Help with control board
Help with control board
(OP)
Hello,
I don't have a background in electronics, but have always been interested in learning more and I found this forum hoping there are some folks looking in here that can shed some light on the control board I'm working on.
The board is from a 1974 Lincoln welder, I'm restoring the machine and it has some electrical issues.
I have the control board out and removed most of the components, checked individually and on some individual parts ran into some issues with testing and theory, more about that later.
The schematic for the machine is L5208T and the schematic for the board is L5268T, both can be found here: Lincoln tig300/300
my first question, it appears to me to be both ac and dc control on this board, maybe that's not correct?
at #23 on L5268T I have 62vac along with 92vdc,both going to the control board, is this correct? and if so is it possible from just looking at the schematic to map out in one color the ac current paths and then map out in a different color the dc paths?
I don't have the experience to do this or know how difficult it would be, but assuming the diodes would determine the current flow it might not be too hard for someone with experience.
Thanks for entertaining my questions & quest for knowledge.
Doug
I don't have a background in electronics, but have always been interested in learning more and I found this forum hoping there are some folks looking in here that can shed some light on the control board I'm working on.
The board is from a 1974 Lincoln welder, I'm restoring the machine and it has some electrical issues.
I have the control board out and removed most of the components, checked individually and on some individual parts ran into some issues with testing and theory, more about that later.
The schematic for the machine is L5208T and the schematic for the board is L5268T, both can be found here: Lincoln tig300/300
my first question, it appears to me to be both ac and dc control on this board, maybe that's not correct?
at #23 on L5268T I have 62vac along with 92vdc,both going to the control board, is this correct? and if so is it possible from just looking at the schematic to map out in one color the ac current paths and then map out in a different color the dc paths?
I don't have the experience to do this or know how difficult it would be, but assuming the diodes would determine the current flow it might not be too hard for someone with experience.
Thanks for entertaining my questions & quest for knowledge.
Doug





RE: Help with control board
The ac & dc share paths and then travel into separate circuits?
I have 2 boards, the original and a replacement, both suffered damage from a shorted remote cord.
If I could understand the how/where the current travels, troubleshooting would be much more precise.
thank you kindly, Doug
RE: Help with control board
FYI: This thread, being apparently hobbiest and thus potentially dangerous, is arguably on the edge of the approved scope of Eng-Tips.
RE: Help with control board
Your reply is off the mark, The issue is not about DC circuit for welding.
The image I posted above is a small rectifying circuit for current control on L5268T and I believe there is an ac component along with the dc that powers the pulse transformer?
This is not the larger bridge rectifier that makes the DC for welding you mentioned, if you had looked at the complete welder schematic L5208T you would recognized both rectifying circuits.
there are 2 schematics, 1 covers the welder itself L5208T and the other L5268T is only the control circuit.
If you're not on the edge, you taking up too much space.
Doug
RE: Help with control board
It is still "missing" an obvious filter capacitor.
And it's still normally called pulsating DC. It would be very unusual to base a design concept on it being DC and (separately) AC. But anything is possible.
Perhaps others will chime in. Good luck.
RE: Help with control board
Here are direct links to the .pdf schematics on another host if you cant browse the skydrive link.
Welder
control board
Thank you kindly- Doug
RE: Help with control board
I've looked through my ge manuals and couldn't find these part #'s.
printed on the semiconductor is GED04-32 / GED04-34
Can you identify these parts?
Q2 & Q3 I have nos replacements, Q1, Q4 & Q5 having trouble matching them up.
Thank you kindly, Doug
GED04-34
control board with labeled components
RE: Help with control board
Hoping a savy chap can identify these and point me to a data sheet.
I found the T1006 crosses to NTE102A.
Regards, Doug