TEK 221 O-Scope Power Supply Problems

Group, I have a "dead" TEK 221 scope that I am trying to repair. Nothing out of t he power supply. The batteries are dead, so I removed them. Will the powe r supply operate without the batteries, power by the AC Line? Can I operat e the power supply out of the scope (disconnected from the scope)? I canno t find any indication that the first inverter is running. Checked transist ors OK. I suspect that the inverter trigger diac is defective. No way to test. Please share any thoughts that you have or past experiences. Thank you, Dave

Reply to
davidahoneycutt
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I have an earlier Tek 213 scope that had a similar problem when I bought it: The problem was that some of the "D" size NiCd batteries were shorted. With the batteries shorted, dead, or missing, the AC power supply would not run. I suspect that the 221 might have a similar design and problem:

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

I got my manual from here

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It's a locked pdf, so I can't cut/paste from it. and it's 91MB.

The miniscope series has weird power supply configurations. This one shuts down if the battery voltage is below 10.3V. Don't try to run it with the battery disconnected...it's a critical part of the regulator. It's 10 NiCd A-cells, but they're only 600 mAH. Should run fine on more modern AA NiCd's. Should also run on NiMH, but the charger will probably kill them with overcharge if you leave it connected to AC.

Be careful probing around in there. There are connections between the line side and the isolated side that you'd not expect without a schematic. And some things that you might think were ground referenced aren't.

Don't want to smoke your scope probe or yourself.

Reply to
mike

If I am not mistaken, those supplies work like some UPS supplies and if the battery is no good or missing, it won't start.

Normally there is some sort of slow charge and once the batteries get up to snuff, the inverter will start.

Not sure if using an external supply is going to allow you to test for this? Some charging circuits and supplies are smart and test the condition of the batteries. You may need to put a resistor in series to fake it if you attempt an external supply test in place of the batteries.

Jamie

Reply to
Maynard A. Philbrook Jr.

I have a 212 on my bench and it definitely will not work without a good battery pack. I rebuilt the battery pack and still had a problem. Some diode in the power supply area had also failed but I can't remember which one. Chuck

Reply to
chuck

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