Products > Test Equipment
TC1 lcr-meter transistor-tester fix
masster:
@indman
Thank you for your reply. I know you researched this tester heavily. The only thing that keeps me from doing a better job in diagnosing the issue is the microscopical size of the parts. I wanted to minimize the intervention on the board because I really hate it working with heavy magnifying glasses for electronics or with a microscope.
Anyway, I have desoldered in turn the following parts: 78T05, the two filter capacitors on the 5V output, the input protections (6V8A and SRV05-4), and the IR receiver.
Shorted parts found: SRV05-4 and the IR receiver. Yes, I know. The latter being faulty was a total surprise.
I find that the quality of the parts used in these tester clones is deplorable (POS), hence the low price. In fact, the seller didn't offer any guarantee. Although after replacing the bad parts the tester will most probably work, it is very unreliable. Who knows what else will break? My advice? Don't waste the money on those China clones. Make one yourself with good quality parts, maybe in bigger size to avoid doing neurosurgery on the board, and definitely I would try finding a better input protection because right now if somebody is messing with the input pins by shorting them inadvertently or forgetting a cap is not discharged, he will look again(!) at a dead tester.
@Per Hansson
You are right. The resistor was soldered upside down. I measured it after desoldering. It has 10k indeed.
indman:
--- Quote from: masster on August 11, 2022, 09:31:43 pm ---Shorted parts found: SRV05-4 and the IR receiver. Yes, I know. The latter being faulty was a total surprise.
I find that the quality of the parts used in these tester clones is deplorable (POS), hence the low price.
--- End quote ---
Your problem does not in any way confirm the low quality of Chinese parts, although such a reality certainly exists.
A short circuit immediately in 2 parts allows us to conclude that there was some surge of increased voltage, which these parts took over. Put it back in place 7805 (if intact) and turn on the tester without SRV05-4 and the IR receiver. The device should turn on and work without them.
Very often the culprit of similar malfunctions is static electricity.
--- Quote from: masster on August 11, 2022, 09:31:43 pm ---Who knows what else will break? My advice? Don't waste the money on those China clones. Make one yourself with good quality parts, maybe in bigger size to avoid doing neurosurgery on the board, and definitely I would try finding a better input protection because right now if somebody is messing with the input pins by shorting them inadvertently or forgetting a cap is not discharged, he will look again(!) at a dead tester.
--- End quote ---
Of course, you are right that a thing made with your own hands will bring much more benefit and experience than a purchased one!
But on the other hand, thousands of Chinese clones work well for many people and they don't bother looking for other options. ;)
masster:
@indman
I have soldered back in place just the 78L05 and 6V8A. The display came back to life, but instead of showing "No, bad part, or unknown part" message, it shows Cell 1.84V between pin 1 and 3.
I remind you that I didn't test any capacitor whatsoever from new. Moreover, when I worked on the board, I used an ESD wristband.
madires:
Most likely the ATmega was damaged too.
indman:
--- Quote from: masster on August 12, 2022, 10:35:51 am ---I remind you that I didn't test any capacitor whatsoever from new. Moreover, when I worked on the board, I used an ESD wristband.
--- End quote ---
It takes a very good reason to make several parts malfunction at once.Wouldn't you agree?
If you rule out static electricity and an undischarged capacitor, it will not be easy to find the cause of such an occurrence with your clone.
I do not exclude the possibility that somehow in an incredible way the voltage that is created to test the Zener diodes (25V) hit the input of the measurement ports of the processor and knocked out the protective assembly, IR and the ports themselves.In my practice there have been several cases where the part for testing was placed on the K contact on one side and on one of the 1-2-3 test contacts on the other side.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version