Mod-Your-151 How-To Guide

[d94jonca]

you'll beat me to it! : i;ve had all the parts for days but wife, kids and boss takes all my time!!!

oh does anyone know if it matters on what side of the motor the diodes go? i realize the diodes have polarity, i but as for wether to place them on the + or - side of the motor, that doesnt matter, does it?

[milwiron]

How many of you have done these mods? How about reporting back on your results and opinions.

I picked up a 151 to finish some small projects while my Miller Syncro is in the shop getting fixed. So far I think it's a pretty decent value for the money. I have the parts coming in from Digikey in a couple days to mod mine and am curious why this thread fell silent.
BTW, the total price for the parts with shipping from Digikey came to 50 bucks.

[Bluewelders]

Mine worked OK, it works a lot better with the output capacitors and the capacitor on the wirefeed motor.

[milwiron]

Here's a list of parts from Digikey www.digikey.com to do the capacitor mod as Bluewelders outlined in this thread. Surplus houses will have cheaper component prices but I was looking for one shipping fee, No single surplus supplier had everything and shipping costs add up fast.

565-3323-ND 100000 uF Capacitor $24.36
GBJ604-FDI-ND Bridge Rectifier 2.18
338-1366 3” Cap. Bracket 10.50
493-1081-ND 100uF Cap (Motor) .21
KAL2550F-ND 50 Ohm 25W Resistor (Cap Bleed) 3.30
RL201-TPCT-ND 2 Amp Diode (Motor Speed) .30

Digikey also has a good selection of fans.

More fans- https://www.surpluscenter.com/sort.a...c&keyword=EBFA

[d94jonca]

i'm still prototyping on this. i've had some very strange results on motor speed and wanted closure before posting my results, but since the question is raised here is my status:

am currently running with a 60mF (thats 60000 uF for you americans ) cap, a separate rectifier for the motor and a smaller cap accross the motor. at least with .024 wire the speed is pretty ok and it welds *very* nice.

as for putting diodes in serial with the motor to further slow it down, my results defy all logic but here goes. i've been trying putting a varying number of diodes in serial with the motor, on the negative side of the motor. i swear to God that the more diodes i put in the FASTER the motor runs. i have no way of explaining this observation but the speed difference is considerable and easily reproducible.

[milwiron]

...as for putting diodes in serial with the motor to further slow it down, my results defy all logic but here goes. i've been trying putting a varying number of diodes in serial with the motor, on the negative side of the motor. i swear to God that the more diodes i put in the FASTER the motor runs. i have no way of explaining this observation but the speed difference is considerable and easily reproducible.

Are those Schottky diodes by any chance? Schottkys wouldn't slow it down much.
Not sure about speeding up other than maybe they're cleaning up the voltage coming from the board???

[yellow]

Ditto to what milwiron said. Just an idea... have you tried placing the diode on the positive side? I don't see why it would be any different but there might be something going on with the speed sensing circuit (if there is one?) on the control board.

[Bluewelders]

I've tried to keep the changes to the wire speed, off of the board so people won't have to solder on the control board.
You might try a 200uf across the motor first, instead of the 100uf.
If that is not enough.
There is a resistor (R9 = 390ohms on mine) that is across the speed pot that can be replaced with a higher value.
You might try a 3.9K resistor in place of , or in series with R9.
If that is still not enough you could try 4.7k
A 10k pot wired in series with R9 temporarily, might be the the best way to find the perfect resistance.

i'm still prototyping on this. i've had some very strange results on motor speed and wanted closure before posting my results, but since the question is raised here is my status:

am currently running with a 60mF (thats 60000 uF for you americans ) cap, a separate rectifier for the motor and a smaller cap accross the motor. at least with .024 wire the speed is pretty ok and it welds *very* nice.

as for putting diodes in serial with the motor to further slow it down, my results defy all logic but here goes. i've been trying putting a varying number of diodes in serial with the motor, on the negative side of the motor. i swear to God that the more diodes i put in the FASTER the motor runs. i have no way of explaining this observation but the speed difference is considerable and easily reproducible.

