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Old 8th November 2009, 04:27 PM   #1
TheGimp is offline TheGimp  United States
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Location: Johnson City, TN
Default Bench test equipment, What's yours?

I posted in another thread about having trouble with my HV power supply, but can't find the thread so I started this one.

Being as I'm just getting back into tubes and have the basic meters, oscilloscope, function generator, frequency counter, etc, I find I don't have some specialized equipment like HV power Supply, DC HV Dummy Load etc.

Since I want to make a test set to measure tube parameters better than my Mercury 1000 does, I am planning on making a tube test set of some sort but haven't decided exactly what. (I already made one specifically to test the Gm of the 6BA6 so I could calibrate m Mercury 1000

Calibration of Mercury 1000 tube test set

I found the problem with my HV PS, I had somehow mixed BUZ104s (50V) in with my drawer of BUZ78s (800V).Luck would have it that I put BUZ78s in every position except the output pass transistor, and twice in a row I pulled a BUZ104 and put it in to replace the one that went. I finally put a BUZ305 in the output and when it worked fine I went back with a magnifying glass an d looked at the fried transistor had replaced. DUH!

Any way I now have a nice regulated 100-350V supply with the current limit set to 60mA. I plan on adding a second supply with a larger heat sink and the current limit set to 220mA (probably change both to adjustable current limit). This will allow me to adjust the B+ and screen voltage supplies independently.

While deciding what to do about parametric measurement of tubes, I can now go on with building an audio amp and testing the design.

Does anyone else build your own test equipment? IF so, what besides HV PS and Dummy Loads do you find useful?
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Old 8th November 2009, 05:51 PM   #2
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Location: Alps:Tube amp designs over 150W, SMPS guru.
I started 45 yrs ago with an Advance A2C audio oscy (rubbish) and an HP 311 analyser whih was given to me-. I ripped the o/p EL84 stage apart from the Advance for the output tranny.
The HP 311 is just as good new and can still be picked up reasonably cheaply. The auto null version is better. My problem was a good quality AF oscillator to 100K with low thd less 0.01%. These aren't cheap so I made myself with a couple of op amps, a wien bridge and a thermistor. For the price,this method still ranks the best with the lowest thd although the settling time can be annoying.
The home tube tester and gen PSU; I'm stuck with able to test only octal power types and EL84' configs. The gen purpose HV psu uses mosfets. It gets shorted quite alot and a question of time before it goes shot.- designing a HV psu which is bullet proof is quite difficult.
The HV supply is 500V 100mA limited. 500V 10mA on Screen supply ; with a neg -100V.
0-10V heater supply and audio input. All this is a considerable build but it's worth it and saves masses of wiring and bodge ups.

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Old 9th November 2009, 01:31 AM   #3
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Location: West Virginia panhandle
I have been able to collect enough commercially built test equipment to build a nice audio workbench and a fairly useful RF workbench. I even have a few pieces for digital / uP work. These have been collected over a 20 year period for little or no cost. Some items were purchased in broken condition, and then repaired. Others were purchased from Ebay, Hamfests, or equipment auctions from all of the electronics companies that failed or downsized in this area. My audio pieces include:

HP 8903A audio analyzer, Purchased at the Miami hamfest 10 years ago for $75 (defective) I fixed it, and have fixed it twice since.

Fluke 407D power supply, 550 volts 300 mA. $25 (and $45 shipping) on Ebay in "untested" condition. I opened it up, looked inside, was amazed that it did anything other than make smoke (all original including the tubes and caps), closed it back up, 5 years ago! It still works despite many attempts to blow it up. It goes unstable with loads far in excess of the spec especially if loud bass notes are involved. Motor run cap across the output makes it happy.

Knight Kit KG-664 power supply, 400 volts 200 mA. Hamfest at closing time, $20 plus an assurance that I wasn't just going to pilfer the new Svetlana 6L6GC's and toss the rest. I have never had the cover off, 10 years ago, works fine.

Tek 2232 digital storage scope. Motorola employees equipment auction $100. Schizophrenic, randomly reboots itself, but usually works.

Sorrensen QRD 20-4 power supply, 20 volts 4 amp. Motorola employees equipment auction $20 I fixed it once, 20 years ago.

HP6448B power supply, 0-600 volts, 0-1.5 Amps. Obtained in exchange for fixing or testing some other test equipment. Has enough energy to blow tubes in half! Runs the 250 watt tube amp without getting excited. It could power 3 of them!

HP 331A distortion analyzer, Motorola employees equipment auction $20 each, I got two both worked, one has since died. 20 years ago

HP 204C audio oscillator, Motorola employees equipment auction $20 each, I got two both still work, 20 years ago

Kepco BHK 1000-.2M 1KV power supply, Ebay $40 in "untested" condition. It works fine and the 8098 tubes in it are worth far more than the selling price.

