The unused NAND U4.4 should have its inputs tied to a rail so they don't float. What about using U4.4 as an additional buffer between the multiplier and the output? If you do that, you may want to add a second decoupling cap to the NAND chip at 1nF or 10nF or both.
As for the input 10Mhz, the TCXO / PLL board in my 6030 has the input coax soldered to pads on the PCB. This is on the upper left of the board in the photo I shared before. Probably the decider would be how easy it is to add remove the board and if you think you will need to. The SMB is the 500MHz output and the other end is soldered onto the PCB directly (I think it replaces the series resistor from the 10Mhz internal line.
The 100Mhz through the pin header is probably ok, but the 500MHz was clearly pushing it so they didn't use it. Maybe prudent to include pads to launch to a bit of coax and a 0 ohm link to isolate the pin on the connector in case there are signal issues? That way you can jumper the signal to the main board with coax if you need.
Actually, if you just add some accessible ground next to the input of the series cap C1, you could remove that and launch to coax. Then you could use the existing cap on the main board, isolating it from the 10MHz line by pulling the associated series resistor and using its pads for the coax.
What about using U4.4 as an additional buffer between the multiplier and the output?Good point about the floating inputs. Changed that. I'm not 100% sure why I would add another buffer between the multiplier and the output. Or do you mean to be able to output the 100MHz on the 10MHz reference BNC?
Yeah, I saw that the 500MHz is connected directly through coax on your PCB. The PCB on my 6010 seems to look slightly different near the J4 jumper and I kinda trust that the header should work if this is the official approach. But yeah, I guess it makes sense to have a fallback solution in mind. Maybe I could even find the space for another SMA connector that is not populated unless the header connection causes issues.
BTW: is that an SMB connector on your TCXO board? Since there must be like 10 connector types which all look the same (SMA, SMC, SMS and what not) and I'm somewhat uncertain which one to use.
Today it occurred to me that it might be a bit optimistic to be able to draw 800mA or so from the 5V supply (OCXO needs like 700mA during warm-up).
I guess it have to try this before ordering the PCBs. The 5V supply circuit looks somewhat robust though. The bridge rectifier for the 5V tap is rated 5A and the MJE2955A PNP transistor is rated for 10A.
Then again, I have no idea how much is currently drawn from the 5V line. If everything fails, I might actually drop the OCXO idea and use an affordable TCXO instead.
Unfortunately, I wasn't able to get a good measurement of the 10MHz clock at J4. With my 200MHz scope and 2GSa/s sample rate, the signal looked like a rectangular DC signal with a lot of ringing. Then again I didn't dare to use the 50Ohm input but used a 10:1 probe on the 1MOhm input. I guess I'd need an active probe for a proper measurement, but still the voltage levels didn't look nearly like I expected (negative ECL stuff) but more like common CMOS levels.
Secondly, I measured the voltage at the 5V test point while I increased the current draw on the 5V pin of J4 in 100mA steps and also monitored the power consumption at the 230V side.
In a nutshell, the voltage drop on the 5V rail was negligible. Like even at 1A it dropped from 5V to 4.996V. At 300mA the voltage was like 4.998V and dropped to 4.997V at 600mA. No problem there.
Finally, I took some thermal images of the bridge rectifier and the transistors of the 5V/-5.2V supply. While the temperature increase on the rectifier looks totally OK (41°C to 44°C), the temperature on the transistor increased from ~48.5°C to 57.6°C. So, yes, there is an increase but it seems acceptable also taking into account that 800mA is about the worst case scenario for the initial OCXO heat up.
Crap, you're right, I somehow forgot I wanted to measure the "100MHz" pin 6 (where the ECL 10MHz is currently located in my case) and not the 10MHz pin
Anyway, yeah I know the measurement is not perfect since my ground connection sucks but at least the levels look OK now.
About the thermal camera: yeah, it's one of these hacked Flir E4s that I totally wanted to have back then and admittedly haven't used much since then.
So I try to use it now and then just to justify the purchase
Hum.. I really hope the signal doesn't look like that in reality.. very slow edges.
haha. Fair enough But surely the justification for test gear is not that you need to use it, but rather that you have it WHEN you need it
Well, at least that's how I justification my addiction.. um.. I mean investments.