One of very few DMMs with dBm (0.775mV - 0dB) reading back then, so useful for people involved with audio signals. Ah, the top Brymens are dream come true for dB measurements, but $$$ 🥴.
Poor meter got the electric chair.. R.I.P. In older 25 and 27 they use three fuses, a 15A, a 3A and a little 630mA in series with the 3A. The little 630mA usually ruptures first (when in mA and uA) and saves the user from buying an expensive 1000v rated hrc fuse. The small ones are really cheap and you have a little place for a spare in the battery compartment, pretty thoughtful of them. Great info on the evolution of the amp protection setups, thank's for sharing!
Thank you for this video. My 40+ year old Fluke 77 display went bad and I was looking to repair it, but with your description of the old circuit design I think I will just buy a new one. I don't do that much electronics anymore being retired I might just go for a lower function model.
There are a lot of very good meters available today. Sounds like you were happy with the 77, so I don't think you will have any trouble finding something similar.
Cool, extra tests. BTW, if you dont wont to give it away for parts, i think I may have a 77 parts unit in which a battery leaked but has a case if you want to save it as part of your test collection (I think I may have stolen that same said fusable resistor from it).
Очень толковый обзор. Очень компетентный обзорщик-испытатель. Очень хороший был прибор. Какой следующий на очереди? Предлагаю его положить в костер. Не надолго, секунд на 60. Потом протестировать.😢
Hey Joe, For the Uni-T UT139C if you slowly change the switch from uA to mA does your DVM reset and/or turn off... But if you move the switch at a normal speed it works okay? For me this only happens between these switch two positions.. (Obviously not counting the off position :) )
My Uni-T UT139C went haywire similar problem to you. It would only work in a few modes and keep resetting in other modes. I checked the switch and it looked okay and nothing looked damaged on the board. I never used it in a way where it should have gotten damage. I ended up buying a Brymen BM257s.
I still have 78 Automotive version of the meter. Not bad for limited general use, pretty tough sucker, but surely it would fail the test just like the 77 😢
