Test is not square

[Chev]

Hello everybody.

First, sorry for my english.

I finally made it work, reviewing the contact on LCD.
But when I do the manual test, the signal I get is not square, is the image.

I connected a 10 volt source (AC) and gives me the signal of the image.

Moreover, the response time is very slow, since I put a battery, for example, until the signal is displayed.

Can you help me?

Thank you.

Chev.

[davef]

Can you display the built-in test signal?

[Chev]

Can you display the built-in test signal?

I'm sorry, I do not understand you, Davef.

The test signal (square) does not appear on the screen.

It appears what you see in the picture.

Thank you.

[davef]

Sorry, I didn't realise that you were trying to look at the built-in test signal!

Well, either the test signal is not on the test output or you have some issues in your input circuit.

I was also confused by the top waveform. If you expecting 50Hz and getting that waveform what timebase setting are you on? Bit hard to see but it looks like 0.2 seconds. Try 10 or 20ms.

Also your 9V battery will struggle to supply enough current for any length of time. What is the voltage at the DC input when the 'scope is runnng?

[Chev]

Thank you Davef.

Well, either the test signal is not on the test output or you have some issues in your input circuit.

And how do I fix it?

I was also confused by the top waveform. If you expecting 50Hz and getting that waveform what timebase setting are you on? Bit hard to see but it looks like 0.2 seconds. Try 10 or 20ms.

I've tried various combinations, 10 and 20 ms, but does not solve anything.

Also your 9V battery will struggle to supply enough current for any length of time. What is the voltage at the DC input when the 'scope is runnng?

I'll watch the battery current and I tell you.
The voltage, around 8,5, more or less.

Thank you again.

[davef]

Test signal ... if it is not on TESTSIG end of R26 you have microprocessor problems. You will need another oscilloscope to look for it.

How about measuring all the other voltages around the board.

When you had the 10VAC source on it what amplitude do you read on the screen, even though you can't see a good sinewave?

[Chev]

Test signal ... if it is not on TESTSIG end of R26 you have microprocessor problems. You will need another oscilloscope to look for it.

How about measuring all the other voltages around the board.

All are close to the manual, but I would have to check them again to be sure.

When had the 10VAC source on it what amplitude do you read on the screen, even though you can't see a good sinewave?

I can not check it now, but I will and I'll tell you.

Thanks Davef.

[davef]

Well, there can only be an open track from pin 17 (TESTSIG) on the uP to the end of R26 or a short on this track. Do a close visual inspection to confirm pin 17 is soldered to the PCB track and that there are no shorts on the track to R26. R26 could be open and/or you have shorted pin 1 of J2 to ground. Or your test probe could be faulty.

If it was my unit I would do a continuity test on the track and check for shorts to ground and that R26 was good. But, it is not my unit! Hope you understand where I am coming from.

[Chev]

Thank you Dave.

I will breathe and I'll get on it.

[Chev]

Well, there can only be an open track from pin 17 (TESTSIG) on the uP to the end of R26 or a short on this track. Do a close visual inspection to confirm pin 17 is soldered to the PCB track and that there are no shorts on the track to R26. R26 could be open and/or you have shorted pin 1 of J2 to ground. Or your test probe could be faulty.

If it was my unit I would do a continuity test on the track and check for shorts to ground and that R26 was good. But, it is not my unit! Hope you understand where I am coming from.

Dave.

These are the data I obtained:
all voltages are almost exactly like manual, except D2, on the positive, instead of 9.39 mark, giving 8.71.

About battery:
8.92 volt.
3 mA

There are continuity between pin17 and R26 (right where it is written R26).

What else I can check?