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Central Electronics 200 Help




 
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Author Topic: Central Electronics 200 Help  (Read 193 times)
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xe1yzy
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« on: November 23, 2022, 05:25:35 PM »

Hello to all,
My CE200 starts to fails on TX audio, when I push the PTT, I can see on the  on board oscilloscope the TX keying signal, but no carrier , no modulation and no CW, If I wait 10 to 15 seconds with the PTT on, the audio start to work, I'm already  clean the relay , but that no solve the problem, any idea?

Regards

Pedro XE1YZY
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xe1yzy
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« Reply #1 on: November 25, 2022, 08:48:27 AM »

Project update,

     I receive an email from Jim WD5JKO, he suggest  me take a look on a couple of 10 ohms cluster resistors on the filament of V1 6BL8 ( Mic amp. and VOX), I found 3 10 Ohms resistors in parallel on each side of the filament, I mesure the resistance and I have 2.5 ohms on each cluster, or 5 ohms in total, according to Ohms low, that suppose a drop in voltage to 4.05 volts, instead of 6.3V.

      Well, I by pass those branches , and the transmitter como back to life, the VOX works OK, and Audio also are Ok, the only difference I noticed, is a more blinks on the limiter lamp, So Jim and I wondering why CE put those resistor to lower the filament voltage ?, maybe a fancy way to reduce the amplification gain of the tube?

Regards
   


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