I picked up a Lincoln tig 300 square wave machine a couple weeks ago.

Code 9298-ff

The guy claimed that the power couldnt be dialed down to anything less
than about 150 amps. Ive receipts for a number of boards he purchased
in '00 etc etc, with no fix.

So I powered it up today to diagnose what is really going on.

1. It will not dial down to less than about 111 amps,using either the
pedal, or the main amp control pot. The machine has digital display
for volts and amps, and with the main control all the way down, I get
an E11, and turn it a smidge, shows 111, then as the knob is turned,
goes all the way to 375 amps as one would expect
Hooking a stinger up, yes...it really is about 111 amps at low, and
all the way up blew an 80 amp breaker on my sub, so yes, that portion
is accurate.

There is no Hi/Low range switch on the machine.

No output on AC. Tiny spark, but no real welding current, using local,
or remote with a known good pedal. Pedal does kick the contactor, and
does vari welding current, but wont bring it down below that 111
volts.

No HF in any configuration. This COULD be dirty points, as its not
been used for at least 8 yrs, but thats not a big issue at the moment.

First thing Ill do is check the main amps control pot, to make sure
its in spec and both sides have the prope variable resistance.

I do have the schematics and drawings, but was looking for some input
on how things actually work..IE..when the main amp knob is turned, how
is it actually controlling the output of the transformer?

With a minimum current of 111 amps, something is not going low enough,
or high enough to vari current to lower values.

Why would it not have output on AC but does on DC? Thats a bit
odd....
Ill clean the AC/DC+/DC- selector switch of course.
It IS a square wave machine, so whatever converts the AC sine to
square wave sine may be an issue. I think thats some sort of chopper
circuit?

Anyone have any ideas or where to start looking? This is a weird one.

The FF designation at the end of the code number means "full
function"..whatever the hell that means. I assume its the timer
circuits for post and pre flow, crater, spot etc ?


Gunner

I picked up a Lincoln tig 300 square wave machine a couple weeks ago.

Code 9298-ff

The guy claimed that the power couldnt be dialed down to anything less
than about 150 amps. Ive receipts for a number of boards he purchased
in '00 etc etc, with no fix.

So I powered it up today to diagnose what is really going on.

1. It will not dial down to less than about 111 amps,using either the
pedal, or the main amp control pot. The machine has digital display
for volts and amps, and with the main control all the way down, I get
an E11, and turn it a smidge, shows 111, then as the knob is turned,
goes all the way to 375 amps as one would expect
Hooking a stinger up, yes...it really is about 111 amps at low, and
all the way up blew an 80 amp breaker on my sub, so yes, that portion
is accurate.

I have one of these, and the Lincoln machine schematic, which is

There is no Hi/Low range switch on the machine.

No output on AC. Tiny spark, but no real welding current, using local,
or remote with a known good pedal. Pedal does kick the contactor, and
does vari welding current, but wont bring it down below that 111
volts.

No HF in any configuration. This COULD be dirty points, as its not
been used for at least 8 yrs, but thats not a big issue at the moment.

Hmm,
First thing Ill do is check the main amps control pot, to make sure
its in spec and both sides have the prope variable resistance.

I do have the schematics and drawings, but was looking for some input
on how things actually work..IE..when the main amp knob is turned, how
is it actually controlling the output of the transformer?

First, when the pedal is up, the display is just reading the

With a minimum current of 111 amps, something is not going low enough,
or high enough to vari current to lower values.

Why would it not have output on AC but does on DC? Thats a bit
odd....
That is a puzzle, and may indicate more trouble.
Ill clean the AC/DC+/DC- selector switch of course.
It IS a square wave machine, so whatever converts the AC sine to
square wave sine may be an issue. I think thats some sort of chopper
circuit?

No, it just fiddles with the SCR timing to control the current.

Anyone have any ideas or where to start looking? This is a weird one.

The FF designation at the end of the code number means "full
function"..whatever the hell that means. I assume its the timer
circuits for post and pre flow, crater, spot etc ?
Yes. There are machines without many of those functions and no

I picked up a Lincoln tig 300 square wave machine a couple weeks ago.

