Lincoln Tig 300 problems

>> 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.

> ]
>
> 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
>

> 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.
>
> Jon

> 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