Tube Testers - advice needed

[jimmywilliams]

I may be working on some older organs/cabs with tube amplifiers. On the one job I did last year on the Hammond B3/Leslie 22H I took all the tubes and had them tested at a repair shop. Only cost 10 bucks but I would rather be able to test them on my own, then and there. I was checking ebay out for tube testers. There are some portable "suitcase" model going pretty cheap. But I know nothing about them. Obviously, I would get one with an instruction manual. Is there any feature(s) I should be looking out for with these? From what I understand, I would also have to be looking at a model from the 60s at least, since some of the older models were not equipped with some of the more modern tube sockets. I also have an old console radio I have had for a long long time and want to finally restore that too. I was also told that sometimes a tube might test out good but still be bad in the "real world"?? Any advice or guidance on tube testerswould be greatly appreciated. Thanks.

[Guest]

Re: Tube Testers - advice needed



You want a Mutual Conductance tester, and preferably one from a source that has properly calibrated the machine.</p>

Good choices are most Hickoks -- 539x, 600-series, 6000, 800-series, others.  Heathkit TT-1 is also excellent, and many others of course, including the military TV-2 and TV-7's.  Some may not have settings charts for "late" tubes, depending on the age of the tester.  </p>

A good reference site is http://www.radiolaguy.com/tubeTesterRest.htm, which discusses calibration and also contains links to other relevant info.</p>

Compared to 10 years ago, the prices of tube testers have really skyrocketed (except for the Hickok 539C, which has always cost an arm and a leg).  $10 to test a batch of tubes is pretty reasonable compared to the going rate for one of the better tube testers.  I do a lot of tube radio restorations and couldn't live without one, but if I had to test a few tubes once in a great while, I might be looking to go another route.</p>

Grant </p>

[Guest]

Re: Tube Testers - advice needed

Just be careful Jimmy. You pay for what you get. I put $100 on a pre-paid Wal-Mart Visa card and won a bid for a Sencore Mighty Mite II *TC114* vacumn tube tester. Beautiful tester. But for some reason, even though it'll power on and uses a good 12AU7 tube inside, it tests grid emission/leakage the same for any tube (good or knowingly bad, as in broken). But it actually meters out and will calibrate, and the short test works great. Anyways, just a word ofcaution about buying a tester on eBay from my own personal experiences. You pay for what you get, so unless you pay around $200-$300 for a winning bid on a Hickok tester, don't be surprised if you get slightly shamed like I did... lol.

[jimmywilliams]

Re: Tube Testers - advice needed



Sorry to resurrect this old thread ...</P>


I have noticed a lot of Heathkit TC type tube testers lately (as opposed to TT). Are the TC models not mutual conductance testers? I also noticed some "Jackson" tube testers that use the phrase "dynamic" - don't know how that differs from mutual conductance or transconductance. Also came across B&amp;K Model 707 (says it is mutual conductance). Anyone else here use tube testers, and have any recommendations? </P>


Thanks.</P>

[indianajo]

Re: Tube Testers - advice needed

I've got a Triplett 3440 tube tester , pretty serious. Needs $100 in electrolytic caps before I use it again, I fished it out of the trash in 1985. Many of the testers sold on e-bay are home constructs that measure something that is not very useful. "Dynamic" has no standard meaning referring to tubes. Read diyaudio.com tube forum, search for "tube tester". They had a built it yourself project thread Tubes get leaky with excessive current flow due to gas leakage, or develop poor gain due to a tired coating on the cathode or a pitted anode. Gain or admittance is measured in "mhos", renamed "S" recently by some academic that didn't have enough to do. My 1968 hammond had no bad tubes, just bad electrolytic caps, dirty corroded connectors and switches, bad dirty trimpots, bad oxidized tube sockets, oxidized tube pins.

