Re: 2445A calibration

Chuck Harris

The motherboard A1 tells the control panel which scope model
it is. It has a jumper to distinguish between a 2445B and a 2455B.
It has a pass through jumper that distinguishes the 2465B and 2467B.

They are well hidden, but they show up on the upper left corner of
the ANALOG CONTROL schematic for the A5 board, B050000 and above
in the 2467B manual.

J512, pin 11 is labeled 45A-55A ID, and,
J512, pin 32 is labeled 65A-67 ID.

The ID's are deleted from the B049999 and below schematic.

On the A1 board the 45-55 jumper is called W120 (gnd or no gnd).

And J512 pin 32 gets passed through the A1 board to J191 pin 2,
which goes to the CRT power supply board, where it is grounded
for a 2467B, and left open for a 2465B.

-Chuck Harris

maxim.vlasov@... wrote:

Thank you gentlemen for all the support!

Looks like slowly but surely I make some progress. Just found that U2420D buffer is sinking 11mA. I measure at the U2420D output -8.8V but TP2421 is -1.25V. 11mA flowing through R2220 (680 Ohm). I've looked at the schematics and 11mA doesn't seem to be the current to be pulled out of TP2421. There are quite a bit of loads, but all of them in a range of dozens of KOhms. Something is pulling up -1.25V rail.
Also noticed, that the buffer was quite warm. So, I've replaced it by TL084N from TI. Same story, but the level changed by 10mV.

Have you observed this on your scopes when repairing?

One more thing - I've got -04 FW version. It seems like the last version was -09 for 2467 o-scope. I wonder whether I can run the latest FW. If so, then in the guts of the o-scope there should be a HW identification register somewhere to tell to the FW whether it's 2445/55/65 or 67, IMHO. Otherwise the code is almost the same.

Thank you,

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