if you look at the HP service manuals, they don't tend to assume the meter impedance anywhere and the test points and voltage measurements are never at high impedance points without large warnings about it.
It's because they expect you to use a 3458A to check PSU voltages. (true story)
Edit: And before that, they assumed a 410b or sumtha'.
Dunno about the "b", but my 410C has a 100 M input impedance on most DC ranges.
I used a lot of AVOs over the years, but only ever saw one which had been smashed completely, as "throw the meter" wasn't a popular game back then!
I've seen a few DMMs which had gone to DMM heaven, although they still looked pristine on the outside.
The first UNI-Ts I used started to give weird resistance readings long before the battery alarm appeared.
Even my dear old Fluke 77 can get confused by a pulsed waveform when it was expecting smooth DC.
My Mum-in-Law's TV had a +150v rail supplied from a rectified overwind on the Horizontal Output transformer.
The filter cap had died, but the Fluke saw the resultant crud as a 108v DC voltage---a bit low, but not likely to cause the observed fault.
A 'scope told a different story, altogether!
In such situations you should practice “know thy circuit” first. Start with AC volts on your DMM then assume that is centred around the DC reading. That’s good enough to assert that the filter cap was not functional. Also the min/max reading on more complex DMMs is good for this.
I’ve had a couple of fucked DMMs but quite frankly the user would have been dead if it was an Avo.
I bet it was the much more rugged later design which the Fluke guy chucked across the room!I was told the anecdote ~1980.
On Fluke ruggedness, I’ve seen a lot of totalled Fluke 25’s at hamfests. YMMV on assigning responsibility there
More local CL finds.
https://newjersey.craigslist.org/ele/d/sparta-tektronix-mhz-oscilloscope/7510713135.html
That 2235 looks to be in good shape and reasonable price. About 1.5 hours away. Very tempting. BD.....does the 2235 have the trouble prone switcher PSU? Also, if I need a vintage transistor I know where to go.
https://newyork.craigslist.org/que/ele/d/ridgewood-oscilloscope/7519309169.html
My first scope. Actually, was my Father's. When I left home to strike out on my own my younger brother got it. The seller is delusional with that $100 USD price. Not interested.
I wouldn’t touch another damn 2235 again. I was a nervous wreck after blowing MOSFETs on the preregulstor on that asshat.
https://www.eevblog.com/forum/testgear/tektronix-2235-repair-thread/
After reading your shit show with that 2235 it's definitely giving me 2nd thoughts. I'll mull it over during the weekend. Hopefully someone buys it by then or it just might be road trip and a glutton for punishment.
On Fluke ruggedness, I’ve seen a lot of totalled Fluke 25’s at hamfests. YMMV on assigning responsibility there
Totalled electrically, or totalled mechanically? The former is possible for any of us on a bad day, the latter would require such a level of creative incompetence that I don't think I want to risk being within 300m of someone capable of doing so.
My favourite "pointless antique mini meter" is the Pifco All in One. They are just a work of art. They are tiny (65mm diameter) and look like a mini alarm clock / pocket watch.
I always think that they look like a model of a naval mine, with all those 'spikes' sticking out.
Re AVO weird battery requirement - on my to do list:
Mikeselectricalstuff coin battery mod
Ah, a nylock so they don't become loose by themselves...
They do this, but it is not cheap.
https://www.ebay.de/itm/265531737706LR44 inside sleeving from the $2 shop is the simplest fastest fix for the now nearly unobtainium 15V cell.
The official Ever Ready BLR121 is a stick of 10 LR54s in a plastic case. The LR54 is quite thin I don't think 10 LR44 would fit in a single stack. I had this slightly kanky one in a NOS bag. Fluke says 7.4 V
Edit: BU508 got it right independently. The BLR121 does have two contact buttons that are 2.1 mm high adding 4.2 mm to the total stack giving 24.7 mm.
Seems to me like an ideal project to apply 3DP to...
There was plenty of smaller, just as capable meters specifically designed for portability such as the excellent TMK500 or the AVO minor for instance, the AVO model your referring to was designed as a lab type instrument.The TMK was a bit fragile, & the "Minor" was, as I commented earlier, regarded as a bit of a "toy". In practice, AVO 8s were used extensively in the field.
