U3402A repair - problems with PSU, UART

[nikodem]

Hi all!

I have Agilent U3402A on my bench for repair now. Before I start any detailed description - could anyone please measure the power supply output voltages on the J602 in a working device?

Thank you in advanced

[pbs74]

I have the Escort 3146A, should be same as U3402A, as Agilent bought Escort and rebranded products.

I cannot find schematics for either model, but voltages for J602 in my Escort were (a bit strange values)
Black: 8.9V
Brown: Gnd
Red: 5V
Orange: Gnd
Yellow: 16.5V
Green: Gnd
Blue: - 1.95V
Purple: Gnd

[nikodem]

I have the Escort 3146A, should be same as U3402A, as Agilent bought Escort and rebranded products.

I cannot find schematics for either model, but voltages for J602 in my Escort were (a bit strange values)
Black: 8.9V
Brown: Gnd
Red: 5V
Orange: Gnd
Yellow: 16.5V
Green: Gnd
Blue: - 1.95V
Purple: Gnd

Thank you, that's suprisingly helpful. My DMM is forcing the blue one to be around 1 V - when I disconnect the cable, it goes back to around -2 V. The resistance on that line is ok (in the range of Mohm, both directions), but this is a valuable starting point for this repair.

Will it be okay if I add some more specific questions regarding that device in the future? beeing able to reference to a working device is really helpful.

[pbs74]

Will it be okay if I add some more specific questions regarding that device in the future? beeing able to reference to a working device is really helpful.

I just got mine as NOS (new old stock) so depending on risk of ask I might turn down, but feel free to ask. I think it is a nice meter, especially for the price I gave. It is within same digits as my Keithley 2000 and very close to my Fluke 189, and although none are recently calibrated, the agreement indicates correct values.

[nikodem]

Will it be okay if I add some more specific questions regarding that device in the future? beeing able to reference to a working device is really helpful.

I just got mine as NOS (new old stock) so depending on risk of ask I might turn down, but feel free to ask. I think it is a nice meter, especially for the price I gave. It is within same digits as my Keithley 2000 and very close to my Fluke 189, and although none are recently calibrated, the agreement indicates correct values.

I got mine as broken, hoping that it will be something relatively simple to repair (this is not the first instrument I'm repairing, but by far the newest, and this means lack of proper service manual and high level of integration)... We'll see where it will get me   

[lern01]

Will it be okay if I add some more specific questions regarding that device in the future? beeing able to reference to a working device is really helpful.

I just got mine as NOS (new old stock) so depending on risk of ask I might turn down, but feel free to ask. I think it is a nice meter, especially for the price I gave. It is within same digits as my Keithley 2000 and very close to my Fluke 189, and although none are recently calibrated, the agreement indicates correct values.

I got mine as broken, hoping that it will be something relatively simple to repair (this is not the first instrument I'm repairing, but by far the newest, and this means lack of proper service manual and high level of integration)... We'll see where it will get me   

How to enter calibration mode for u3402a. thanks!