Ok usually I read a thread all the way through before I just post, but at 100+ pages.... im sorry if I am asking some questions that have already been answered. A while back a client hired me to fix an audio amplifier and he ordered two of there guys,
EBay Special, TC1 Transistor Testor and ESR meterl, so I could quickly test some of the transistors and the ESR of the caps. Well he liked messing with electronics too but doesnt know much, so one was for him. He blew his out in the first hour, I had assumed testing a charged cap.. I took it apart gave it a quick look and just assumed the avr got friend with out much testing.
Well now mine is having the same problem as his after months of steady use, I was testing a small 10v 470uf cap (I had shorted the caps leads on piece of copper, I tested it once no problem, then hit test again the middle of the second test killed it) right after fully charging the units lithium battery and all the sudden the screen went black and the test button failed to do anything. This had happened to me a few times before but all the other times this has happened all I had to do was hold the test button down for about 30 seconds and then press it again, im assuming this just fully turns of the micro and resets the board. This time that trick did not work for me, this is the same exact problem with the first tester that blew up.
I opened the case disconnected the battery and charged it on a separate charger, didn't resolve anything. I read through the PDF file for these last night and found out just how versatile these things are! I also found the trouble shooting section and now I believe there is something wrong with the power system from what I read. This unit also has a boost converter and transformer, for testing LED's and Zeners i am guessing. It is putting out about 15 volts but the chip AL605 gets extremely hot to the touch, I also could not find a 5 volt rail anywhere on the board, the linear regulator was only putting out like 2.5v or something, if I recall correctly. I tested the bus lines on the screen to make sure the screen wasnt just broken, and there is no data on the lines when I press test.
I just printed out the base tester schematic (published in the pdf file, transistor tester plus a little more) and the pinout of the Atmega32PA4 (this is the AVR this clone uses) and plan to take more trouble shooting steps a bit later today. So I guess here are my questions,
#1 Is there a known common problem with the TC1 version tester that matches the problem I have described, If not what is anyone elses take on what happend and whats wrong with it. I dont think the charge from the first test is enough to blow the micro out when testing a second time.
#2 Is there open, upgraded and modifiable firmware for this TC1 model, that work if I were to add the ISP header. I had always assumed no until I did a bit more reading in to these things. This is especially necessary if I have to replace the avr chip, or at least a hex file and fuse settings.
#3 My unit has the screen soldered in with headers, when the original broke I de-soldered the lcd and saved it for whatever reason, can anyone tell me exactly what display driver chip these use?
#4 Lastly if I were to just replace this one or buy a second, what is the most hardware/software hack-able model, Ive seen the "new 2017" version but id like to get one with a color LCD to start off with. I guess im looking for one with a nice screen I can add all the options too.
If you havent see this document is really good it is version 1.13, the older versions dont contain near the amount of info, it talks about different LCD driver choices using a mega etc etc
http://www.avrtester.tode.cz/upload/ttester_en.pdf*Edit* I forgot one thing, I know these arent the best ESR testers but they do the job, does anyone know how if the DIY 5 transistor tester allen posted works better for esr?