| Electronics > Repair |
| Tektronix DPO4054 stucked at tektronix splash screen |
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| analogRF:
IIRC, there is a 2GHz VCO that gets divided by 4 via that U380, so there should be 500MHz on its output (it's differential output but you can probe one line and see) if there is nothing, check to see if the VCO and U380 have received power already. I am not sure but they might be turned on only when the scope software starts which is way down the line in the boot process. In fact the last step is running the scope software which checks a lot of stuff first... |
| JohnPi:
The 5 V on the board is OK (~ 5.1 V). U380 also has 5 V; I can't see signals at its input or output, but my SA picks up strong 440 MHz and 880 MHz around there. If that is what is expected and it wasn't dividing, I wouldn't see this (divided from 2.2 GHz ?) The inputs are also biased around 5V; the outputs at about 4.6 & 4.4 V which seems about right. With the scope off, I measure ~ 60 Ω at the inputs and ~ 87 Ω at the outputs -- that also seems about what I would have expected. The coin cell (left side) is glued down (not replaceable ?); it measures 3.0 V. If it wasn't glued. I'd replace it, but 3 V is probably OK for now. For reference, here's the back of the scope. U830 is on the bottom right. |
| analogRF:
the VCO is 2.5GHz and the chip divides by 5. My bad :-[ :-[ |
| JohnPi:
But I see 440 MHz, definitely not 500 MHz (2.5 GHz ÷ 5); also there's an 880 MHz component --> it's not a 50 % duty cycle signal. The ÷ 5 means that the output would not be 50 % duty cycle. Just in case it was the coin cell, I forced 3.5 V on it and powered on -- no difference. There is a small pushbutton on the main board; when I press it, the display turns off and turns on again after a couple of seconds when released. Any hints on how to see the boot log ? Where are the Tx/Rx points ? |
| Jwalling:
--- Quote from: JohnPi on November 22, 2020, 04:56:05 am --- Any hints on how to see the boot log ? Where are the Tx/Rx points ? --- End quote --- A question I've seen asked a number of times (myself included), but never gets answered for some reason! |
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