[Arden]

Re: Tube Testers - advice needed



[quote user="indianajo"] My 1968 hammond had no bad tubes, just bad electrolytic caps, dirty corroded connectors and switches, bad dirty trimpots, bad oxidized tube sockets, oxidized tube pins.
[/quote]</P>


Ok, so how does a person go about diagnosing / repairing issues like you have quoted here? I have a Baldwin Orgasonic, Yamaha DK 50, and Gulbranson that are all in need of repairs and I don't want to take them to the dump. I'm fairly smart and have been figuring out mechanical and electrical things in industrial envioronments for all of my life. So how do I get started fixing / understanding how my organs work?</P>


ANY input would be appreciated!!</P>


Arden</P>

[Royal]

Re: Tube Testers - advice needed



Arden, a few decades ago, I sent my son to VA Tech. Great school. </P>


Here is what I do for all the free (less than $100) organs that I have picked up over the years:</P>


Look for is some sign of life. Some noise resembling a note regardless of how ugly the note is. Remove the back cover. Thoroughly vacuum and blow out with compressed air. Then(good intense light) a thorough visual inspection. Plug her in. Any noise? Check all the stop tabs. Are you certain that it is getting power and the cord and the on/off switch works? Check for light bulbson to verify power. If no power there are often some fuses that can easily be checked. Once you are convinced that it is getting power, but still no soundscheck for the headphone connector making good contact. Try the organ with headphones. If tubes are they all lit? If still I can't get the organ to grunt, I often check the tubes on my tube tester. If one or more is bad, I replace it/them. (It rarely is a tube.) Try again for sounds. If I can't get any noise from her at this point, I usually try to assess what this organ may be worth either to me or to someone else. At this point, at least 90% of the "grandfather played but..." or "have to downsize" organs will kinda work. They just need contacts thoroughly cleaned with electronic contact cleaner. And exercise. If a key or stop doesn't work, exercise it a few hundred times. Remember that "No use is abuse!" If nothing by this time, I remind myselfthat from this point on, I am probably losing money, - likely big money exceeding the worth of the organ. If the organ is worth it (and it rarely is) I buy a schematic and or service manual, getout my O-scope, volt ohm meter, signal generatorand and start checking out the circuitry. If you decide not to repair,salvage whichever components may be of value, give the old girl a nice funeraland scrap. </P>


Roy (Learned from my grandfather 50+ years ago and became an electronics technian when repair shops still existed.)</P>

[indianajo]

Re: Tube Testers - advice needed



I started with TV's in 1962, taking the tubes to the corner store for testing, then on to car radios in 1966. I had to ask my chemistry teacher, an old Navy radio repairman, for help diagnosing the bad vibrator in the car radio. I shocked myself silly with 440V on the 6V car radio. Before starting on tubes, read aikenamps.com tech support button technician safety button on how to not kill yourself with tubes. I've had some basic electronics in college, "Electronics for Scientists" 1968 version had a lot about tubes. Second year physics ran through the math of resistors, capacitors, inductors, circuits. You don't need to go to college. The boy scout merit badge books used to be good starters, but they don't sell them in Sears anymore. I found "Electronic Devices Electron Flow Version" tech school text by Thomas L. Floyd at the Goodwill last fall for $2, very useful purchase for learning transistor circuits. The predecessor book to this discusses basic circuit and passive device (resistors, capacitors, inductors, transformers) theory, I don't know what that is called. But the book is very well written. Text from community colleges are more useful for real life repair than academic colleges, they have less math and more useful practical knowledge like why some designs are better than others.
</p>

