HIRANE AS100PH spot welder not reaching full power output

[turbotom282]

Hi all,
Have done a search regarding similar situation with Hirane on this forum, but the last forum member (FML) who had some experience with HIRANE repairs seem to be not active anymore.

My spot welder does not reach full power, the transformer tests out ok and produces full power when powered directly and dead shorted but when the neutral wire is connected back via the SCR I do not get full power and only limited output.
The SCR seems to be functioning as I get some power out of it but my knowledge of SCR is limited.
What could be causing the SCR not to supply full power ?
All components on the PCB board look to be intact.
Has anybody had a similar situation or know of any shops familiar with them.

Regards.

 

[eddie49]

G'day and welcome!

An SCR is a gate-controlled diode, so when it is triggered into conduction it would rectify the AC mains to half-wave DC. To get controlled AC power, you would need two SCRs, wired back-to-back. As a single device, this is known as a TRIAC, and I think your spot welder must use one of those rather than an SCR. A TRIAC controls power by allowing a variable portion of both the positive and the negative half-cycles of the AC supply through to the primary of the transformer. There are some notes about "phase control" in Post #35 here:

E

Post in thread 'Sip Autoplus 120 problems'

Mar 27, 2022

After speaking to Tec Arc, their response was to alter the trim pots on the pcb. I've done that, and the wire speed is probably fine now.
However it still only works when the power is on about 5 or so.

Does the upper trim pot have any effect on the power setting "5" starting point? If you turn the trimmer, can you get the arc to start at a lower setting than 5?

On a straight step-switched transformer MIG, the DC voltages at the tip would vary between about 15v and 30v.
This machine uses a TRIAC circuit that provides phase control, allowing a variable portion of the positive and...

• eddie49

If full power is not possible, the fault may be in the control circuit that triggers the gate of the TRIAC. The pulse it supplies may start too late in the half-cycle. I have not found a circuit diagram; a photo of the control board may help to guess what could be wrong. As a first step, you could verify that the potentiometer used to adjust power works correctly across its full resistance range.

 

[Jack_K]

I don't know if Hirane would possibly help with information? http://www.hiraneproducts.com/hirane_english/e_index.html

Last time I checked they didn't have a seller in Australia anymore.

 

[Ace Paul]

make sure everything is spotless.

If you got I/r thermometer

Use it 10 times in a row see if one of joints hotter than another.

Have you sharpened the tips?

If you press together (power off). Can another person pull the work piece out?