Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Dolmetscher007 on March 20, 2025, 07:32:07 pm
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I have watched hundreds of hours of YouTube videos about building and fixing tube amps, but I admit that I have zero hours of actual hands on experience. A few years ago, I bought a... BK Precision 388B Manual-Ranging, Average-Sensing Digital Multimeter, with Logic Test and Transistor Gain, 20 Amp, 750VAC, 1000VDC, 40 Megaohms, 40 Microfarads, 4 MHz (https://www.amazon.com/dp/B000B632BC?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_2).
I don't remember what I was thinking exactly. I think I read somewhere that manual-ranging multimeters were "better" or... something like that. But... either I don't understand multimeters in general, or I just don't understand this one.
I built an capacitor-draining resistor tool that has an alligator clip on one end for clamping onto a chassis, that goes through a 25 watt 850 Ohm cement resistor connected to a brass rod and cocooned in layers of heat shrink. (Saw it on YouTube). When I put my multi-meter into continuity mode to make sure that my solders had worked, and there was a solid connection between the alligator clip and the top of the brass rod, my meter didn't read anything, no alarm sound. I thought that maybe the little "Continuity alarm" only rings if there is little-to-no resistance. So, I thought I'd try the Ohm setting. The Resistor is 850 ohms, so I set the multi-meter to 400 ohms, thinking that this is the closest setting. The next closest setting says 4k. When I tried to measure my brass rod tool... it just shows the letters "OL". But when I set the multi-meter to the 4k settiing, it shows 0.847 kOhms of resistance.
This all seems rather complicated to me. Why does the thing have incremenrts that all begin with 4? 400, 4k, 400k, 4M, 40M? The Volts are the same. 400m, 4, 40, 400, but then 750 /1000 (???)
On YouTube, everyone just has a Fluke that just has settings like V, Amps, Ohms, Farads... and it just does it's thing.
Also... there is a DC/AC button. When I'm just trying to measure the resistance of a resistor... I don't know what to set this to.
Also... there are four holes on the front.
From right to left...
- Red: V Ohms
- Black: COM
- Yellow: uAmA
- Yellow: 20A
I am using the red and black holes, because I had red and black alligator clip leads, and it just seems right. But I don't actually know what I'm doing as far as these holes are concerned.
If anyone can give me some insight on this m-meter, I'd be super thankful!
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Yes it is too complicated and worst buy for a beginner
Picture 1 ; An example of automatic range voltmeter witch are the best buy
Picture 2 ; Your B & K
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When I'm working with amps, I need a few basic meter functions:
Be self-ranging (exc. for ampere ranges)
Measure voltage up to 600VDC, 1000V is better
Check current, even cheap meters can handle 5A, which should be plenty
Check resistance
Check continuity
Nice to have:
"Range" control to override the auto-ranging
MinMax capture of AC readings
Lighted screen
Diode/transistor check
Others will likely have opinions but these functions give me everything I need. Most top line meter makers sell basic cheap models. $40-50 will buy a lot these days. Of course, eBay has many examples really cheap; I've gotten a couple of decent no-name meters over there.
Cheers