Quote:
Originally Posted by Pinörkel
Quote:
Originally Posted by mhennessy
Your pictures on the Tekwiki are excellent. I'm comparing your vertical unit to my one, as it is right in front of me now, and they look very similar indeed. I suspect that R1015 might be a replacement, given that it's a different type to R1012. Otherwise, all looks good to me.
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Thanks for the compliment. I tried to make the images as good as possible. Yes, R1015 might be a replacement one. However, to me, TQ seems to have had a habit to not always use the same components, but the stuff the currently had a supply of. You can see this when you compare my images of circuit boards of the S2A and S2C plugins ( http://w140.com/tekwiki/wiki/Telequipment_S2). |
You might be right - does the soldering on that resistor give any clues?
That said, looking at the resistors on the timebase module, I'm seeing the usual types that were used by Telequipment - nothing unusual there. In the case of the vertical calibrator, that top resistor is a type that I've not seen before in a Telequipment unit. Given the balanced nature of the circuit, I'm sure they would have made the effort to put two identical ones in.
But having said that, Les has just sent me a photo of his unit. It looks like he has a very early one - perhaps even a prototype, as he says it came a TQ site. The PCB in his unit does not have a silkscreen, so no component designators, etc. There can't be too many like that about!
Anyway, on Les's unit, I can see that the 910R resistors do look like your top one. And they measure high (around 1k1). Which suggests that they are carbon-composition rather than film.
Given that the value of these resistors will affect the calibration - both at LF and HF - I suggest that we can't derive a calibration procedure from Les's example. But overnight, I have been thinking about this, and have a couple of ideas that might work - bear with me for a while, as this holiday is going to be a very busy one for me, but in those moments when I need a distraction, I'll put some effort into this.
Spoiler: it will need a pair of bench power supplies, a high bandwidth oscilloscope and a function generator that goes fairly high. And an edge connector. I'm hoping that the calibrator is just tuned for maximum flatness within the passband - that would be most logical, but I'm not making any assumptions at this time.