I need help

[tototngz]

Hi . My gpx 5000 is broken
the problem is this mosfet in the photo are broke
I don't know the numbers of them
Can anyone help me in this ?

[eclipse]

FDMS2672

How did you scrape off the paint ? Paint stripper?

[kt315]

why you are not able to read micro marking on another chip nearby? i see they same.

[Mechanic]

FDMS2672

How did you scrape off the paint ? Paint stripper?

Hi guys,

Nope, FDMS2672 is for the -5v tx. The one you want for the -15v is si7464 or equivalent. I also have si7450 and si7462, but check the datasheets against the si7464 as I have used that one and know it works and was in stock once!

For the paint, DON"T USE PAINT STRIPPER FFS! Hot air, about 200c the paint becomes soft, scrape it with a nice flat blade screwdriver without sharp corners and it peels off. Clean up with a solvent that removes flux, with a bit of rubbing(cotton tip) and a little heat helps with the clean up too.

Cheers Mick

[WM6]

For the paint, DON"T USE PAINT STRIPPER FFS! Hot air, about 200c the paint becomes soft,
scrape it with a nice flat blade screwdriver without sharp corners and it peels off. Clean up with
a solvent that removes flux, with a bit of rubbing(cotton tip) and a little heat helps with the clean
up too.

Cheers Mick

Hi Mick

Your advice's are always life solving. Thank you.

Just to mention: Chinese use flat blade shaped wooden chop sticks instead of screwdriver, that
can be in hands of someone to hard.

Best regards

[Daves]

I searched but couldn't find it.

[Mechanic]

I searched but couldn't find it.

Second part in my list appears to be available.

https://octopart.com/search?q=si7450...cy=USD&specs=0

The other part that can be used is IRF640. Different package, check the datasheet to match the pins to pads, secure with a good amount of hot glue, but as it is a to-220 getting mounted to an smd footprint, I really don't like that method as it is asking for trouble, however I have seen that fix from the official repair center.

[Mechanic]

Hi Mick

Your advice's are always life solving. Thank you.

Just to mention: Chinese use flat blade shaped wooden chop sticks instead of screwdriver, that
can be in hands of someone to hard.

Best regards

Thanks WM6, that is a really good suggestion. I have used toothpicks in the past to clean the paint from between the pins, but now days I just scratch the pins a little, add hot air and solder, then when the solder is melted all round, just flick them off and clean up the paint after. I think a flatblade chopstick might just find its way into my kit as the wood doesn't seem to scratch the soldermask.

Cheers Mick

[eclipse]

Nope, FDMS2672 is for the -5v tx. The one you want for the -15v is si7464 or equivalent.
Cheers Mick

I 've checked both datasheets for these parts /FDMS2672 and si7464/ and they seem equivalent for the important part /200V, NMOS, pinout/

[Mechanic]

I 've checked both datasheets for these parts /FDMS2672 and si7464/ and they seem equivalent for the important part /200V, NMOS, pinout/

Not quite all the important specs, GS voltage. The gate on that fet swings about 18v.
The fet for the -5 tx only has 10v GS, whereas the other one is 20v.

Also, sorry for getting excited about the suggestion of using paint stripper. I've seen and repaired the aftermath and it is just nasty.

Cheers Mick

[eclipse]

Vgs for both devices is 20V and Vth is 2V to 4V so in my view those are interchangeable devices.
The paint stripper is just nasty business. Smells terrible and it caused some damage on the skin of one my fingers.

[Mechanic]

Vgs for both devices is 20V and Vth is 2V to 4V so in my view those are interchangeable devices.
The paint stripper is just nasty business. Smells terrible and it caused some damage on the skin of one my fingers.

My bad, you are correct. Perhaps I have the wrong part number recorded for the -5v tx fet.
I find it odd that they would use 2 different fets when the one for the -5 tx would work for both.

[eclipse]

Thanks, cheers!