Topics

Is it possible to test 2465B power supply boards outside of the scope?


Grayson Evans
 

Wondering if anyone has been able to test the 2465B power supply boards (A1A2, A3) together, without reinstalling into the scope?
This would allow checking the supply voltages and ripple to at least make sure the mods/fixes worked.
I can't tell by looking at the schematic if the regulators require a load in order to work properly, or some circuit path needs to be connected.
The maintenance manual shows test points throughout the power supply schematic with waveforms, but I don't see how in the world to access these locations if the unit is installed in the scope.
Thanks,


Chuck Harris
 

I do that all the time. You would be committing a very
dangerous act if you were to work on the power supply while
it was installed in the scope.

To make the supply work, you need a dummy load. The manual
tells you the resister values necessary in the back where the
trouble shooting flow charts are..

-Chuck Harris

Grayson Evans wrote:

Wondering if anyone has been able to test the 2465B power supply boards (A1A2, A3) together, without reinstalling into the scope?
This would allow checking the supply voltages and ripple to at least make sure the mods/fixes worked.
I can't tell by looking at the schematic if the regulators require a load in order to work properly, or some circuit path needs to be connected.
The maintenance manual shows test points throughout the power supply schematic with waveforms, but I don't see how in the world to access these locations if the unit is installed in the scope.
Thanks,






Grayson Evans
 

Thanks Chuck. I looked in the back of the maintenance manual among the flow charts and all I can find to test the regulator board is this note:
"All regulators (except +10) required some load to regulate, the lower voltage supplies require greater loads. The regulators between +15 and -15 [+5, -8, -5?] may be loaded using 100 ohm resistors of the proper power rating. "
This seems to leave out the 87V and 42V outputs.
Is this what you are referring to or did I miss info somewhere else in the manual?


Chuck Harris
 

If you go to the back of the 2465B manual, around about page 472, by paper
page count, there is a flow chart (10), labeled: Power Supply Troubleshooting.

The next page is labeled: Inverter Troubleshooting Notes.

On that page it gives a schematic for a PRIMARY TEST LOAD (for testing of the
primary side circuitry without the regulators), and then below
that schematic is:

+5VD Test Load

It states: "Some load is required for the inverter to run. When the Power Supply
module is removed from the instrument or when the Regulator Board is disconnected
from the Inverter Board's output, the test load described below may be used to
check the operation of the inverter...

TEST LOAD. Connect a 2 ohm, 25W resistor... from +5VD ... to ground."


The 5VD supply provides the only feedback controlled voltage regulation on
the supply. As such, the 5VD load sets the operating point for the inverter.

The analog regulators need a little load, but not all that much to perform
their job... essentially enough to overcome the leakage through the series
pass transistors. The manual says 100 ohm is enough for the +/-15V.

They don't specify the load for the 87V, 42V, 5VA, -5V, or -8V, just about
anything light will do... 10 or 20ma.

The idea is you want the inverter running, and the 2 ohm load will see to
that, and you want the analog regulators supplying enough current so they
will actually go into regulation, ... Then, you can tell if there are any
show stoppers that are going to blow up the scope.

-Chuck Harris

Grayson Evans wrote:

Thanks Chuck. I looked in the back of the maintenance manual among the flow charts and all I can find to test the regulator board is this note:
"All regulators (except +10) required some load to regulate, the lower voltage supplies require greater loads. The regulators between +15 and -15 [+5, -8, -5?] may be loaded using 100 ohm resistors of the proper power rating. "
This seems to leave out the 87V and 42V outputs.
Is this what you are referring to or did I miss info somewhere else in the manual?







Grayson Evans
 

OK, Thank you, I think I got it.
I need to load the 5VD line with t he 2 ohm load, and the regulator outputs with 100 ohms (or whatever for 10-20 mA).
Put 120V to J205/204, short J206/207, turn on the switch and check for smoke!
I will probably build a little test board with the resistors and wires to connect to various pins on the board.

So you have done this? and it worked?


Chuck Harris
 

Absolutely! I do it with every power supply that I recap
for myself, or my customers. I wouldn't dream of putting
a freshly fixed power supply in an instrument without testing
it first.

-Chuck Harris

Grayson Evans wrote:

OK, Thank you, I think I got it.
I need to load the 5VD line with t he 2 ohm load, and the regulator outputs with 100 ohms (or whatever for 10-20 mA).
Put 120V to J205/204, short J206/207, turn on the switch and check for smoke!
I will probably build a little test board with the resistors and wires to connect to various pins on the board.

So you have done this? and it worked?