UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - 6-gang FM stereo tuner heads

G0HZU_JMR · 6th Nov 2022, 11:43 pm

I just tried a 470kΩ 0805 chip resistor in parallel with a 0.7pF PPI 1111N cap in place of the probe. This was an attempt to check the accuracy of the jig at 100MHz.

When this was connected at the peep hole test point the jig predicted a resistance of 380kΩ in parallel with just over 0.8pF.

I also tried a 220kΩ in parallel with the 0.7pF cap and the jig predicted 178kΩ in parallel with just under 0.9pF.

I'm not sure why the jig reads a bit low for Rp but it might actually be correct. The effective Rp of these resistors may well fall up at VHF. I'm using cheapo thick film 0805 resistors for this test. it would be nice to know what the true Rp of these chip resistors is up at 100MHz.

6th Nov 2022, 11:43 pm	#213
G0HZU_JMR Dekatron Join Date: Sep 2010 Location: Cheltenham, Gloucestershire, UK. Posts: 3,077	Re: 6-gang FM stereo tuner heads I just tried a 470kΩ 0805 chip resistor in parallel with a 0.7pF PPI 1111N cap in place of the probe. This was an attempt to check the accuracy of the jig at 100MHz. When this was connected at the peep hole test point the jig predicted a resistance of 380kΩ in parallel with just over 0.8pF. I also tried a 220kΩ in parallel with the 0.7pF cap and the jig predicted 178kΩ in parallel with just under 0.9pF. I'm not sure why the jig reads a bit low for Rp but it might actually be correct. The effective Rp of these resistors may well fall up at VHF. I'm using cheapo thick film 0805 resistors for this test. it would be nice to know what the true Rp of these chip resistors is up at 100MHz. __________________ Regards, Jeremy G0HZU