New user with Cosmo 170 (SIP) and a headache

[BChild]

So whats the answer then - do I try to order a replacement board from SIP (not sure how much this would be) I figure this would also have a 100 ohm pot so save me modding my existing one

Obviously something is getting hot but nothing is jumping out as the cluprit

 

[malcolm]

Guess what I found while I was looking for the instructions for the oven. Can send it across for £15 if you like. (Says MX066 on the box - 30 amps, and 12 or 24V input).

 

[BChild]

So I emailed SIP to see about a replacement PCB just in case

Subject: Circuit Board for SIP (Cosmo) 170

Hi

I'm not sure if you are the best place to ask the question but I am looking for a price for a replacement circuit board for a SIP 170 (Cosmo branded)

the reason is I am struggling with variations in wire speed

It is slow to start off on the lower settings which means the carc is unstable

On middle settings once the wire speed is set after a period of 5 to 10 mins adjustments have to be made to reduce the wire speed to slow it down to provide an acceptable weld

In fact even without welding you can hear definate increases in the wire feed motor speed

Having checked everything out it seems that the only thing left that could be a cause is the circuit board hence my question

Regards

Ian

Very prompt reply - was impressed

Dear Ian

I would not look to the PCB, the problem you describe is normal related to a bad connection heating up, this causes an increasing voltage drop, the longer you weld the hotter the connection the higher the voltage drop, so as you weld you have to keep turning the wire feed speed down to compensate.

1 Check and clean all the bolted power connection in the welder, this fixes 95% of the welders.

2 Check the relay on the PCB for burnt contacts, this can normally be seen as a black deposit on the inside of the relay cover, requires either a new PCB or the relay replacing on the PCB.

The PCB is SIP part code 10008, for a distributor please contact our sales dept on 01509 500500.

Best Regards
Andrew

 

[BChild]

Guess what I found while I was looking for the instructions for the oven. Can send it across for £15 if you like. (Says MX066 on the box - 30 amps, and 12 or 24V input).

View attachment 11461

Yes please

And how does one install this thing?

 

[BillJ]

I would not look to the PCB, the problem you describe is normal related to a bad connection heating up, this causes an increasing voltage drop, the longer you weld the hotter the connection the higher the voltage drop, so as you weld you have to keep turning the wire feed speed down to compensate.

1 Check and clean all the bolted power connection in the welder, this fixes 95% of the welders.

2 Check the relay on the PCB for burnt contacts, this can normally be seen as a black deposit on the inside of the relay cover, requires either a new PCB or the relay replacing on the PCB.

I would say this is valid for an unmodified welder where the welding current can cause a large voltage drop across a dodgy connection. I'd be surprised if it were the problem on yours with its independent motor supply and a motor that draws barely an amp.

Weldequip supplies these boards but I think it's an expensive way to get a 100R trimmer fitted. Personally, I'd also avoid introducing a completely new set of variables by fitting a different controller until the trimmer has been eliminated as the cause. It is a known weak point and a cause of speed variation.

 

[BChild]

I would say this is valid for an unmodified welder where the welding current can cause a large voltage drop across a dodgy connection. I'd be surprised if it were the problem on yours with its independent motor supply and a motor that draws barely an amp.

Ahhh - I must admit I failed to inform SIP about the list of mods - I did however mention it in my reply thanking him for his prompt reply

Weldequip supplies these boards but I think it's an expensive way to get a 100R trimmer fitted. Personally, I'd also avoid introducing a completely new set of variables by fitting a different controller until the trimmer has been eliminated as the cause. It is a known weak point and a cause of speed variation.

Yeah - got your PM and I think you may have a plan (or half a plan that we can work on)

 

[BillJ]

the problem you describe is normal related to a bad connection heating up, this causes an increasing voltage drop, the longer you weld the hotter the connection the higher the voltage drop, so as you weld you have to keep turning the wire feed speed down to compensate.

Reading this again, he's talking ball-cocks!
If the voltage drop increases as you weld, then the voltage to the speed control PCB will decrease and so will the speed. Therefore you would need to increase the wire speed setting the longer you welded, not decrease it.

Or am I missing something?

 

[BChild]

Reading this again, he's talking ball-cocks!
If the voltage drop increases as you weld, then the voltage to the speed control PCB will decrease and so will the speed. Therefore you would need to increase the wire speed setting the longer you welded, not decrease it.

Or am I missing something?

