This one makes me angry. Who thought this mod was a good idea?!?!?
https://www.ebay.co.uk/itm/184634587029
That is hideous, just how much control did they want over it then FFS. I admit that I did do a similar bodge once on a Philips bench meter, but that was necessary because the part of the fascia where the pot would be mounted had suffered the normal Philips plastic rot, and it was the only to bring the meter back into normal service.
@bd139, hows it going now, do you think that you'll be home tomorrow?
I guess they didn't buy the right TE for the job, we had a similar version of that TTI function generator built into the benches at work, for most jobs it was impossible to set the frequency control accurately enough, so they rarely got used for anything. Instead the programmable TTI function generators (TG1010) or Farnell LFM4 signal generators with large vernier dial were preferred.
David
The thing is you shouldn’t really expect precise frequency control from an RC function generator. They’re a “close enough” device. Even if you stick a ten turn in there it won’t be stable because of drift anyway. Over the years I’ve generally used them for sweeping large ranges by hand and looking for phase flips and filter responses. And if you’re looking at narrow filter peaking then it’s usually a ~5% pass band in one range. Honestly at non RF frequencies, accuracy isn’t that big a deal for analogue stuff. Digital display is fairly optional as well if the dial is within 5%. Occasionally they get used for clocking digital circuits and various pulse circuits but you’re mostly not bothered there either.
The LFM4 is a nicer instrument for sure however. As for the synthesised generators I’d only use them for RF to be honest.
I didn't expect precision from the TTI function gen built into the bench* but some people would still try & use it, then complain they couldn't meet the spec required, I would give them something more suitable to use.
*The 10 benches were ordered by people with
no clue and filled with the small TTI function gen (useless for what we needed), a matching TTI DMM (good but rarely used by others), a Leader 20MHz CRO (rarely used by anyone). The only built in items that were used often were the TTI dual PSU and a 150V Glassman PSU. Unfortunately these benches instead of using nice rack mount stuff, had custom made shelves with cut-outs in the exact shape of the TE fitted (except the rack width Glassman PSU).
I butchered the one I used to fit a larger Tek CRO instead of the Leader and swapped the TTI function gen for a second TTI DMM to check the output of the Glassman PSU.
We only worked on low frequency stuff (no RF), at least one job did require accurate setting at 50Hz (with some variance during the test). The Farnell LFM4 were always used with a counter and often used for slow sweeping, we only had two programmable function gens originally, they did buy another two eventually.
All history now as they EOL'd the lab years ago.
David