Blown cap on old dwell gauge - kal equip 2851

[redwire]

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

Dwell was used for setting point gap, this box can run off a 9V battery so it can do old small engines- moped, lawn mowers etc.

OP see if your multimeter is pooched. Measure ohms on some resistors, compare to another multimeter etc.
My estimate - the burnt resistor was 82Ω.

[stj]

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

no, the dwell meter is for ajusting the distributer advance or spotting a vac leak on the line
they are still used on some raced up cars like the B series honda engines with variable cam gears.

[snakeintheeaglesshadow]

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

maybe,
if you turn the meter off and on, is the lead value always the same?

Yes it seems to be the same 'empty' 01.0 value after a few power cycles. Does that change the values of the resisters I should try?

cars don't use tachometers anymore?

hmm... electric cars wouldn't have tachometers I suppose but any gasoline ones it's still somewhat interesting information. Might not be useful information for automatic transmissions however...

It's actually designed for tuning a carburetor. The RPM is a useful data point to do so.

[eccerr0r]

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

My car doesn't have points ignition, but is old enough to use the tach.

cars don't use tachometers anymore?

hmm... electric cars wouldn't have tachometers I suppose but any gasoline ones it's still somewhat interesting information. Might not be useful information for automatic transmissions however...

[stj]

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

maybe,
if you turn the meter off and on, is the lead value always the same?

[snakeintheeaglesshadow]

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

Do not drink and dwell lol.

Ha! Or don't dwell at all and upgrade to HEI.

if the meter wasnt zero'd then it probably had 0.4 to 4ohms in the leads, sockets, switch etc.

You mean touching the volt meter probes together and subtract the number from the resistor's value? I did that now and the 'empty' value is indeed 01.0. Meaning the final value of the burnt resistor is 4 ohms?

[stj]

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

if the meter wasnt zero'd then it probably had 0.4 to 4ohms in the leads, sockets, switch etc.

[redwire]

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

The old burnt resistor was GREY-RED for the first two stripes, so it's 82 something something, either 8.2Ω or 82Ω yet you measure 5.0Ω on the burnt part. Hmmm.

I would put in 82Ω and see how it works. If the new part is the wrong value, both Ohms ranges (Rx1, Rx1,000) will read way wrong.
You would put a potentiometer for the test resistance and see What it the meter reads.
Or, connect a known resistor to the test leads and put a 1k potentiometer in place of the mystery burnt resistor and dial in the right reading, then measure the pot to get the value.

I would say the meter was in Ohms function and saw power which overloaded it. It's too easy to be measuring Volts and hit the slide switch. Oops. Smoke. Why does the middle slide switch say "Volts" yet the line goes down to Ohmsx1? So confusing. Do not drink and dwell lol.

[snakeintheeaglesshadow]

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

I finally found my multi meter and was able to test the resistance. The meter reads 05.0. However, the resistor practically crumbled while removing so I'm not sure how accurate that can be.

Does that narrow-down the correct resistor at all?

[snakeintheeaglesshadow]

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

Did you try to see if it would work? Volts and ohms are easy to check. For tack and dwell you would need an old car with points.

I did try to use the tach function. My car doesn't have points ignition, but is old enough to use the tach. If I recall correctly, it worked for a split second then died, and now won't turn on at all. I'm pretty sure I attached the leads incorrectly. Probably attaching one to 12v that shouldn't have been.

I will test the resistor in the next couple of days and report back.

[desert-rat]

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

Did you try to see if it would work? Volts and ohms are easy to check. For tack and dwell you would need an old car with points.

[snakeintheeaglesshadow]

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

Um, how many batteries are in this? A pair of AA's and a 9V?

Yes indeed. Three batteries total. I would kill for a set of instructions to know why haha.

Usually these run off the 12V power at coil(+) for tach, dwell. Maybe the battery is for small engines.
Unless... this meter must have an ohmmeter function? That would explain the smoke lol.

It does have this function! I probably should have put all of the functions in the title. Attached is a pic of the front. It does dwell, tach, volts and ohms.

I would measure the burnt resistor value and see if its good for a guess at what it was or its dead.

Ok that will be my next task. I think I found a few good youtube tutorials.

For ohms function (slide switch to the right?).

Precisely! Volts/ohms. The other switch is for tach/dwell.

[redwire]

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

Um, how many batteries are in this? A pair of AA's and a 9V?
Usually these run off the 12V power at coil(+) for tach, dwell. Maybe the battery is for small engines.
Unless... this meter must have an ohmmeter function? That would explain the smoke lol.

I would measure the burnt resistor value and see if its good for a guess at what it was or its dead. For ohms function (slide switch to the right?). One leg of the burnt resistor connects to GND.

The small transistor is the inductive pickup amp and although nearby it is not a suspect.

[snakeintheeaglesshadow]

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

Where does this red wire go? It mistakenly got +12V power on it which is what smoked the resistor.

That goes to two AA batteries. Just FYI the other red wire in the pic goes to a 9v battery.

[redwire]

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

Where does this red wire go? It mistakenly got +12V power on it which is what smoked the resistor.

[desert-rat]

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

Check it with an ohm meter. If you need a new one the color bands are a key to its value.

[stj]

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

but is it blown, or just got hot enough to burn the paint??
thats the reason to test it

[snakeintheeaglesshadow]

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

Wow what great input! Very impressed by this community.

I would say it's 82R based on the grey band and smoke, so power shorted to that wire.

Can you recommend a specific resistor(s) to try?

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.

I found it among my late father's hot rod stuff. No instructions of course, so I just plugged it up. Incorrectly, obviously.

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.

Ah ha! I think I know where I went wrong attaching it. With no surge protection built-in, must be pretty easy to fry.

On the attached pic I attached the each colored lead to it's corrsponding connector on the board. I'm thinking the correct attachment points to engine are:

Red = ignition coil positive
Black = ground
Blue = ignition coil negative
Inductive pick-up = spark plug wire

desolder it and check its resistance

Would this work even if blown? I figured it stops 'resisting' when such.

[stj]

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

a lot of times a resistor can get that hot and still work - it just got very hot from the real fault
so always worth metering it

[desert-rat]

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

Yeah that's a res. Can you read the colors on it ? And yeah check whatever it is connected to.