BitAnnihilator Posted January 11, 2022 Share Posted January 11, 2022 I'm trying to install a composite mod based on the PDF in the DIY thread/Ben Heck's circuit, however when I connect it to my LCD monitor I get a very dim almost black picture when the pot is at 0 ohm. The RF output appears to be fine with no issues, it's just when it's through the composite circuit. I took voltage measurements and +12v at the circuit is almost spot on (12.08v). One weird thing I'm noticing is if I put my meter on the composite RCA I'm seeing close to 6V, not 0.7v-1v like I'd expect. I've double verified my layout (I'm using a small perfboard rather than hiding it in the RF box) and all of the wires and circuit match the PDF to a T, I've also verified all components (there's not much, 1K pot, 1K resistor, 2n3904 NPN). What would be the next things to check from here? Quote Link to comment Share on other sites More sharing options...
ChildOfCv Posted January 11, 2022 Share Posted January 11, 2022 (edited) The Ben Heck Hack is a simple emitter-follower circuit. If you read the voltage on the input side, you'll notice it's a slight amount higher than the output voltage. The transistor just helps to tap that voltage without sapping too much from the source. There's a better composite mod you can get from console5.com which is based on an op-amp. If you insist on using transistors, though, I'd suggest a modified circuit to reduce the load on the RF even more. Edited January 11, 2022 by ChildOfCv Quote Link to comment Share on other sites More sharing options...
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