Tektronix TDS 1012B Repair

[Orion63]

Hi, I have this TDS 2012B which is now showing weird symptoms as follows :
1. When I power it ON, the scope starts up after a long delay (around 2 mins) with the message USB Controller - FAILED.
2. After that it starts up and I can see the CH1 and CH2 waveforms for a brief moment and the scope becomes dead. No display (black screen) no lights.
3. Then, even if I re-cycle power nothing happens, same black screen, No lights.
4. After say 5 minutes, when I power-up the above steps 1-3 repeats.

Any suggestions on the possible cause of failure ?

Regards

[coromonadalix]

the power supply section could be bad ?  the first thing to check are the voltages on the capacitors or any test point you may find

try to find a service manual if there is one

[tautech]

Which is it ?
1012B or 2012B ? 

If the display backlight is down have you checked the display for activity with a bright torch ?

[Orion63]

Sorry for the typo. It is TDS1012B. Replying to the post, the backlight comes back just for a few minutes after I shutdown and power up the scope again.

[tautech]

Replying to the post, the backlight comes back just for a few minutes after I shutdown and power up the scope again.

Have you checked if the display is active when the screen is black ?
A bright torch will illuminate any activity if the backlight is down.

[Orion63]

Thanks for the reply. I will check and update.

[Orion63]

 @tautech, I checked the scope today. I do not see any activity on the display with a strong light shone over it once it goes black. Also the 1KHz Probe signal disappear.
Does it mean it is a power supply board problem rather than the Main Board ?
Secondly, what can be done about the USB Controller - Failed message ? Any idea which components responsible for this ?
Could the delayed acquisition be due to this failed USB Controller ?

[tautech]

@tautech, I checked the scope today. I do not see any activity on the display with a strong light shone over it once it goes black. Also the 1KHz Probe signal disappear.
Does it mean it is a power supply board problem rather than the Main Board ?
Secondly, what can be done about the USB Controller - Failed message ? Any idea which components responsible for this ?
Could the delayed acquisition be due to this failed USB Controller ?

I lost a TDS2012B in very similar circumstances and it threw up a Fail for the USB controller but it would still boot quickly as normal and IIRC the probe compensation output went to 2.5 KHz.

In this case the I found a corroded pin on a 100 pin IC that resulted from these DSO's having top vents and something that fell onto that pin and with atmospheric humidity the pin corroded through. Attempts at repair have been unsuccessful as the pin is very fine and corroded close to the IC package.
Since I have not been a fan of top vented instruments.

Certainly check the PSU is to spec however with a fault like this I do suspect it's a MB problem.
The manuals here may help:
https://w140.com/tekwiki/wiki/TDS1012

[Orion63]

Thanks for the reply @tautech.
Does anybody on the forum know which Power Switcher is used in this TDS 1012B scope ? I can see a chip from Power Integrations.
The marking is not clear, something starting with TOP.... The clip holding the heatsink has scrapped away the rest of the marking. I can only see the words... TOP
Thanks & Regards.

[tautech]

In my busted TDS2102B it is a TOP244YN

[Orion63]

Thanks again, @tautech.

[Orion63]

Hi, I could not rectify the issue on this scope. I will turn my efforts of repair another faulty 1012B that I had bought along with the previous one. The issue with this scope is that, when I power up, I can see the backlight coming on and the 3 green LEDs (near the PRINT button on top left of the Panel) light up and stays on forever. But I cannot see any script running on the lighted screen, nothing at all. However, on the PROBE COMP terminal, I can see a 2.5V, 2KHz square wave.
Any ideas if the scope can be pulled out of this booting process ? Or could it be a Hardware Issue ?
Regards

[lern01]

Hi, I could not rectify the issue on this scope. I will turn my efforts of repair another faulty 1012B that I had bought along with the previous one. The issue with this scope is that, when I power up, I can see the backlight coming on and the 3 green LEDs (near the PRINT button on top left of the Panel) light up and stays on forever. But I cannot see any script running on the lighted screen, nothing at all. However, on the PROBE COMP terminal, I can see a 2.5V, 2KHz square wave.
Any ideas if the scope can be pulled out of this booting process ? Or could it be a Hardware Issue ?
Regards

In general, it should be a firmware error, and you can probably fix it by brushing the firmware again.

[lern01]

Hi, I have this TDS 2012B which is now showing weird symptoms as follows :
1. When I power it ON, the scope starts up after a long delay (around 2 mins) with the message USB Controller - FAILED.
2. After that it starts up and I can see the CH1 and CH2 waveforms for a brief moment and the scope becomes dead. No display (black screen) no lights.
3. Then, even if I re-cycle power nothing happens, same black screen, No lights.
4. After say 5 minutes, when I power-up the above steps 1-3 repeats.

Any suggestions on the possible cause of failure ?

Regards

Has the USB Control Failed problem of your oscilloscope been fixed? My TDS1002B also had the same problem. I brushed the EPROM and checked that the crystal oscillator frequency of the control chip was normal. If it's fixed, can I share it?

[Paulo Peres]

I had a very similar problem with a TDS2004B. The scopes share some design solutions.
The power supply was unstable. I changed the filter cap of the first DC stage and it gets a little better. The caps closer to heatsink at the last stage are prone to fail, too.
The mainboard also had a USB issue. I removed the USB controller (CY7C67300) and it becomes more "normal" (i. e. don't freezes/reset randomly anymore).
I also managed to buy a substitute (unfortunately, an used one). Doesn't worked.
I don't know if is the "new" chip or if there are more damage.

[Paulo Peres]

Another thing.
If you had another scope, you could put a probe in the calibration output of the TDS during boot.
The square wave changes its frequency according to boot progress. If it delays to boot but keeps changing, the boot are in progress. Its just taking more time (of course, could be bad, but at least you will see something).
Unfortunately, I don't have a table freq x boot stage.

[lern01]

I used a USB to detect the normal TDS1012B comparison, with the diode gear, red pen ground, black pen connected to the chip each pin, found that the voltage drop is similar. The crystal frequency and waveform of the USB control chip are normal, sinusoidal waveform, 12MHZ. The operating voltage is also normal, and the EEPOM voltage is normal.Replaced the USB controller chip (removed from the TDS1012C), the oscilloscope white screen, changed back to the original, and started normally. The BIOS program in the USB control chip is different. Generally speaking, the USB control chip is not very likely to be bad.
Who knows what the USB self-check process is like?

[lern01]

I had a very similar problem with a TDS2004B. The scopes share some design solutions.
The power supply was unstable. I changed the filter cap of the first DC stage and it gets a little better. The caps closer to heatsink at the last stage are prone to fail, too.
The mainboard also had a USB issue. I removed the USB controller (CY7C67300) and it becomes more "normal" (i. e. don't freezes/reset randomly anymore).
I also managed to buy a substitute (unfortunately, an used one). Doesn't worked.
I don't know if is the "new" chip or if there are more damage.

My power supply is normal, with other motherboards, such as TDS1012B, the function is normal.