You know me by now - he's talking about electrickery - so I'm in no position to argue

My only thought was as heat builds up in a bad connection surely resistance is lower

 

[BillJ]

My only thought was as heat builds up in a bad connection surely resistance is lower

For most materials, resistance increases as temperature rises.

 

[Jake SS]

Reading this again, he's talking ball-cocks!
If the voltage drop increases as you weld, then the voltage to the speed control PCB will decrease and so will the speed. Therefore you would need to increase the wire speed setting the longer you welded, not decrease it.

I would think that he is saying that the arc volts is decreasing, so the motor speed would have to be decreased to compensate for less arc volts.
Otherwise the wire would "hammer".

 

[BChild]

I would think that he is saying that the arc volts is decreasing, so the motor speed would have to be decreased to compensate for less arc volts.
Otherwise the wire would "hammer".

That makes sense but for the wire feed increasing even without welding

 

[Jake SS]

That would be open circuit voltage, no load except for motor.
So if something was hot then as it cooled would increase open circuit volts which would increase motor speed if not welding.
But if welding and overheating then arc volts would decrease, so might have to decrease speed.

Have not read all posts (way too many). So I do not know all details.

Best option is to burn it and buy a descent machine

 

[BChild]

Have not read all posts (way too many). So I do not know all details.

Best option is to burn it and buy a descent machine

Yeah it's been contemplated on a number of occasions

On a serious note I hate being beaten so I'll leave the burning ceremony untill after I've fixed it (that will be revenge) or if I've exhausted all the possibilities (admitting defeat)

 

[BillJ]

I would think that he is saying that the arc volts is decreasing, so the motor speed would have to be decreased to compensate for less arc volts.
Otherwise the wire would "hammer".

It does say in BChild's query to SIP that the motor speed increases over time (i.e. in absolute terms, not relative to welding power) but I can see how he could have missed that, not being as familiar with the problem as those of us who have read the latter part of this thread, so he's forgiven

It would be interesting to get Andrew's opinion on the problems we see on the SIP and Cosmo MIGs and the solutions (or bodges ) we have collectively come up with. With only a few of these mods, my 130T welds really nicely now.

 

[BChild]

It does say in BChild's query to SIP that the motor speed increases over time (i.e. in absolute terms, not relative to welding power) but I can see how he could have missed that, not being as familiar with the problem as those of us who have read the latter part of this thread, so he's forgiven

I probably didn't describe it as well as it could be described

It would be interesting to get Andrew's opinion on the problems we see on the SIP and Cosmo MIGs and the solutions (or bodges ) we have collectively come up with. With only a few of these mods, my 130T welds really nicely now.

I think so too - he's read all 22 pages of this thread so it's a start!

I didn't link to the thread either so he is either

1. A bloody good detective and tracked me down to here

or

2. Already brouses the forum in which case he probably has an opinion on the mods carried out but would rather not say anything

Personally I believe that if SIP took some of the problems and solutions on board they could make a very nice hobby welder but I'm sure as always the bean counters get involved and profit becomes the driver rather than making something that is good right out of the box.

This is slightly short sighted (from a customer loyalty perspective) as anyone who has had an SIP that hasn't worked out of the box wouldn't consider a more expensive model from the same brand.

Or am I being to optimistic about purchase choices and in this day and age it's all down to price and nothing else matters

I may be on my own here but examples are

1. my boiler failed this summer after 30 years of service - it was a glow worm and had been very reliable untill the gas valve failed and I couldn't light it anymore - I bought another glow worm I doubt it will last another 30 years like the original but I expect a good service from it

2. I've had good service life from some makita power tools so wherever I need to replace a power tool I tend to prefer that brand and I'm prepared for it not to be the cheapest

3. I've owned exclusively Vauxhall/Opels since 1988

the last one might not be the best example seeing as I had to buy a welder and learn how to weld

 

[malcolm]

Or am I being to optimistic about purchase choices and in this day and age it's all down to price and nothing else matters

There's plenty of info on the net these days for anyone researching a product.

I reckon the SIPs could get a lot of good press on the net if they took some ideas on board. Can't be more than a couple of quid in electronic bits to stabilise the feed from the main transformer so the wire feed worked properly and the adjustment knob could be reduced to a fine tune. It would make them handier than the Clarkes.

