yes, 12 volts and 24 ohms will work with any TO-220 triac. The TO-92 triacs are too small.
All the triacs I have ever seen use from 5ma to 50ma for the gate drive. It's just experience talking.
You can look up YOUR triac...can't you? I'm too lazy to search 100 posts to find the number.

 

Okay, I replaced the bad resistors but no change. The unit still turns on, runs for five seconds and then shuts off again. Cut the power, turn it back on and away it goes for another five seconds. Starting to get very frustrating. Next move???

 

I would check the triac first.

 

Will do. I will let you know how it turns out. I have one left so I shall just replace it and see what happens.

 

New TRIAC installed, same old story. Five second run, quits. Shut off switch, back on, five second run, quits ..........
Question. The speed control on this seems to have varying resistance between any two pins. Is this normal and can it cause the above problem? Two of the pins which I feel are the fixed resistor, range from 46 Kohms to 53Kohms. The other two readings go from 2 ohms to 49 K ohms

 

OK. You are there. Probe around until you find a voltage that behaves like the symptoms. Be careful.

 

Can you take out the pot and try to get the readings and see if they match.
Side pins should be stated as in the pot. The center pin should vary smoothly when pot is turned . Any jumping of the resistance says trouble.

 

I have checked every pin both AC & DC and included my findings on the attached chart. I have also removed the potentiometer from the board and measured it. It seems to be working just fine.


I will gladly edit this if someone can tell me what format to put my spreadsheet file into.

 

Hmmm ! Pot seems fine.
My next try would be a another IC. Need to rule out the semiconductors to be sure it is passive component issue.
And that is why I never buy just one piece ever.

 

Is there anything from my voltages that looks out of place though? I don't like being a parts replacer. I like understanding why I am replacing parts. Can you help me out a little bit in that direction or is this just how it is done in this industry. Sorry, I am from another industry and I don't like replacing things unless I know there is a fault and I can prove it. Something in those voltage readings must indicate a problem somehwere?

 

Need to some time to go thru them.

 

God willing, I have lots of that. Will wait to hear back from you.

 

Bill
Look for a voltage that changes like the symptoms. Look for a voltage the is high for five seconds and then goes away when the motor stops. Look at each pin of the IC as you turn it on. You have to be the on-site detective. Look for clues

 

Hi Lestraveled. I monitored all the voltages as you asked and posted them above. I keep looking at the pins for the TRIAC but not exactly sure what they mean. Also, not sure which pins are AC and which are DC. If I knew that, things might become a little more clear.

 

To beat a dead horse. Try jumping pins #16 and #18 with a temporary wire. It should probably be soldered to keep it from coming off during motor running vibration. This comes from the last sentence on page 4 of the data sheet.

Still say that there is a wire missing from the motor to the board. In one of your other posts you said, if I remember right, that the cap and resistor components are on board at pin #8. This is the speed sensor area of the board. The motor would start and run until the internal voltage on the speed sensor circuit are depleted, and not recharged by the parts connected to pin 8 and the motor. This is also in the data sheet. This voltage is supplied by jumping pins 16 and 18 when no speed sensor is used.

 

Shortbus, I am not saying you are right or wrong. I just don't know the difference TBH. I am fairly new to this and I can do a lot of things, but this circuit is over my head and I am on here asking for help. You say speed control and yet the router owner says it worked perfectly fine before the board blew. I get it and I find a burnt cap C155, a 22k ohm resistor with very low resistance and a resistor underneath the TRIAC that looked like it blew up but still read proper resistance. I have rep[laced all those parts plus the TRIAC twice and the IC. If I understood how it worked, it would be fixed. I have looked for wiring from the motor to indicate speed but see nothing. If you look at post #29, pins 16 and 18 are joined through an 820 k ohm SM resistor. Pin 8 goes to several things which I can't make heads or tails of. If someone explains it to me, I get it.

 

Just saying that unless this is a very early model vary speed router, they use speed feed back to keep the torque at the same level as full speed. The early ones didn't have the speed sensor and when running at lower speeds they would stall out in the cut.

 

So if I jump 16 to 18, which I will go do right now, it should run?? If so, should I be able to vary the speed or will it be constant? If that works, where does the problem lie?

 

Have you made any corrections to your reverse engineered diagram.
If so post it, I like to check it.

 

Okay today I jumped pins 16 to 18 and things actually got worse. The motor started up much slower and only lasted about 2.5 seconds before it cut out. Shut it off and it starts right back up again exactly the same way. this is getting very frustrating. I have gone over the board and I see no changes to be made to the diagram I made. I have rechecked all components and tracings and keep coming back to IC or TRIAC. Since I have changed both (TRIAC X 2) (IC X 1), I am at a loss but I want to fix this thing.