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Tektronix TDS2012B Voltage 5V or 3.3V

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Mr Lurpak:
I am repairing a Tektronix TDS2012B scope. It has light in the top mid 3 lights and display backlight - nothing else is responding. I have tested all the power ref according to the service manual I could find. However, on J201 (going to display) pin 11 state +5V DC - I have 3.3 and seems like circuit in general runs on 3.3 volts. I also found an older post where someone posted a "working" voltage check and it states 3.3v as well I have attached that one as similar to my readings. Can someone confirm if the +5V is correct or just missing update in manual or the 3.6V is the right one - makes big difference for trouble shooting.

In addition I am pretty sure the USB controller chip (CY7C67300) is not good as 2-3 pins are either corroded or "melted" (hard to say what caused it) but wanted to make sure if the power was OK before replacing it.

If anyone else had similar fault and repaired them, please skip in.

Cheers.

tautech:

--- Quote from: Mr Lurpak on September 28, 2024, 08:59:27 am ---I am repairing a Tektronix TDS2012B scope.......

--- End quote ---
Welcome to the forum.

What is the actual fault ?
Is there a fault message ?

Mr Lurpak:
Thanks.

Blank screen, with backlight and 3 lights top middle is on. Nothing else, no boot, no error code. All voltages going into mother board (from Power supply) via J101 is present and correct according to service manual.

Hence, why I checked all voltage according to service  manual. but some state PIN 11 on J201 should be 3.3V and NOT the 5V as manual state - which could 100% explain no boot, no screen.

tautech:

--- Quote from: Mr Lurpak on September 28, 2024, 09:19:33 am ---Thanks.

Blank screen, with backlight and 3 lights top middle is on. Nothing else, no boot, no error code. All voltages going into mother board (from Power supply) via J101 is present and correct according to service manual.

Hence, why I checked all voltage according to service  manual. but some state PIN 11 on J201 should be 3.3V and NOT the 5V as manual state - which could 100% explain no boot, no screen.

--- End quote ---
Have you performed this test from the manual and what was the result ?

NOTE. Without a functional display module, the simplest way to verify that the
oscilloscope is on and functioning is to check for a signal at the PROBE COMP
output. The PROBE COMP output generates approximately a 5 V, 1 kHz square
wave.

Mr Lurpak:
Yes, I did (just forgot) it only shows 2.5V but I don't yet have another scope to test it with so just used a multimeter and since it is 1KHz not sure if I can trust the reading?

However, it still to some extend indicate a power fault hence why I asked if anyone actually knows if PIN 11 on J201 is supposed to be 5V or 3.3V as some else suggested in different blog on here. If 5Volt is correct I have a lead to go after but not sure If I am following a red herring?

Cheers

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