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Old 5th February 2013, 07:45 PM   #1
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Default DIY tube matcher / ideas for tube burn in / bias match station

I have a couple of bogen MO200 chasis and want to put together a tube burn in station that will let me measure and grade Ip based on bias current. In my mind, for my use, the ability to measure transconductance is not needed since I have a tube tester for that. In my senerio, I have 75 or so 6550 tubes and I need 48 with the lowest Ip draw. So I'm thinking of putting together something that will both put the tubes in a real wolrd environment and let me select the tubes individually to measure Bias. I'm thinking a basic tube power am circut with bias resistors and meter controlled by a rotatry switch . I have 6l6's, el34s, KT88's, KT90's as well as the 6550's. I have one schematic for a ppower amp that has the ability to use all the tubes I indicate so I am thinking of starting with that. Main goals is

Plate Voltages 325, 400 VDC (or higher if it makes sense)
Bias Voltages -60, -48, -36, -24, -14 VDC
Test Frequency - not sure about this one...normally when we bias tubes it's with no input signal...do we think a test frequency is needed?

So basically, does anyone know of any projects with schematics of something simular to this. No sense in re-inventing the wheel if someone has already done this.

Last edited by speakerfritz; 13th February 2013 at 09:32 PM.
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Old 6th February 2013, 12:58 AM   #2
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came across this smoke tube test circuit. not a whole lot out there.
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Old 6th February 2013, 09:19 AM   #3
mvd is offline mvd  Germany
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Hello Speakerfritz

For matching Tubes maybe this Schematic is usefull as a starting point:

Röhrenprüfgerät für Gegentakt-Röhren

Only problem is to find an amperemeter with positiv and negativ range and zero at center position.

Best regards
Michael
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Old 6th February 2013, 09:49 AM   #4
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Quote:
Originally Posted by mvd View Post
Hello Speakerfritz

For matching Tubes maybe this Schematic is usefull as a starting point:

Röhrenprüfgerät für Gegentakt-Röhren

Only problem is to find an amperemeter with positiv and negativ range and zero at center position.

Best regards
Michael
Interesting idea to match tubes all over their working range. The ammeter may indeed be a problem, but wouldn't it be possible to use a low value (10R?) resistor instead with a DVM across it? DVM can show both + and - without a problem.
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Old 6th February 2013, 06:26 PM   #5
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Quote:
Originally Posted by ErikdeBest View Post
Interesting idea to match tubes all over their working range. The ammeter may indeed be a problem, but wouldn't it be possible to use a low value (10R?) resistor instead with a DVM across it? DVM can show both + and - without a problem.
yes...thats how I would do it.
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Old 6th February 2013, 06:27 PM   #6
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Quote:
Originally Posted by mvd View Post
Hello Speakerfritz

For matching Tubes maybe this Schematic is usefull as a starting point:

Röhrenprüfgerät für Gegentakt-Röhren

Only problem is to find an amperemeter with positiv and negativ range and zero at center position.

Best regards
Michael
Thats food for thought....thanks
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File Type: jpg Gegentakt-RoePruef.jpg (19.7 KB, 156 views)
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Old 13th February 2013, 08:44 PM   #7
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Default DIY tube matcher

actually found one...kinda figured someone else been there done it.

PriceLess Amp Restoration
Attached Images
File Type: jpg match1.jpg (15.1 KB, 125 views)
File Type: jpg match2.jpg (15.6 KB, 123 views)
File Type: jpg match3.jpg (15.5 KB, 120 views)
Attached Files
File Type: doc Tube Matcher.doc (25.5 KB, 39 views)
File Type: pdf tube matcher layout.pdf (195.5 KB, 40 views)
File Type: pdf DIY tube matcher schematic.pdf (27.1 KB, 46 views)
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Old 13th February 2013, 09:31 PM   #8
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somebody did some modifications to the initial circut.
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File Type: jpg Modified tube matcher.jpg (191.0 KB, 132 views)
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Old 15th February 2013, 12:30 AM   #9
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hmm, how many and what make tubes where you planning on? ahh i see, power tubes.

you could do it the classical way, variac-insulation transformer 230 vac in series whit a 50-100watt ish lightbulb and all grids on anode, whit a resistor in series whit them to limit the current. t


this jig en order to burn in just needs to keep the cathode activity up, you can do it in a fancy way whit stabilized voltages and the Whole deal. but in the end where talking about a burn in rack. Not a tester


testers on another hand. you just need some power supplies, a bounch of sockets and a lot of meters to measure all the voltages/currents and from that you can test everything an engineer needs to know.

i made my own tester, its not fully finished yet. but it can already do a lot more than a hickock will ever do.

best advice: search for the sussex valve tester. and overbuilt it for power tubes. its not a burn in setup the sussex will overheat . rarely if any testers/matchers are made to burn in tubes, its entirely different


Btw, have another good look at your circuit. if you burn those tubes in whit multiples at a time. and one of them develops a short G1-K your gonna lose every tube in that rack, so its good to take some precautions.

V4lve.

Last edited by v4lve lover; 15th February 2013 at 12:44 AM.
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Old 15th February 2013, 12:45 AM   #10
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v4lve lover , I have about 100 6550 tubes. need to sort thru them and pick 48 that are close in Ip. I have two VTL MB-1250 amps that use 24 6550 tubes each. I'm thinking of using a Bogen MO-200 as the donor for the chasis and power supply. The MO-200 has 8 octal sockets and would just need a make over. I do have a real good calibrated transconductance tube tester and I usally test the tubes and include a bias probe on the tester to grade the Ip at the same time. But if I setup a MO-200 as a tube matcher...I can grade 8 tubes in one shot. I was also thinking about just taking one of my other amps, and jumping pin 5 all together so that the bias voltage was exactly the same....and then use a variac to bring the amp up to a safe bias consumption....mark the line voltage and repeat the process. I have an amp that could do 10 tubes that way. But the matching circut is so simple. might as well go that route.
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