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R4B s-meter only reflecting half way when turned on in stand-by, low receive.
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Hello all, I hope I can explain this correctly. I have a R4B and sometimes when I turn the radio on to the STBY position, the S-meter reflects all the way over to around the 40 decibel mark on the meter. Then when moved to the ON position, I get full volume and normal deflection of the S meter as to the incoming signal.?
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But sometimes, (and it's starting to happen more often now), when I turn the radio on to the STBY position. The meter will only go to the mid section (around S-9) and when put in the ON position, the receive volume is low and the S-meter barely moves. Stays around 1 to 3 S-units on the meter and seems to respond in a very "tight" way by movement.?
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Any idea what this could be? Or what is the cause? Thanks in advance! 73
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Dale, KD5UVV?? |
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This is one of those problems that can have several causes and sometimes, it's more than a single problem. The meter not deflecting on STDBY indicates a possible bad connection through the switch or the relay but I suspect the switch more.? If the contacts develop high resistance, the meter can indicate a partial reading of the meter.? This is because the circuit expects either a short or an open. To check this, put your switch in the normal MUTE position with a shorting plug in the MUTE jack.? If the meter goes full scale with the plug out and S1 with the plug in, you could have a dirty switch. With the shorting plug in, you should see S1 with the RFG fully CW and should see full-scale with the RFG fully backed-off. Your lack of signal receive indicates resistance either in that switch again or, more likely, in the relay contacts. These can be gently cleaned with a piece of white paper soaked in DeOxIt.? Pull through the NO contacts and then gently press the armature and run through the NC contacts. Finally, a really gassy tube can cause fairly wild symptoms.? There are several tubes that affect the AGC circuit.Because Drake used an extremely high AGC impedance (megohms) means that it doesn't take much unwanted grid current to send things wacky.? The faulty tubes I've seen causing these issues are the 6BZ6, 6BE6 and 12BA6's. Steve Wedge, W1ES Time flies like an arrow.? Fruit flies like a banana.
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On Wednesday, January 15th, 2025 at 2:15 PM, Dale KD5UVV via groups.io <bayou50@...> wrote:
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Thank you for the information Steve. I think I'm going to try to find someone that knows what they are doing to check, fix and align this R4B, it's such a nice receiver!?
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Any recommendations for a good Drake tech from anyone out there, will be much appreciate. As I see a few of the "go to" Drake techs seem to have stopped their operation.? ??
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Thanks again, Steve. 73
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Dale, KD5UVV |
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I'm still doing repairs; you can take this offline and I can give you more details. Steve Wedge, W1ES Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Wednesday, January 15th, 2025 at 7:09 PM, Dale KD5UVV via groups.io <bayou50@...> wrote:
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