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Hi Calvin

I checked the A27 parts list. Following chips seem to be used:

NE5018F DAC - can be found on eBay

1826-0881 ADC - this is actually an ADC856C. I am unsure whether this can be replaced easily, but I only searched for approx. 5min :-)

MP7533MP - a pin compatible replacement from Maxim is available, called MX7533. Should be available at the usual distributors (Mouser, Digikey, whatever).

Best

Tobias

-------- Original message --------

From: "Calvin Guan guancalvin@... [hp_agilent_equipment]"

Date: 10/23/17 04:39 (GMT+01:00)

To: hp_agilent_equipment@...

Subject: Re: [hp_agilent_equipment] Re: 8340A Fault - ADC

???

Hi Lex,

Yes, it???s ADC fault. The instrument has Fault annunciator lit. I asked the guy to press [shift][manual], and the ADC lights are blinking the the Entry Display. The other faults that would turn on the Fault annunciator are PEAK, TRACK, KICK, and CAL. Although the PEAK and TRK aren???t not blinking, I don???t know if they are also fault as ADC failure may automatically disable PEAK and TRACK.???

I read the 8340B A27 assembly schematic from keysight. Unfortunately, the ADC Clock control and input MUX part is mostly messed up, but the ADC chip itself seems very simple.The 8341A service manual schematic is not humanly readable.

Good thing about it is there are no other abnormal annunciator are lit. UNLEVELED is off, UNLOCK is off. My gut feels it???s something simple but I could be totally wrong.

If the store owner is nice enough, I *might* be able to visit the him to see the instrument in person. What basic tests would you suggest me to run?

Thanks,

Calvin

On Oct 22, 2017, at 5:38 PM, lexternegron@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:

Hello,

It depends on who you're buying from. Personally I would go for it if I knew the basic diagnostic self tests were working, the seller isn't selling a physically damaged unit and if I had the money.???I have to ask though. Did you mean ALC? There is no fault light indicator for ADC. Possible scratch or sticker residue????It can be anything from a faulty reference to something as serious as the RF module(s) for the ALC section.

I have the manuals but it would be a written essay on here explaining or posting pics of everything in detail. Check all manual paperwork from Keysight. Its all there but everything is imho mislabeled. Search for all 8340/1/A/B models (4 models in total). This also sounds similar but may not be the same problem as another member here had.

Link to another faulty unit:???

All in all I would need further information obtained from diagnostic tests. Also its ultimately up to you but as I said, I personally would buy it and accept whatever consequences I may receive.

-Lex

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