# Porter cable 7538 soft start triac?



## glawing (Jan 8, 2008)

I have traced the electric curcit with a ohm meter and it all lead to the triac, can anyone tell me hoe to test it as I don't think it can be tested with the ohm meter?

Thanks Geno


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## Dr.Zook (Sep 10, 2004)

I can't answer your question Geno, but welcome to the Router Forums.


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## bobj3 (Jan 17, 2006)

Hi Geno

May I ask why you want to test it ??

Without a tech manual you will be just spining your wheels..


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glawing said:


> I have traced the electric curcit with a ohm meter and it all lead to the triac, can anyone tell me hoe to test it as I don't think it can be tested with the ohm meter?
> 
> Thanks Geno


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## Woodnut65 (Oct 11, 2004)

Hi Geno: The Ohm meter will tell you if a path to the Triac exists, but not if it is working. With out a manual it is kind of a best guess situation. I think that it would prove to be more productive to check the output side of the Triac on the AC voltage scale of the meter. I think that it adjusts the voltage on start up, to ramp up to the operating voltage. It would seem that you should see the voltage step up when the meter is on it and you start the router up. That's my thought on it, hope it helps.
Woodnut65


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## glawing (Jan 8, 2008)

bobj3 said:


> Hi Geno
> 
> May I ask why you want to test it ??
> 
> ...


I wanted to test it because the motor would not run. I have tested it and the triac was good but the voltage ramping device was bad and have ordered a new soft start that includes the triac and this device.

Thanks Gene


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## Ryebread (Sep 15, 2008)

*Testing Triac*

Testing a triac with an ohmeter is quite simple.

A triac is a bi-directional latching conduction device. The controller in your router is telling the triac when to turn on and allow line voltage to the motor. Depending on the router and the controller, this allows it to do various things like speed control, soft start, and some more advanced things like foldback motor load controlling. 

In case you have overloaded the triac it is likely that it has failed short. If your router has been plugged in to the wall and you have experienced any sort of electrical storm or other line surge events, your triac may fail open (this is difficult to test with a simple ohmeter). To test to see if it is short, touch the probes to the A1 and A2 legs of the triac and measure the resistance (refer to the datasheet at this link: ) If the resistance is less than 100 ohms or so, you've got a dead triac and every time you turn on your router, it will come on at 100%. Testing to see if the triac has failed open is trickier and would require you to look at the terminals while the router is on and would likely require you to use an oscilloscope. A triac from mouser.com or digikey.com is about $1 in small quantities and is easy to replace with a soldering iron.

Hope that helps.


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## Clouseau (Oct 12, 2009)

Gene: Did the parts fix your router. I need to go deeper into mine. I have continuity from the plug through both switches to the brushes. Previous owner thought a switch was bad. Not the case. Both switches are good. I need to find a parts list and a schematic.

Dan


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## Clouseau (Oct 12, 2009)

Found a schematic. How would one determine the required triac from on of the above suppliers. Direct replacement part is $60-70.


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## Ryebread (Sep 15, 2008)

*Triacs*

The triac, if it has failed, is simple to replace and relatively inexpensive.

You can purchase them in small quantities from sites like Digikey or Mouser. Go to Digikey and search for p/n BTB16. 16 Amps is the maximum operating current of the triac (which would be suitable for a small router) and 600V is the blocking voltage of the device... or rather, the voltage that, if present, would break over the device and turn it on. Since you are probably plugging directly into 120V, the maximum voltage on the part will be 170V (120*sqrt(2)), so 600V is more than sufficient.

If you have a large router, then it might be a good idea to use a 24 Amp part.

To replace it, just remove the heatsink, de-solder the legs, insert the new one and reattach the heatsink.


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## Clouseau (Oct 12, 2009)

I eliminated the triac and heat sink. It runs fine without it.


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## ceddarwally (Jan 27, 2011)

*PC 7538 soft start*



Clouseau said:


> I eliminated the triac and heat sink. It runs fine without it.


Hi Clouseau (Inspector??). Read your fix and also removed soft start and working fine without it. A litle more torque to hold on to at start, but minimal. Easy to remove - remove 4 top screws, lift out triac and term block. Remove two black wires from terminal block and wire nut them together. Cut the small blue wire down into the existing wire nut far enough so the tail cannot short to anything thus leaving the two white wires connected still in the nut. Throw away the triac and block. You now have a standard router without soft start.

Thank you Inspector for your posting - kept me from throwing away a perfectly good router ($60 triac and installing not worth it for an old router).

My post only to help others - probably a number of units out there with blown triacs!

Wally


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## bobj3 (Jan 17, 2006)

Hi


Once you get the triacs item out of the router use the item below to get the speed control back.

Heavy Duty Speed Control 20 Amp.
#9410 • $34.95

MLCS Router Speed Control and Billy Pedal Foot Switches

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## coxhaus (Jul 18, 2011)

I know this is an old thread but I am removing the triad and plane to use an external speed controller. I am going to buy it from MLCS but they are out of the heavy duty ones. Do you think I can use the regular duty speed controller with the PC 7538 router as I would like to order it now?


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## Stick486 (Jan 4, 2013)

coxhaus said:


> I know this is an old thread but I am removing the triad and plane to use an external speed controller. I am going to buy it from MLCS but they are out of the heavy duty ones. Do you think I can use the regular duty speed controller with the PC 7538 router as I would like to order it now?


seems like it would but there isn't any margin for error...


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## Stick486 (Jan 4, 2013)

coxhaus said:


> I know this is an old thread but I am removing the triad and plane to use an external speed controller. I am going to buy it from MLCS but they are out of the heavy duty ones. Do you think I can use the regular duty speed controller with the PC 7538 router as I would like to order it now?


found these..

Grizzly.com
Router Table Accessories - Heavy Duty Router Speed Control
http://www.amazon.com/MLCS-9410-20-Amp-Router-Control/dp/B001NIK6PC


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## coxhaus (Jul 18, 2011)

I just noticed on the Amazon ratings people are saying the dial set on high does not run full power. Is this a known problem?


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## coxhaus (Jul 18, 2011)

Has anybody bought one of these speed controllers and had any problems trying to run full speed?


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