New user with Cosmo 170 (SIP) and a headache

Well.. I did not try to upload a file. I did not read carefully.
It was 9Mb. not 9kb. Sorry for that.
But here i attach a jpg of the schematics.

That's a nice schematic. I simply scanned mine from the manual...

I switched the low-voltage side too but I used a relay with a 240V coil driven from the primary of the welding transformer rather than a low-voltage coil on the secondary (it was what I had available). I also used a 24V DC regulated power supply instead of the transformer and bridge.

I used the normally-closed contact on the relay as a brake to reduce run-on when the trigger is released. This makes a big difference.

The schematic below is not for a 170 but the same principle applies.



It is possible to go as low as 100R on the trim-pot. In fact later SIP/Cosmo units use 100R. I fitted one to mine and it works well.

Guys where the hell were you earlier in the thread!!! Bottom of page 4 and start of page 4

Nice schematics and I may have to use the relay option as mine does run on fractionally

Originally Posted by BChild Guys where the hell were you earlier in the thread!!! Bottom of page 4 and start of page 4 Nice schematics and I may have to use the relay option as mine does run on fractionally

With a 24v transformer, the motor would tend to run faster and overrun somewhat.
At 120a output the motor normally would have had about 20v max. (24v/20v=+20%), through it and the pcb.
At 30a output about 15.5v max. (24v/15.5=+55%).
Has anyone measured the high/low speed voltages through the motor , before and after the transformer mod ?
Robert

BChild: On page 4 and 5, i was still annoying about the way it worked.
I had not found this page at that time. I read the tread, and found that there was someone who wanted the schematics. I had it already. Only needed to upload it.
I had to make the schematics from the pcb to find out how the circuit is working. It was an easy job to modify it when i knew the circuit.
The reason why there is no capacitor in the circuit, is that it works as a simple "pulse width regulator". It is better that way because the motor will get more torque than if the circuit has a cap, and you have to reduce the voltage. But you will loose some of the max speed. Not a problem as it is running fast enough anyway.

If you measure the voltage level after the rectifier, you will read somewhere between 17-20V DC.
Reason is that you are measuring middle value.

Originally Posted by Jaeger_S2k I'm not having a go at you, but I think it's important to know the potential REAL cost of these 'good value for money', 'they join metal together' type units is.

OK

SIP Cosmo 170 Costs (Inc modifications)

£152.00 Purchase cost BINB - "Old Stock" (included delivery)

£2.00 Wire Brace (1st mod to wire feed)

£4.70 Relay Bridge (2nd WFM Mod)
£21.10 Transformer (-----"------)
£10.00 Wire & Connectors (-----"------)

£29.00 Euro Torch Connector (3rd mod - Euro Torch)
£20.00 Gas Solenoid (-----"------)
£32.00 Euro Torch (-----"------)
£7.00 (Postage) (-----"------)

I'll add in the 10 turn pot and counter unit once it's all fixed properly

£277.80 Total

I haven't priced my time - not even sure how I would do that but I would guess I've spent several hours either modifying the welder or researching the how to side

Incidently I see on the SIP web site a very similar machine to mine can be purchased with a euro torch for £413.99 (RRP £708.56 )

http://www.sipuk.co.uk/tools/info_SIP25037.html

Originally Posted by BChild OK SIP Cosmo 170 Costs (Inc modifications) £152.00 Purchase cost BINB - "Old Stock" (included delivery) £2.00 Wire Brace (1st mod to wire feed) £4.70 Relay Bridge (2nd WFM Mod) £21.10 Transformer (-----"------) £10.00 Wire & Connectors (-----"------) £29.00 Euro Torch Connector (3rd mod - Euro Torch) £20.00 Gas Solenoid (-----"------) £32.00 Euro Torch (-----"------) £7.00 (Postage) (-----"------) I'll add in the 10 turn pot and counter unit once it's all fixed properly £277.80 Total I haven't priced my time - not even sure how I would do that but I would guess I've spent several hours either modifying the welder or researching the how to side Incidently I see on the SIP web site a very similar machine to mine can be purchased with a euro torch for £413.99 (RRP £708.56 ) http://www.sipuk.co.uk/tools/info_SIP25037.html

You'll be happy then?

I think you're estimate on time is, let's say, conservative I must have spent a couple of hours reading your interesting and compelling progress

Charging time, easy £25 per hour. First hour usually £35 each hour after £25.

I'd recon you've got easy 8 hours of tinkering, fiddling, coffee and biscuits, fitting, refitting, coffee and biscuits, writing, reading, coffee and biscuits, waiting! Fitting and failing, coffee and biscuits, refitting and testing etc.

It's a great result though, as many people don't cost their time into the equation so in that aspect a fine result.

Hope it prompts others to take little annoying idiosyncrasies of their machines and try to make them better, there are a lot of wire feed related issues with less expensive welders and as it's quite critical to success you're tenacity will I'm sure encourage others to do the same.

You know it could become the 'must have' welder, you should start buying them modifying and selling them on, get one over to TechnicalAl, Malcolm and others and ask for testimonials.

weldquip could be asking for exclusive distribution rights

well done that man!

Hi all,

Long time lurker, first time poster.

Firstly, thanks to everyone who has contributed to this thread, it makes for fascinating reading.

I have a four year old Cosmo gas/gasless 225 purchased here in Oz.

I have completed the wire feed mod with great success and have got on with the transformer mod up to the bridge rectifier but have struck a snag-- when I make the connections to the feed motor and turn the machine on the wire feed immediately springs into life, so somehow I have managed to bypass the torch switch.

I have followed the photos in bump's thread with great diligence but no success. My unit is slightly different to those described here so I'm hoping somebody who's more familiar with the wiring can set me straight.

The schematic is:


The relay is not on the PCB but is mounted under the feed motor here:


This means of course, that the PCB is different:


This is a photo of the general arrangement before modification:


The green connector (D in the photo) appears to be same as all the others, the blue wire goes via a thermocouple to the trigger, the red wire goes to a tap on the main transformer, the white wire goes to the feed motor +ve and the black wire goes to the rectifier heat sink at A.

The feed motor -ve connects to the post at F.

The relay is fed from the connectors at B and the PCB is fed with 240v at C from the main 240v switch at E.

Once I connect the bridge rectifier to the feed motor and the black wire at A is when the problem starts.

Hope that's all clear and the photos are big enough.

Any help would be greatly appreciated.

TIA

Originally Posted by crankbuoy I have completed the wire feed mod with great success and have got on with the transformer mod up to the bridge rectifier but have struck a snag-- when I make the connections to the feed motor and turn the machine on the wire feed immediately springs into life, so somehow I have managed to bypass the torch switch.

I think (an electrics are not my strong point) that you have connected to a permanent live rather than the torch switched live but your PCB is different to mine so I can't instantly identify which one you need - I'm sure someone will be along soon enough to help

Welcome anyway

This is the reason why, when I posted my wire-feed modification, I posted a schematic rather than a procedure of the form (coined by another member) "cut the blue wire..."
There is no guarantee that even two of the same model are wired up the same since the design evolves over time. Trying to follow such a procedure without knowing for certain that it applies to your own welder may give undesirable or even dangerous results (since some of those wires carry mains voltage).

I think you will only be able to do this by following the schematic and identifying the wires from that, or by getting someone else here to do it, having first established that the welder they are working from is exactly the same (not sure how you would do that).

I'm not trying to be discouraging here, merely cautious. If in doubt, get someone who knows what they're doing to carry out the modification.

As BChild says, it does appear that you have connected the output of the bridge directly to the motor rather than to the controller PCB, which should then supply the motor.