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Roger,
I presumed it (the BFO) was not working because a) There is no audible evidence of function, that is, it is not producing beat notes against CW b) I tried probing in that area with a scope and saw no evidence of oscillation c) I injected a sine wave from an external signal generator into that circuit, and could then make out CW notes. You might be right, it might be working but at the wrong frequency. On the other hand, item (b) suggests it's not working at all. 73 Pete AC7ZL Roger D Johnson wrote: H. P. Friedrichs wrote: I cannot seem to get the BFO working, however. The resistors around the BFO seem to check out ok. The condition of the caps are unknown at this time, though I have not run across bad silver micas or the pF dogbones. How did you determine that the BFO is not working? I'm thinking that it might be working and just off frequency due to bad caps. 73, Roger |
#2
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H. P. Friedrichs wrote:
I presumed it (the BFO) was not working because a) There is no audible evidence of function, that is, it is not producing beat notes against CW b) I tried probing in that area with a scope and saw no evidence of oscillation c) I injected a sine wave from an external signal generator into that circuit, and could then make out CW notes. You might be right, it might be working but at the wrong frequency. On the other hand, item (b) suggests it's not working at all. What are the plate and cathode voltages on the BFO tube? I am thinking you might have a bad resistor. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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