TDS220 bootup??


Pwrelectronics
 

Got a TDS220. Does not get used much. It sat unused for at least a year. Cord plugged in, switched off (these have a hardware on/off sw on the AC line).

So, went to use it, turned on and I get orange lines on the screen. ????

Tried turning it on an off a few times and then it booted up and seemed to work OK.

The next time I tried it, same story with the orange lines. I eventually discovered a light slap on the scope would pop it out of the orange lines thing and it would boot and pass the self test and work normally.

If left on a while and turned off and then immediately back on right away, odds are it boots fine again. But let it set even a minute or so and then back to needing a shock.

I've had this scope for well over a decade and this only started in the past year or so.

What should I look at? After the obvious with bad connections someplace, could the xtal be "lazy" now for some reason and the oscillator on the main micro not starting?

thanks,


boid_twitty
 

TDS220 is monochrome. Orange lines?

RL


Roy Thistle
 

TDS220 isn't colour ... so maybe you are seeing the ccfl? (trying to start, undercurrent?)

Anyway, I have a TDS220 from the dumpster... that probably should have stayed in the dumpster. (They are not really that good of an oscilloscope.)

I haven't posted about mine here. I wasn't sure there was going to be too many people that could help.
Not recommended for long term use... but, what happens if you connect it to a power bar with a switch.... and use the power bar switch to cycle it? (always keeping the on/off button on the top of the scope in the on position [pushed in])

--
Roy Thistle


Pwrelectronics
 

Yes orange lines... When slapped, the screen goes to the normal monochrome white and boot-up messages. The orange lines are in a specific pattern (these are horizontal lines) and it appears the back light is working.

I am presuming that the orange lines are what you get when there is no input to the display board from the motherboard? I am only assuming the issue is with the mother board because it goes to the boot up self test when shocked. If the issue was with the display board, I would expect that it would come up as "normal" with a mechanical shock well after the mother board booted and not see the self test messages at that point.


 

Have you followed the oscilloscope repairman's motto? Thou shalt check voltages.

Begin at the beginning. Check the supply rails. If those are good then you can move on to check voltages at major components (like the CPU chip). For something this modern you might not even need a schematic: e.g. the voltage regulators may be pre-packaged parts so you can tell what they're doing just by looking at the part number (or a few components around them). Checking the power supply for the logic chips is as simple as finding an identifiable logic chip and probing its power pin.

The bigger trick may be getting it to perform the malfunction on demand (e.g. with the case off, though this does not sound temperature related).

For a problem like this one, which goes away when physical force is applied, you should suspect a bad solder joint, or something similar. That would actually be a best case outcome, as it would be easy to fix.

Also, it never hurts to do a simple visual inspection of the boards and components. It's unlikely, given your symptoms, but maybe something burned up or spilled its guts.

-- Jeff Dutky


 

On Fri, Apr 30, 2021 at 07:01 PM, Pwrelectronics wrote:


What should I look at? After the obvious with bad connections someplace
Does the scope have an optional I/O module e.g. GPIB ?
If so, make sure it is seated as far as it goes. The pins
on the motherboard are very short and if the module doesn't
make good contact on all pins there could be boot problems.
You could also remove the module completely and see if the
problem persists.
/Håkan


Harvey White
 

I've had orange lines on a color display when the display is powered up but not initialized properly.  There's supposed to be a clock input to the display.  When it's not correct, the duty cycle on the display LCD can give you that odd looking orange.

How you could get this on a monochrome display I don't know.  I do think that it has to d with bad connections to the display.

Harvey

On 4/30/2021 4:19 PM, Pwrelectronics wrote:
Yes orange lines... When slapped, the screen goes to the normal monochrome white and boot-up messages. The orange lines are in a specific pattern (these are horizontal lines) and it appears the back light is working.

I am presuming that the orange lines are what you get when there is no input to the display board from the motherboard? I am only assuming the issue is with the mother board because it goes to the boot up self test when shocked. If the issue was with the display board, I would expect that it would come up as "normal" with a mechanical shock well after the mother board booted and not see the self test messages at that point.