U951 is a 3 legged regulator. It will look like a transistor with a metal tab and from the diagram it may or may not be located on the main board. It's probably on a heatsink... might be on the board, might be wires to it at a separate location.
U953 is a fuse, looks like this probably,
U953 is a fuse, looks like this probably,
Attachments
Thanks - U953 I can find (it looks just like the pic you sent) but I'm having some trouble finding U951 - I'll look more and probably reply tomorrow.
Thanks again for your quick response!
U953 is mounted so tightly to the board I can't get a probe in there to measure. If I can find the specs for that and U951 I would just pull the board and replace both.
Question: If a "fuse" blows - doesn't that mean there's another component that also failed? So could that mean that replacing the U953 and U951 might not be enough to solve the problem?
It's 50/50 whether something has caused the fuse to blow... assuming it has of course.
Experience says that the reg may well be faulty, and for what they cost just replace. Any 7812 variant (not 78L12 though) as long as it is physically the same will be fine. Some types were ALL plastic backed and so need no insulator... something to watch. Any metal one would be fine as long as you got an insulating kit to go with it.
Those fuses are hard to come by generally and surprisingly expensive... you could replace with a 1 ohm 1watt resistor for testing... if the resistor goes up in smoke it's no loss.
I think one step at a time, replace those parts and see where that leads
Experience says that the reg may well be faulty, and for what they cost just replace. Any 7812 variant (not 78L12 though) as long as it is physically the same will be fine. Some types were ALL plastic backed and so need no insulator... something to watch. Any metal one would be fine as long as you got an insulating kit to go with it.
Those fuses are hard to come by generally and surprisingly expensive... you could replace with a 1 ohm 1watt resistor for testing... if the resistor goes up in smoke it's no loss.
I think one step at a time, replace those parts and see where that leads
This is the regulator,
http://www.datasheetcatalog.org/datasheet/panasonic/AN78M20F.pdf
some were all plastic... you need to check. If you use a metal one such as the common 7812 you need this,
http://www.datasheetcatalog.org/datasheet/panasonic/AN78M20F.pdf
some were all plastic... you need to check. If you use a metal one such as the common 7812 you need this,
Attachments
I located U951, and it's on the transistor Joint PCB assembly. Looks like a trans - it's 3 legged, and attached to the heat
sink. Two legs show 0.31 volts and the other one, 0.00V.
Would that indicate that it's the culprit?
My digicam needs recharging or I'd send a pic.
No voltage on U951 indicates the fuse has blown.
As you say... why? I would replace the reg too.
Can you get parts locally
As you say... why? I would replace the reg too.
Can you get parts locally
Is 953 the reg? Should I replace both 953 and 951?
There's a local electronics shop that specializes in salvage and has some new parts - I'll stop there tomorrow, otherwise it's Digikey or Mouser, and a week wait for parts.
The legged part is the reg... what do its markings say ?
Also just be 100% sure the glass fuse F951 (page 35pdf right hand side) is OK as that feed the whole lot before all this. Almost certainly is OK but check.
Also just be 100% sure the glass fuse F951 (page 35pdf right hand side) is OK as that feed the whole lot before all this. Almost certainly is OK but check.
So any 7812 will be OK... very common part. For the fuse U951 you can fit as mentioned a 1 watt 1ohm to test.
With all the usual warnings etc... and for test only... you can, providing you monitor the 12 volt supply (the output of the reg is the right hand pin as you look down on it) link the plastic fuse out... switch on and measure. Also have a finger on the reg... if it gets very hot instantly switch off.
With all the usual warnings etc... and for test only... you can, providing you monitor the 12 volt supply (the output of the reg is the right hand pin as you look down on it) link the plastic fuse out... switch on and measure. Also have a finger on the reg... if it gets very hot instantly switch off.
Just enough charging time to take this pic:
The U951 is mounted to the large heatsink and is to the right of U952.
U953 is at the 7:00 position next to the oversized blue cap on legs that I tipped out of the way. You can see it's mounted flush to the PCB.
Shall I replace the U952 as well?
The U951 is mounted to the large heatsink and is to the right of U952.
U953 is at the 7:00 position next to the oversized blue cap on legs that I tipped out of the way. You can see it's mounted flush to the PCB.
Shall I replace the U952 as well?
Attachments
U952 is another part of the circuit... no reason to suspect any problem there.
Same test applies... it's just a fuse... voltage same both ends, it's OK
Same test applies... it's just a fuse... voltage same both ends, it's OK
I think just replace the reg and fuse... you have to do this now anyway to take this further.
With a bit of luck that may well be all the problem is... it happens... the regs do fail, I have changed hundreds over the years in all sorts of kit.
With a bit of luck that may well be all the problem is... it happens... the regs do fail, I have changed hundreds over the years in all sorts of kit.
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