VTVM substitute?

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My Sears Craftsman DVM is insensitive to AC frequencies except 50-60 Hz. I've proved this with my organ, where I had 8 V pp coming out at 360 hz and was reading zero on the Sears. I've heard other dual slope integrating DVM's are the same. Meters advertised as "RMS" may have more frequencies they respond to. Old style VOM's with 100000 ohms/per volt may be useful. I did AC debug with my Simpson 260 on the 2 VAC scale before I blew it up. Now I use a $40 B&K 2120 scope, but the 10x probes are $55 each from mouser. Watch, the $55 probes are only rated to 300 Volts.
 
Cheap modern DMM's are not well suited for your application,especially if you need to measure full audio bandwidth AC voltages : DMM's usually have very limited AC frequency response and no dB scales. For this kind of application old AC VTVM's are hard to beat and dirt cheap on the second hand market. There are plenty of models available but I would stay away from kit form VTVM's like HEATH,KNIGHT,EICO,etc... which suffer from doubtful building quality and calibration. Try to pick up any old HP (Hewlett Packard) 400 series (D,H,L,E...) AC VTVM which are a pleasure to use,stable and very robust industry standards. As demand is very low you should not pay more than $ 30.00 for a good condition HP400 on the used market.
For DC voltage measurments only any DMM with a 10Megohm (or more) input impedance will fit the bill and will not impose an excessive load on your (tube) circuit.
 
VTVM has high input impedance as compared to a typical analog voltmeter. I believe just about any DMM now will have a high enough input impedance. I could be wrong, though ;)

You're not wrong. Vacuum Tube Volt Meters were just high impedance input, typically 10-11 Megohm. This is a constant regardless of the sensitivity setting in contrast with a Volt Ohm Meter which pulls a larger current out of the circuit. A 20 K Ohm/volt meter loads 200K when set to a 10 Volt scale. On the 100 Volt setting the meter loads 2 Megs, A 50K Ohm/Volt meter loads lighter than the 20 K Ohm unit __ BUT__ when getting to higher voltage settings the 50 K Ohm meter on the 1000 Volt scale will load the circuit with 50 Megs vs 11 Megs for the VTVM / DVM so there ARE places where the 'old' technology still has an edge. Of course using a 100:1 (High Voltage) probe takes the load to around a GigaOhm. When I worked on Sony mixed field tube color cameras in the '80s, the electrostatic deflection ran on a 200 Volt supply but the impedance was so high that the 11 Meg load of the meter screwed up the operation so I had to use a High Voltage probe to get accurate readings. Another place you need a High Voltage probe is measuring the G2 voltage on CRTs.

So, Firepowerfreedom, any decent DVM will be fine. BTW my 'decent' DVM is a pair of old Fluke 8060s. The AC RMS readings are flat to 100KHz and the dB readings are excellent. Wouldn't trade 'em for anything.

 
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I agree with stratus46. The Fluke 8060A is a great meter for audio work. The 8050A is similar but in a bench type case. The Fluke 87 series have decent frequency response through the audio band but do not have the db feature.

Not to hijack the thread but does anyone have a manual for a Leader LEM-73A electronic analog meter? I picked up 4 of them at a hamfest that need work & can't find a manual anywhere. TIA
 
So, Firepowerfreedom, any decent DVM will be fine. BTW my 'decent' DVM is a pair of old Fluke 8060s. The AC RMS readings are flat to 100KHz and the dB readings are excellent. Wouldn't trade 'em for anything.
firepower for freedom lives in the middle like me, not in LA or Seattle. Flukes here on CL where you can try before you buy, are going for 90% of what new ones do. What "any' meter here is, is a harbor freight or sears, both insensitive to non power line AC signals. On the other hand the market for scope is limited by education and experience, so I got a working B&K 2120 for $40. Yes, there is E-bay, but if there is a problem you have to pay freight both ways. Firepowerforfreedom, buy a fluke meter, a VTVM that people here don't know what they are, a scope, or nothing. I've never even seen a 100000 ohm per volt simpson meter here on CL, only 20000 ohm/volt ones usless for tube electronics meters. Yes, you can do DC measurements, but he is fixing an organ where bad contacts and electrolytic caps are the problem mostly. Old hams do die out here, but their heirs don't know what they are selling and if they even say "meter" in the ad they are doing well. You have to look at the picture on those ads.
 