[d94jonca]

thanks for all the ideas guys! the diodes are regular rectifier diodes, for sure not schottkys. i *did* contemplate moving the diodes to the positive side of the motor. i couldnt either think of why it would matter but figured it couldnt hurt trying. anyway, now that blue was kind enough to offer additional tips on how to regulate motor speed i'll probably try increasing the motor cap and otherwise attack the control board directly. or perhaps just leave it as is. as stated above the speed isnt *too* bad and the arc stability is *much* better

[Bluewelders]

If you need a schematic of the board, I can draw one up for you.
It's a really simple board.

[Bluewelders]

In looking at some of the notes I took, it seems that versions of the boards sometimes have different part numbers.
So if you decide to work on the boards, you will need to work out what to do,to what component.

[milwiron]

thanks for all the ideas guys! the diodes are regular rectifier diodes, for sure not schottkys. i *did* contemplate moving the diodes to the positive side of the motor...

My results adding diodes to slow down the motor were the same, it sped up, maybe doubling the speed.
I’d guess the diodes are smoothing out some voltage ripple.
My conversion is done. I won’t have a chance to play with it for a day or two. I’ll report my observations.
Thanks Bluewelders for all your guidance.

[drum365]

Is this model discontinued? I haven't been able to find it on Harbor Freight's web site.

*EDIT* - Never mind. I see it is HF part no 97503. Nothing in the description says anything about "dual mig 151" but I can see it printed right there on the case in the photo.

[Ravenous]

I've inherited an Italian made Clarke turbo weld 100EN 110v welder. It has a choke and a rectifier and the gun is cold until the trigger is pulled. Can I use the same components with a 110v fan instead of course? I know it isn't a harbor freight model but I was going to get the 151 until this fell in my lap.

[rookie_steve]

. . . am currently running with a 60mF (thats 60000 uF for you americans ) cap, a separate rectifier for the motor and a smaller cap accross the motor. at least with .024 wire the speed is pretty ok and it welds *very* nice.

He-he, the "uf" thing isn't an American thing, it's an electronics thing. Most capacitors are measured in micro farads, not milli farads. In fact the "u" in uf is the symbol for micro-farad.

If you were just joking, then my post is for those who might not understand and then start giving their electronics supplier capacitance in milli-farads. They would know you didn't know what you are doing.

Later,
Steve

[rookie_steve]

Nice job mobes . . . great photos and explanations. Might even try that myself.

Thanks,
Steve

[Bluewelders]

If it is the same circuit as the British Clarkes.
The capacitor changes should be about the same, at least 40,000 uf for 100amps.
Many of the small welders have the connectors for a fan on the back of the power switch.

The wire feed control board is of a different type, than is used by HF.
You will probably have to make or buy a voltage regulator for it.

I've inherited an Italian made Clarke turbo weld 100EN 110v welder. It has a choke and a rectifier and the gun is cold until the trigger is pulled. Can I use the same components with a 110v fan instead of course? I know it isn't a harbor freight model but I was going to get the 151 until this fell in my lap.

[DougAustinTX]

Does that new pancake (muffin) fan put out more CFM of air than the original bladed type fan? That seems counter-intuitive to me. I have upgraded several HF mig boxes that came with NO FAN at all, and the fans I have put in actually look like the one you took out at the first part of your project. Nothing in my opinion makes things live longer than keeping them cool. Good job by the way on the descriptions and photos. I love seeing projects like this.

[Bluewelders]

The original fans seem to just kind of flail the air around.
It has no shroud and the blade is located away from the intake vent, it probably blows air around that is already hot.
With the new muffin fan you can feel a good amount of air blowing out of the vents.

[milwiron]

The original fans seem to just kind of flail the air around.
It has no shroud and the blade is located away from the intake vent, it probably blows air around that is already hot.
With the new muffin fan you can feel a good amount of air blowing out of the vents.

Agreed, the fan I stuck in is rated at 130 cfm. It "seems" to move about twice as much air as the stock fan.
I never had any real trouble with the stock fan but I figured as long as I had it apart I'd change it.
The weather has been crappy here for days, I still haven't had the chance to try out welding with the mods on my machine yet.

