Bad day in the office / L33 details

[macsonny]

Hi All,

 

Just discovered that I've somehow managed to break off L33 on my 520STFM. Look like there are normally 3 of them in a row and I've broken off the top one.

 

The broken part has "102" with the 2 underlined stamped on it.

 

Anyone know what the value of this item is and any specifics I need to know when purchasing a new unit?

 

Thanks

 

macsonny

[TGB1718]

It's a 1000uH inductor, however it looks like it has 3 terminals so may have 2 inductors internally.

 

The center terminal looks like it's connected to the ground plane, unfortunately I can't find a circuit diagram

of this revision board that shows these inductors type.

[TGB1718]

Just found a diagram that shows the device, as I suspected it's a double device with an internal capacitor to ground.

Sorry for the fuzzy picture, but this is the best I could find.

It's connected in series with one of the Floppy Disk lines (they all have one of these), again it's so fuzzy I don't know which

line it's connected to.

 

The good news, as long as you can source one I don't suppose it matters which line its on.

 

I got this detail from the 1040ST circuit diagram, so the actual component names may be different, but functionally they

are identical. 

[TGB1718]

If you have trouble sourcing one of these, you could solder 3 vertical wires into the circuit board and lay this device on top of the

remaining 2 and see if there's enough of the stumps on the device to solder these wires onto, not ideal, but maybe worth a try.

 

Failing that you could put a shorting link across the 2 outer pins (please avoid the centre pin), it should work ok, but you never

know how much noise could be on that line (this is the last resort  )

 

[snarkdluG]

Not all motherboards have filters. Some just have 0 ohms resistors in place instead. Some have filters on the MIDI ports but not on parallel/seriell ports. Maybe due to noise on the revision of board or just pure luck on what they had at stock in the factory perhaps. Who knows?

 

[macsonny]

It looks like the filters are for the MIDI port. My unit boots fine now as it appears the booting issue was with my 4 meg upgrade - not the inductor. 

 

The inductors are right next to the MIDI ports so I figure it's filtering for the MIDI as you have suggested. I might just leave for now as everything seems to be working now.

 

[TGB1718]

2 hours ago, snarkdluG said:

Some have filters on the MIDI ports

You are right, L33 is on the Midi out port, it's not on the signal lines, but on a pullup resistor, so unless you

plan to use Midi it's all good, personally I think there's no real need for the inductor there, I think a link

would be ok.

[JamesWD]

These are what i had in my ST that i used to replace :

 

https://uk.farnell.com/murata/dss1nb32a102q91a/cap-1000pf-10-100v-6a-radial-th/dp/3471207?CMP=e-email-sys-orderack-GLB

 

If you look at the datasheet it is exactly the same internals as detail 2 from the ST schematic 

[macsonny]

12 hours ago, JamesWD said:

These are what i had in my ST that i used to replace :

 

https://uk.farnell.com/murata/dss1nb32a102q91a/cap-1000pf-10-100v-6a-radial-th/dp/3471207?CMP=e-email-sys-orderack-GLB

 

If you look at the datasheet it is exactly the same internals as detail 2 from the ST schematic 

Thank you! Perfect.