Anyway, my organ made some sounds when I bought it, (I wouldn't have bought it dead) but volume was feeble and a lot of features didn't work. I read the descriptions on the internet to determine how the features were supposed to work, and decided they weren't working. I downloaded a schematic diagram from the internet, very cool. First a bass note didn't work, the switch acuating lever was broken and I made a new one by drilling a hole in a hacksaw blade. I next decided to replace electrolytic capacitors. You can tell from the date on the can they are dried up. 15-20 years is life on electrolytics. Also old electrolytic capacitors are known to explode. The organ had the motor electrolytic capacitor replaced in 1997, the burnt off insulation on the main power wires to the capacitor had never been replaced. Replacing 2 electrolytic capacitors in the power supply doubled the volume, 4 in the power amp doubled it again and made the string bass feature work, three in the preamp/mixer doubled the volume again. When it started shaking the music on the rack I decided volume was okay, I didn't need to repair my tube tester. Replacing the capacitors on the preamp/percussion unit made percussion tabs start working again. Replacing electrolytic capacitors on the transistor preamps pepped up the highs and lows. Certain tabs (sounds) didn't work. I looked at the schematic to see what switches they flowed through, then bought a can of contact cleaner and sprayed off all the tab switches and level sliders. At the same time I removed all the tubes and sprayed out the sockets. That solved a lot of problems. Some tube sockets were scratchy and hissed and popped while playing, you can determine which one by rocking the tube, then clean those especially. Be sure to power off the unit and check for lethal voltages with a meter before cleaning any socket with a pick. Two times the vibrato feature dropped out entirely. I looked at the names of the preamp boards on the layout, sprayed off and touched the trimpots on the boards that sound went through, and the last one I sprayed of before It started working was the one that was bad. I hold a key down with a roll of nickels when spraying non-water cleaner, that way you know where the problem was. I still have a few keys that sound but the percussion is missing. I/m going to have to disassemble the key enclosure to access those contact and spray them off or erase them. However, all features are working on 98% of the keys, so I didn't have to test the tubes at all. I still have one feature, reverb, that is ittermittant, after it drops out it starts up again if I rock a tube in its socket, so I think that socket is bad. I tried to replace that tube socket, the new socket came in too big to fit and I'm still looking for a fix on that one.
</p>

Certain organ tubes are unavailable, are identical to tubes in my Dynakit amp that are 40 years old, so when I bought the tube sockets I bought some modern different number tubes to see about replacing the unavailable ones with something available that had a different pinout. To test the new tubes I bought, I did replace the electrolytic capacitors in the tube tester, put a known good tube from the organ in it, and got a power fault light before I even got to the conductance test. So I know why the tube tester was in the trash. It is not urgent, the organ works pretty well except for reverb, so I'll deal with that next winter when outdoor jobs are impossible. I have a manual and a schematic diagram for the tube tester.
</p>

[Arden]

Re: Tube Testers - advice needed

[quote user="Royal"]


Arden, a few decades ago, I sent my son to VA Tech. Great school. </P>


Here is what I do for all the free (less than $100) organs that I have picked up over the years:</P>


Look for is some sign of life. Some noise resembling a note regardless of how ugly the note is. Remove the back cover. Thoroughly vacuum and blow out with compressed air. Then(good intense light) a thorough visual inspection. Plug her in. Any noise? Check all the stop tabs. Are you certain that it is getting power and the cord and the on/off switch works? Check for light bulbson to verify power. If no power there are often some fuses that can easily be checked. Once you are convinced that it is getting power, but still no soundscheck for the headphone connector making good contact. Try the organ with headphones. If tubes are they all lit? If still I can't get the organ to grunt, I often check the tubes on my tube tester. If one or more is bad, I replace it/them. (It rarely is a tube.) Try again for sounds. If I can't get any noise from her at this point, I usually try to assess what this organ may be worth either to me or to someone else. At this point, at least 90% of the "grandfather played but..." or "have to downsize" organs will kinda work. They just need contacts thoroughly cleaned with electronic contact cleaner. And exercise. If a key or stop doesn't work, exercise it a few hundred times. Remember that "No use is abuse!" If nothing by this time, I remind myselfthat from this point on, I am probably losing money, - likely big money exceeding the worth of the organ. If the organ is worth it (and it rarely is) I buy a schematic and or service manual, getout my O-scope, volt ohm meter, signal generatorand and start checking out the circuitry. If you decide not to repair,salvage whichever components may be of value, give the old girl a nice funeraland scrap. </P>


Roy (Learned from my grandfather 50+ years ago and became an electronics technian when repair shops still existed.)</P>


[/quote]</P>


My wife graduated from Tech in 95 (Tree Hugging!), as did several members of her family, my friends, etc. It is indeed, an excellent school. They pay too much attention to the football team, in my humble opinion - but it's just that MHO.</P>


And yes, I remember when repair shops existed! Wehad one at the shopping center near where I grew up (along with two drug stores with SODA FOUNTAINS!! where you could get a "real" cherry coke - and then test your tubes back near the pharmacy counter. And the replacement tubes were stocked in the cabinet underneath. Usually a quick fix to the TV with the jitters...</P>


