Hi, just “playing” some time with the scope.
Now, with latest firmware (113-06201-092) seems to be OK (as voltage adapter used one old USB cable for Nokia 3510i, with
Prolific PL2303 chip - perfect job)
Make some tests/mods to reduce at maximum the power consumption for portable use.
- Desolder the backlight resistor (R23 - 0 ohm).
- Test some ideas to generate the AV- voltage (MAX7660 and others), but not big improvement, revert to original.
- Replaced the LM7805 with other low-drop 5V regulator (found in my “archive” one L487).
Now it is possible to operae the scope even if power supply is 5.4 Vdc!
My plan is to use the scope with NiMH batteries (5x 2500mAh, Energizer AA size)
Total consumption is now approx. 100mA - Using one old scope probe, found that a 2.2pF capacitor between pin 5 of U2B-TL084 was the proper compensation for
input without attenuator.
Still working for display of Vpos marker and trace line at same level (if replaced the L4 coil with 10-30 ohm, at middle screen is OK,
but at lowest/highest positions, the trace is 3-4 lines behind VPOS marker). I will try to alter the value of R3, but for the moment
no time available.