Originally posted by mp20748
I don't have a manual, so I have no way of knowing the pin assignments on the FL's. First the three FL's would need to be removed. Then the resistors are put in place with a bead on each of them. If the FL's pin assignment is similar to an IC, then the resistor would go to pins 1? and 4?.
Again, if the pin assignmemt is similar to an IC. The resistor would go across pins 1 and 4. The actual signal path is also 1 and 4. [/b]
Not according to the manual:
2 no connect
4 capacitor (1uF) to common 1080_H signal
The layout is different to anything I've seen. The pins go in a circle.
From corner of pcb, pins 1 then 5 on one side and pins 2,3,4 on the other edge of FL.
So it goes 1,5,4,3,2 clockwise.
I shall attempt to post some zipped bmps of the relevant section of the manual at www.mogford.com/audio/30k1.zip
To the chap who asked me about the manual, it is a CD I bought and is of high quality. It's a protected pdf. As soon as I find where I bought it from, I'll post that info here.
Pin 5 has a cap (30pf) going to pin 4.
I'm thinking that pin 5 is a selectable roll-off or boost feature for the FL, and may be a feature for 720p to 1080I equalization. [/b]
A 30p cap across pins is not shown. Mind you, it may have been added as a mod.
Your explanation for reason of pin 5 is very plausable. If the response is now re-optimised by bypassing the FL then there is no need for a 720/1080 response switch. I think you've answered my query on this point. They possibly found it necessary to alter the filter because of the different digital quantisation noise between 1080 and 720.
The FL's have 5 pins. two are for grounding, and two for signal path. the 5th has a cap going to one of the signal path pins. [/b]
Pin 2 appears to be a N.C. Pin 4 Signal path being called 1080_H.
There are three coils and three caps in each FL. [/b]
Oh, I haven't opened up mine yet. I'll wait until the new year, later in Jan.
There are two pins on one side of the FL's, with three on the other side of the FL's. Connect the resistor to the two pins on the side that only has the two pins (that are farthest apart).[/b]
Pins 1 and 5.
And there is something else that effects the response, but we'll get to that later on. [/b]
What could that be?
There are no further response altering components after that. This assumes the output triple opamp IC7103 (BA7623F) is good enough.
Hmm, I just downloaded the datsheet for BA7623F. It doesn't quote anything better than 10MHz. Perhaps it's better than that in reality(maybe?). I'll also post the opamp datasheet at www.mogford.com/audio/ba7623f.pdf
(I do know of a better triple opamp OPA3691, gain would have to be set to 1 though.)
I look forward to hearing the info from the practical modification.