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564smeter [2015/12/14 09:59]
n1eu created
564smeter [2015/12/14 10:02]
n1eu
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 ALC and I recall reports of Tentecs sometimes losing diodes in that  ALC and I recall reports of Tentecs sometimes losing diodes in that 
 circuit from nearby lightning while connected to an antenna. circuit from nearby lightning while connected to an antenna.
 +-----
 +//(Omni V s-meter comments that may be applicable)//​
 +
 +As far as I know the manual with circuit diagrams that you can download ​
 +from Tentec is all the "​service"​ manual there is. Looking at it I have 
 +found that there is an S-meter sensitivity adjustment R45 on the IF/AF 
 +board along with an S-meter offset R43. It looks like R43 sets the zero 
 +and R45 sets sensitivity from low to very high. I don't know the value, ​
 +but there is no fixed resistor to limit hypersensitivity. Providing the 
 +AGC is enabled, you should be able to adjust R45 to any sensitivity you 
 +like, providing the pot hasn't gone bad with age. If the pot has an open 
 +resistive element it may only work set up way too high. The pot may have 
 +an identification resistance on it to allow finding a generic ​
 +replacement or to allow a will guess for value, at about 1/2 the pot'​s ​
 +total resistance to be put in as a fixed resistor.
 +
 +The other thing that can cause an S-meter to be hypersensitive is leaky 
 +bypasses on the AGC line so that AGC control is poor, e.g. that it takes 
 +a large AGC voltage to reduce the RF and IF gain. Maybe the RF gain 
 +controlled stage is on another board and the cable between them is open. 
 +It might be two common Tentec service procedures are in order. One is to 
 +tighten all the board mounting screws to make sure the grounds are good. 
 +The other is to apply a quarter drop of DeoxIT to each cable connector ​
 +pin and slide the connector off and on a few times to get a solid 
 +connection again.
 +
 +If all that's needed is setting R45, you will have to judge by ear what 
 +signals are strong and weak, like we did before we could run AGC on a 
 +receiver on CW or SSB, and adjust the meter for a satisfying reading ​
 +that matches your perception by ear.
 +
 +If R45 proves to be open, Cramolin who makes DeoxIT makes a pot restorer ​
 +product that might work.

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