Hello Evan,
I have verified that bias circuitry works properly. I have even checked that the finals have full power suply voltage on their? drains (13.3V) and that its DC value drops to ca 1V when I press the key.
So it looks like I need to check the path via the LPF filter.
I have found that the HV voltage measured on R213 remains 12.6 V even when I start to transmit.
Is the voltage multiplier broken then?
73,
Wojtek
Hello Wojtek,
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I had similar problems with my DE.? That turned out to be overheating drivers in one instance and a failure in the Q9 and Q101 equivalent circuits (the DE documentation did not have Q101 listed).? Verify that there are 12 volts on the drain of Q9 (the tab) when the PTT is pressed.? Also, verify that Q12 to Q15 are on with a 0.6-volt drop from Base to Emitter.? This may be difficult to determine if one has failed since the two are connected in parallel.? The other test is to verify the voltage on the emitter resistors to check for the transistor being on.? They should all be close to the same.
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Another possibility is that the PA_Bias1 circuit has failed. Verify that D6 has 5.6 volts on the banded side when the PTT is pressed.
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Here is the relevant circuitry:
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I agree with Gordon that a shorted IRF510 is unlikely. The first step is to check for proper soldering on the devices.??
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I also strongly agree with Gordon about installing the AlN insulators instead of the mica.? Do this while you add the external fan. As Gordon said, the AlN will make the heat sink even hotter.
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The sbitx uses a bar to hold down the transistor, so you do not need a hole and screw insulator.? If you have other applications, buying the insulators with the hole may be a better choice.
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Post on 开云体育:
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Note: Ashhar Farhan has stated that these are not needed with the new mounting method for the finals.? They do not hurt, so cheap insurance helps with heat dissipation.
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73
Evan
AC9TU
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-- Wojciech M. Zabo?otny
My GPG/PGP keys:
standard: 8192R/7E17F00A (B53C 1F09 BEA9 ED46 51B6 ?2C2E 4344 F292 7E17 F00A)
confidential: 16384R/1FEDB03C (3412 2330 E225 D57D 70C3 ?2340 B294 9408 1FED B03C)
