DT830D Digital Multimeter Repair and Fuse

Unfortunately this meter has un-fused shunts, so if you were to overload it, then chances are that the PCB traces or some SMD resistors will burn. If you have damaged you meter in this way, then you will need to look for burnt traces and components. If you are able to find any, then consider yourself lucky as you will have to replace them.

If you are repairing a meter with burnt resistors and you need to figure out their values, then DT830D Circuit Component Values article will help as it contains photographs showing the resistor values. If the factory has a circuit diagram, they can supply then please do email it in to me.

The ICL7106 COB (Chip on Board) design is one of the most cost effective designs. As you can see, this neat construction would have been part of an automated process. I would not be too surprised to find high-end meters using this same design construction in the future, because it is so cheap to make.

This is where the battery fits.

Continuity Test Buzzer Delay Repair

This meter has a very annoying delay in the buzzer when you are testing for continuity. It takes around 3 seconds before the buzzer sounds, and when you take the probes away, the sound continues for a further 3 seconds. This is of course unusable because the delay can cause great confusion.

This seemed to me like a switch bounce delay that programmers often use, however it is very excessive. However, my contention was that since the delay routine depends upon the microcontroller clock speed, it must be the clock speed that is slow, because why would anyone mess with the bounce parameters, especially since it worked so well on the DT830B.

One external capacitor determines the microcontroller clock speed so I decided to change it to see. I replaced the original 100 nF one with this 180 pF ceramic disc, and it worked! However, changing the clock speed changes the sample rate of the ADC and this change screws up the accuracy figures! Therefore, I decided to install the original capacitor back. If you are the programmer working at the factory, then you may need to reduce the delay parameter in your bounce code!

The piezoelectric buzzer is nice and loud, however most of the sound remains inside the plastic case because there is no speaker grill for the sound to come out of.

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