I posted the speed controller 1st class this afternoon - it's in a box so there might need to be someone there. It's easy and quick to fit, and I'd be inclined to fit it to rule out everything else from the increasing wire speed equation. When my welder did the same it turned out to be a failed capacitor on the board. No idea how that was diagnosed - I posted the board to TechArc and they did their magic.

 

[BillJ]

I posted the speed controller 1st class this afternoon

And I posted a 100R trim-pot 1st class this afternoon so BChild will have great fun tomorrow applying both mods to see how they compare

 

[BillJ]

I reckon the SIPs could get a lot of good press on the net if they took some ideas on board. Can't be more than a couple of quid in electronic bits to stabilise the feed from the main transformer so the wire feed worked properly and the adjustment knob could be reduced to a fine tune. It would make them handier than the Clarkes.

Well, it looks like they're now fitting a 100R trim-pot to current models so that's a good start.

The metal liner seems to have replaced the previous plastic liner, which gives the "flexi" wire-feed mechanism an easier time. Mine had this fitted from new. Another excellent move.

The motor brake I and BChild have incorporated into our mods is a really nice feature to have - it came almost free once I decided to use a relay to switch the power to the motor PCB. As I say, "nice to have" but probably a complex and costly luxury on a low-cost welder.

Running the wire-feed from the welding voltage to give an automatic coarse wire speed adjustment related to the power setting is a good feature and if it worked properly, as you say, the knob would be a fine speed control. However, all SIP/Cosmo users must be familiar with the resulting unstable feed where as soon as the arc is struck, the wire speed slows, often breaking the arc so that it speeds up again, then arcs, then slows, etc, giving a "machine-gun" effect to the welding process.

While regulating the welding voltage down to a single, stable voltage for the motor drive would add pennies to the cost of the welder, having 8 selectable, stabilised voltages (one for each power setting) could be rather more complex and expensive (in my opinion as a BEng in electronic engineering) but perhaps there's a clever way to do it at fairly low cost.
Given the current alternative, I'm much happier with a single, stable voltage and having to adjust the wire speed knob as I change power settings. That isn't a "selling feature", though. It would be really nice if it could work as intended AND be stable. It would be a challenge to implement, though, and keep the price low. There - a challenge for the SIP engineers!

Finally, knowing how cheap and easy it is to brace the "flexible" wire-feed mechanism, I'm surprised they haven't done it already. The simplest way I can think of to achieve this would entail modifying a single moulded component and would mean that changing the feed wheel would require removal of three screws instead of two. Then again, in my experience (of one SIP MIG), it works OK out of the box and only fails after some months of use. I'd be very happy for SIP to convince me that they care not only about magazine reviews but also about their customers who will be using these products year after year.

Given that only a minority of SIP's target market will ever find this forum, or at least find it before they have made their purchase, the bad press that the modern SIP/Cosmo MIGS get here may not impact their sales significantly. However, there are quite a few people on the forum who, when seeking advice about buying their first MIG, have been steered well clear of SIP and have bought something else instead (often a Clarke).

The SIPs are so nearly a great, low-cost MIG welder. I bought mine because the 25A minimum current is great for car bodywork. To be honest, the low price seemed a bonus - had it cost £50 more I'd still have bought it over a Clarke. I realise, of course, that many people are simply looking at the price tag, especially since many in the target market know very little about welding - like I did - and that some people can only justify purchase of a MIG if the price is at Chinese levels. It's a bit of a tightrope for a manufacturer.

If this were a Chinese brand, we probably wouldn't be having this discussion. It would be cheap cr@p and we wouldn't expect any more. SIP, however, have a good name to keep up. At least around here, that name is turning to mud and I'd hate to see that happen after being so happy with my SIP arc welder of decades ago and my 150l SIP compressor (which suffered from an inadequate regulator, now I think about it. Hmm...).

Anyway, waffle over - time to give someone else a turn

 

[BillJ]

2. Already brouses the forum in which case he probably has an opinion on the mods carried out but would rather not say anything

If one of my Tech Support colleagues commented on one of our products on an open forum, even if the comments were intended to be good ones, our management would come down on them like a ton of bricks for not getting Legal to clear it first. Imagine, then, them broadcasting to the world in general that they acknowledge that there are shortcomings in our products and that even a bunch of DIY bodgers can do better (ignoring cost)!

I think they would be "getting their coat"

 

[BChild]

And I posted a 100R trim-pot 1st class this afternoon so BChild will have great fun tomorrow applying both mods to see how they compare

Arrived yesterday - many thanks - I think I'll fit that first