Hey Don, Sounds good!
How would you like to build a curve tracer also? I built a tube curve tracer for audio tubes about 10 years ago. I found the schematic the other day. Come to think of it I also have the the actual unit. The idea is to use unfiltered half wave as the plate supply - simple sweep eh? Build a step generator to put successive voltges on the grid - one higher than the previous with each plate voltage cycle. Measure the plate voltage against the current on the x & y traces of a scope. And you get the family of curves for that tube. Let me know if you want a copy of that old schematic. de KA4JVY Mark --- Merz Donald S <[EMAIL PROTECTED]> wrote: > Just thought I'd throw out an update on this. I am building an emission > tester for older, mostly 800-series transmitting triodes. It will be able to > measure emission current at zero bias or adjustable bias (using an external > bias supply) at any plate voltage up to about 2500V. The HV is full-wave, > lightly-filtered DC. Filament voltage is adjustable 0-10VAC. I have an old > metered, rackmount regulated supply that uses dual 6L6's for regulation. It > will do 100V--so he becomes the bias supply. > > I gutted an old Beckman, tube-type frequency counter to use the cabinet and > chassis. I just happened to have this unit laying around here. It has a > unique cabinet design with sides that come off and modular chassis > construction--even though, underneath the covers, it's a conventional 8.75 > inch high, 19" rackmount unit. This design allowed me to remove sections of > the chassis to accommodate the 2 big Variacs and the big HV iron. The top of > the cabinet pops off with just 2 Dzus fasteners. I am going to put holes in > the top with the tube sockets underneath, mounted on an inverted chassis > bolted to the top cover. This way the whole unit won't have any protrusions > or non-internal wiring and none of the tube socket connections will be > exposed or accidentally accessible. > > I drilled and painted the panel Sunday. I then immediately discovered that > the 0-300ma meter I was using did not have enough range at upwards of 2500V. > I needed at least 6-800ma. So I replaced that meter with a 0-1000ma Simpson. > But of course, the hole size is different. So now I have to cut a larger > meter hole on my already-painted aluminum front panel. I took comfort from > the fact that the black wrinkle didn't turn out that great anyway... > > Most of the parts for this thing came from a supply I bought at a hamfest in > 2003. For $40, it had a 7.5 amp 120V Variac, 2700V transformer (amps rating > unknown but probably in the 500ma range), 4 K2AN silicon HV rectifiers and a > bodacious capacitor bank of paralleled 800MFD, 450VDC caps. The meters I am > using are from the junkbox (note to self: Don't buy any more meters at > hamfests...), as are the sockets and miscellany. But anyone seeking to build > one of these with new parts would have a big bill on their hands. Check the > prices on new 7.5 amp Variacs these days... > > I expect to be able to test to following tubes in this unit: 203, 211, 805, > 808, 810, 838, 852, 25T(G), 35T(G), 100TH, 250TH and RK-65. The test is far > from definitive. But it will tell me whether the spares I am saving are worth > saving. > > The top cover is big enough that I will still have some space for tetrode and > pentode sockets. Screen and suppressor supplies would have to be external. > But that is phase II--or something I may never do at all. > > 73, Don Merz, N3RHT > > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Merz > Donald S > Sent: Tuesday, September 21, 2004 3:27 PM > To: 'Amradio (E-mail); 'Glowbugs (E-mail) > Subject: GB> UPDATE: Testing Transmitting Tubes > > > Well, here's where I am with this... > > -- The guy who built the tester that AES is using says that he has some > information on that unit that he will pass along. > > -- Another guy says that he has built an adapter for the Tektronix 577 curve > tracer for transmitting tubes. He says that he will write this up for > Electric Radio. > > -- Two guys said that they built custom testers for the 4CX250 tube. One of > them was expanded to test other tubes and was demo'ed at Dayton. The other > was used in the guy's job. No details seem to be available for either of > these. > > -- I checked the