[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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