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Kontron/Tabor 6010 universal counter still worth getting?

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0xdeadbeef:
Regarding the hole: it could prove difficult to put it exactly where I could screw it to the case without some trial&error. Probably I'd need to increase the size just to achieve this.
Actually my plan is to either just stick my PCB into J4 and trust in gravity or maybe to 3D print some kind of fixture that I can screw to the case and that just hold the PCB in place from above.

BTW: Reworked it again to use a 74ACT14 (Hex Inverter with Schmitt Trigger) instead of the Quad NAND Schmitt trigger so I can parallel four outputs for the reference output.
Even with four 200Ohm resistors in parallel this is pushing it (especially since these logic gates usually can't deliver more than 100mA in sum - if at all) a bit but the original implementation just uses one output with a 51Ohm resistor.

0xdeadbeef:
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.

Ash:

--- Quote from: 0xdeadbeef on March 07, 2018, 06:33:14 pm ---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.

--- End quote ---

Hum.. good call. I hadn't even through of the OCXO power consumption. The power supply in the 6010 will be pretty solid because the ECL and other "fast" logic they used draws quite a bit of power. I assume it will only be an issue during the initial period of bringing the oven to temperature, then settle down to something lowish.

Could you measure the rail voltage and jumper in the OCXO cold and see if the rail droops? Maybe if you have an adjustable current sink, you could slowly apply the load and see if the power supply will cope?

Ash.



0xdeadbeef:
My OCXO (C-Mac, LVCMOS, 3.3V supply) draws 700mA for 5 minutes or so, then it drops to ~350mA (at room temperature).
My plan was to use an electronic load to increase the current draw on the 5V line slowly towards 800mA or so and check if the voltage drops.
I'm just too lazy to set up this test today. Chances are this will only happen when I have some more time at the weekend.
Anyway, the bridge rectifier CR28 is quite a beefy part even though it's unclear if it's the 5A (parts list) KBL-005  or the 8A (schematic) version KBU8A.
There are no markings visible on the accessible side but from the looks of it, I would tend to say it must be a KBU type (hole in it), so probably the schematics are correct.
When I'm at it, I will also check the voltages and the 10MHz signal on pin 10 of J4.

[Edit]
What I quickly tested today is the power consumption. It's about 23W in idle ("0" displayed) and ~24W if all LED digits are used. Assuming an optimistic 90% efficiency of the transformer, this would mean like 21.6W on the DC side.
There's a 12V tap, but the +/-12V supply is limited to some opamps and the 5ppm oscillator, so I would assume that the 12V part is probably taking less than 1W ... maybe 0.5W or so. For the sake of convenience, let's say 21W are caused by the +/-5V supply. So by rule of thumb, there could be like ~4A drawn on the +/-5V rail.  This is a bit more than I expected and probably I made a mistake somewhere and/or the transformer efficiency is more like 85% or so.
Still, there probably is a margin for the OCXO, especially if the bridge rectifier is actually the 8A type. If it's the 5A type, the first few minutes would be pushing it a little bit.

0xdeadbeef:
So I finally got my ass up and did some measurements.

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.
At the same time, the power consumption at the 230V AC supply increased by 1W per 100mA. So it increased from 24W at 0mA to 32W at 800mA. Which actually means the efficiency for the 5V rail must be quite exactly 50%!?
Or in other words: the default current at the 5V rail can't be much higher than 2A and there should be more than enough headroom for my 800mA additional current draw.

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.

As a side note, I also measured my OCXO again. Actually the 700mA/300mA values were from the datasheet and I only remembered the measured values weren't totally off.
So the initial current (at 23.5°C room temperature) was 587mA and after some minutes it settled to ~225mA. 

-> Looks like I'm fine

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