SE/30 RP12 replacement part, bourns filter

[lowlytech]

RP2 on my SE30 has a case of the green legs on both sides and there is about 4 bad traces in that area.  Pulled up the RP12 last night to get a better idea on repairing the traces and thought I would replace the chip while I have it out.   Checking if this is the right replacement part from Mouser..

https://www.mouser.com/ProductDetail/652-4120R-601-201L

 

[superjer2000]

I can't say for sure as I haven't tested it, but I found some other older threads that showed this to be the right replacement for the Bourne filters on an se/30.  https://www.mouser.ca/ProductDetail/652-4116R-1LF-47. (I think there is only one type of filter in the se/30?)

ive ordered some but haven't needed to use them yet.  I think the threads were with uniserver on thinkclassic but I can't find them readily now. 

 

[lowlytech]

I do recall in my google searching, running into a post somewhere that showed someone subbing a 16 pin filter for the original 20 pin one.   That or maybe apple themselves changing to a 16 pin later in the SE's lifetime?   So is this filter just a resistor network, or is it suppose to have capacitors in it as well?  The original filter I pulled out shows typical ohm readings on the middle most pins, but a few act like something is discharging as the value fluctuates.

 

[lowlytech]

Well not sure what is different, but the original filter I pulled now tests 44.8~45.2 ohms across all the pins except the four on the ends which are common ground.  The new filter I got today (4120R-601-201L) tests 50.0 ohms across, with the same four pins on the corners as a shared ground.  Will 5 ohms make a difference in this application? I guess I could put the original filter back in, but after trying to clean it up the legs are still pretty much tarnished with green/black.

One other thing, mouser lists this as 20 pin 200ohms.  Am I measuring wrong since I only get 50 ohms?

 

[BadGoldEagle]

Topic already discussed here: 







4120Rs are 20 pin packages and 4116Rs are 16 pin packages. 

4120R-601-250/201 are available on farnell. 

 

[lowlytech]

I take it that the L vs LF on the part number 4120R-601-250/201 should be an okay substitute? The last post from that thread was in 2013.  Throughout that thread it sounded like they had some issues locating stock.  The 2nd post shows a datasheet with capacitors within the filter.  I am not seeing this on the current datasheet, however the part numbers seem to indicate the same chip.   I think I will end up installing a 20 pin DIP socket and that way I can easily swap the chip, assuming the one I have now won't let the magic smoke out of the board.  

 

[BadGoldEagle]

uniserver uses this part # to replace the original filters. It works as it should and as you mentioned, it’s a drop in replacement. I need to get one for my SE 1/40.

 

[trag]

Okay, that was confusing. 

Going back to the first post...   If one follows the link in that post:

https://www.mouser.com/ProductDetail/652-4120R-601-201L

Mouser lists the proper filter replacement.   However, the datasheet they list as going with that Bourns part is wrong.  Mouser has the Datasheet wrong.  It's been puzzling me for a couple of days.  If you look at the part number decode on the datasheet, which Mouser links, the middle number should just be a 1, 2 or 3.  Not a 601.

Here is the proper datasheet for that part: 

https://www.bourns.com/pdfs/601.pdf

4120R-601-250/201 is indeed an Resistive/capacitive network.    Mouser drops the 250/ from its in house part number but lists the proper Bourns manufacturer part number.  This combined with the wrong datasheet concerns me.  I'm not convinced Mouser is shipping the proper part.

The part that Superjer2000 lists is just a resistor pack.    It provides no filtering, although it could reduce ringing on over powered lines.

I'm not sure which part BaldGoldEagle is referring to.  At one point Uniserver recommended a part that is just a resistor pack.  And maybe Apple used those in some machines.    So they may be good enough.  However, with no capacitive element, they aren't really filters electrically speaking.

View attachment 601.pdf

 

[lowlytech]

Found this reference that matches the datasheet that has capacitors inside the filter.  

http://jerome.vernet.pagesperso-orange.fr/SE 30/Repair Mac.html#NoPointer

The mouser part I ordered 652-4120R-601-250/201L definitely does not test the same for resistance and/or capacitance from the original yellow 115-0002; c 5SB filter that was there, assuming the original part is still good.

 

[Mk.558]

Digikey has them in stock. https://www.digikey.com/short/ppd2mf

I could assume that if you measure 50 ohms across then you should be okay -- the original may not meet that exact spec because of resistance tolerances. 10% tolerance is a lot for a resistor, however.