Troubleshooting Tachometer Circuit for 80's Honda Accord | Expert Help Available

In summary, the discussion centered around a tachometer circuit from an early 80's Honda Accord that was retrofitted into another older Honda that only had a mechanical tach option. The user had twisted the yellow and blue leads together to get the tach to work, but this caused the pink resistor to overheat and partially burn the PCB. The discussion then focused on troubleshooting the issue, with suggestions to check the zener diode and replace it if necessary. The user was also advised to create a circuit diagram for better understanding.
  • #1
neen
10
0
This is a tachometer circuit from an early 80's Honda accord.

IMG_1245_zpsdc1c97da.jpg


I twisted the yellow and blue leads together and was able to get the tach to work (retrofitted into another older Honda that only came with a mechanical tach option). The twisted pair was ran off of the negative of the coil and the black was sent to ground. This caused the pink (resistor?) to overheat to the point that it partially burnt the PCB and melted the solder off. I can easily enough re-solder the circuit but I want to know where I screwed up at...I'm thinking that either the blue or yellow lead needs to be the switched 12v power source. Can you guys point me in the right direction?

Here is the reverse side.
IMG_1244_zps8dfd28b6.jpg
 
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  • #2
It would be really useful if you would make a circuit diagram out of that, it is hard to impossible to see where the individual parts are connected, or what exactly they are.
I expect that one of the inputs (yellow or blue) should come from a voltage source (you need some reliable way to power the IC, for example).
 
  • #3
The heated area of the circuit board is under the pink coloured power resistor. My guess is that the adjacent component is a zener diode, and that together they form a crude voltage regulator. Zener diodes tend to fail short circuit, if that happens the resistor gets the full voltage and overheats. It is unusual for the resistor to fail immediately the diode shorts, but you should check the resistor anyhow.

Check the resistance of the zener diode. If very low in both directions replace the zener with the same part number, (probably between 5 and 9 volts). Resolder the resistor and you should be out of trouble. (I have crossed my fingers for you).
 

1. How do I troubleshoot a faulty circuit board?

Troubleshooting a circuit board involves identifying the specific components, checking for loose connections or damaged parts, and using a multimeter to test for continuity and voltage. You may also need to refer to the circuit board's schematic diagram for guidance.

2. Can I repair a damaged circuit board?

It is possible to repair a damaged circuit board, but the success of the repair depends on the extent of the damage and your level of expertise. Small repairs such as replacing a damaged component or fixing a broken connection can be done, but larger damage may require a replacement board.

3. How do I prevent damage to my circuit board?

To prevent damage to your circuit board, make sure to handle it with care and avoid exposing it to extreme temperatures, moisture, or physical stress. When installing the board, follow the manufacturer's instructions carefully and use proper grounding techniques to avoid static electricity.

4. Can I use any replacement components on my circuit board?

No, it is important to use compatible replacement components on your circuit board. Using the wrong components can cause further damage or malfunction. Refer to the board's schematic diagram or contact the manufacturer for the specific components needed.

5. Is it possible to upgrade a circuit board?

Yes, it is possible to upgrade a circuit board by replacing certain components with newer, more advanced ones. However, this may require technical knowledge and expertise, and it is important to ensure compatibility with the rest of the board's components.

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