Tektronix TDS2012B Voltage 5V or 3.3V

[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]

I am repairing a Tektronix TDS2012B scope.......

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]

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.

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

[Mr Lurpak]

BTW does anyone have, or know where to find a schematics of the TDS 2012B? 1000 or 2000 series

[tautech]

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?

Then somewhere in fault finding manuals it is listed as a USB fault, how do I know, been here, done that and earned the busted Tek Tee shirt.

I suggest you ignore the 3.3V reading and proceed with replacing the IC.....something I never did and just boxed the scope up to be a gentle reminder of my experiences with my first Tek. 

[Mr Lurpak]

Nice, I will 100% replace chip. I just checked again since you gave me a good hint. The pin 11 on J201 is directly connected to VCC and AVCC (usb power), on USB controller chip so make sense that it should only be 3.3 V as that is VCC to USB (and CY7C67300 has operation voltage of 3.3 volts) so guess Tektronix might forgot to update service manual - or old one I have).

Haha I will not go into how many hours/days I spend trying to figure out why 5V was missing.

[Mr Lurpak]

Just quick update and help for others.

So I did replace the CY7C67300 USB controller chip and now the scope is actually running and can be used (past the POST/BOOT) so yeah success. However, I still have a USB error in the POST check. but will have to look into that. There might be other USB related component damaged or I have maybe missed a pin when soldering the 100 PIN IC in.

But it did fix the initial problem and the Tektronix service manual is WRONG as the pin11 and internal VCC is 3.3 volt NOT 5V.

Chhers and thanks for the help here.

[tautech]

Just quick update and help for others.

So I did replace the CY7C67300 USB controller chip and now the scope is actually running and can be used (past the POST/BOOT) so yeah success. However, I still have a USB error in the POST check. but will have to look into that. There might be other USB related component damaged or I have maybe missed a pin when soldering the 100 PIN IC in.

But it did fix the initial problem and the Tektronix service manual is WRONG as the pin11 and internal VCC is 3.3 volt NOT 5V.

Chhers and thanks for the help here.

Nice. 
Can you save a screenshot to USB ?