Great. I wouldn't worry too much about unplugging the cables for the photos.

What I want to know is are the ICs socketed?

Where are those components labelled FL? These are the inductors supplying power?
We need to probe both ends of each FL.

Wise idea to build a temporary shelf for the scope. As you say, it is better to be facing the scope while probing.

For photos, use a tripod. It would be better to use manual focus if you have it on your camera. Flash should be ok. If not, make sure you have bright lights.

Good luck. Take your time.

 

I hope the next video you take is you playing "Bridge over troubled water" with your CVP-50 for us all here....

Allen

 

I hope the next video you take is you playing "Bridge over troubled water" with your CVP-50 for us all here....

Allen

And not humming "Oscilloscope over troubled piano"

 

Sorry for the delay guys, I have had a few issues. One major one is that I have forgotten how to use my CRO properly. I am currently reading the manual to get the best out of it. (It took me almost an hour to remember the formula for frequency) Also, one of my Oscilloscopes died when I was playing with it. (I didn't think what I was doing anything wrong, all I did was had the 1KHz Cal signal running and I must have hit a wrong setting and it screwed up the input, it was only a cheepy so no big deal) So I thought I better make sure I don't bust a second one. I will have to get you guys to have a look at my busted CRO at some stage. (Another project)

Its all happening ASAP.

Thanks.

 

Thank you so much for that nicely written piece of text.

 

You cannot destroy a scope by messing around with the front panel unless you input a couple of kilovolts into the inputs.

I would not be surprised if the problem with the scope is incorrect setting with the trigger settings.

 

This is the Post where I will be posting all measurements. (It seems logical to me to have them in one location)



Hello, Sorry for taking so long, but you know life.


I have finally made some measurements. And I have started from the PS reading Voltages and Ripple voltages.

The following is measured from connector CN1. Which is the main power connector to the Main Board. This is a 13 Pin connector.


Pin_______Ideal_______Actual________________Ripple

1________(-12)______(-11.91)_________Negligible Approx 100mV
2
3________(GND)
4
5________(+12)______(+12.01)________Negligible Approx 100mV
6
7________(GND)
8
9
10_______(+5 )______(+5.04)_________Negligible Approx 100mV
11
12
13_______(+B)______(+8.83)_________Significant Ripple @ Approx 500mV

Note all pins after noted voltages are tide to preceding pins. Pin 13 is the exception.


In the next stage I wanted to test past the first components directly connected to CN1. These are noted as SNx6 on the Schematic. They look like small coils, you can see the Copper windings. They are encased in black square boxes with the winding visible from the side. As this is a double sided board, I could not see, or get to all pins, so I had to find the nearest component they were connected to. Hence I probed IC59 for both -12 and +12.

IC59
Pin5 measured at -11,91
Pin1 measured at +11.96
GND was taken from CN1

+B was passing also over SN (Coil) @ +8.83
+5 was tested on previous occasion @ CPU and Sub CPU

This seems to tell me the the power supply is OK and power, at least somewhat to CN1 and past the 6 Coils (SNx6).


Next voltage I hunted for was the Plus and Minus 6.5V. Again note sure where this is originating from, I attacked IC52 (TC4051) as this seemed the nearest place to measure.

IC52 Ideal Voltages +/-6.5V respectively.

Pin 16 = +6.25
Pin 7 = -6.25
Used Pin 9 for GND.



Well nothing I can see wrong here. I will Keep plugging away. I have a few more voltage dividers to check.

BTW, Can anyone tell me what those SN components might be. ?
Also, are all GND's equal ?
What does FL stand for all over the Schematics. (Oh Inductors)


Thank you.

Now that I have it all set up, I will be updating sooner.

Regards
Steve.


02/08/2012 (Day 2)

Edit. Today I will take the HiRes Images. Done see below. #49
Update. Seemingly NO MIDI Data sending or Receiving, to or from an external MIDI device.

