Bang and Olufsen AC Voltmeter RV9A 10Hz-10MHz 1977 teardown repair
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- Опубліковано 25 січ 2025
- B & O also knows as Bang and Olufsen instrument line, made this AC voltmeter RV9A in about 1977 dated from IC codes, it was stored a bit too humid and had a few leaked caps in the powersupply,
but I was able to repair it, so it is still working, now only a little bit of paint and recalibrate is needed.
link to full data and schematics : peel.dk/B&O/
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#voltmeter
#teardown
#repair
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I use auto generated subs, i am sorry there are a few spelling errors,
maybe one day they can do it better..
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(Thanks to all my Sponsors / Traders / Swappers / Sellers / Buyers, without your support and constant flow of cool items in/out, none of this would be possible)
It’s amazing that you were able to bring the Bang & Olufsen RV9A AC voltmeter back to life! That’s a testament to both your skill and the enduring quality of B&O’s craftsmanship, even in their instrument line. Repairing the power supply and tackling the effects of humidity is no small feat-well done! A fresh coat of paint and a recalibration will surely make it as good as new. It’s always inspiring to see vintage equipment restored and kept in use. Great work!
Interesting - didn't know B&O made test equipment back then. Apart from the mechanically unsupported cooling fin on that voltage regulator directly next to components that age faster when heated (the electrolytic capacitors) a very nice construction. When you have the documentation and a little bit of time to fix or restore them, these instruments can last forever.
15:05 - It looks like the board is mostly COVERED in flux (all but the white areas)!
looks like flux areas affected how the silkscreen color aged
Back when this instrument was made, I think cleaning PCB's with CFC's (like Freon) was common. The place I worked at in the late 80's used one, I actually ended up with it, but the cleaning fluid was $$$ and in 55 gallon drums only so I never used it properly. One side was heated which evaporated the fluid, then the other side was cooled which condensed the vapor back into liquid, the dirt settled out to the bottom of the tank. If you didn't leave the boards in long enough, they came out looking like that. I'm pretty sure this was a pretty common cleaning method across multiple industries back then, all killed off when CFC's were banned shortly after this in the early 90's I think.
Remember as apprentice in avionics repair shop filling a square glass container up with a brown freon glass bottle and then clean pcb.
Yep, we cleaned PCB’s with Freon all the time until the middle 90’s (military and avionics equipment). If you didn’t clean it properly, that white residue would remain. IPA never worked as good. That tip of yours with trimming the legs of the bridge rectifiers is a trick I learnt back in the 80’s . Never failed me. 👍👍👍
Great piece of equipement. I've been working om a wow and flutter meter from B&O, same vintage.
In my case the tantalum caps where in very poor condition. Value drift, high ESR and leakage currents. I would revisit them asap.
Love the channel,
Cheers from the Netherlands.
Как для восьмидесятого, достаточно хорошо. Лойс
Those old plastic-case ROE brand electrolytic caps are notorious for going bad. I have had a few that has gone shorted too.
I don't know why Roederstein sealed some of their axial electrolytics in a Bakelite case. There was also the EKM series which were in an extruded aluminium case with an Alodine coating.
It looks like it would be reading correctly if the meter zero was adjusted with the power off.
That looks like Lye burns on your hand... I made that mistake once.
it is just permanent marker and dry skin, I am all perfectly fine thanks :-)
@@TeardownOZ2CPU Wasn't Lye Burns a Scottish poet? :)