Fault finding Autolynx3

[jo1010]

Collected a cheap autolynx 3 that was said to have wire feed problems. Starting to investigate ....the wire feed is extremely weak can't even push wire through the fingers, and also stops completely (but there is still an arc available at that point). Machine switches on ok, fan runs, torch button pulls in the contactor, and (mostly) the wire feed runs, although the pot knob for wire speed does feel very well worn...

However I started by looking at the power side of things and this is disturbing....
1. OCV is very high. Steps up regularly with the volts control switch from 1 through 6 but goes from 113v to 150v. At this point I compared my other good autolynx3 which shows a range from 70v to 113v.
2. My thought was that TR1 might be shorting, so I've checked output from TR1 disconnected from the rectifier bridge...that test showed regular step thru from 2vac to 4.7vac (volts switch settings from 1 thru 6). Comparing with the good machine again values are similar (2.5vac to 3.2vac). So maybe TR1 is ok? Dusty but no burning visible and plates are a little rusty....
3. I then checked the rectifier bridge. Some diodes were failed so I swapped in a complete working bridge from a spare machine. However the test for DC output still shows high...120v to 143v.

Can't get my head round why this voltage is so high..is TR1 bad after all? So is there any point going further into diagnosis of TR2 and the PCB ( I did notice the wire feed motor does receive 37v (thirty seven - same as my good machine).......

 

[Martin-Sy]

My thought was that TR1 might be shorting, so I've checked output from TR1 disconnected from the rectifier bridge...that test showed regular step thru from 2vac to 4.7vac (volts switch settings from 1 thru 6)

That does not sound right. Are you sure your measurements are correct?
Output from TR1 is a maximum of 4.7V ac (the input to the rectifier) and yet the rectifier output is 150V dc???

 

[eddie49]

I have tracked down a hand-drawn circuit diagram for the wirespeed controller of the Autolynx 3 in Post #21 here:

L

Thread 'MUREX AUTOLYNX 3'

May 4, 2016

Hi everyone
Just bought a autolynx 3 on e bay which was listed as spares or repair, wire feed on fullspeed, thinking I could repair wire feed speed board 1415016, expected an output power transistor shorted out, however when I have opened up I found the PCB missing, what a bugger.
Does anyone have an internal schematic diagram of this PCB, if not a photograph of the front and back of the PCB would be a great help...

• LECKYBELL
• Replies: 23
• forum: Murex & BOC

The components labelled "R1" and "R2" are not resistors, they are relays.

Ref. the strange high voltage readings - are you perhaps measuring with one meter lead on chassis earth?

 

[jo1010]

Thanks guys! DMM was having a bad day maybe I'd knocked the range button accidentally idk....anyway I've re-checked TR1 output to rectifier with leads disconnected from rectifier ....look good now (19vac evenly thru to 30vac).
I checked the dc rectified outputs with output leads disconnected and that too seems sensible...(31v thru to 58v).

However I checked the ocv again (test leads on torch contact tip and earth clamp) and that is as measured before about 119v thru to 144v. So whatever is going wrong must be around TR2 and PCB circuitry? I'll continue now and have a look through those areas in the next few days - the PCB sketch will be very useful....