Oscilloscope is in a boot lock

[LoveLaika]

I have a Tektronix TBS-1072B oscilloscope. I don't know how it got into this state, but it's in some sort of boot lock state, if that's the right term. I turn it on by pressing the power switch. Some buttons light up and the display shows up, I see the Tektronix name and logo, and an image pops up showing the model name. Then, the screen goes dark, and the process repeats again...and again. Essentially, it's stuck in some boot sequence on startup and it won't properly initialize. Does anyone know how to perhaps factory reset this oscilloscope? Or perhaps, any one know of a way to perhaps get some sort of start-up log from it as it boots up to see why it's like this (like through a serial port or something)?

[djsb]

Maybe there is an internal CMOS battery that needs replacing? Just guessing.

[LoveLaika]

Thanks for your thoughts. Opening it up, I found the CMOS battery on the side of the main board, but it looks fine. Measuring it, it reads 3 volts, the correct voltage for a CR2032 BR2325 battery.

For what it's worth, I found the service manual for the device, but it doesn't really help much with this situation.

EDIT: Sorry, wrong battery type.

[djsb]

Is there a procedure for updating the firmware? Have you tried removing the battery and then starting the scope without the battery installed, and then replacing it and trying again? Done at your own risk, of course. How about disconnecting, applying switch lubricant and the reconnecting all the connectors?

[perieanuo]

hi, if you wanna remove the battery, save before what's kept in the memory, you won't find that data easily.
normally, you should get the debug comm port, solder some ftdi to tx/rx and see what's in the start-up log first
see similar https://forum.tek.com/viewtopic.php?t=137905

[wasedadoc]

I don't know anything about that oscilloscope but such "boot loop" can be caused by the power supply that is no longer able to provide sufficient power later in the boot-up sequence as more sections are enabled.

Any sign of bulging or leaking electrolytic capacitors in the power supply circuitry?

[djsb]

The TekScopes group might be able to help

https://groups.io/g/TekScopes

You have to join in order to ask a question. The group mainly has info on the older equipment but there are people on there who are very experienced with general fault-finding. Good luck.

[Phil1977]

Beside looking for incontinent caps I´d definitely check the bus voltages with another scope*


*this is finally the proof you NEED at least two scopes in your access.

[djsb]

A few questions.
1/ Do you use this scope regularly?
2/ How old is it?
3/ Is it plugged into the mains supply permanently (on standby) or switched on and off at the power socket when needed?
4/ Has it been working RELIABLY up to this point?
5/ Has there been any INTERMITTENT problems, glitches etc that could give an indication of developing problems.
6/ Has the firmware been updated recently? Can you still get firmware updates?

[LoveLaika]

Apologies for not replying sooner. Let me try and answer as best as I can.

1. I was given the scope to repair. I would say it's usage is about 10 hours a week, by students.
2. It is not old. While the model is outdated, I don't believe we had it for very long, but I can't say for sure.
3. Yes. It remains plugged into the mains power supply (via a power strip) and switched on/off via the switch.
4. Yes, it has been working reliably up until now.
5. There has not been any intermittent problems as of now.
6. The firmware has not been updated recently.

[LoveLaika]

Power supply board looks functional, and testing whatever test point voltages I could reach on the processor board, some of the ICs are powered with 3.1 to 3.6 volts. Getting values like that, it seems that the voltages are correct. I don't know what else to look for.

[cncjerry]

On a lot of tek scopes you can measure the power supply voltages on the BNC input connectors.  If the voltages come up too slowly, you can get a loop.  I have a TDS3054C that does the same thing but after a while it will come up.  It's a power supply problem in my case.

You need to hang a meter on the voltages and see if any are coming up slowly, at least that was the issue with mine.

Jerry