Need help syncrowave 250 wont output

[Rkmetalworks]

Hello i have a syncrowave 250 with the serial # that begins with kh4 ....i bought it hoping it would work and sure enough i plugged it in and it just turns on and has no output....so i opened it up and found the large pc1 circuit board has what seems to be a defect resistor and solder but i want some expert advice as to what my options are and if possible how to confirm that this is the culprit

[Aeronca41]

I am no welder expert but have fixed a lot of stuff over the past 50+ years. Assume you're talking about the bluish-white resistor in the last two pix between the transistor and the transformer that someone has obviously replaced? Looks like someone may have found a blown resistor and replaced it; wonder how they found out the value? Schematics for boards are generally not in current Miller owner manuals. Anyway, if the resistor blew, it was most likely caused by some other failed (shorted) component, probably a transistor. Pretty hard to troubleshoot without a schematic unless you have a Huntron Tracker, are adept at using it, and just start shot gunning components. Perhaps someone else may have more encouraging info-don't mean to be a pessimist but my guess is you need to have the board repaired or replace it. Assume you have checked all the switches, plugs (internal and external), and connections you can find for looseness or corrosion. Wish I could be more help, hope someone else can.

[Rkmetalworks]

Yea i cleaned and gapped the contacts ...looked through the machine and i could see that the pc2 board has been repaired as well where a small trace connection had burnt up and the previos owner soldered a wire to reconnect the trace wire...but yea anyone else know any more about this pc1 like a diagnostic troubleshooting procedure

[H80N]

First of all.... what is your configuration..... ??

switch settings ...??

symptoms....??

full serial number??

without those... there is very little for a repair tech to work with...

Especially since you have taken it apart.... 9 out of 10 times there will be NOTHING VISUAL to indicate the problem...

It could easily be something as simple as the LOCAL/REMOTE Switch being in the wrong position...

Input voltage jumper link settings..??

[ccawgc]

the location on the pcb look like the SCR gating system. If the resister was burnt, then the pulse transformer is open and the cause is a bad weld SCR..
You are going to need to test the SCRs and make sure they turn on. Basic ohm meter is not able to turn on a SCR. You can measure where the SCR plugs into the pcb with an ohm meter. red to white socket with SCRs unplugged, Check all four sets. If good they will all read the same and be low ohms.
A near short if good. You will be reading the pulse transformer winding.. Then measure the red and white gate leads and see what they are. same thing they all should read near the same thing. around 50 ohms. could be 15 to 60. But they all should read the same with in 2 ohms.
This test will only find the SCR with an open or shorted gate. won't tell you if it will turn on.
Make some tests and post what you find.

Is that R2 that was replaced? if so it is in the primary of T1. I would look at R2 and D1. edit to above when testing the low ohms should be replaced with a diode.
The diagram I was looking at has a diode in series with the transformer secondary.
Check Q1 and make sure it is not shorted. any pin to all pins.
If Q1 shorted it can take out both T1 and R2.
Lets Us know what you find.

[H80N]

Why worry about board level tests until the config.... hookup... & settings are confirmed to be correct......?????????????????????

[Rkmetalworks]

i own another syncrowave and have owned multiple others so settings for output are guaranteed to be in the correct position
If you think it will help diagnosing here is what i have done
Out put settings : ive tried remote with my pedal no output ...did panel scratch start no output
High freq : tried start and continuous made no difference
Amps set to 60 amps
Dc neg setting
Used the pedal from my good and working syncrowave to test
Full serial kh483382

[H80N]

i own another syncrowave and have owned multiple others so settings for output are guaranteed to be in the correct position
If you think it will help diagnosing here is what i have done
Out put settings : ive tried remote with my pedal no output ...did panel scratch start no output
High freq : tried start and continuous made no difference
Amps set to 60 amps
Dc neg setting
Used the pedal from my good and working syncrowave to test
Full serial kh483382

Jumper links strapped for your house power.....??? 230vac..??

Have seen them wrong many times

[H80N]

CB-1 set..........reset..............???

Manual..............

https://www.millerwelds.com/files/ow.../O353Q_MIL.pdf