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Buy a Fluke, after checking in the specs that it will do true RMS measurements to a suitably high AC frequency. Any new one will do that, mostly thinking of second hand here.

All cheap/inexpensive $5 DMMs that I have checked have horrid build quality, and I wouldn't trust them for high voltage work.

While old skool test equipment may do the job, the good meters are too thin on the ground to be worth searching for IMHO (unless you are a collector). Also, with an old meter you ought to check for problems before using them.

Just find a nice, second hand Fluke, unless you want to splurge on a new one. If it works, then it will still be lightyears ahead of any VOM, even if it has never been recalibrated.
 
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So, I've got my service manual for my Conn 427 Caprice tube organ, and it requires a VTVM for some of the calibrations. Is there any substitute for a VTVM?

Or, if there isn't, can somebody point out an audio VTVM with db measurements that's less than $50?

Thanks,
Austin

Yes, any good true RMS digital or analog multimeter. But I kind of doubt you'll find a really good one for $50. Several have mentioned FLUKE. I concur, but they cost $200-$400 or more. There are other brands that surely cost less, but that are not as good/accurate.
 
I had Fluke meters long ago. About three of them including an 8060A. All had display problems in less than 2 years and had to be repaired with spare displays from Fluke. They hardly last in our environment with 3 months of almost 100% RH and high temps.
But my cheap Taiwanese DMM's and a Wavetek ( 14 years !) has lasted all through these years with absolutely no display problems. No more Fluke's for me !

I also have a very nice Sanwa analog meter with Fet input. Very nice !
Yes , some old technology is still very useful today.

Anyone have a service manual for a Kenwood VT-176 millivolt meter ?
 
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I had an original FLUKE 87 which lasted me years and years until it died. I couldn't afford to replace it, so I ended up with a PROTEK 6500.

I had Fluke meters long ago. About three of them including an 8060A. All had display problems in less than 2 years and had to be repaired with spare displays from Fluke. They hardly last in our environment with 3 months of almost 100% RH and high temps.
But my cheap Taiwanese DMM's and a Wavetek ( 14 years !) has lasted all through these years with absolutely no display problems. No more Fluke's for me!
 

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I had Fluke meters long ago. About three of them including an 8060A. All had display problems in less than 2 years and had to be repaired with spare displays from Fluke. They hardly last in our environment with 3 months of almost 100% RH and high temps.
But my cheap Taiwanese DMM's and a Wavetek ( 14 years !) has lasted all through these years with absolutely no display problems. No more Fluke's for me !

One of my Flukes is from 1985. The display is fine though if dropped a few times the 40 pin chip behind it might come partially out of the socket and look like a display problem.That has happened twice. The other 8060 was bought on eBay for $80 about 10 years ago. The seller wasn't happy about the price and the main reason I got it cheap was he had typos in the description and I found it sort of by accident so it didn't get any other bids. This meter is also doing fine but I don't know the actual age of the unit.

LA is a desert so maybe that helps.

 
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Originally Posted by geraldfryjr
Any good jfet input vom should be ok aswell.

A high impedence meter is required so that it doesn't drag down the tube circuit drawing to much current causing either a false reading or a change in operating conditions around the tube circuit being tested. jer

Fjet input vom?



no jfet, junction field effect transistor or just plain fet vom.
I think radioshack still has model that they carry for under $50. jer
 
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They don't have it anymore.
If your going to invest in a meter get a quality one it will be well worth the investment in the long run.

Since you are working on tube circuits it would be wise choice to get one that measures capacitance as well.

some capacitors become leaky and their values can change a great deal as they get old.

Also try to get at least a minimum of 2 gigohm resistance range, as 470 megohm to 10 gigohm is not uncommon in tube circuits jer
 
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