Can a bridge rectifier be replace with a different type machines rectifier ?

[eddie49]

The cheapest solution would be 3 or 4 of these £3 blocks in parallel:

Single Phase Diode Bridge Rectifier 50A 1000V KBPC5010 New A3J4 | eBay

Find many great new & used options and get the best deals for Single Phase Diode Bridge Rectifier 50A 1000V KBPC5010 New A3J4 at the best online prices at eBay! Free delivery for many products!

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However, to share current equally they must all be at the same temperature, so would need to be mounted on one common heatsink.

 

[stevethegrease]

I agree with the comments above about old electronics. Old= unreliable and probably unobtainable crap - look at old British bike electrics- terrible. A bridge rectifier is 4 Diodes in a square arrangement . if there are 24 then the components are doubled up ( probably because the current rating wasn't available in one component back then), or there is more than one rectifier. Modern components are really cheap and very reliable as in the above posts. Some bits of ally ( maybe the originals) as heat sinks and some bolt terminal diodes and you are away. Sorted. Dont mix old and new - the old will likely fail fairly rapidly.

 

[gaz1]

I agree with the comments above about old electronics. Old= unreliable and probably unobtainable crap - look at old British bike electrics- terrible. A bridge rectifier is 4 Diodesin a square arrangement . if there are 24 then the components are doubled up ( probably because the current rating wasn't available in one component back then), or there is more than one rectifier . Modern components are really cheap and very reliable as in the above post.

well they was reliable then and did a good job but would i replace with old when new is far better

as goes for reliable both parts arnt as good as the other however some older parts out last the new parts due to design faults under powering them for cheapness when building new machines

 

[Welder Crafts]

The cheapest solution would be 3 or 4 of these £3 blocks in parallel:

Single Phase Diode Bridge Rectifier 50A 1000V KBPC5010 New A3J4 | eBay

Find many great new & used options and get the best deals for Single Phase Diode Bridge Rectifier 50A 1000V KBPC5010 New A3J4 at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

However, to share current equally they must all be at the same temperature, so would need to be mounted on one

The cheapest solution would be 3 or 4 of these £3 blocks in parallel:

Single Phase Diode Bridge Rectifier 50A 1000V KBPC5010 New A3J4 | eBay

Find many great new & used options and get the best deals for Single Phase Diode Bridge Rectifier 50A 1000V KBPC5010 New A3J4 at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

However, to share current equally they must all be at the same temperature, so would need to be mounted on one common heatsink.

They look good but I'd have to do some modifications to get them going

 

[Welder Crafts]

What if I get 24 10amp stud diodes and fit them in the same as the old diodes wouldn't that save me the hassle of changing any of the diode arrangements?

 

[Welder Crafts]

Or maybe the stud type don't come in 10amp

 

[Welder Crafts]

￡6.67 22%OFF | MDQ 150A-1600V Black Single-Phase Diode Bridge Rectifier 150A Amp High Power 1600V

Page Not Found - Aliexpress.com

Would one of these work?

 

[eddie49]

Wouldn't the 60 amp diodes cause a difference within the lower mig welding settings? Or does it not make much of a difference?

The welder power settings select different input voltage taps on the primary of the main transformer, which results in an output voltage on the secondary varying from about 15 to 30 volts. The rectifier accepts this AC input and converts it to DC. From about 0.7 volts up to whatever it's maximum safe rating is, the rectifier does not care about the voltage.

 

[Welder Crafts]

The welder power settings select different input voltage taps on the primary of the main transformer, which results in an output voltage on the secondary varying from about 15 to 30 volts. The rectifier accepts this AC input and converts it to DC. From about 0.7 volts up to whatever it's maximum safe rating is, the rectifier does not care about the voltage.

Alright thanks for the insight was a bit curious if it made a difference I guess that's clarified

 

[eddie49]

Using 24 small stud diodes would not be needed, when modern components with higher ratings are available today.

The 150 Amp diode block that you found on AliExpress would do the job. It would have to be mounted on a finned heatsink, such as this one:

Heavy Duty Aluminium Finned Heatsink | eBay

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bolted down using silicone thermal paste, and preferably cooled with a fan ( if the welder does not have one already ).

 

[Ross365]

The problem with having lots of diodes is that if any of the multiple connections gets iffy and one diode is not in line, the others have to carry its load and then we're on a pathway to failure. Fewest number of connections, fewest chance of problems. All silicon diodes drop around 0.6-0.7 volts across them irrespective of their power rating or the date they were made, so the welder will have the same voltage on the tip. The finned aluminium heat sink proposed above by eddie should make a neat and very reliable replacement for what you have.

 

[Welder Crafts]

Using 24 small stud diodes would not be needed, when modern components with higher ratings are available today.