Code 9298-ff

The guy claimed that the power couldnt be dialed down to anything less
than about 150 amps. Ive receipts for a number of boards he purchased
in '00 etc etc, with no fix.

So I powered it up today to diagnose what is really going on.

1. It will not dial down to less than about 111 amps,using either the
pedal, or the main amp control pot. The machine has digital display
for volts and amps, and with the main control all the way down, I get
an E11, and turn it a smidge, shows 111, then as the knob is turned,
goes all the way to 375 amps as one would expect
Hooking a stinger up, yes...it really is about 111 amps at low, and
all the way up blew an 80 amp breaker on my sub, so yes, that portion
is accurate.

There is no Hi/Low range switch on the machine.

No output on AC. Tiny spark, but no real welding current, using local,
or remote with a known good pedal. Pedal does kick the contactor, and
does vari welding current, but wont bring it down below that 111
volts.

No HF in any configuration. This COULD be dirty points, as its not
been used for at least 8 yrs, but thats not a big issue at the moment.

First thing Ill do is check the main amps control pot, to make sure
its in spec and both sides have the prope variable resistance.

I do have the schematics and drawings, but was looking for some input
on how things actually work..IE..when the main amp knob is turned, how
is it actually controlling the output of the transformer?

With a minimum current of 111 amps, something is not going low enough,
or high enough to vari current to lower values.

Why would it not have output on AC but does on DC? Thats a bit
odd....
Ill clean the AC/DC+/DC- selector switch of course.
It IS a square wave machine, so whatever converts the AC sine to
square wave sine may be an issue. I think thats some sort of chopper
circuit?

Anyone have any ideas or where to start looking? This is a weird one.

The FF designation at the end of the code number means "full
function"..whatever the hell that means. I assume its the timer
circuits for post and pre flow, crater, spot etc ?


Gunner

Political Correctness is a doctrine fostered by a delusional,
illogical liberal minority, and rabidly promoted by an
unscrupulous mainstream media, which holds forth the
proposition that it is entirely possible to pick up a turd by the clean end.

I picked up a Lincoln tig 300 square wave machine a couple weeks ago.

Code 9298-ff

The guy claimed that the power couldnt be dialed down to anything less
than about 150 amps. Ive receipts for a number of boards he purchased
in '00 etc etc, with no fix.

So I powered it up today to diagnose what is really going on.

1. It will not dial down to less than about 111 amps,using either the
pedal, or the main amp control pot. The machine has digital display
for volts and amps, and with the main control all the way down, I get
an E11, and turn it a smidge, shows 111, then as the knob is turned,
goes all the way to 375 amps as one would expect
Hooking a stinger up, yes...it really is about 111 amps at low, and
all the way up blew an 80 amp breaker on my sub, so yes, that portion
is accurate.

There is no Hi/Low range switch on the machine.

No output on AC. Tiny spark, but no real welding current, using local,
or remote with a known good pedal. Pedal does kick the contactor, and
does vari welding current, but wont bring it down below that 111
volts.

No HF in any configuration. This COULD be dirty points, as its not
been used for at least 8 yrs, but thats not a big issue at the moment.

First thing Ill do is check the main amps control pot, to make sure
its in spec and both sides have the prope variable resistance.

I do have the schematics and drawings, but was looking for some input
on how things actually work..IE..when the main amp knob is turned, how
is it actually controlling the output of the transformer?

With a minimum current of 111 amps, something is not going low enough,
or high enough to vari current to lower values.

Why would it not have output on AC but does on DC? Thats a bit
odd....
Ill clean the AC/DC+/DC- selector switch of course.
It IS a square wave machine, so whatever converts the AC sine to
square wave sine may be an issue. I think thats some sort of chopper
circuit?

Anyone have any ideas or where to start looking? This is a weird one.

The FF designation at the end of the code number means "full
function"..whatever the hell that means. I assume its the timer
circuits for post and pre flow, crater, spot etc ?