Kepco BHK 2000-.1M 2KV power supply, Dayton hamfest $20, condition unknown. I haven't plugged it in yet!

This is just my audio workbench. I have managed to collect this and other test equipment for little money, so I have not needed to build much. I have purchased a few boatanchors (mostly on Ebay) that didn't work, or didn't last long, but I didn't spend much money or time on them.
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
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Old 9th November 2009, 01:52 AM   #4
jleaman is offline jleaman  Belgium
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Default sweet thread,

I was just about to start one of these,

I'm about to buy a few new tools,

First, a bench top meter,

Click the image to open in full size.
39999 Digit Autoranging Bench Top Multimeter UT804

Then a hand held scope,
Click the image to open in full size.
UNI-T UT81B 40MSa/s Oscilloscope digital multimeter

and, a new bench top psu.
Click the image to open in full size.

Atten Electronics : Test & Measurement Manufacturer, OEM, ODM, Spectrum Analyzers, Digital Oscilloscope, Power Meters, Power Supplies, Soldering Stations, Rework Stations, RF Microwave, Training Kits

last week i bought from them a Fluke meter for work, nothing special because im only mesuring small voltage, ie alam voltage from 5-24V. I thought it would be a cheap crappy Fluke meter, but actually its nice i like it alot.

Meter i bought,
Click the image to open in full size.

Good customer service from them also, will be buying more from them.

I like the hand held scope, perfect for audio, cheap and 4 year warantee :0

Last edited by jleaman; 9th November 2009 at 01:57 AM.
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Old 9th November 2009, 02:01 AM   #5
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Location: Portland,Oregon
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BK precision 1474 scope (30Mhz)
Interstate Electronics F34 Function gen. (3mhz)
Sinclabs 13.8V 10A PSU
Heathkit/Zenith SP-2717 Adjustable HV power supply,for tube circuits (0-400V 100ma,0-100V for -Vbias)
VectorVid WP-705B Adjustable power supply CV/CC 0-64V 0-2.5A
Sigma AF-250L AM/FM analyzer
A couple other 13.8V supplies.
Temp. controlled soldering iron,and a big gun,for heavy duty stuff.
A couple DMM's..clipleads..hand tools..the junkbox..and a few other things.
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Old 9th November 2009, 02:10 AM   #6
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Location: Llanddewi Brefi, NJ
The only new stuff I have is my Fluke DVM -5 years old -- and an EICO VTVM which I bought when I was in high school.

Here's the stuff I use all the time -- Tek TM5006 with some autoranging DVM's, one measures temperature, PS5010 power supply, SG5010 oscilator and AA5001 analyzer, Tek 2465 and 3012B scopes, Genrad Variac, Heath IP-17 HV supply, HP 3577 network analyzer, AP Analyzer, well worn Boonton 1120 with homebrew filters (very useful).

My amp testing power supply is encased in a HP 6131 chassis with a honkin big Antek trafo and some big Mallory computer caps -- it will power amps up to a couple hundred watts.

The stuff I find useful -- Fluke and HP True RMS meters with thermopile detectors, a Tektronix 5223 boat anchor with the differential amplifier, a 3581 wave analyzer, the Collin very, very low noise preamplifier, a Keithley nano-voltmeter, Wavetek sweep generator, HP3336, HP3586.

I have a Hako soldering station -- this and the TM5006 are turned on after the first cup of coffee is brewed.
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Old 9th November 2009, 03:41 PM   #7
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Location: Hickory, NC
Tek 576 curve tracer modified for vacuum tube tracing.
Tek 7603 scope with usual plug-ins and 7L5 spectrum analyzer.
Tek SG505 low dist. sinewave oscillator
Tek AM503 current probe
Tek P5200 HV diffl. probe
MAudio 24 bit sound card and Audiotester Softw. for FFTs
Xantrex HV power supplies, Heathkit SP-17A HV supply
Variac controlled Hammond 378CX HV xfmr with 193Q inductor/capacitor filter
several DMMs, Extech LC meter, GME C meter, GME L meter, Heathkit 2240 digital LC bridge
Heathkint IG-1275 function generator
several OPTI-MOS SS amps (useful for amplifiying low dist. sine wave sources up for tube grid driving or testing OTs)
Magnetek/Triad N-90MD medical grade isolation XFMRs
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Last edited by smoking-amp; 9th November 2009 at 03:47 PM.
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Old 9th November 2009, 08:53 PM   #8
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Not much here.
5A Variac
RCA WO-33A oscilloscope (broken)
Exetech MN26T multimeter
Oneac 2A isolation transformer
Sola CV transformer
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Old 9th November 2009, 09:17 PM   #9
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Tektronix oscilloscope:


Extech MM:


Homemade lab supply:

Picture 1108.jpg


Picture 1122.jpg

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Old 10th November 2009, 12:35 AM   #10
TheGimp is offline TheGimp  United States
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Steak Onions and Squid caps?
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