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Posted by Gunner Asch on April 28, 2008, 4:58 am
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On Mon, 28 Apr 2008 03:08:41 GMT, BobH
>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
The welder came wit a file folder full of schamtics and receipts for
boards. The schmatics hve values for the various components, so Ill
have some data.
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.
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Posted by Bruce L. Bergman on April 28, 2008, 3:17 am
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On Sun, 27 Apr 2008 14:44:28 -0700, Gunner Asch
>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 >>--
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Posted by Gunner Asch on April 28, 2008, 4:35 am
Please log in for more thread options On Mon, 28 Apr 2008 00:17:11 -0700, Bruce L. Bergman
>On Sun, 27 Apr 2008 14:44:28 -0700, Gunner Asch
>
>>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.
>
> Do a methodical search and you'll find it.
I will indeed. It was sweet welding with AC and 6011. Nearly as good
as the Dialarc 250
>
> 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.)
Its later than 1989, so there shouldnt be any seleniums.
>
> --<< Bruce >>--
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.
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Posted by Joseph Gwinn on April 28, 2008, 9:22 am
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> On Mon, 28 Apr 2008 00:17:11 -0700, Bruce L. Bergman
>
> >On Sun, 27 Apr 2008 14:44:28 -0700, Gunner Asch
> >
> >>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.
A big metal can or more likely a big plastic and metal block, with two
very heavy leads plus one or two much thinner leads (or screws), in
either case bolted to a big heatsink.
The SCRs are in the Rectifier assembly on page 38 of
<http://content.lincolnelectric.com/pdfs/products/navigator/OBSO_IMS/im36
1a.pdf> (pdf provided by another poster).
A shorted SCR will have low resistance regardless of polarity. Likewise
a shorted rectifier.
Joe Gwinn
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Posted by Jon Elson on April 28, 2008, 1:29 pm
Please log in for more thread options Gunner Asch wrote:
>
> 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
between big heat sinks. They are on the output side of the main
transformer, deep in the interior of the machine. There are two
SCRs and two diodes in a bridge. They are used in all modes of
the machine, I believe, to control current in both directions.
So, the bridge is just a controllable switch in series between
the transformer and electrode. Therefore, since AC current IS
controllable, I really don't think the SCRs could be bad. In
fact, most of the control systems have to be working for it to
get this far. Since boards were replaced, a bad switch or
connection seems more likely.
Jon
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