Gunner

I picked up a Lincoln tig 300 square wave machine a couple weeks ago.

Code 9298-ff

The guy claimed that the power couldnt be dialed down to anything less
than about 150 amps. Ive receipts for a number of boards he purchased
in '00 etc etc, with no fix.

So I powered it up today to diagnose what is really going on.
Snip
Anyone have any ideas or where to start looking? This is a weird one.

So I powered it up today to diagnose what is really going on.

1. It will not dial down to less than about 111 amps,using either the
pedal, or the main amp control pot. The machine has digital display
for volts and amps, and with the main control all the way down, I get
an E11, and turn it a smidge, shows 111, then as the knob is turned,
goes all the way to 375 amps as one would expect
Hooking a stinger up, yes...it really is about 111 amps at low, and
all the way up blew an 80 amp breaker on my sub, so yes, that portion
is accurate.

I have one of these, and the Lincoln machine schematic, which is
all they will give out to the general public. The current
controls are potentiometers. I wonder if a wire has got a bad
connection, leaving one end of the pot disconnected. Maybe you
could read the voltage across the current set pot and I can
compare it to my machine.
]

On Sun, 27 Apr 2008 14:44:28 -0700, Gunner Asch
gunner@NOSPAMlightspeed.net> wrote:

I picked up a Lincoln tig 300 square wave machine a couple weeks ago.

Code 9298-ff

The guy claimed that the power couldnt be dialed down to anything less
than about 150 amps. Ive receipts for a number of boards he purchased
in '00 etc etc, with no fix.

So I powered it up today to diagnose what is really going on.
Snip
Anyone have any ideas or where to start looking? This is a weird one.

Yeah, and you already know what the first step is, call that guy you
mentioned a while back at Arco Welder Repair. Two sentences, and
he'll say "STOP - Check this..." But they've let their domain name
lapse, there's a "Domain Available" NetSol squatter page up now.

I'd have to agree with the majority - the former owner has already
tried swapping boards, so odds are it's not a board. Bad power SCR or
Triac in the output sections, bad potentiometer or cabling in the
controls, bad safety switch, open coupling capacitor, bad
opto-isolator, etc.

Do a methodical search and you'll find it.

That, and/or make like Jimmy Durante and follow your schnoz - if a
component has met an electrically violent end, the nose knows. Stuff
your proboscis in there and take a deep sniff, and track down the
crispy critter.

(Note: Offer not valid if there are selenium rectifiers or other
components that make particularly nasty IDLH fumes when the Magic
Smoke escapes. But those are getting few and far between.)

--<< Bruce >>--

Gunner Asch wrote:
I picked up a Lincoln tig 300 square wave machine a couple weeks ago.

Code 9298-ff

The guy claimed that the power couldnt be dialed down to anything less
than about 150 amps. Ive receipts for a number of boards he purchased
in '00 etc etc, with no fix.

So I powered it up today to diagnose what is really going on.

1. It will not dial down to less than about 111 amps,using either the
pedal, or the main amp control pot. The machine has digital display
for volts and amps, and with the main control all the way down, I get
an E11, and turn it a smidge, shows 111, then as the knob is turned,
goes all the way to 375 amps as one would expect
Hooking a stinger up, yes...it really is about 111 amps at low, and
all the way up blew an 80 amp breaker on my sub, so yes, that portion
is accurate.

There is no Hi/Low range switch on the machine.

No output on AC. Tiny spark, but no real welding current, using local,
or remote with a known good pedal. Pedal does kick the contactor, and
does vari welding current, but wont bring it down below that 111
volts.

No HF in any configuration. This COULD be dirty points, as its not
been used for at least 8 yrs, but thats not a big issue at the moment.

First thing Ill do is check the main amps control pot, to make sure
its in spec and both sides have the prope variable resistance.

I do have the schematics and drawings, but was looking for some input
on how things actually work..IE..when the main amp knob is turned, how
is it actually controlling the output of the transformer?

With a minimum current of 111 amps, something is not going low enough,
or high enough to vari current to lower values.

