Keithley 2000 error 500.2

[zed65]

Hi, I got this damaged Keithley 2000 from our Philippine friend
Someone had a go with it before me..

It thrown some errors at first:
301.1 - HI OHMS
304.1 - INPUT /100
500.2 - 4W SENSE

After some cleaning of the board and the front/rear switch it has only the 500.2 left.
Meter reads -7.78640 on DCV 10v with nothing connected. If I go up to 100v range meter only reads -0.24v.
If I probe HI the -7v collapse and meter reads -0.44 and so does my handheld meter which i probe with.
Anyone got any clue where to start?

As I can see my unit is from -99 to -00, mine has only the small ASIC (not any footprint for the Altera).
It also have the Caddock R117 resistor.

[z01z]

There's a repair manual describing each internal tests (well, except for the ones introduced in later firmware) and what they do, and also describes some basic checks like supply voltages. If not done yet, it could be a start.
A reversed schematics is also available.

On the 10V range the input resistance should be >10G, you should see changing numbers there. When you connect your meter, the current flowing creates a voltage drop on the input resistance of the meter. If the meter's input resistance is 10M, you have a 44nA current flowing there, which is way too much (should be in the range of 10s of pA), though your meter can have its own bias current added.
There are several topics here on the forum about fixing K2000/K2015s with excessive input bias current, I'd recommend to check them out.

[zed65]

Some progress, I have replaced the K101 and K102 relays and done some more cleaning.
Now I got the "usual" stray voltage of around 1v on the 10v range.

But the 500.2 error is still there.
When I run the test I get -0.000245 and the limit are 0.0001
I have a copper pcb with 4 banana plugs soldered directly on to it, maybe the resistance is to large in that setup.

The meter reads correct on everything I have thrown at it

I have also discovered that my meter are missing some parts, the shield is gone and the push rod to the front/rear switch are gone.
Do anyone have these parts or can I buy them from Keithley/Tek?

[pigrew]

I have also discovered that my meter are missing some parts, the shield is gone and the push rod to the front/rear switch are gone.
Do anyone have these parts or can I buy them from Keithley/Tek?

You can buy them from Tek. I just got a TF-245 resistor network network from them. You fill out a quote form on their website (it allows you to provide a text description of the part you want), and then it'll tell you a price, and then you call their phone number and order over the phone. It was about $20 of shipping (I asked for cheapest method), plus $20 for the resistor network, in my case.

Sorry I don't know what could be wrong with your meter. You may want to try with three banana-cables. First, connect the + to - on the left and  the + to - on the right, and finally use the third to connect between the two negatives. This allows the input voltage (left terminals) to be close to zero. I've had it pass the tests with crappy cables in that configuration.

EDIT: According to the repair manual, the push rod is "2001-322A" and the the "motherboard shield" is 2000-306B. I'm not sure if that's the correct shield....

-Nathan