QUESTION, about -5 reading as +5 @ D2-D5 Series (see below) #50 Confirmed typo. TY Mr Chips.

IC1 (KPU) Checked for +B @ Pin29. Measured at +3.7V with a Ripple of Approx 250mVP-P. The source voltage of +B was measured at +8.8V (Today it measured +9V). It runs via a 4.7KOhm resistor to Pin 29 on IC1. (Note I find this +3.7V questionable. If its meant to be a HI (Normally +5 TTL). Seems a strange value. However, this is all guess work as the Schematics give no clue what this should be. I will hunt for Data Sheet. (Could not find Data Sheet)

QUESTION, Significant P-P Ripple along +B (Ranging from 500mV P-P (Source) to 250mV P-P @ Pin29 IC1) ?????


IC1 (KPU) Measured CLK and all ok @ 4MHz.
KPU stands for Keyboard Processing Unit.


03/08/2012 (Day 3)

Printed the SM and uploading Mainboard Images to Flickr.
Mainboard images > http://flic.kr/p/cJNQkA (If you would like more please ask)

When viewing, please notice the modification. Source unknown. I am assuming its an inhouse mode purely from how well its done. I don't believe this is on the schematic. (I have not checked)

Ran the units Test procedures as pure service manual with no results.

 

Great. I wouldn't worry too much about unplugging the cables for the photos.

What I want to know is are the ICs socketed?

Where are those components labelled FL? These are the inductors supplying power?
We need to probe both ends of each FL.

Wise idea to build a temporary shelf for the scope. As you say, it is better to be facing the scope while probing.

For photos, use a tripod. It would be better to use manual focus if you have it on your camera. Flash should be ok. If not, make sure you have bright lights.

Good luck. Take your time.

Mr Chips,


No the ICs are NOT socketed. (Some are pin soldered through the board others are Surface Mounted. (Only 2 are which look like Eproms)
I will find and probe those FL's today.
Photos also today.

I have purchased another CRO, so I should be able to upload my Waveform images.

Thanks
Steve

 

Quick update, more voltages to check tonight. Below are the Images of the Main Board. Please let me know if these are acceptable. If not, I can try again. I used a Digital Cannon EOS 450D.

There are 2 shots of the Main Board. Then 4 shots dividing the Main Board into 4 Parts for a closer view. (One rar file)

http://www.sendspace.com/file/uwjkdm

NOTE (TO DOWNLOAD the Images (rar), got to site mentioned. and scroll down to "Click here to start download from sendspace" in the BLUE box with the BLUE ARROW. (Other download links are deceiving)



Thanks

Will post more later.


I am still determined to hunt this fault down. At this stage I have not even had a hint of the problem. Baby steps.

Thanks
Steve

Also I am going to connect an external MIDI device to see if there is any activity. (He's hoping)
Update. Seemingly NO MIDI Data sending or Receiving.

Back to the remaining PS Voltages. (Its going to be a long night) (The Power of Positive Thinking, N.V Peale)

BTW, I am thinking it might be best to write up all my tests in one post. Other wise this will get messy. ? I will date them. ( See previous post ) Then again it may not flag that I have updated and you guys might forget about me. LOL. I might do both.

A quick thank you to MR Chips. How on earth you spotted where that +B went is beyond me (IC1 PIN 29) Well done.

UPDATE These are now on Flickr http://flic.kr/p/cJNQkA

 

QUESTION, Can someone please have a look at the following Image taken from the Schematic. The voltages in red are the measured. The -5 is reading as +5 ? Is this a typo on the Schematic. ? (Voltage read at +5 with GND taken from D2 Cathode)

http://www.flickr.com/photos/84062034@N07/with/7696888992/


Confirmed typo. TY Mr Chips.

 

Yes, that is a typo. The correct marking should be +5.

 

As far as I can tell, the SN and FL are simply the first two letters of the component identifiers:

SN3-205 10μH
FL5R200QNT 20μH

These are all inductors used as power supply filters.

