Miller 375 Plasma Burt Cap..

[eccerr0r]

Re: Miller 375 Plasma Burt Cap..

well, that's no fun, this is a 3 or more layer board with embedded layer via connections I guess that's the end of remote debug for me, need a continuity checker along with the board for me to work on multilayer boards without a schematic.

Just a word of warning: this board is extremely fragile to work on, so be careful: if you damage the plated vias, game over.

The only thing left to suggest: if the semiconductors all look good (i.e. no shorts) it might be worth to just replace that 100Ω resistor and see what it does, make sure you use a DBT and just run it without welding/cutting to see if it at least powers up... I suspect it's simply completely dead at the moment prior to any parts removal?

[KG7AMV]

Re: Miller 375 Plasma Burt Cap..

Yea, reason why i am not using solder wick.. Proper desoldering tips..

I will test the transistors, photo the PCB reassemble with any failed /damged part replaced.

[KG7AMV]

Re: Miller 375 Plasma Burt Cap..

Miller Support Got Me A Schematic For The Machine To My E-mail Box This Afternoon Will Upload Soon..

Bus Precharge Circuit and R123 is 10ohm PTC Thermistor has to be something cheaper..
http://www.brweldingsupplies.com/mil...-10-ohm-25-deg


+1 For Miller...

Schematic Drawing

[eccerr0r]

Re: Miller 375 Plasma Burt Cap..

Ah... yeah, normally SMPS have thermistors there, it's very typical along with a relay to get higher efficiency. I was thinking about how practical a regular resistor would do there...may work fine too but I've never worked on welders before...

oh... main reason for posting... after being infatuated with varactor diodes (yes for radio ).... that MOV RV1 in that schematic is hideously wrong.... I think two inverse series zeners would be a better representation for a MOV than two inverse parallel varactor diodes...

[KG7AMV]

Re: Miller 375 Plasma Burt Cap..

Just need to find a source that is not a Welding shop or miller part # $13+ ouch..

[R_J]

Re: Miller 375 Plasma Burt Cap..

Do you have a picture of the original R123 ptc thermistor? or did they have that white ceramic resistor in its place?

[KG7AMV]

Re: Miller 375 Plasma Burt Cap..

Do you have a picture of the original R123 ptc thermistor? or did they have that white ceramic resistor in its place?

Ceramic Resistor was in R123..

[R_J]

Re: Miller 375 Plasma Burt Cap..

So they are replacing the 10Ω resistor with a ptc thermistor? too bad they don't provide a picture of the 200656.

I guess that resistor was a 10Ω, I hate when they mark 100 and its actually 10 multiplied by 0
This digikey 570-1024-ND would likely work but it is $9.24

[KG7AMV]

Re: Miller 375 Plasma Burt Cap..

Yea, I also hate parts labeling like that..

I Also Notice that PM1 Has Miller Part # What Could it Be? Seems to be the only proprietary #'d part.

[KG7AMV]

Re: Miller 375 Plasma Burt Cap..

I Also Notice that PM1 Has Miller Part # What Could it Be? Have not seen any Other Proprietary Parts on The Board.




Here Are The Extracted Schematic Images

[R_J]

Re: Miller 375 Plasma Burt Cap..

Does it have 4 legs or 5 ? it could be similar to the ALFET ALF08NP16V5 but this is a fet, the schematic shows similar but with transistors. So it's a TO-247-5 package
You could use Go Advanced and attach the documents , that way all the pictures don't have to download each time we go to the thread,

[KG7AMV]

Re: Miller 375 Plasma Burt Cap..

5 legs..

[R_J]

Re: Miller 375 Plasma Burt Cap..

I did find a similar item on alibaba

[CapLeaker]

Re: Miller 375 Plasma Burt Cap..

Yea, I also hate parts labeling like that..

I Also Notice that PM1 Has Miller Part # What Could it Be? Seems to be the only proprietary #'d part.

That isn't a Miller stamp... Maybe Microchip, Micrel etc?

[eccerr0r]

Re: Miller 375 Plasma Burt Cap..

The logo appears to match that of in the schematics....

This device seems to be some two way insulated gate controllable bidirectional diode... weird.

[R_J]

Re: Miller 375 Plasma Burt Cap..

There is a bit of information here https://www.elektroda.pl/rtvforum/topic3329021.html
Here is a translate of the miller reply to the person

I wrote to Miller and here's the answer:
Miller part number 218760 is a proprietary part not available as a service item. There is no third party source for the part.
The subject is closed. Thanks.

[KG7AMV]

Re: Miller 375 Plasma Burt Cap..

R123 Is a Thermistor Miller Part # 200656 I Found For 12.88.

Their Description "THERMISTOR PTC .10A 600VRMS 10 OHM"

Still Seems like an Excessive Price For a Thermistor? Anyone have a source for alternate source? I tried Digikey, Mouser, Etc... But Nothing with them specs..

http://miller4less.com/product_info....ducts_id=99742

[eccerr0r]

Re: Miller 375 Plasma Burt Cap..

The only test I can come up with for the 218760A is to ensure there's no connectivity between pins when it's out of circuit much like a MOSFET. Otherwise probably SOL other than getting another from Miller if it needs to be replaced.

Likewise for 200656 it seems Miller wants custom fees for custom parts...

[R_J]

Re: Miller 375 Plasma Burt Cap..

R123 Is a Thermistor Miller Part # 200656 I Found For 12.88.

Their Description "THERMISTOR PTC .10A 600VRMS 10 OHM"

Still Seems like an Excessive Price For a Thermistor? Anyone have a source for alternate source? I tried Digikey, Mouser, Etc... But Nothing with them specs..

http://miller4less.com/product_info....ducts_id=99742

I posted this: This digikey 570-1024-ND would likely work but it is $9.24

[eccerr0r]

Re: Miller 375 Plasma Burt Cap..

570-1024-ND is quite large, hopefully it will fit: it's over 1.3" in diameter... At least it's thinner, however.

I'd be tempted to stick a regular resistor there, however...