And I have been searching around, and found a replacement part for the RF-Modulator. It is a DIY part, that you order with the use of gerber files, and there is a list with parts. A socalled BOM. It does not have the actual RF modulation in it, however it gives a much clearer picture with the use of eighter Composit or S-Video cables.
EDIT:
The RF replacement part, is this one:
RF-Replacement
I found it on this Reddit post:
On Reddit…
A common theory (and the one I subscribe to) is that the chips are stripped from boards (e-waste) and then re-marked with a Rockwell logo and R65C02 part number because that’s what’s most recognized by buyers and thus most in demand. And the NMOS parts work well enough in most situations that buyers don’t complain too much. (E.g., anybody doing a Ben Eater system will probably have no issues at all, and never even know that their supposedly CMOS part is actually NMOS.)
Getting NMOS for CMOS, or slower parts, is pretty common. Getting an actual different chip seems to be fairly rare, and I think is likely not intentional mislabling (as with NMOS vs. CMOS) but just that a another 40-pin chip got dumped in the wrong pile.
That is mostly e-waste from China and India or possible Pakistan right?
Well, I’m sure that the e-waste mostly comes from West, originally. :-) But yes, it’s probably processed in South-east or East Asia. But I wouldn’t rely on the sellers location, because someone in the West might be sourcing chips from the recyclers anyway. If it’s really important to you to get a 65C02, and you don’t want to order a bunch from different vendors and test them, order from a reputable supplier that sources from original manufacturers (DigiKey, Mouser, etc.). But in our case here we want NMOS parts, so that’s going to be a bit tougher as they’re no longer manufactured, as far as I know. By far the easiest route is probably just to order a bunch of “R65C02” parts from a recycler and test until you find an NMOS one.
Is this one of the drop-in-place replacements that deliver composite video instead of the RF signal? (I spot markings for a C and Y signal.)
Edit: Ah, I see, already mentioned above.
I thought the RF modulator were those silver boxes with the Channel 3-4 switches on the back.
They looked more or less like this, but without the coax connector – simply antenna lugs.
No, those are merely switches to allow you to choose the input signal to your TV antenna connector: your TV antenna or your microcomputer/video game console. The inputs to the switch must already be RF-modulated signals.
The two outputs (300 ohm twin-lead balanced and 75 ohm coax unbalanced) are the same signal, just on a cable with different characteristics.The characteristics need to be matched between an output and an input to maintain signal quality. The box includes a balun to convert between the two forms; you also see these as standalone units that look like the following.
Yup…
The project page-link is on the board it self. Rather cheap the get them made. It was 22 US Dollars including shipping. That was with a 5 Dollar coupon they throw at you, for signing up. Of course it is without parts, however I got 6 PCB’s for the price. 
That is an RF-Modulator as well. The difference is, that on the C64, the modulator is designed to be part of the machine it self.
EDIT:
Sorry… Did not see the post below, that the one you posted are not an actual modulator… Sorry for my mistake.
My SixyClone board arrived the other day. It took me some time to take a decent picture, as my camera does not like the board for some reason. I must say that I am impressed. High quality and feel like better quality than the original. And it looks so sweet with the black and gold and white letters. I am deeply impressed by this board, and I think it is well worth the money. As I have done my 500-Desktop machine already (I really thought it would take me a whole year), then this will be my new 2020 project. To make a complete and as new as possible Commodore64. Ready for the next 30 to 40 years of use.
Someone posted this link on Reddit. Lots of SixtyClones pictured.
EDIT:
Looking closer to the pictures, then I realise that some of them are KU-Clones and not SixtyClones. (KU-Clone is a clone of an early C64 machine)
“bwack” on YouTube, have started working on his C64 CIA chip replacement project again.
My black case arived today… Love it.
Of course it is not perfect, as it is made on the original 1986 injection molds.
Most work is done now… Need to check it through with multimeter, install an RF modulator “replacement board” and do a smoke test before I insert chips and test for real…
Cleaned the last bits of flux off my SixtyClone, and checked if all socket’s are connected fully to ground.
Then checked if there were solder bridges between all legs on all sockets.
Then checked if volt in pins are all connected to the right voltage lines.
Did a smoke-test, without any chips inserted, and nothing blew up.
Finally measured voltages on all volt-in pins on each socket.
All 5 volt pins have exactly 5.02 volt and all 12 volt pins have exactly 12.20
All volt lines are completely stable, and nothing drops or raises (might be due to no chips)
This is really looking promising… And thinking about the fact that the last big thing i build by soldering
was a variable bench PSU in primaery school around 1990, then I kind of did good so far.