AWA index and found only one reference to testing > transmitting tubes. It's a 50 word mention on page 21 of Volume 22, number 1. > There is one diagram. The test the guy is proposing is a minimal emissions > test using a known good tube as a reference. He does this for triodes only > using AC both on the filament and on the plate & grid (which are connected > together). It has the virtue of being simple. But it hasn't many other > virtues. > > -- Finally, there is the e-mail below from the AWA's Ed Gable. This seems to > be closest to the lines along which I am thinking--a scaled down emission > tester. > > The GE Ham News Hartley oscillator tester is more complicated than I want to > get into. And the Ham News static tester is very similar to the AWA tester > described below. > > So this is where I am headed, though still open to better ideas. Keeping it > simple, so triodes only at this point. > > 73, Don Merz, N3RHT > > > -----Original Message----- > From: Edward Gable [mailto:[EMAIL PROTECTED] > Sent: Monday, September 20, 2004 2:11 PM > To: Merz Donald S > Subject: Re: Testing Transmitting Tubes > > > Hi Don: We built a tube tester for Big TX tubes at the AWA Museum. > > 1. Use big filament Xfmr and variac to accomodate any FIL voltage. Use FIL > voltmeter. > 2. Use variace on HV supply for 0 to about 1500 volts. Need about 300 Ma, > but not too much filtering. > 3. Put voltmeter and ammeter in HV supply. > 4. Parallel wire a bunch of convenient tube sockets and allow for clip > leads for socket-less tubes like 833. > 5. To test, get tube data for tube. Look at chart and see what the tube > current should be for a > tube with zero bias. For example, a type 810 might draw 200 Ma @ 1500 volts > with zero bias. > 6. Connect the grid to the filament (zero bias condition) > 7. Turn the FIL on and set proper voltage for the tube under test. > 8. Turn up the HV variac and watch the current & voltmeters. See if the > current vs voltage is close > to the spec. It varies a lot from tube to tube, but low emission, > non-useable tubes really show up > this way. > > SAFETY FIRST !!! > > 73, > > Ed Gable k2mp > Curator, AWA Museum > > ----- Original Message ----- > From: "Merz Donald S" <[EMAIL PROTECTED]> > To: "'Amradio (E-mail)" <[email protected]>; "'Baswaplist' (E-mail)" > <[EMAIL PROTECTED]>; "'Glowbugs (E-mail)" > <[EMAIL PROTECTED]> > Sent: Monday, September 20, 2004 10:19 AM > Subject: Testing Transmitting Tubes > > > > Has anyone built a transmitting tube tester? Or seen any plans on the web? > The only thing I have seen on this subject is the issue of GE Ham News that > covers the subject (Vol 6, #3, May/June, 1951). I have some power supplies I > can use to run the static test. But I need to build something to hold the > tube sockets, filament transformers and plate current meter. I hate to > reinvent the wheel and would be happy to follow a pre-existing design if I > could find one... > > > > Any ideas? > > > > 73, Don Merz, N3RHT > > > > The information contained in this e-mail may be confidential and is > intended solely for the use of the named addressee. > > Access, copying or re-use of the e-mail or any information contained > therein by any other person is not authorized. > > If you are not the intended recipient please notify us immediately by > returning the e-mail to the originator.(A) > > > > The information contained in this e-mail may be confidential and is intended > solely for the use of the named addressee. > Access, copying or re-use of the e-mail or any information contained therein > by any other person is not authorized. > If you are not the intended recipient please notify us immediately by > returning the e-mail to the originator.(A) > > The information contained in this e-mail may be confidential and is intended > solely for the use of the named addressee. > Access, copying or re-use of the e-mail or any information contained therein > by any other person is not authorized. > If you are not the intended recipient please notify us immediately by > returning the e-mail to the originator.(A) > ______________________________________________________________ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] > __________________________________________________ Do You Yahoo!? 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