Keysight 34461A ADC error

[Lobisomem]

Hi,

I have the 34461A and recently it boot with an error icon on the top right corner of the display. I did a self test (quick and full) and got the following errors:

+624 Self-test falied: Coarse ADC error
+625 Self-test falied: ADC offset
+626 Self-test falied: ADC noise

I sent these informations to the only keysight representative in my country (Brazil) to get a quotation to repair. They charge me something around 1,000 US dollars. I figure that they will not change some faulty ADC that cost something around 50 USD. They will change the entire board. And like a good third world country, when you import something (like the board of this DMM) the taxes are insane. Hence the price they charge me. Or they are just too greedy.

So, can anyone point me to some schematic of this DMM? Or better yet,  point me to the ADC or other component that I can replace to get this multimeter  fixed?

Thanks in advanced.

[Kleinstein]

There is a schematics for the 34410 around somewhere in the web. AFAIK the ADC should still be essentially the same.
Compared to the older 34401 the ADC is a whole lot more complicated. AFAIR there are 2 extra auxilary ADC chips for the coarse and fine part and chances are the problem is around the coarse one. A point to check is the supplies (e.g. bad tantalums ? ). It is not just the ADC chip that can wrong - there are other related parts too.

I can fully understand the KS would swap the whole board, unless it would be an error that comes up very frequent.