Electronics > Repair
TDS3012B blank screen
AlcidePiR2:
Dear All,
I had started this repair of a TDS3012B nearly four years ago, but did not succeed. I checked the power supply, but this is fine.
The problem is the blank screen ( although lighted)
When I saw the new thread
https://www.eevblog.com/forum/repair/tds3014-adventures-(seeking-75-75mhz-oscillator)/
I had some hope. I just checked the 75 Mhz and 48 Mhz oscillators, but unfortunately, boith are fine and provide the desired signal.
I am thus back in the darkness and will appreciate any suggestions.
AlcidePiR2:
As you can see, I have made a very delicate investigation on the DS1742W chip to check the residual voltage of the battery.
Previously, I had attaked such chip by the bottom. This time I did it from the top.
I used a magnet to search where was the battery, and then used a drill.
The problem on the top is that you access first the - side of the battery which is connected to the ground.
You have then to dig a little bit more to get the + side of the battery.
I found 2.89 V which is very fine and should not be a problem. So the fault should not come from this chip.
james_s:
The scope will boot with the DS1742 battery dead, I don't think that is your problem. When I was working on mine I tried installing a plain 6116 SRAM chip in its place and everything worked fine except the time would not advance and all settings were lost when the scope powered off.
AlcidePiR2:
Maybe this could help to localize the problem. I have checked that there is no signal at the front panel square signal test.
james_s:
I don't know about the TDS series but in most Tek scopes the probe calibration oscillator is a separate circuit that only requires power. Have you checked the power rails? The main power supply puts out 15V and then on the main board there are more regulators to get 3.3V and other voltages used.
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