Need help identifying old components

[minyaninja]

Hi! I'm trying repair an old Casio CPS-700 digital piano. I don't know when it was in production but my guess is it's from 80-90.
I have very basic knowledge in electronics but I'm decent at soldering so I tought I'd give it a go.
Initially the first problem I saw was a broken off capacitor but the board also had rust and corrosion from some spilled liquid I'm guessing. I cleaned up the board but in the process a component broke off and my best guess after researching is that it is a switching diode. I could not identify the symbol for this component on the board.

The piano is not mine from the beginning but has been in my posseion for 15 years and it has been working but stopped working probably when the capacitor broke off. The spilled liquid is not my doing and I wasn't aware off it until I disassembled the piano a few days ago.
Since the board had rust and corrosion on it I was thinking of getting my hands on all the affected components in case they need a replacement. But other than the diode there are 3 other components I can not identify.
One component is marked "YR 104K" which I think is a Y-type capacitor but I couldn't find any info on it. The other to components have 3 terminals and "222" marked on it. On the board they are inside a white triangle with EF/PC labeled on the middle pin.

The affected area of the liquid spill is highlighted
See attached images.

Any help will be greatly appreciated

Kristoffer

[Refrigerator]

Pic. 3, those are diodes but unfortunately there are no markings on the board that would tell if they're zener diodes or regular silicon diodes.

[Refrigerator]

Pic. 5 looks like a regular 2.2nF ceramic capacitor

[Gyro]

One component is marked "YR 104K" which I think is a Y-type capacitor but I couldn't find any info on it. The other to components have 3 terminals and "222" marked on it. On the board they are inside a white triangle with EF/PC labeled on the middle pin.

The "YR 104K"  is an ordinary 100nF 16 Volt ceramic disc capacitor, it looks fine, just clean the legs.

Pic 4, EF is a simple 3 pin RF noise filter - two ferrite beads and a capacitor from their junction to the middle pin (ground). If it still shows continuity between the outer pins and open circuit (or small capacitance) to the middle pin, then just clean it up and put it back. It's not critical.


P.S. Note that the 1uF 50V BP orange electrolytic is bipolar, not a standard polarised one.

[Gyro]

Pic. 3, those are diodes but unfortunately there are no markings on the board that would tell if they're zener diodes or regular silicon diodes.

Judging by the number of identical looking diodes scattered around the board, I doubt they are Zeners. 1N4148 would probably be a suitable replacement.


EDIT: There is actually a Zener on the board for comparison - it is above the red rectangle in the first picture, situated to the left of trimmer VR 30KB and clearly marked LTZ-MR15. This is probably further indication that the unmarked ones are ordinary signal diodes.

[minyaninja]

Thank you both for your replies, very helpful.

For reference I de-soldered 2 other types of diodes present on the board to get a better look on the symbol underneath.
And I do not know if it matters but there is also a ESB blue banded diode and a JSB black banded diode on the board.

[SilverSolder]

The other two diodes in the "rust zone" also need replacing, the steel leads are badly corroded.

I'd try some 1N4148  as @Gyro suggested.

[andy3055]

Thank you both for your replies, very helpful.

For reference I de-soldered 2 other types of diodes present on the board to get a better look on the symbol underneath.
And I do not know if it matters but there is also a ESB blue banded diode and a JSB black banded diode on the board.

That diode must be a Zener. See this page Item D103:  https://www.manualslib.com/manual/867918/Casio-M-300.html?page=10

[andy3055]

See also this: http://parts.pioneerelectronics.com/part.asp?productNum=RD4%2E3ESB2

[minyaninja]

Pic. 5 looks like a regular 2.2nF ceramic capacitor

Maybe it was unclear from the picture but it has 3 pins. So just to verify, is it a regular ceramic disk capacitor? 3 pin capacitors does not seem to be in the category of capacitors in my local electronics shop so I don't know what to search for or in what category to look in.

Here's a link to the shop https://www.electrokit.com/. It's in swedish but is available in english too.

I've attached a picture from the back side since it wasn't clearly visible from the fron side.

[Gyro]

They're an unusual one. I suspect that they might be dual ceramic disc capacitors to keep the component count down. With luck you can just unsolder them , clean up the legs if necessary and re-solder. They probably have tinned copper legs rather than steel anyway. As there are two in the affected area, you can do capacitance and continuity comparisons. The alternative is that they are similar to EF but I don't see anything to suggest magnetic bits.

You're really lucky that it is a single sided PCB, it would be a pain if you had to cope with plated through holes too.


Edit: identity (of package, not rating) confirmed... https://www.ebay.com/itm/P00914-1-Pc-Lot-dual-0-01-mfd-250-VAC-20-line-filter-ceramic-disc-capacitor-/291916538905  They're dual ceramic caps, yours will be low voltage ones.

[amyk]

Check the continuity. They may not be dual caps, but something like this: https://www.murata.com/~/media/webrenewal/products/emc/emifil/knowhow/20to22.ashx

[minyaninja]

I browsed through numerous casio service manuals and did find out what EF (EMI filter) and PC (Three polarity capacitor) refered to. I also found the exact part for the diodes that need replacing - https://octopart.com/1ss133t-77-rohm-323636.
Here's a link to the filter altough I'm not sure if it is the same rating as mine aliexpress.
As for the 3 pin capacitor, there is continuity between pin 1 and 3 but I have no way of measure the capacitance. I searched for all partnumbers specified for this component in the various manuals but couldn't find anything.

I'll do as @Gyro suggested and clean it up and see if it works when I have the other parts.

[Gyro]

Ah, @amyk was correct on the capacitors then - basically a lower inductance version of the EF parts.

I wouldn't worry too much about the capacitance readings, these things are unlikely to be critical in this application.