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PS-2 Board Repair part inquiry

Alan MancusAlan MancusOGR Forum Member DIGITAL SUBSCRIBER
are the voltages measures from ground or from the 2 black wires and 2 red wires rthat feed the board from the track rails.? would it help if i measure voltages on a good board compared to a bad board? also are there any type of circuit fuses on the circuit boards i could check? Any info would be helpful! thanks for any input you can give me. are the audio ic's available or not able to be purchased.
again thank, and have a very merry christmas to all who have helped. Alan
          Originally Posted by gunrunnerjohn:

There are no diagrams, even for MTH techs.  Those appear to be a closely guarded secret.

 

 

G GGGOGR Forum Member

If that is the small PCB board with 3 wires, red or green, yel and black that is a small 352A transistor part of the charging circuit.  I have not invested the time in tracking PS-2 5V other than the basics.  You can't get to the parts or you will find obsolete parts.

 

I think MTH was refurbing at one point, but they were still failing.

 

In general, AC is rectified for PV and also for PV for the 5VDC regulator.  Once you know you have good DC voltage out of the rectifier, every thing else is checked against the PCB DC Ground with is battery negative, and the blue wire pins.

 

Any testing against the AC Reference of outer rail will toast all the DC electronics, or at least most of them.  G

Last edited by GGG
Alan MancusAlan MancusOGR Forum Member DIGITAL SUBSCRIBER
Hi again i have trouble shot a ps2 5 volt board and processor board, this problem i had duscussed with john gunnerman, im replacing the 5 volt boards with the 3 volt ps2 boards but while i want taknig off the conectors on the old 5 volt boards i was curious what had failed on the boards as when the train is on the track it draws excessive current because the track swithc light iwas very dim, i found on the micro board a 28n05l i believe it to be a fet or voltage regulatr but the center pin is shorted to the outer pin on the  fet or regulator i cab't tell what it is but i tried to cross reference the part in my newest nte cross reference circuit book. could not find a cross reference. the only numbers on the chip was 28no5L and other number was AA831, im wondering if this is worth fixing also .Is there a chance the micorprocess board is nok>
Sincerely interested. any info form you or john would be appreciated.
Sincerely alan mancus  P.S. this is the boards i had previously talked about and the 330 uf 35 volt capacitor was puffed out but did not read direct short but it did read  only 130 uf instead the 330 uf is was suppose to be!
  Posted by GGG:

If that is the small PCB board with 3 wires, red or green, yel and black that is a small 352A transistor part of the charging circuit.  I have not invested the time in tracking PS-2 5V other than the basics.  You can't get to the parts or you will find obsolete parts.

 

I think MTH was refurbing at one point, but they were still failing.

 

In general, AC is rectified for PV and also for PV for the 5VDC regulator.  Once you know you have good DC voltage out of the rectifier, every thing else is checked against the PCB DC Ground with is battery negative, and the blue wire pins.

 

Any testing against the AC Reference of outer rail will toast all the DC electronics, or at least most of them.  G

 

G GGGOGR Forum Member

It is a fet, when you say shorted to the outer leg, do you mean the tab?  The center non attached leg is the same as the tab.  If it is shorted to one of the other legs that is a short on the FET.  I suspect that is one of the FETs that goes bad.  Hard to get to without separating the board, which is more trouble than worth in my opinion.  G

Alan MancusAlan MancusOGR Forum Member DIGITAL SUBSCRIBER
yes it is shorted center leg to right leg, i9 just could not cross reference the part. . do you have them and do you think it is worth trying to repair how much are the fets from you! and yes i knew the center leg was ground on the tab.
thanks again Alan  Mancus Originally Posted by GGG:

It is a fet, when you say shorted to the outer leg, do you mean the tab?  The center non attached leg is the same as the tab.  If it is shorted to one of the other legs that is a short on the FET.  I suspect that is one of the FETs that goes bad.  Hard to get to without separating the board, which is more trouble than worth in my opinion.  G

 

Alan MancusAlan MancusOGR Forum Member DIGITAL SUBSCRIBER
yes i have already seperated the boards thats how  i knew it was shorted . do you also have the  352a transister and if so how much.p.s. what is the fet used for.? thanks for any help you can supply Originally Posted by repair technician:
yes it is shorted center leg to right leg, i9 just could not cross reference the part. . do you have them and do you think it is worth trying to repair how much are the fets from you! and yes i knew the center leg was ground on the tab.
thanks again Alan  Mancus Originally Posted by GGG:

It is a fet, when you say shorted to the outer leg, do you mean the tab?  The center non attached leg is the same as the tab.  If it is shorted to one of the other legs that is a short on the FET.  I suspect that is one of the FETs that goes bad.  Hard to get to without separating the board, which is more trouble than worth in my opinion.  G

 

 

Alan MancusAlan MancusOGR Forum Member DIGITAL SUBSCRIBER
I separated them with a little heat from my soldering station and slow rock motion while heating the solder joint of the pins while hold both boards at the same time! it would have been much easier if you have 2 people one to rock the boards and one to heat the pins at the same time!thanks everybody for all your help! the only issue now is the FET parts i still need if i may purchase from one of you! again thanks Alan Originally Posted by gunrunnerjohn:

I'm curious how you separated the 5V board set without wrecking them!

 

 

G GGGOGR Forum Member

Order the LR2905 from digi key.  Some boards have shorted pins and seems like they can come apart, others won't work that easily as you bend pins and damage the internal traces.

 

I think you need to put the part back on, and hopefully it will work, but who knows you may have some other fault that caused the fet to go.  Like a short on an internal trace.  Which happens a lot on 3V processor boards.  G

Alan MancusAlan MancusOGR Forum Member DIGITAL SUBSCRIBER
don't forget George the boards I'm troubleshooting are 5 volt ps2 boards, I'm replacing the 5 volt boards with 3 volt boards but in the process I'm hoping to fix the old 5 volt boards by replacing the shorted FET! OK thanks for the info so i can buy the FET 2905 from international rectifier threw digikey again thanks Alan! Originally Posted by GGG:

Order the LR2905 from digi key.  Some boards have shorted pins and seems like they can come apart, others won't work that easily as you bend pins and damage the internal traces.

 

I think you need to put the part back on, and hopefully it will work, but who knows you may have some other fault that caused the fet to go.  Like a short on an internal trace.  Which happens a lot on 3V processor boards.  G

 

Alan MancusAlan MancusOGR Forum Member DIGITAL SUBSCRIBER
Hi john the proto 2 5 volt boards i found a shorted FET on the processor board waiting for the parts to come in and also repaired my z40-4000 transformer this evening,,transformer been running now for approximately 1 hour now. It's always a great sense of feeling when you repair something yourself with a little help from all you great guys on these forums. thanks everyone for all you're help Good luck with your repairs. Alan.Originally Posted by gunrunnerjohn:

I've never been patient enough to separate them.

 

 

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