Differences
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1254pbigelow [2007/03/27 16:44] n5na |
1254pbigelow [2007/03/27 16:46] n5na |
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- Lots of birdies and display induced signals on the lower half of the AM broadcast band. | - Lots of birdies and display induced signals on the lower half of the AM broadcast band. | ||
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* Remedy: Have attempted to shield out the multiplexing emissions by spray painting a graphite EMI/RF shield to the inside of the front cover. It helped a little bit. | * Remedy: Have attempted to shield out the multiplexing emissions by spray painting a graphite EMI/RF shield to the inside of the front cover. It helped a little bit. | ||
+ | |||
- Reduced sensitivity on the lower half of the AM broadcast band. | - Reduced sensitivity on the lower half of the AM broadcast band. | ||
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* Remedy: Put a jumper across R72, eliminating that input filter. | * Remedy: Put a jumper across R72, eliminating that input filter. | ||
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- FM intermod from strong FM stations. Just add 90 (2* 1st IF) to the received frequency | - FM intermod from strong FM stations. Just add 90 (2* 1st IF) to the received frequency | ||
to detetmine offending frequency. | to detetmine offending frequency. | ||
- | Remedy: Have tried with some success (but none totally satisfactory): | + | |
+ | *Remedy: Have tried with some success (but none totally satisfactory): | ||
* Snap-on RF choke on power cable | * Snap-on RF choke on power cable | ||
- | * Soldered on a shield on trace side of the board around the 1st Mixer section | + | |
- | * Incorporated FM trap (from Radio Shack) in the antenna lead | + | * Soldered on a shield on trace side of the board around the 1st Mixer section. |
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+ | * Incorporated FM trap (from Radio Shack) in the antenna lead. | ||
- The rotary Encoder loosens up with use causing the frequencies to jump around (sometimes) when tuning from one step to another. | - The rotary Encoder loosens up with use causing the frequencies to jump around (sometimes) when tuning from one step to another. | ||
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* Possible Remedy (have not tried yet): Sandwiching a large, black, felt washer between the tuning knob and the tuning knob recess to reduce play. | * Possible Remedy (have not tried yet): Sandwiching a large, black, felt washer between the tuning knob and the tuning knob recess to reduce play. | ||
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- Hum from the power supply. | - Hum from the power supply. | ||
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* Possible Remedy (have not tried yet): Install a 15V IC regulator in the power supply. | * Possible Remedy (have not tried yet): Install a 15V IC regulator in the power supply. | ||
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- Deafening thump upon turning on the 1254 when using headphones. REALLY LOUD. | - Deafening thump upon turning on the 1254 when using headphones. REALLY LOUD. | ||
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* Remedy: None yet although I suspect a large capactior may resolve this one. | * Remedy: None yet although I suspect a large capactior may resolve this one. | ||
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- A little bit of "thumping" due to slow synthesizer lock. Not too bad, really, considering | - A little bit of "thumping" due to slow synthesizer lock. Not too bad, really, considering | ||
the price. | the price. | ||
Paul | Paul |