# Test Equipment



## Paul Running (Apr 12, 2020)

Has anybody here ordered any goods from a site called duloudeng? Their pricing seems to be erratic, some ridiculously low prices on some items (a Fluke 435 power analyzer for CAD$4.47). I was interested in their selection of test equipment. Any advice would be appreciated.





Test, Measure & Inspect


Test, Measure & Inspect



www.dluodeng.com


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## greco (Jul 15, 2007)

WOW..That site is really messed up!
Not only the prices are all over the map...
Dimensional Measurement


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## nonreverb (Sep 19, 2006)

Chinese wholesale site. There's a few of them out there. I'd be careful...quality and authenticity are not their forte.


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## Latole (Aug 11, 2020)

You believe in Santa Claus ?


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## jb welder (Sep 14, 2010)

There are no laws protecting you from counterfeit items sold from other countries. At least not enforceable ones.
Add 'style' to the brand names in all the descriptions and that should be about right.


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## knight_yyz (Mar 14, 2015)

If you are working wityh 12-24v, I don't see a problem using a cheap chinese meter, but if I am playing with high voltage and 
amperage, I'll use the real deal.


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## Latole (Aug 11, 2020)

knight_yyz said:


> If you are working wityh 12-24v, I don't see a problem using a cheap chinese meter, but if I am playing with high voltage and
> amperage, I'll use the real deal.


I agree,


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## vadsy (Dec 2, 2010)

a 12,000 dollar unit for a one time payment of $4.47? imma buy two....,


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## Paul Running (Apr 12, 2020)

jb welder said:


> There are no laws protecting you from counterfeit items sold from other countries. At least not enforceable ones.
> Add 'style' to the brand names in all the descriptions and that should be about right.


Yeah, with today's technology it is becoming more difficult to detect counterfeits...some of these people are getting very good and not just at art.


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## Paul Running (Apr 12, 2020)

I still use my VTVM for measuring over 120VDC & AC. I learnt my lesson well when I realized how sensitive the digital circuitry is...it's not forgiving like the glass analog is...they blow-up real good.


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## nonreverb (Sep 19, 2006)

I've always tried to find brand name equipment used or new. It makes life a lot easier in the repair game. Especially when it's one's primary income.


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## Latole (Aug 11, 2020)

Paul Running said:


> I still use my VTVM for measuring over 120VDC & AC. I learnt my lesson well when I realized how sensitive the digital circuitry is...it's not forgiving like the glass analog is...they blow-up real good.


Low cost voltmeter are not protected like good one as Fluke are.
Low cost voltmeter are not fool proof


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## nonreverb (Sep 19, 2006)

Paul Running said:


> I still use my VTVM for measuring over 120VDC & AC. I learnt my lesson well when I realized how sensitive the digital circuitry is...it's not forgiving like the glass analog is...they blow-up real good.


True Paul, It's just making sure it's correctly calibrated being analog n' old.


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## Paul Running (Apr 12, 2020)

You are correct Rich, the tube operated equipment do require more maintenance for accuracy...just something about watching a needle against the scale for visual perception, I seem to understand the reading quicker and stronger in my memory, plus I was first trained with analog gear...maybe a biased opinion on my part.


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## Paul Running (Apr 12, 2020)

The meter that I use for monitoring plate current...large scale for old eyes.


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## nonreverb (Sep 19, 2006)

Here's a bunch of equipment I should use more often but never do...


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## Latole (Aug 11, 2020)

Those Simpson ( I have one ) have too low impedance; reading could be false in some amp circuit . Don't use them.
Other , probably same. Good for museum or garbadge


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## nonreverb (Sep 19, 2006)

Hence why I never do. Besides, they don't go to the voltages I need them to. I have three Flukes to do the job (s). The small one pictured, is low voltage only and works well but I just don't bother...


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## loudtubeamps (Feb 2, 2012)

nonreverb said:


> Hence why I never do. Besides, they don't go to the voltages I need them to. I have three Flukes to do the job (s). The small one pictured, is low voltage only and works well but I just don't bother...


Nothing like the smell and feel of Bakelite though.
I have an old Simpson similar to the one you have on the left.
Back in the day, I used to hit cash converters and second hand /pawn shops alot.
Many scores on those yellow dmm's , flipped them all and doubled my money on most.
Maybe I was lucky to be in the right place at the right time other's might call it a Fluke.


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## Swervin55 (Oct 30, 2009)

loudtubeamps said:


> ... other's might call it a Fluke.


I see what you did there.


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## Frenchy99 (Oct 15, 2016)

I`m always on the look out for good equipment on the use market but even use, the Flukes are expensive.


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## nonreverb (Sep 19, 2006)

Frenchy99 said:


> I`m always on the look out for good equipment on the use market but even use, the Flukes are expensive.


They're out there Pierre! I stumbled upon an auction a few years back and got three Fluke 77's for $5 apiece.


