Rick, I have been 'reading the mail' on this discussion and have a somewhat off topic question. I acquired a 5334B that has a 'noisy' channel C. It originally did not read when fed a signal. I then adjusted R328, the peak detector, and then it correctly read the signal. However, when I disconnect the signal, it continues to 'gate' and read some numbers.
Any thoughts? Also, is it possible to add a 'channel C' to a unit that does not have it. I have noticed that the unit I have without a channel C has most (if not all) of the parts populated on the board except for the 8 pin IC that plugs into the socket, U302, which appears to be an MB506. Is all that is required is to plug in an MB506 and add a connector to the front panel, or is there a firmware issue as well? If a firmware issue, is it possible to 'rewrite' an EPROM or some such to deal with this? Thanks, Joe -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Rick Karlquist Sent: Sunday, February 15, 2009 1:54 PM To: [email protected]; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] DIY Frequency extension for HP Agilent 53181A, 53131A or 53181A Richard H McCorkle wrote: > Hi Samuel, > > I suggest starting by downloading the component level information for > the 53131A and 53132A from tha Agilent site at the following links. > > http://cp.literature.agilent.com/litweb/pdf/5989-6308EN.pdf > http://cp.literature.agilent.com/litweb/pdf/5989-6307EN.pdf > > The 53132A document includes a schematic of the channel C board with > parts list and may assist in getting you started. I see that they have a factory select resistor that unbalances the input slightly to keep the prescaler from oscillating with no input. This a simple, obvious "solution" to this problem. It is also non-optimum, for three reasons. It desensitizes the prescaler, it uses a factory select part that may not work consistently over temperature, and it still results in a range of input power where the counter displays garbage. In the 5334B C channel, I used a diode detector that turned on the counter at a repeatable input power. Thus you never got garbage on the display due to low input power. The detector used the well known circuit where you bias the diode on with a few 100 microamps of DC and have a compensating diode that is not excited by RF. A difference amp subtracts the compensating diode voltage. Simple, but effective. It is also interesting to note that in 1987 I used the MB506 prescaler. Here they have simply upgraded to the MB510. Not likely to be any better on noisy sources. Rick Karlquist N6RK _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
