From: "Jose V. Gavila" <[EMAIL PROTECTED]> Subject: [time-nuts] HP-5370A update Date: Mon, 24 Jul 2006 18:28:30 +0200 Message-ID: <[EMAIL PROTECTED]>
> Hello my friends! Jose, > It is time <pun intended> for some update... Hehe... > OK, I said, go back to the basics: is the CPU clock working?. Some > oscilloscope probing later showed that it was not. Good point to start!. So > I went to A8 (REFERENCE FREQUENCY BUFFER) assembly troubleshooting, as it > is the source of the 10MHz clock to the CPU clock circuit. Manual shows > some waveforms and yes!, one of them was bad... obviously, the one which > has to do with the 10MHz CPU oscillator. Some more probing later I decided > one of the transistors in the circuit could be bad. But I replaced them > (both 2N2904) to not avail... Then I saw a couple tantalums and a > suspicious small resistor which seemed overheated. Looking at the manual it > was no less than a fuse resistor. And it was open... and one tantalum was > shorted. Yes, this supply goes only to the 10MHz CPU clock generator circuit! > > After replacing the burnt resistor and the tantalum (with a 105C 10uF/50V > electrolytic as I hate tants!), I powered up the unit... and IT WORKED!!! Whee! Good thinking and good that you had a simple and classic problem which you could resolve easy enougth! > I think I made a good buy :-)! You did. May I congratulate you both on the buy and repair effort! It must give you much joy! ;O) > Unit has some cosmetic damage and one button does not work properly (it > sticks) but with a careful cleaning and some front panel work it should end > as an 8.5+ looking instrument. > > Now I have to learn how to properly use it. I will sure ask you ;-) I am pretty sure the necessary knowledge is here on the list. > Best regards and sorry for the ramblings but I am a very happy camper today! I bet you are, if your not then we better come and spank you. You made a good buy and a good repair-effort. As I very recently had the same experience with my Cs-beam and really understand you. I was however not set back as much as 57 EUR, but that is another matter. I am however deeply in depth to a fellow time-nut for his contributions in time, money and spare part, so I will have to compensate him at some time, maybe a beer session or something. Cheers, Magnus _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