Why would it not have output on AC but does on DC? Thats a bit
odd....
Ill clean the AC/DC+/DC- selector switch of course.
It IS a square wave machine, so whatever converts the AC sine to
square wave sine may be an issue. I think thats some sort of chopper
circuit?

Anyone have any ideas or where to start looking? This is a weird one.

The FF designation at the end of the code number means "full
function"..whatever the hell that means. I assume its the timer
circuits for post and pre flow, crater, spot etc ?


Gunner

I think it would be worth looking for a shorted SCR. They are not on a
board, so it doesn't sound like they got swapped by the previous owner.
It ought to show up poking around with an Ohmeter and the power off. I
looked at the PDF of the owners manual and did not see a schematic of
the machine. Can you post a pointer to the schematic?

Good Luck,
BobH

On Mon, 28 Apr 2008 00:17:11 -0700, Bruce L. Bergman
blnospambergman@earthlink.invalid> wrote:

On Sun, 27 Apr 2008 14:44:28 -0700, Gunner Asch
gunner@NOSPAMlightspeed.net> wrote:

I picked up a Lincoln tig 300 square wave machine a couple weeks ago.

Code 9298-ff

The guy claimed that the power couldnt be dialed down to anything less
than about 150 amps. Ive receipts for a number of boards he purchased
in '00 etc etc, with no fix.

So I powered it up today to diagnose what is really going on.
Snip
Anyone have any ideas or where to start looking? This is a weird one.

Yeah, and you already know what the first step is, call that guy you
mentioned a while back at Arco Welder Repair. Two sentences, and
he'll say "STOP - Check this..." But they've let their domain name
lapse, there's a "Domain Available" NetSol squatter page up now.

Dennis sold Arco to one of his employees I think..he sold to someone
and retired in August. So that option is out, the new guy is not the
type to give out free info.

I'd have to agree with the majority - the former owner has already
tried swapping boards, so odds are it's not a board. Bad power SCR or
Triac in the output sections, bad potentiometer or cabling in the
controls, bad safety switch, open coupling capacitor, bad
opto-isolator, etc.

What would the SRCs look like in that size? It works ok on AC, its
when I switch to DC that its full bore.

]

Thats what Im going to check tommorow. Oddly enough..it works fine in
AC stick mode.

The moment I put it to Tig, or DC stick, its full bore balls to the
wall. What the manual calls Stick Blast.

After posting the previous and reading some posts, I reread the manual
went back out and set everything to stick default, removed the pedal
and got it to work on AC stick normally.

But any DC mode and its 300 amps even though the amp meter reads 111

Oh, this is different than what you originally described. Well,

What would the SRCs look like in that size? It works ok on AC, its
when I switch to DC that its full bore.

The SCR's are huge, the size of a white hockey puck, clamped

Gunner Asch wrote:
]

Thats what Im going to check tommorow. Oddly enough..it works fine in
AC stick mode.

The moment I put it to Tig, or DC stick, its full bore balls to the
wall. What the manual calls Stick Blast.

After posting the previous and reading some posts, I reread the manual
went back out and set everything to stick default, removed the pedal
and got it to work on AC stick normally.

But any DC mode and its 300 amps even though the amp meter reads 111

Oh, this is different than what you originally described. Well,
if the current control is OK on stick mode, then most of the
really expensive stuff must be OK.

The first thing I'd do is flip every panel toggle switch 20
times to clean up the contacts. See if that helps at all.
I'm pretty sure there are microswitches or something similar
that tells the electronics where the AC/DC polarity handle is
set, they may need exercising, too.

This sounds like two different symptoms, at least. The current
meter doesn't read right at the low end, and the current control
isn't working right in TIG mode. Of course, there really is
little difference between the TIG and stick modes except
open-circuit voltage. There are a bunch of Molex connectors on
the boards. I have had a lot of trouble with this connector
type in rough environments. My machine is in the basement, but
if yours is in the garage or whatever, I'd definitely pull and
reseat every one of those connectors on the PC boards behind the
control panel. It just hinges down for easy access. That may
well fix the problem.