All of my "FREE!! - less than $100" organs "function", some with more features than others. I was not sure if the innards should be vacuumed or "blown" out. I will do both. Can you suggest a good contact cleaner? I had some at work (several different brands - 3M and one in a green can - but both said "keep away from plastic"! Well, the only contacts I've seen since I worked on a locomotive in New Orleans were cased in plastic! So I need one that is "plastic safe". </P>


My Baldwin makes a VERY loud hum as soon as I power it up. I recently read about electrolytic capacitors "dying" from lack of use, and the hum being "line voltage hum" from the amp. So, how do I diagnose the bad cap? I understand they must be taken out of the circuit to test. That seems like a lot of unsoldering / resoldering...??</P>


If it turns out that they still can't be brought to life, are thekeyboards / pedal boards useful for constructing a Hauptwerk virtual organ? I just can't bring myself to haul these babies to the dump. Yet.</P>


Thanks,</P>


Arden</P>

[indianajo]

Re: Tube Testers - advice needed



Bad electrolytic capacitors have production dates older than 1990. Besides drying up, the rubber seals on the wires go bad. Reforming ones older than that is a complete waste of time, good if your not going to let the organ sit a month without playing. Electrolytic capacitors look like aluminum cans, or cans with plastic shrink around them. Mark your plus with a sharpie on the board before replacing. Use rosin core solder, not acid. Wear safety glasses. I use old wire dipped in rosin to suck up solder off the old capacitor. Tantalum electrolytic capacitors look like peanut M&amp;Ms. I replaced 1, 2, 5, 10 uf electrolytic capacitors with ceramics, which will never need to be replaced. Wikipedia warns about microphonics on ceramics, I did not have that problem, and my Hammond is LOUD. Timing (oscillator) caps need to be +-10%, filter and bypass noise to ground caps can be +80-20. That saves a lot of money. Electrolytics come in various design lifes, I buy the long life ones because I don't like doing work over. My 18 month old digital TV converter already has lines in it from bad electrolytic caps that warm up in 5 minutes. Bargain electrolytics are often old. </p>

Most modern contact cleaners are gasoline in a can, and are dangerously flammable. Naptha, aromatic hydrocarbons, benzene, aliphatic hydrocarbons, heptane, hexane, pentane, octane, isooctane, are various euphemisms the manufacturers have on the cans to lull you into thinking they are safe. I used some Freon TF cleaner left over from the eighties, before it was banned from manufacture. Industrial supply houses have fire safe contact cleaner that has chlorinated or brominated hydrocarbons that aren't as flammable. Look for the words chlorine or bromine in the hydrocarbon name. They cost $20 a can. You can't mail order these and be sure, as mail order houses won't tell you what is in the can before you buy it. A lot of users here recommend "Deoxit" which has oleic acid in it, but I'm a little nervous about using acid without trying halogenated hydrocarbons first. Freon TF is a halogenated hydrocarbon, and fixed my problems. Don't spray deoxit with the power on, I think it might have water in it.
</p>

[Royal]

Re: Tube Testers - advice needed



Arden, </P>


Follow Indianajo's advice re cleaners remembering that there are as many different "plastics" as there are cleaners. Some cleaners may be ok for some plastics and not for others. Test some inconspicuous spot to be sure. I have 4 or 5 different cleaners that I use. </P>


Re electrolytics: I don't even test them if they are old (and they almost always are) - too much work. Just replace and be sure that if the problem remains it is not the old cap. </P>


Roy</P>

[Arden]

Re: Tube Testers - advice needed



"Re electrolytics: I don't even test them if they are old (and they almost always are) - too much work. Just replace and be sure that if the problem remains it is not the old cap."</P>


From reading these posts, I think I can safely say that many of my problems are just lack of "exercise" for tremolo switches, etc., that seem to work intermittently. And possibly some judicious cleaning with a "safe" contact cleaner.</P>


the one that has me most concerned (Baldwin with loud hum): I have looked behind the keyboard. The guy I got it from said an organ tech told him it was "a big silver thing in the middle right under here" that was the cause of the problem. I did replace a large (larger than the rest), but no effect. I'm thinking it's in the main amp / power supply. Haven't lookedyet, but would guess there is a half a dozen caps in there - so do I replace them all? Not a problem to do so - my soldering / desoldering skills are pretty good - but at this point it seems a little overwhelming. what is a good place to buy new caps? I got the others from "Musician's Friend" (I think); very reasonable cost.</P>