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## Frenchy99 (Oct 15, 2016)

nonreverb said:


> They're out there Pierre! I stumbled upon an auction a few years back and got three Fluke 77's for $5 apiece.



Wow... thats a deal...


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## loudtubeamps (Feb 2, 2012)

nonreverb said:


> They're out there Pierre! I stumbled upon an auction a few years back and got three Fluke 77's for $5 apiece.


 Now you've done it Rich...by this time next year Pierre will have a room dedicated to hi end dmm's.


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## Paul Running (Apr 12, 2020)

If you're looking for something to build, consider an analog plate-current monitor. I built this to monitor plate-current of single or dual output pentodes, dedicated to octal tube bases: 7AC and 8ET, a good chunk of NA output tubes. It is hard-wired for 0 to 100mADC. I could have used a dual meter concept however, I went with the dual-muliplex mode, the ole slide-switch route. I am in the process of adding a modified LED module for dark settings...for those long sessions when you what to watch some TV at night and just set your amp under test in the corner, in glimpsing range of the meter...for those intermittent or reliability issues - or you could spark-up a bowl lay back and just watch that meter. Don't get couch-locked though...you may not move if the meter starts pegging.


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## Paul Running (Apr 12, 2020)

Built a new load box today, 8 ohm resistive...rated 100W (2 paralleled, 16 ohm resistors). I can now test higher-powered amps for extended periods of time. I have been considering an active load and it will require further research into the emulation...anybody have some tips?


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## Frenchy99 (Oct 15, 2016)

Paul Running said:


> Built a new load box today, 8 ohm resistive...rated 100W (2 paralleled, 16 ohm resistors). I can now test higher-powered amps for extended periods of time. I have been considering an active load and it will require further research into the emulation...anybody have some tips?
> 
> View attachment 345689
> View attachment 345690
> View attachment 345691


Nice !

I bought some resistors to build one myself but havent yet. 
Can I ask why the fuse ?


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## greco (Jul 15, 2007)

Paul Running said:


> Built a new load box today, 8 ohm resistive...rated 100W (2 paralleled, 16 ohm resistors). I can now test higher-powered amps for extended periods of time. I have been considering an active load and it will require further research into the emulation...anybody have some tips?
> 
> View attachment 345689


Looks "COOL" in every regard! Congrats!


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## Paul Running (Apr 12, 2020)

Frenchy99 said:


> Can I ask why the fuse ?


I added that as a series component, I have a fixed value L-pad that I use with the load box for 200W testing. I will sometimes install a fast-blo fuse in the holder...mainly testing for transients during certain test conditions. The fast-blo fuse will be more sensitive to a transient response...a slow blo may not fuse enough to open. Even though I have a scope, it is not smart...no delayed trigger and no memory so, I cannot track and hold a high frequency transient...one thing for sure, sometimes I do miss the calibre of equipment when and where I worked...you make do with what you got and sometimes you get creative.


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## Paul Running (Apr 12, 2020)

Here's the other one that I built. An 8.87 ohms, 50W resistor mounted to a 45W CPU cooler. The camera freeze-framed (The J. Geils Band) the fan which is on during this shot. The power to the fan is provided by a 12VDC wall wart.


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## Lincoln (Jun 2, 2008)

Paul Running said:


> Here's the other one that I built. An 8.87 ohms, 50W resistor mounted to a 45W CPU cooler. The camera freeze-framed (The J. Geils Band) the fan which is on during this shot. The power to the fan is provided by a 12VDC wall wart.
> 
> View attachment 345703
> View attachment 345706
> View attachment 345708


finally a use for that drawer full of old CPU fans I saved!!


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## Paul Running (Apr 12, 2020)

Lincoln said:


> finally a use for that drawer full of old CPU fans I saved!!


I get those odd ball feelings sometimes a lot, kind a of a gut feeling...do I keep it or do I turf it? If it's small I keep it...end up with a pile of storage cabinets. I have my wife keep most containers for that very reason...I may be a pack-rat for certain things, it's almost like a security blanket.


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## Lincoln (Jun 2, 2008)

Paul Running said:


> Here's the other one that I built. An 8.87 ohms, 50W resistor mounted to a 45W CPU cooler. The camera freeze-framed (The J. Geils Band) the fan which is on during this shot. The power to the fan is provided by a 12VDC wall wart.
> 
> View attachment 345703
> View attachment 345706
> View attachment 345708


I'm guessing that while using that, you'd be monitoring output on a scope to confirm that things are happening? I've got 4 of those same resistors in 10 ohm. Been thinking of making a dummy load for a while now. Be nice to have a watt meter inline.


