03-07-2017, 10:00 AM
This one? http://www.radiomuseum.org/r/metex_digit..._3800.html
Looks like this might be the manual for it: http://wrack.ped.muni.cz/datasheet/soubory/3800.pdf
In AC mode, it's a bit vague - it says <10M in parallel with >50pF. Frequency response is given as 40Hz to 1kHz, with no limits given. The latter is easy to check with some form of signal generator, but I do wonder about the capacitance. Especially as ">50pF" could mean 1uF if we took it literally (though obviously I'm just being silly there
). Perhaps it's worth checking with a known-good cartridge of similar type, if that's feasible to arrange? But here's where the 'scope wins, as it'll be 1M in parallel with 20pF (plus the cable capacitance), or 10M in parallel with single-digit values of pF, depending on your x10 probe.
I can certainly appreciate that lugging a 'scope to your workshop could be difficult. And depending on how dry the cellar workshop is, perhaps it might be best to leave it at home?
When working on older gear, I have found that the balance between 'scope and DMMs has shifted slightly towards the DMM. That's partly because of the simpler nature of the circuitry, and partly because I've bought some nice DMMs in recent times, having only had a CPC cheap one for about a decade (and was horrified to see how inaccurate it was when I finally treated myself to a posh Fluke). Not that accuracy is a bit deal for radio repairs, but sometimes it's needed.
But having said that, the times when I've given myself the run-around were when I didn't use the 'scope!
Looks like this might be the manual for it: http://wrack.ped.muni.cz/datasheet/soubory/3800.pdf
In AC mode, it's a bit vague - it says <10M in parallel with >50pF. Frequency response is given as 40Hz to 1kHz, with no limits given. The latter is easy to check with some form of signal generator, but I do wonder about the capacitance. Especially as ">50pF" could mean 1uF if we took it literally (though obviously I'm just being silly there
). Perhaps it's worth checking with a known-good cartridge of similar type, if that's feasible to arrange? But here's where the 'scope wins, as it'll be 1M in parallel with 20pF (plus the cable capacitance), or 10M in parallel with single-digit values of pF, depending on your x10 probe.I can certainly appreciate that lugging a 'scope to your workshop could be difficult. And depending on how dry the cellar workshop is, perhaps it might be best to leave it at home?
When working on older gear, I have found that the balance between 'scope and DMMs has shifted slightly towards the DMM. That's partly because of the simpler nature of the circuitry, and partly because I've bought some nice DMMs in recent times, having only had a CPC cheap one for about a decade (and was horrified to see how inaccurate it was when I finally treated myself to a posh Fluke). Not that accuracy is a bit deal for radio repairs, but sometimes it's needed.
But having said that, the times when I've given myself the run-around were when I didn't use the 'scope!