Thanks for ALL of your guidance and suggestions. I LOVE my organs, and since they are not taking up any needed space, I have half a mind to keep them anduse them with their individual limitations...</P>


Arden</P>

[indianajo]

Re: Tube Testers - advice needed



I replaced every electrolytic in my Hammond except for the harp circuit that works, and has 90 tight tolerance timing electrolytic capacitors of a weird value at $5 each. I like my Hammond and intend to keep it. I tend to hang on to things, people that like trading a lot may do less to their organ. When replacing electrolytics, I start at the power supply and work out from there. I learned about power supply caps on my Dynakit amp in 1972, when the MacIntosh factory guy said my 10 year old power supply cap was holding output power of my amp from 70 design to 10 actual watts. My rectifier tube was weak also. I tried a new rectifier tube in the Hammond H182, a Sovtek, it didn't help anything, so I am saving that tube for the ST70 amp when it needs one again. </p>

I buy axial and radial lead electrolytics from newark.com who has a huge stock in NC and can get to me in 2-3 days for $5 shipping. A lot of people use mouser.com in Ft Worth. I found they were higher priced on wire. Newark shows hours life on capacitors, so you can select the longest life ones available. They also can screen out out of stock items if you don't like waiting and paying more than one shipping fee. Be sure to check the size on the capacitor with the manufacturer's link to make sure it will fit your hole. Be sure to check "no back order" to slow down your order and cut out multiple shipping fees. They still do it sometimes, but always all shipments on the same day. If Newark ships you the wrong thing, they sometimes give you the replacement for free. You get more respect if you order $50 in stuff at a time, as I have been doing.
</p>

Aluminum tall can capacitors with 3 -4 sections are made only by FP and are available from tubesandmore.com phoenix, triodeelectronics,com (tubes too) and tonewheelgeneralhospital.com of kansas city. Also some organ repair places listed on the type repair threads of this website. These are $20-$30 apiece. Different places stock different values. If you can buy an insulating header, drill a hole without getting metal in the tube sockets, screw the header below the chassis, and install cheap axial electrolytics instead of the cans, you will save a lot of money. These vendor have some weirder value high voltage (tube) electrolytics that are not always available at newark. Triode replaced a wrong thing for free for me once, too. It was $2, so I didn't have to ship it back. </p>

When I change parts, I play the organ after each one or two. That way if I make a mistake I know right where the problem is. I check every time for lethal voltage after turning off, also, before touching any metal.
</p>

Testing contact cleaner for plastic compatibility is up to you. You can check PVC on a child's toy. Polycarbonate (lexan) relay housings is usually tougher. The most problematic plastics are the clear ones use in meter displays etc.
</p>

[Arden]

Re: Tube Testers - advice needed



I seem to remember or have read recently that there are some residual high voltages in the capacitors. How do I safely discharge them or test for voltage levels before replacing my capacitors? I have a Simpson 255 Analog meter, as well as a Fluke 87 DMM. I have a book on tube-type amplifiers coming next week and since I won't be doing any trouble-shooting prior to that, I'll probably just wait and read a little before I start operating on my organs.</P>


Thanks for ALL the input and suggestions. You all are great!!</P>


Arden</P>

[trobbins]

Re: Tube Testers - advice needed



To discharge caps, you can make up a clip lead with two insulated probe clipson either end and a 1kohm resistor in the lead (somewhere convenient and insulated - can be half watt). But best to turn off organ and let all the circuits discharge for say a minute, and then use the clip lead on the specific part of interest, and then measure the voltage on the part. Take the clip lead offbefore actually having a go of it with the soldering iron etc. Sometimes the residual charge in an electrolytic can cause the voltage that was previously 0V with the clip lead on, to redevelop once the clip lead is taken off - this is usually only a few volts and not a concern, but be mindful that the larger power suppy caps may need the clip lead on for a minute or so to alleviate the residual charge.</P>


It just takes one jolt to make you appreciate howcautious you really need to be. As such, whenever hands are near to circuitry, its best to understand what the consequences may be if you do happen to get an accidentaljolt.</P>


Ciao, Tim</P>