Electronics > Repair
Hioki 3532-50 LCR Repair (One major problem solved, SM still wanted)
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KungFuJosh:
Progress?

Their engineer suggested the following changes:

R1 392
R2 472
R3 823
R4 622
R5 392
R6 822

Unfortunately, the resistor kit I bought was limited, and I don't have the 39, 62, or 82 variants. So I tried with 33, 56, 75 instead.

This is what it looked like:


I also replaced the 10k pot on the PCB with a 25k trim pot. The original pot was mechanically unhappy. It's more stable now with the trim pot. I might try and find the replacement 10k pot, but, eh, I don't know if it's worth the effort.

Since the change made some improvements, I tried changing R4 to 7.5k and that helped horizontally, but not vertically. So I tried changing R3 to 100K, and it was too much. Now I'm ordering a better resistor kit to put the suggested values in. I'm much more confident in the possibility of this working now though.
KungFuJosh:
I screwed around some more, and it got a little better:

Suggestions -> substitutions:

R1 392 -> 4.7k
R2 472
R3 823 -> 100k
R4 622 -> 7.5k
R5 392 -> 4.7k
R6 822 -> 10k

I might try a 5.6k at R2. I ordered the resistor set, but that doesn't come until tomorrow. 😉

The 25k trim pot is useless with those values. It has be set to contrast fully on to see what's there. I know I have other trim pots...somewhere.

I'm guessing/hoping that tomorrow with the correct values, everything will look betterer.
KungFuJosh:
This is getting interesting. I changed R2 from 4.7k to 5.6k, and it shifted the contrast center so that the trim pot became useful again. The image still wasn't great, so I increased it to 7.5k and we have better contrast, and more usable range on the trim pot.

However, that shifted a vertical section out:


Since I'm guessing, and don't have a schematic or datasheet to go from, I'm going to experiment with R4 next and see what happens if I increase that value.
KungFuJosh:
After some more experimenting, it looks pretty good!



Here's my current R values:

R1 5.6k
R2 7.5k
R3 100k
R4 5.6k
R5 7.5k
R6 10k

I'll ask the seller to ask the engineer if he thinks that can be improved upon.

Thanks,
Josh
Martin72:
Could you please take a good photo of the board side of the new display?
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