[milwiron]

I've finally had a chance to test the capacitor mods I finished last weekend. The machine definitely has more guts. I’m not much of a wire welder but I’d say it wouldn’t have much trouble with 5/16 or maybe 3/8" steel. I'll grab some thicker scrap at work this week and try it.

The slightly faster feed motor is no problem. Since it has more punch at each power setting I’m running a faster wire speed anyhow.

[Bluewelders]

Mine acted like a different machine as far as power and the weld profile, and the way the arc sounds is far better.
Did you try 200uf of capacitance across the wirefeed motor to slow it some more ?

[milwiron]

Mine acted like a different machine as far as power and the weld profile, and the way the arc sounds is far better.
Did you try 200uf of capacitance across the wirefeed motor to slow it some more ?

I do have 200uF across the motor, it does help.
It's a ballsy little machine now, I've got about $230.00 total invested in mine at this point, I don't know if there's anything else around that'll touch it for the price.
I'll probably change the ground cable and clamp but other than that I'm very happy with it.

Thanks for all your help Bluewelders, your guide worked perfectly.

[transit]

Mine acted like a different machine as far as power and the weld profile, and the way the arc sounds is far better.
Did you try 200uf of capacitance across the wirefeed motor to slow it some more ?

With all this rain I’ve been bored. A while back I upgraded my Century 170; unlike the 151 it has a capacitor, 100,000umf. I added a second cap of the same value in parallel, what a difference. With the 170 set to supply 150 amps into a 3/16 in. sample T joint, smooth arc and excellent penetration [one side filet]. I removed the second cap, the arc was not as smooth and the current dropped to 100 amps, penetration was not as deep and there was some spatter.

I finally have ¼”, 5/16” and 3/8” stock to test with.

The ¼” T joint welded [one side filet, one pass] smoothly without any preparation, no beveling was required. I bend tested the joint, only the start and stop showed incomplete penetration.

The 5/16” T joint welded [one side filet, one pass] smoothly without preparation. The bend test showed almost 100% penetration.
Retested the 5/16” stock using the same settings with a bevel and the penetration was 100% start to stop.

The 3/8” T joint welded [one side filet, one pass] smoothly without preparation. The bend test showed almost 80% penetration.
Retested the 3/8” stock using the same settings with a bevel and the penetration was 100% start to stop.

I see at the higher power settings, heat and current, the arc is very stable and smooth with no detectable spatter. The bead shows little or no freeze lines just one long continuous bead. The short circuit frying bacon sound of the arc with some spatter is now a smooth hisses like an air leak without spatter.

[Bluewelders]

You had some good results, and you did some interesting testing.
Someone needs to do a before and after test of the 151, to get a real baseline for what the mods do.
I wonder what it would actually cost the manufacturers to add a capacitor to the machine.
A Capacitor seems to make them at least, twice the welder.

With all this rain I’ve been bored. A while back I upgraded my Century 170; unlike the 151 it has a capacitor, 100,000umf. I added a second cap of the same value in parallel, what a difference. With the 170 set to supply 150 amps into a 3/16 in. sample T joint, smooth arc and excellent penetration [one side filet]. I removed the second cap, the arc was not as smooth and the current dropped to 100 amps, penetration was not as deep and there was some spatter.

I finally have ¼”, 5/16” and 3/8” stock to test with.

The ¼” T joint welded [one side filet, one pass] smoothly without any preparation, no beveling was required. I bend tested the joint, only the start and stop showed incomplete penetration.

The 5/16” T joint welded [one side filet, one pass] smoothly without preparation. The bend test showed almost 100% penetration.
Retested the 5/16” stock using the same settings with a bevel and the penetration was 100% start to stop.

The 3/8” T joint welded [one side filet, one pass] smoothly without preparation. The bend test showed almost 80% penetration.
Retested the 3/8” stock using the same settings with a bevel and the penetration was 100% start to stop.

I see at the higher power settings, heat and current, the arc is very stable and smooth with no detectable spatter. The bead shows little or no freeze lines just one long continuous bead. The short circuit frying bacon sound of the arc with some spatter is now a smooth hisses like an air leak without spatter.