Gold Mod 3(a) to improve picture quality says to short out L2, but on the G1MFG 13cm receiver schematic (that is closer to the video circuit of a 23cm, than a 13cm, receiver) shows shorting out L1. None of my receivers,
had L1 or L2 shorted out. Shorting out either inductor removes half of the audio sub-carrier filtering so could only make things worse.
Additional information about L1 & L2 in the de-emphasis article says: L1 & L2 which are marked as being 6.8uH – are in fact 4.7uH. This must have been a short term production problem or else an
inductance meter somewhere needs service, as all of the 6.8 uH inductors I checked were 6.8 uH.
I have to wonder how much of the information found, came about to correct problems caused by incorrect 4.7uH inductors, and how much of this information remains to cause problems for receivers with 6.8 uH inductors being incorrectly modified.
In the de-emphasis article, the schematic at top of page 2 differs from other information I found.
R5 (4.7K) does not exist (at least on current receivers) and some component values are different.
Why stop now? While nit-picking I may as well add that (one of) the Gold receiver instruction sheets says "there is a wire link on the underside of the Gold receiver PCB which" . . . etc., etc., etc.,
Again, this must be some more old info as I have never seen any links!
Above I added "one of" to the instruction sheet reference because I now have numerous instruction sheets. If you don't like the ones at g1mfg.com you can find other versions on the
TVHAM web site.
It is interesting (actually - makes no sense) that my 13cm & 23cm receiver video and sound sub-carrier filter circuits are nearly identical and for the same frequencies, but use different capacitor values (i.e. different filter
characteristics). The 13cm receiver has better video quality than the 23cm receiver and it was no surprise to see the 23cm video quality improve after changing 23cm receiver components to match 13cm receiver values.
It is interesting that 13cm receiver (with fair video) components are close to the values shown on the G1MFG 13cm receiver schematic, but the schematic is more accurate for the 23cm receiver (with poor video) video circuit which
uses different component values than shown on the schematic.
It seems that every place information for a mod is found, that there are differences in the circuit and component values which seldom match what is in the actual circuit. Most never realize the component differences as how many
are crazy enough to remove and measure components, or have the equipment to measure component values. I only did so because I was looking for solutions to problems. I have to conclude that there have been many receiver circuit versions supplied.
Enough gripping! Back to the mods . . . .