noregret4life

Posts: 1,092

Country:

Thanks: 1

Thanked 17 Times in 11 Posts

I was given an older Casio AP-21 today.
When i turned it on...

It first powered up fine, all lights went on.
I started to check all the keys, they were playing fine.
About half way the sound started to distort, bunch of the LEDs including power started to go on and off.
Then the unit powered off.

Now when i hit the power button, i see the power LED blink once, then stays off. None of the other LEDs light up, and there is no response from any keys or buttons.

However, i can hear feedback from the 2 speakers when i raise and lower the volume. So it seems that the AMP is still working but the rest of the piano is dead???

I opened the top to check the fuses, and everything seems to be in order. Also looked around for anything burned and couldn't find anything either.

I'm just a beginner and was very excited about the unit.

I downloaded the repair manual a few hours ago and found out the the Main PCB is to be replaced.
MAIN PCB JCM425-MA1M

There is no one online that sells it, and i really have no clue where to turn.

Is there anything that can be done?

I assume i have to take it to a repair shop, but i am just fearing the costs could be more than what the damn thing costs entirely.

Any experts out there? I can send all the tech drawings layouts and so on.

The parts seem very like you can find most of them at radio shack.

Woolly

Posts: 972

Country:

Thanks: 28

Thanked 26 Times in 16 Posts

Sounds like a power supply problem. Have a look at the main circuit board, and roughly trace from where the power comes in, back through any associated components. It actually sounds typical of a voltage regulator or bridge rectifier going - when these are on the way out, they tend to work intermittently till they give up all together. Look for any areas on the PCB which seem to have been getting hot.

__________________


To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.



2005 BMW LT - 16 countries, 2 CONTINENTS & counting
2004 MB SLK 350 Andradite Green (6 speed manual]
1999 Ducati ST2
2003 Vauxhaul Vectra
1974 Triumph Bonneville 750 T140V
1937 Norton 500 single
(all still current)

noregret4life

Posts: 1,092

Country:

Thanks: 1

Thanked 17 Times in 11 Posts

Woolly, thanks for the info.

I checked the power supply, and according to the service manual, it is outputting the correct voltage. According to the service manual it states that my "Main PCB" needs to be replaces. and according to Casio parts its $500. Which the piano is not worth.

Here is the service manual. Maybe it can help.
http://myfreefilehosting.com/f/d59fc301d7_4.82MB

I am not sure if the main PCB board can be repaired.
Just a shame, it is a really nice unit.

Thanks for the help

rlbawk

Posts: 275

Country:

Thanks: 16

Thanked 10 Times in 10 Posts

Not sure of the model number but I have a friend whos son had a Casio that actually caught their house on fire. Apparently there was a power supply problem and it was a known issue with them that they found out after the fact. You may want to check on that part of it, his wasn't even turned on at the time.

noregret4life

Posts: 1,092

Country:

Thanks: 1

Thanked 17 Times in 11 Posts

The Power supply outputs 21v AC and 8v AC as it should at the pins. So it seems to be working fine. On Page 12 in the service manual i posted above, it states that if they voltages are correct, the problem lies with the Main PCB.

I just wish i knew which part of the Main PCB needed fixing. May need to bring it to an expert, but they are going to charge an arm and a leg for this, which may not be worth it.

Woolly

Posts: 972

Country:

Thanks: 28

Thanked 26 Times in 16 Posts

Sorry, meant the power supply of the main PCB, not the lump you plug in. Read it again, bearing in mind you're looking at the board, not the power adaptor.

__________________


To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.



2005 BMW LT - 16 countries, 2 CONTINENTS & counting
2004 MB SLK 350 Andradite Green (6 speed manual]
1999 Ducati ST2
2003 Vauxhaul Vectra
1974 Triumph Bonneville 750 T140V
1937 Norton 500 single
(all still current)

noregret4life

Posts: 1,092

Country:

Thanks: 1

Thanked 17 Times in 11 Posts

Wolly, After your first message, i've been at it all night. (didn't see the last one till after it all)

You were 100% correct. I found the issue and it was with the Stepdown regulators which blew. I was tracing the wiring to the main PCB module and used the diagram to check all voltage along the way. All checked out but 1, which just happened to be the same voltage as the power supply on the other end of the board where the Main PCB connects to the amp/power board.

Traced it all back to a 10v to 5v regulator that needs to be replaced. $0.40 !!!!!!!! + $5 shipping... Hell that sounds much better than the $500 quoted by Casio!!!!

To test that it was actually this regulator that blew, i connected 4 AA 1.2v batteries, and powered the circuit directly after the regulator... Piano turned on just fine!

Thanks again for the help and the nudge in the right direction.