[time-nuts] HP 105B Problem?
Ed Palmer
ed_palmer at sasktel.net
Sun Aug 9 03:27:29 UTC 2009
Hi Greg,
Greg Burnett wrote:
> Hi Ed,
>
> IIRC it's normal for the circuit check meter readings to behave "squirrelly"
> as you've described for the 3 output checks. I think this function is pretty
> much only to "crudely" show that you have (or don't have) each output.
>
It's not exactly 'time nuts' quality is it? :-)
> As for your 100kHz & 1MHz dropping-out when you load your 5MHz output into
> 25 ohms, this might be a sign of a marginal condition of your output
> section - e.g., 5MHz signal dropping too low when loaded with 25 ohms?
>
That's what I'm assuming. According to the schematic for the older
version, the path feeding the divider is well isolated from the path to
the output for both the 5 MHz and 1 MHz stages. I expected HP to do at
least that well when they modified the design to include the 10811.
That's what makes me wonder if there's a circuit fault.
> However in practical use I think various destination instrument's timebase
> inputs might require a bit more voltage than you'd have at best into 25 ohms
> anyway. So I'd probably not load the 105B into such a low impedance.
>
Agreed. At this point, I'm just trying to figure out what I can and
cannot do.
Ed
> Best,
> Greg
>
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