The 150 Amp diode block that you found on AliExpress would do the job. It would have to be mounted on a finned heatsink, such as this one:

Heavy Duty Aluminium Finned Heatsink | eBay

Find many great new & used options and get the best deals for Heavy Duty Aluminium Finned Heatsink at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

bolted down using silicone thermal paste, and preferably cooled with a fan ( if the welder does not have one already ).

Alrighttt I think I might go with block type I have a few finned heatsink which I pulled out of some electronics some time ago its about 250mm long might just put the whole thing in and with some thermal past and see how it does

 

[charliecambs]

Wouldn't the 60 amp diodes cause a difference within the lower mig welding settings? Or does it not make much of a difference?

Just a comment really I have a Special Car 120.
It was working when purchased (other than the stitch timer) I decided to have a look ( as a retired electronics engineer ) at the board but decided that i wouldn't risk repair as i had no need for stitch.
What did happen though was that nothing operated after re inserting the board - this turned out to be the multi-plug contacts dry joint to the board obviously strained by movement.

I'd also suggest carefully checking the wires running from the chocolate block into the machine. Due to age mine had crumbling rubber insulation which wasn't immediately visible and one day after moving the welder (blooming heavy!) there was a big flash and bang as the switched live from the contactor touched the case!

Despite its age it welds really well and seems to have good duty cycle for no "turbo" fan. I would thought any bridge of similar current rating would be fine if it fits into the case/wiring

 

[mtt.tr]

I would use the bolt type only because connection would be far simpler

 

[Welder Crafts]

Just a comment really I have a Special Car 120.
It was working when purchased (other than the stitch timer) I decided to have a look ( as a retired electronics engineer ) at the board but decided that i wouldn't risk repair as i had no need for stitch.
What did happen though was that nothing operated after re inserting the board - this turned out to be the multi-plug contacts dry joint to the board obviously strained by movement.

I'd also suggest carefully checking the wires running from the chocolate block into the machine. Due to age mine had crumbling rubber insulation which wasn't immediately visible and one day after moving the welder (blooming heavy!) there was a big flash and bang as the switched live from the contactor touched the case!

Despite its age it welds really well and seems to have good duty cycle for no "turbo" fan. I would thought any bridge of similar current rating would be fine if it fits into the case/wiring

Gonna do a full overhaul on the machine before I even attempt to plug it in thanks for the input..
Mine has a huge fan in there don't know if the previous owner added it or it came like that and yea the machine sure is heavy I get PTSD from the time I thought I was herculese and lifted it up four steps

 

[Welder Crafts]

Thank you all for your input I really appreciate it gonna get ordering and will let you know how it goes once I get it all together.

Considering it doesn't go kaboom

 

[Jack Ryan]

I think someone suggested a simple bridge like this (200 amps):

Baomain Bridge Rectifier MDQ-200A 200A 1600V Full Wave Diode Module Single Phase: Amazon.com: Industrial & Scientific

Baomain Bridge Rectifier MDQ-200A 200A 1600V Full Wave Diode Module Single Phase: Amazon.com: Industrial & Scientific

www.amazon.com

Multiple diodes used to be used because that was the technology of the day. The trouble is, they need to be reasonably well balanced both for forward voltage drop and for heat dissipation. If they are not and one goes, the rest will often follow.

I would go with the single bridge. I have not repaired a welder using one but there are lots of YouTube videos showing how to convert an AC MIG to DC using this type of bridge rectifier.

Jack

 

[eddie49]

I would go with the single bridge. I have not repaired a welder using one but there are lots of YouTube videos showing how to convert an AC MIG to DC using this type of bridge rectifier.

I also have no experience of this type of "large diode block". Rather than stud-mount, they follow current industrial practice for high-power semiconductor device formats such as IGBTs, multi-SCRs, and dual Schottky diodes, and they can be bought cheaply. They have the advantage of bolted connections, which as mtt.tr said, would make them a simple replacement for the typical finned multi-diode assemblies in transformer MIGs. I assume these modules can only reach their specified current ratings when used on a solid flat finned heatsink with a fan.

Do any of the AC MIG -> DC videos show sample welds after conversion?

 

[Jack Ryan]

I assume these modules can only reach their specified current ratings when used on a solid flat finned heatsink with a fan.

I doubt these come with full specifications but if you check a known brand it will list the heat sink requirements, thermal conductivity etc. I would be tempted to thermally mount the rectifier to the case either directly or indirectly via a finned heat sink. Then see how hot it got - the duty cycle is probably low anyway.

If I had to, I' add a fan if there wasn't one already.

Do any of the AC MIG -> DC videos show sample welds after conversion?

They generally do but I haven't kept track of them so I can't provide a link - sorry.

Jack

 

[Welder Crafts]

A lil update on the the welder.
The bridge rectifier arrived this morning.
fitted it after work.
lo and behold it works

Now all I need to get is some thermal paste and mount the rectifier on a heatsink. Then put it through some torture.