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Old 10th Mar 2018, 3:41 pm   #5
G4WYZ MikeyP
Triode
 
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Join Date: Nov 2012
Location: Chorley, Lancashire, UK.
Posts: 21
Default Re: Racal 9081 phase detector problems.

Thank you for the info, I've found the fault.

On the Highest Frequency range when the frequency reaches 492MHz there is a slight shift in voltage IC11/7 causes the Q18/IC17 to oscillate at 3.9kHz. Removed using a 100nF decoupling capacitor now tunes down to 256MHz but with no end bottom stop.
This tends to point that the ROM is U/S, as I had to change IC11, which is a dual 4 channel multiplex, one channel was faulty.
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