GM328 Contrast fix. Read the video description for more help and downloads look at the manuals.

This is how to fix the contrast setting on the GM328 TR tester. Some manufacturers have taken it upon themselves and may have changed the firmware from the original code. This could have also change the order of the settings, so this may not work with every transistor tester being sold these days. But it still worth a try, after all you can’t mess it up worse.
I am not responsible or liable if you change any other settings and your tester stops to work correctly. The manual is in this description at the bottom.
Note: This translation might not be for the latest version. Also not every unit has all the same features, it depends on who made the hardware. Some manufacturers also change the software menu, for that you can try my instructions in the video, it probably still works. It's the same firmware, just modified a little so most of the instruction are still the same.

A discussion on the different hardware versions can be found on:

This is the English version of the manual and design:

Download latest firmware German and English including schematics. Scroll down for English download.

This is the Wikipedia for the transistor testing firmware in German:

Do this at your own risk.
You have been warned!

[madrafboy]

Thanks a bunch this advice worked for my version GM328A V1.20 2015.05. Helpful people like yourself save a lot of hassle. I will leave the contrast alone from now on LOL.

[jwh]

Worked great! I thought I bricked it, 5 mins after trying it out. I wish Amazon had shipped it with a manual. Thanks for the tip!

[MrCocosoft]

Thanks Dave you saved my bacon with exactly the same problem - always great to be able to reach out to fellow enthusiasts for help when needed. I've subscribed thanks again for posting this one.

[darrencady]

Many, many thanks. You have just saved my unit from the bin. You're good man.

[layeraddict]

Thanks man.Saved my lcr -t4 tester with your instuctions.

[east-westguitars]

Thanks a million for this. I was going to fix it with a hammer..

[johnferro]

thanks dave, like others here i thought i killed mine after playing with the contrast settings. i actually purchased this for checking caps, inductors and to a lesser degree resistors. will this check those components or is this strictly for transistors? also how do the pinouts work on the dip?? this unit really should have come with instructions. Thanks again!

[userPrehistoricman]

I thought my screen was broken. Thanks for the fix.

[fer_fdi]

Please, can someone tell me if this boards are supplied with Karl-Heinz Kübbeler firmware in the Atmega? Or they come with Markus Frejek firmware and you have to reprogram the Atmega to use Karl-Heinz improvements/refinements?

[jorgewashington]

Thanks for posting Dave. Is there a manual for version 112? I was able to find one for 111 but not for 112. From what I gather there is one for 112 floating around but cant find it.

[iot_enthusiast]

I tried to lower the contrast and kept the button pressed hoping that it would circle back with the highest contrast but for some reason it did not and I now I see only the green background and not characters. Powering off and on a few times did not solve the problem. I would appreciate any ideas that helps remedy this situation.

[Gradientetecnology]

Help-me, apertei o contrast ate sumir todos caracteres e agora nao aparece mais nada, o que fazer para ressetar, ? Obrigado.

[damainx]

Off-topic, but, does anyone know where I can get an enclosure for this?

[jonmichael]

do these units test leakage on transistors?

[gearsbetweenears]

You Can find anything on You Tube, Thank You!!!!

[KorAllRBare]

Damn!.. Didn't work for me, :| :( I still have an all white screen~sigh
So seeing the main chip is the only chip I can't test and verify integrity with my Multi-Meter, and because all the other components check out to be right on, even after removing them and putting them back on the board, I Obviously got a Chip with some bad programming~sigh

[Smelter]

Has anyone tried playing with the frequency section? I am looking to use mine as a simple frequency generator. The menu lets you select from a number of set frequencies, but I have yet to find which pins to connect to my oscilloscope. The software version I have is 1.12k, but the "manual" does not specify which to use.

[izahandyman]

This happened to the one I bought from ebay. You couldn't fix mine because you don't where contrast is. I almost had it working but it didn't save my settings to eprom. This is junk Chinese crap they make. No Manual, they don't tell the unit has to be calibrated mine wouldn't even detect a resistor. They shouldn't even let crap like this into the United States. It is toy not a test instrument.