The inevitable callback on RCA 17PT8072

[Electronic M]

Looks like they used a couple of adjacent parallel traces to form a capacitor to bridge the IF signal across the deleted tube...A very interesting approach!

It was not uncommon for manufacturers in the day on cheaper 'stripped down' models of sets (particularly stereo consoles) to delete sockets from PCBs and bypass signals and other electrical paths across the old socket pins....Though usually it involved soldered on wires or components, and or PCB traces strategically broken at the factory, rather than a alternate PCB foil pattern...

[old_coot88]

Originally Posted by Electronic M

Looks like they used a couple of adjacent parallel traces to form a capacitor to bridge the IF signal across the deleted tube...A very interesting approach!

Heh. Quite a 'gimmick'.

[init4fun]

Originally Posted by old_coot88

Heh. Quite a 'gimmick'.

Yes Sir , I am familiar with the "gimmick" capacitor from my tube FM radio work . It would usually appear as two wires lightly twisted together but of course not electrically connected together . An easy way to get a couple of picofarads without an actual component and somewhat adjustable by twisting tighter or loosening the twists . A neat way to accomplish a desired result

[Phil Nelson]

Not to go too far off topic, but speaking of unusual traces . . . when recapping my CTC-4, I noticed these two squiggly guys:



??

Maybe that's commonplace in PC boards, but I don't work with them often.

Phil Nelson

[kvflyer]

Originally Posted by Phil Nelson

Not to go too far off topic, but speaking of unusual traces . . . when recapping my CTC-4, I noticed these two squiggly guys:



??

Maybe that's commonplace in PC boards, but I don't work with them often.

Phil Nelson

I suspect it is an inductor?