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I just broke my Tek 213 :-(

groupsio@...
 

I bought a working Tek 213 "handheld" scope/multimeter on eBay. It even worked on battery power. The multimeter needed calibration so I opened up the case and I swear that's all I did, but now it doesn't work. Nothing looks loose or broken, but when I turn the power switch on, the LED doesn't light and nothing appears on the screen.

The battery reads 2.7V. Some of the test points, like +6.5V and 15V, read a low voltage (1 or 2 volts) even when the switch is off. They stay that low when the switch is on.

Any ideas what to look for?

Thanks,
Bob

David Holland
 

I don't own a 213, but if its internals are anything like the 211, it
isn't hard to let the little plastic mylar sheets (that insulate the
PCBs from the shielding that's inside of the case) slip while
re-assembling and smoke power supply transistors.... <been there,
done that - on a 211>

I think I'd start with the transistors in the PSU... I believe Q484,
and Q486 would be the analogs to the ones I fried in my 211.

After that, I'm out of ideas...

David

On Sat, Sep 7, 2019 at 9:28 PM <groupsio@...> wrote:

I bought a working Tek 213 "handheld" scope/multimeter on eBay. It even worked on battery power. The multimeter needed calibration so I opened up the case and I swear that's all I did, but now it doesn't work. Nothing looks loose or broken, but when I turn the power switch on, the LED doesn't light and nothing appears on the screen.

The battery reads 2.7V. Some of the test points, like +6.5V and 15V, read a low voltage (1 or 2 volts) even when the switch is off. They stay that low when the switch is on.

Any ideas what to look for?

Thanks,
Bob


greenboxmaven
 

If you took any of the boards or connectors apart, could you have plugged them back together one pin off? I did that with a 211, fortunately, no harm was done.

Bruce Gentry, KA2IVY

On 9/7/19 5:32 PM, groupsio@... wrote:
I bought a working Tek 213 "handheld" scope/multimeter on eBay. It even worked on battery power. The multimeter needed calibration so I opened up the case and I swear that's all I did, but now it doesn't work. Nothing looks loose or broken, but when I turn the power switch on, the LED doesn't light and nothing appears on the screen.

The battery reads 2.7V. Some of the test points, like +6.5V and 15V, read a low voltage (1 or 2 volts) even when the switch is off. They stay that low when the switch is on.

Any ideas what to look for?

Thanks,
Bob


Miguel Work
 

I have two of them and I have repaired four more, is a nice machine, but is complex to work but the pins that join boards are delicate, and work with it without extenders requires a deep knowledge of his construction. Study schematics before touching anything

Regards

Miguel
-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de groupsio@...
Enviado el: sábado, 7 de septiembre de 2019 23:32
Para: TekScopes@groups.io
Asunto: [TekScopes] I just broke my Tek 213 :-(

I bought a working Tek 213 "handheld" scope/multimeter on eBay. It even worked on battery power. The multimeter needed calibration so I opened up the case and I swear that's all I did, but now it doesn't work. Nothing looks loose or broken, but when I turn the power switch on, the LED doesn't light and nothing appears on the screen.

The battery reads 2.7V. Some of the test points, like +6.5V and 15V, read a low voltage (1 or 2 volts) even when the switch is off. They stay that low when the switch is on.

Any ideas what to look for?

Thanks,
Bob

Steve Hendrix
 

I don't know that particular instrument, but that seems like an odd battery voltage. Is it possible the battery voltage got into a range that leaves the instrument hung, unable to start up but also unable to fully reset? If it's easy to disconnect the battery, I'd try disconnecting the battery and powering up from line power first. You probably already thought of charging the battery enough to get the output voltage into its working range.

Steve Hendrix

At 2019-09-07 05:32 PM, you wrote:


I bought a working Tek 213 "handheld" scope/multimeter on eBay. It even
worked on battery power. The multimeter needed calibration so I opened up
the case and I swear that's all I did, but now it doesn't work. Nothing
looks loose or broken, but when I turn the power switch on, the LED
doesn't light and nothing appears on the screen.

The battery reads 2.7V. Some of the test points, like +6.5V and 15V, read
a low voltage (1 or 2 volts) even when the switch is off. They stay that
low when the switch is on.

Any ideas what to look for?

groupsio@...
 

The batteries are two NiCd D cells, so 2.7 volts is just right.

- Bob

groupsio@...
 

I broke it just by opening the case! How's my track record so far?

I have two of them and I have repaired four more, is a nice machine, but is
complex to work but the pins that join boards are delicate, and work with it
without extenders requires a deep knowledge of his construction. Study
schematics before touching anything

Roger Evans
 

I second Dave Holland's reply. When I first tried to remove a 212 from its case it was reluctant to come out in one piece without distorting the joints where the four sides join together. It is quite likely that something moved even if it wasn't deliberate on your part.

Looking at the circuit of the PSU even with the power switch off there is a conduction path from the battery positive via the primary of T490 to Q488 collector and then via CR550 to the +6.5V test point. I assume that Tek decided that the current drain through this path at very low voltage was not a problem. In the power down situation there is also a current path from the +6.5V rail via R362 and VR362 to the +15V rail so that could account for a very low but non zero voltage on the +15V test point. The voltage on +15V must be less than the voltage on +6.5V for this path to conduct. The symptoms are consistent with the invertor not oscillating when you turn the power on. The internals are very cramped and easy to make a mistake or slip when fault finding.

Roger

Roger Evans
 

A second thought - if the voltage you measure on +6.5V is only a volt or two then there must be a significant current drain since you just have the resistive voltage drop across T490 primary and one forward diode drop of about 0.6V. You can measure the battery current drain by checking the voltage across R447 if this is readily accessible.

Roger

groupsio@...
 

I've taken out the batteries (they're Radio Shacks!!!), removed the high voltage warning plate, and lifted off the A/D board.

I can see that there's two mylar sheets. They don't look like they've moved or even that they could; they're held in place with cutouts or holes that pins and spacers go through.

I've also taken off the amplifier board. I sure hope I can put this thing back together.