On Fluke ruggedness, I’ve seen a lot of totalled Fluke 25’s at hamfests. YMMV on assigning responsibility there
Totalled electrically, or totalled mechanically? The former is possible for any of us on a bad day, the latter would require such a level of creative incompetence that I don't think I want to risk being within 300m of someone capable of doing so.
Both!
I nearly bought one at the last hamfest to prove it
In such situations you should practice “know thy circuit” first. Start with AC volts on your DMM then assume that is centred around the DC reading. That’s good enough to assert that the filter cap was not functional. Also the min/max reading on more complex DMMs is good for this.
I’ve had a couple of fucked DMMs but quite frankly the user would have been dead if it was an Avo.
On Fluke ruggedness, I’ve seen a lot of totalled Fluke 25’s at hamfests. YMMV on assigning responsibility there
Totalled electrically, or totalled mechanically? The former is possible for any of us on a bad day, the latter would require such a level of creative incompetence that I don't think I want to risk being within 300m of someone capable of doing so.
Both!
I nearly bought one at the last hamfest to prove itMaybe we could have rebuilt it from parts?
There was plenty of smaller, just as capable meters specifically designed for portability such as the excellent TMK500 or the AVO minor for instance, the AVO model your referring to was designed as a lab type instrument.The TMK was a bit fragile, & the "Minor" was, as I commented earlier, regarded as a bit of a "toy". In practice, AVO 8s were used extensively in the field.
Yes, well... what TE manufacturer doesn't like a customer base with a built-in high rate of turnover...?
mnem
tzzzzt.
In such situations you should practice “know thy circuit” first. Start with AC volts on your DMM then assume that is centred around the DC reading. That’s good enough to assert that the filter cap was not functional. Also the min/max reading on more complex DMMs is good for this.
Ohh, I "knew my circuit" well enough, but at work, my instrument of choice was an Oscilloscope.
I didn't have one at home, so had to make do with the Fluke 77.
I did check by trying it on ACV, & got a reading of zero, but what I didn't know then, was that those very early 77s only worked up to 1kHz on that range, & then "hit a cliff".
(I still have the original booklet that came with the meter, & checked that my figures were correct, before posting)
I had assumed that it would read ACV OK at 15kHz, & expected a reading in line with your suggested one.
I guess one lesson to be learnt there, was to read the booklet!
I'm glad I still had the booklet---Googling brings up a lot about the later "versions", which are pretty much new designs, rather than refinements of the original.
On Ma-in-Law's TV, I borrowed an old BWD single beam 10MHz 'scope from work, & that revealed the true state of affairs.
QuoteI’ve had a couple of fucked DMMs but quite frankly the user would have been dead if it was an Avo.What had happened to them?
Those 2 HP calculators have arrived, well-packed, delivered by Evri.
It seems that the 17BII, on the right can be switched in and out of the RPN mode when required manually, need to read the manual later for more info, but now its boy dropping off at work time and a spot of shopping, in this stupid heat, I must be mad.
Welcome to the dark side
We have "="-keys?
Welcome to the dark side
We have "="-keys?We have calculators with "natural display" - So you can focus on the task at hand & don't have to translate "to" and "from" calculator
Those 2 HP calculators have arrived, well-packed, delivered by Evri.
It seems that the 17BII, on the right can be switched in and out of the RPN mode when required manually, need to read the manual later for more info, but now its boy dropping off at work time and a spot of shopping, in this stupid heat, I must be mad.
Just a slight warning for whoever has to deal with the soviet transistors(2G302 in the attached picture); it came out as CADMIUM COATED thru the mazes of my memories.
If anybody can confirm/deny my (almost)long forgotten memories, I(and the future owner) would be really grateful.
I've no idea and you did say "slight warning", but is it that big a deal? Cadmium coated nuts and bolts were popular until a few years back, and its use is now restricted, but they may be come across in old equipment. Welding cadmium coated steel is a different matter. I've got a few yellowish metal canned transistors on old boards. It would certainly pay to wash your hands after handling them.
Something I have across and is extremely dangerous, is beryllia in insulators. It's probably OK as long as you don't break it up. There are usually warnings about it. There are PCBs in some capacitors and transformers. There are fuseholders with asbestos. There are also mercury filled switches.