I built my kit a few months ago and it has performed perfectly up until a few days ago when it began having problems.
I was running it off 9v batteries and it flattened them within a few days, measured the current draw without the screen attached at it measured 70-80mA with no load. Made a stabilized mains power supply with an output of 9.2v but the current draw stayed the same. A touch of alcohol showed that the 7805 was getting quite warm, but all the voltages in the power section seemed OK.
My main problem is that if I connect the probe leads to a DC voltage, such as one of the depleted 9v battery's, which is now about 6v, it takes 1 or 2 seconds for the trace to move. Doesn't matter the time base or any other setting, it always has a very long delay.
Any ideas?
Slow response
Re: Slow response
It's hard to imagine a hardware fault that would cause your problem. Perhaps the EEPROM is corrupted.
Try restoring the factory default values. Hold down [+] and [-] buttons simultaneously for 2 seconds.
Of course you will need to do the Vpos alignment again too.
Try restoring the factory default values. Hold down [+] and [-] buttons simultaneously for 2 seconds.
Of course you will need to do the Vpos alignment again too.
Re: Slow response
The reset didn't do anything I'm afraid.
Checked the voltages and they are all within a few millivolts of expected except for 2.
Input voltage: 9.07, measured with a Fluke 21 meter.
Collector of Q1 is 0.076v instead of 0.2v
Test point #25 is -11.6v instead of -8.1v
Freq, Duty, PW and Cycl are all blank, they never change. The display shows a good 1 Khz square wave from the onboard test oscillator.
When I do a reset with no probe leads connected it shows Vmin -36.58, Vpp 36.17, Vave -36.38 and Vrms 36.38.
Any timebase less than 1 second there is no response from the trace or trigger LED.
20mS the trace responds very, very slowly.
At 5mS the trace moves and responds to input but the trigger LED is intermittent.
At all timebase setting below 0.5mS it works fine, but still no Freq display.
It's got me stumped how it's getting -11v from a positive 9v input.
Checked the voltages and they are all within a few millivolts of expected except for 2.
Input voltage: 9.07, measured with a Fluke 21 meter.
Collector of Q1 is 0.076v instead of 0.2v
Test point #25 is -11.6v instead of -8.1v
Freq, Duty, PW and Cycl are all blank, they never change. The display shows a good 1 Khz square wave from the onboard test oscillator.
When I do a reset with no probe leads connected it shows Vmin -36.58, Vpp 36.17, Vave -36.38 and Vrms 36.38.
Any timebase less than 1 second there is no response from the trace or trigger LED.
20mS the trace responds very, very slowly.
At 5mS the trace moves and responds to input but the trigger LED is intermittent.
At all timebase setting below 0.5mS it works fine, but still no Freq display.
It's got me stumped how it's getting -11v from a positive 9v input.
Re: Slow response
Well it just got worse.
The trace now slowly moves upwards until it disappears from the top of the screen, the 1Khz test pin is working perfectly but the screen won't show it, just a straight line and I can't update the firmware, just get the 'bootloader not responding' message.
I know you only get what you pay for and I paid about $20 for this, but at the moment my only regret is that I didn't put that $20 towards a real oscilloscope.
Just added it to the "Scrap, strip it for parts" box.
The trace now slowly moves upwards until it disappears from the top of the screen, the 1Khz test pin is working perfectly but the screen won't show it, just a straight line and I can't update the firmware, just get the 'bootloader not responding' message.
I know you only get what you pay for and I paid about $20 for this, but at the moment my only regret is that I didn't put that $20 towards a real oscilloscope.
Just added it to the "Scrap, strip it for parts" box.