Cordovox piano G keys dead

[roughshawd]

Got this farfisa style electronic piano... It has an intonation problem in the c-c#d-d#-e section, and no g's will play. It is a pp23 unit, Italian piano, from the famous accordion maker. I bought the schematic and will attempt a fix... Does anyone know anything about these??

 

[roughshawd]

First remove 2 extreme corner screws to remove woodgrain cover. Boards are under keys accessed by removing two(2) screws on the bottom on the piano and lifting keys on hingesin front of the tone wiring harness...

Holy moses.... Full implementation on each key, that's 68 circuits...

 

[roughshawd]

First remove 2 extreme corner screws to remove woodgrain cover. Boards are under keys accessed by removing two(2) screws on the bottom on the piano and lifting keys on hingesin front of the tone wiring harness...

Holy moses.... Full implementation on each key, that's 68 circuits...

Axial where radial belongs...heh heh

 

[Martaine2005]

You could start by replacing all those electrolytics. But pull a couple around the G circuit and test them.

 

[roughshawd]

Yes, what I was thinking was the circuit between the octaves and the keys, in the (sol) or G note circuit may be failed cause all the G is the only thing that really wrong, it has tuners to correct the
intonation... Great idea!

 

[roughshawd]

Do Re Mi Fa Sol La Ti Do
C D. E. F. G. A. B. C

This is the G circuit..
Labeled 'sol' on the schematic.

The radial cap is probably ok...

I have never attempted to change an IC, and never hope to change one..
But from the lack of present sound
I certainly should find one...

 

[roughshawd]

The chips are all this kind ...

 

[roughshawd]

Do you think it's safe to replace the original K06 chip with a similar E06 chip?
Same make manufacturer , and chip number...saj011, just not k06...

 

[roughshawd]

Maybe the tuning pot has gone fritz...

 

[roughshawd]

Middle circuit is the "sol" or G key circuit. As you can see someone has dropped a large blob of solder on one of the transistor legs. So I'm not the first hacker in here…..
The board is contained within a box below the key set, accessable by removing two(2) screws, one on either end of the box. I will use some up close images for assessment before I pull the board.

 

[roughshawd]

Solder glob fell out while pulling the box...
(See image note electronics afficianados, protection shield to catch small parts and hinder shorting of boards)...

 

[roughshawd]

On the schematic, there is a table that says, CX CXIpf, it lists the notes the keys play from Do(C) up to Ti( typed Si, which is probably a typing mistake for Ti or B) and a corresponding value. Where C or Do is 6250 and Si, Ti or B is 6615, F being 4685 and F# being 8830. What are these values?

 

[roughshawd]

This shield is probably supposed to be fastened down.

 

[roughshawd]

Found one of the screws....

 

[roughshawd]

I put the screw in, closed the lid, nothing works...
There is 4.5v on the +9 IC rail....

 

[roughshawd]

Put the screw in the tone controls, and now nothing works...

Loose + broken connection somewhere in the wiring? I couldn't find a single wire trace. continuity tested all of them.. there is no wiring in this device... completely missing!!!

 

[roughshawd]

I'm thinking...

Anything that could change the input output on the chips might cause the failure I am experiencing, so I'm checking the resistors between the chips and the key switches, for low resistance or a blown component. 3.3 circuits ok. There is a hand written .1 k on the schematic which is rubbed, and looks like 1k...

 

[roughshawd]

All those 3.3k are reading between 2.8 and 3.2. there is some resistance there... Why I said they were good, maybe change the ones at 2.9 and lower??

 

[roughshawd]

I don't know what this is. Looks like a hairline fuse someone put in it.

 

[roughshawd]

Reflow required..