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## nonreverb (Sep 19, 2006)

Paul Running said:


> Here's the other one that I built. An 8.87 ohms, 50W resistor mounted to a 45W CPU cooler. The camera freeze-framed (The J. Geils Band) the fan which is on during this shot. The power to the fan is provided by a 12VDC wall wart.
> 
> View attachment 345703
> View attachment 345706
> View attachment 345708


Here's a piece of Paul Running equipment given to me 20 years ago....still use it to this day. The only change I made was the fan I added for extra cooling.


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## Paul Running (Apr 12, 2020)

Lincoln said:


> I'm guessing that while using that, you'd be monitoring output on a scope to confirm that things are happening? I've got 4 of those same resistors in 10 ohm. Been thinking of making a dummy load for a while now. Be nice to have a watt meter inline.


That's my main problem. I should be using a storage scope so, that I can freeze the trace and store it for study...transients occur too quickly for my eyes to catch it...if the fuse blows, it may lead me to believe that a transient is occurring. One of these days I will probably take the plunge and buy one...I'm the same way with most things...sometimes wait to long to pull the trigger.


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## Paul Running (Apr 12, 2020)

nonreverb said:


> Here's a piece of Paul Running equipment given to me 20 years ago....still use it to this day. The only change I made was the fan I added for extra cooling.


Hey Rich...I totally forgot that piece...age and memory is inversely proportional for me.


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## greco (Jul 15, 2007)

Paul Running said:


> ...age and memory is inversely proportional for me.


That is one I have to remember!


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## nonreverb (Sep 19, 2006)

Here's some more test equipment I have. The power supply has been modified a bit. I use it for zapping shorted scanners and percussion circuits in Hammond tonewheel organs.


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## Paul Running (Apr 12, 2020)

Very nice Tube testers...those models are commanding high value now. The modern types are so complex now but I think yours have a cooler look.


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## nonreverb (Sep 19, 2006)

Paul Running said:


> Very nice Tube testers...those models are commanding high value now. The modern types are so complex now but I think yours have a cooler look.


I got both of them when I bought the assets of a tube amp tech who passed away here in town. I use the Stark most often as it's easier to set up....That said, for tubes I plan on selling, I use the Hickok.


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## Paul Running (Apr 12, 2020)

Here's a little discharge adapter that I made. It's a 5K, 3W resistor, heat shrunk with a banana plug at one end and a banana jack at the other end. You can use it for discharging most devices, especially HV caps. It's a safe habit to practice...a lifter is not comfortable. I believe that banana plugs and jacks are still popular with instrumentation...I have not purchased any modern test sets recently. I just hate it when the industry does that...change interfacing, look at USB connectors, can we not be happy with one style... I mean the name starts off with the word universal, what the hell is universal about USB...it ain't the fuckin connector?


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## Paul Running (Apr 12, 2020)

*Inductance Meter*
Here is a simple device that will provide a ball-park inductance measurement. It is based on an AC voltage (60Hz), dropped across a test inductor…a series R-L circuit. Essentially, a voltage divider between a known value resistance that is in series with the inductor under test. It is quick and easy to use; you can read the inductance directly off of a DVM, with the proper ratios.
It consists of a 24VAC TFM and 3 common resistor values: 1K, 10K and 100KΩ;
(a TFM output voltage of 26.526V is ideal).








On the × 100mH division scale, 1KΩ resistor, the AC voltmeter will read 100mH per volt and accurate to 500mH or 5.00VAC DVM reading…connecting a 200mH choke results in a 2.00VAC reading.
The × 1 scale uses a 10KΩ resistor and reads 1H/volt sensitivity up to 5H.
The × 10 scale with a 100KΩ resistor, 10H/volt and accurate up to 50H.

XL = 2πfL, XL will be 377Ω per H @ 60Hz.

The number *377* is a constant for the product of *2×π×60Hz*...it’s a magic number, one to remember, next to your favorite sequential number.
Extra notes:
When scaling for lower inductance ranges, use a lower voltage TFM (12.6VAC).
The range resistor values correspond to direct-readings on a DVM.

On the ×10 scale: a 1VAC reading equals 10H with an impedance of 3K77Ω per volt.
On the ×1 scale: a 1VAC reading equals 1H with an impedance of 377Ω per volt.
On the × 0.1 scale: a 1VAC reading equals 100mH with an impedance of 37.7Ω per volt.

Due to the simplicity of this adapter, the Q-factor is not taken into consideration. Most true bridge LCR meters will take this factor into consideration. Most low value inductors will have a low “Q” at 60Hz and will measure a higher than true reading.


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## greco (Jul 15, 2007)

I hope @Frenchy99 sees this.

Thanks for posting all these interesting circuits.


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## Paul Running (Apr 12, 2020)

If your thinking of getting a scope or already have one, here's an early edition from Tab on them:


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## cbg1 (Mar 27, 2012)

nonreverb said:


> Here's a bunch of equipment I should use more often but never do...
> View attachment 338876


Spent more than my share of time with one of those leather cased Northern Electrics....


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