause troubles. Use the correct part.

Bryce.

[Audronic]

Tape Deck Works Ok..


Replaced IC 302 and all's OK


Thanks for all the helpful advice


Ray

[Bryce]

Cool. Great repair. Very unusual that IC302 was damaged, they're actually very robust normally.

Bryce.

[Audronic]

OOPs The Fat Lady Stopped Singing 


The Random characters have come back to visit Damn------


Removing The AY-8912 at the moment.
If that does not fix the intermittent, then Big Cutters on the 8255


I hope it is a Merry Christmas.


Yours (Mildly Peeved)   Ray 

[Audronic]

Replacing the Ay-3-8912 appears to fix the Intermittent problem.


This is the second ay-3-8912 that i have had to replace in the 2 Faulty CPC's ??


It now is a Merry Christmas.


Ray

[AMSDOS]

Replacing the Ay-3-8912 appears to fix the Intermittent problem.


This is the second ay-3-8912 that i have had to replace in the 2 Faulty CPC's ??


It now is a Merry Christmas.


Ray

Hopefully it's not something else causing it to fault out.

[Audronic]

@amsdos


The 2 ay-3-8912's that i have replaced were in:-
1) 464
2) 6128

Both machines I purchased where known to be faulty.
I wanted a technical project, the best way to learn a new (to me) machine.

Ray

[AMSDOS]

Understood.