Blown cap on old dwell gauge - kal equip 2851

[redwire]

Re: Blown cap on old dwell gauge - kal equip 2851

here doesn't look right ..

You're right trace should be flat but I have seen that as a solder blob from the tinning process, on PC boards made in the 1980's like this one.

The dwell meter reminds me of Sun, Sears Craftsman etc. circuits. PCB marked 01-4221B so it might be made by them.

[petehall347]

Re: Blown cap on old dwell gauge - kal equip 2851

that transistor looking thing might be shorted ..best check its id number then test it .

[petehall347]

Re: Blown cap on old dwell gauge - kal equip 2851

here doesn't look right ..

[redwire]

Re: Blown cap on old dwell gauge - kal equip 2851

I followed the circuit a bit, but can't tell what all the wires go to. The burnt resistor connects to the red wire near the LED, see pic.

I would say it's 82R based on the grey band and smoke, so power shorted to that wire. It's a weird fault, someone must have connected up the wires wrong to the board. +12V power is supposed to connect to the top right corner. The CD4069 IC then gets 9VDC power.

OP a resistor does not burn up unless there is an overload caused by another issue. So replacing the resistor will just smoke it again. The other resistor looks OK it just has a purple body. I can't see any cooked pcb traces, it's just solder-dipped might appear that way?
The transistor typically connects to the ignition coil/points, but here it's missing all the surge protection parts so I'm not sure where they are.

[petehall347]

Re: Blown cap on old dwell gauge - kal equip 2851

looks like a track got burned through .

[stj]

Re: Blown cap on old dwell gauge - kal equip 2851

desolder it and check its resistance

[snakeintheeaglesshadow]

Re: Blown cap on old dwell gauge - kal equip 2851

Thanks both for the quick replies. Sorry I couldn't respond until now.

Attached are pics of the trace side and (I hope) a clearer pic of the numbers of nearby components.

I believe it connects:

The very purple resistor (?) to the left of it
The black three post component (not sure what it's called)
Two white 'blocks': .1J100# and (horn?)33nJ250 (obviously not so sure on the symbols)

[R_J]

Re: Blown cap on old dwell gauge - kal equip 2851

Looks like a resistor to me also, post a clear picture of the trace side of the board. Also post the number on the component next to the burnt resistor.

[petehall347]

Re: Blown cap on old dwell gauge - kal equip 2851

looks more like a resistor to me ..what does it connect to ?

[snakeintheeaglesshadow]

Hi,

Can anyone help ID this cap, or any tips on how to figure it out? As you can see, it's clearly fried. Unfortunately the burn marks obscured the color bands. I couldn't get a good zoom on it with my phone, so I hope the pics are enough. I can try again if not.