Locate all the SN and FL components and measure the voltage at both ends of the coil with respect to GND.

We're hoping to find one that is blown (open circuit) feeding a dead capacitor (shorted to GND).

Look for burnt or damaged decoupling capacitors.

 

For no particular reason. 2 shots of the project.

http://www.flickr.com/photos/84062034@N07/7702515312/

http://www.flickr.com/photos/84062034@N07/7702519910/

 

I have not been able to view the photos you posted in post #49 (because of the rar format).
I will give it another try on a bigger computer.
Any chance you can post smaller photos on flickr?
It may be best to post small areas of the board instead of one huge photo.
I don't mean to be a nuisance.

 

I have not been able to view the photos you posted in post #49 (because of the rar format).
I will give it another try on a bigger computer.
Any chance you can post smaller photos on flickr?
It may be best to post small areas of the board instead of one huge photo.
I don't mean to be a nuisance.

Not a nuisance at all. I am glad for the help. I have taken a break from it tonight though I did spend a few hours printing the Service manual. (Was getting frustrating viewing it on the PC)

I will take more shots, and upload to flickr. Let me know if you have any success with the rar. If not I will upload them to flickr.

Thanks heaps.
Steve

Edit let me know if you find those pics use full. (But if you can't open them that doesn't help) I can re-upload as a ZIP if you like ?


UPDATE. Don't worry, I will upload them to flickr regardless. It can't hurt.
Mainboard images now on flickr http://flic.kr/p/cJNQkA

 

Mainboard images (Previously were one rar file as per Post #49) are now on Flickr.

http://flic.kr/p/cJNQkA

The board is also divided into 4 separate images for further resolution/close up. (See flickr)

I will take some better shots. ASAP


When viewing, please notice the modification. Source unknown. I am assuming its an inhouse mod purely from how well its done. I don't believe this is on the schematic. (I have not checked)

Please see Post #47 for full progress. (This is where I will be updating all progress and measurements)

 

I did a little more testing tonight. I had a theory that If IC1 Keyboard Processing Unit (KPU) is functioning, and I am assuming it is because its CLK is running, that I should see some MIDI OUT data activity with a Key press.

Why? Because the Keyboard is obviously connected to the KPU as is the MIDI. I was trying to prove that this IC was OK. So far this test has been a failure. Tomorrow I will double check this as I may have not connected the Scope up to the correct GND when testing. (I only found this out later)

What concerns me is that if this IC is dead this unit is a goner. Also, I noticed that someone has Penciled some numbers on the back of this IC1 (KPU). (Looks like a date) If this IC was the original failure, the dead display my only be a consequence from some other person fooling with the unit and inadvertently knocked out the display. (i.e there is actually 2 faults completely unrelated) Clearly one of the biggest problems purchasing broken goods is not knowing the units history. And they will never tell you the truth. (Or rarely)

I have been studying the block diagram looking for what might cause both the Keyboard and the display to go simultaneously. Assuming one fault.

Are assumptions dangerous (joke)

The most common point I can see on the Block Diagram is IC9 the PPIA 82C55. So working on the "one fault" hypothesis, this component looks to me it would indeed take out the display/control panel and Keyboard.

Tomorrow is another day. We might get lucky

Cheers
Steve

 

Ok, I've extracted the photos from the rar file.
I will be looking for those FL and SN filters.
Seems to me that it would be easier to go directly to the power pin (Vcc or Vdd) of the chip and measure the voltage.

 

Ok, I've extracted the photos from the rar file.
I will be looking for those FL and SN filters.
Seems to me that it would be easier to go directly to the power pin (Vcc or Vdd) of the chip and measure the voltage.

Its not uncommon for me to over think things. When will I learn.

Will do.

Thanks

 

As far as I can tell, those FL components are ferrite inductors so I don't expect them to blow.

I will have to look over the circuit and look for operational clues on all the major processors.