• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Found 2000 tubes and gear

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#22
I have been in and around the surplus business.

My advice, sell as much of it as soon as soon as you can.

Decide what is valuable and what isn't and don't look back.

Do not let people cherry pick your stock,
sell it in as big of lots as you can.
 
#23
Let's not forget the guitar players - the RCA plack plate 6L6GC is a favorite. Likewise the 6V6 for lower powered amps.

And old radio nuts like me know that NOS 1L6s go for $40 (used in '50s Zenith shortwave portables) and the 6E5 "magic eye" tubes (used in many '30s console radios) go for nearly as much.
 
#24
JasonL,

internet communication can be tricky, no body language, you know, and next time mark jests. OK? 🙂

Dave and Thatch_Ear,
please do feed hints for beginner's amp project, I would not know where to look.
If i look at the tubes, a Williamson amp using triode-wired EL84 for output and 6CG7/6FQ7 for input and phase splitter would appeal to me. But i have no idea where to look for circuitry already hassled out. Maybe use triode wired 6L6GC instead of EL84, rest of the parameters should need no change then for the Williamson circuit.
Maybe not sacrifice the fancy 5691/5692 for the beginner's project although they would fit perfectly.

Rick,
don't dillydally, run and salvage the books! Anything faintly related to analog and regulating circuity, amp design, measuring, oscilloscope circuitry, scope manuals is worth keeping. And post a list! 🙂

The GE data book is a condensed tube parameter list; it is the most complete i have ever seen. I 1st look into it if i inquire over parameters or see a type i do not know. I can then decide upon comparing parameters if the tube in question is similar enough to give it a try in a known circuit. Or i can say, gain=3 makes me happy, plate resistance fits and transconductance is sufficient for the intended purpose. Depending on the knowledge i have.

Amp project: if you build a Williamson style amp, you cannot got wrong sonically. Look in the Sound Practices from Summer 1993, p.10 ff; there is a modern adaption of the Williamnson amp described. V1: 6DJ8/6922, V2: 12BH7, V3+4: 6L6GC, 807 or similar. I know a guy who built it, he is raving about it.

It depends on what output transformer you can obtain. You should need 4kOhm primary plate2plate for 6L6-GC or the like, and 10-12kOhm for the EL84. Latter might be hard to find.
 
#25
BIG RETRACTION:
MISTAKEN IDENTITY!!

ApexJr. maybe the best trader on the face of the earth for all I know. It was stupid of me to post something like that on the basis of my faulty memory. My apologies to Apex JR. and to all the people that read my earlier post!!!
 
#27
old eqt.

Good morning,

Aud Mot--thanks for the good advice; it may take a while to organize before selling in lots but time will be on my side after setting the eqt aside

Tom Bavis--good to know the value of some of these tubes

dice45--thanks for the third party encouragement. If I find books and literature as you've described, I'll post titles, etc.

planet10 suggested I consult Duncanamps for schematics. I briefly visited the site but have not had time to find the suggested Williamson amp. If I find it, I'll build it unless pursuaded otherwise.

Next task, dig around and locate those transformers!

Thanks,

Rick
 
#28
Re: old eqt.

For a 1st project i'd actually recommend a little SE amp (i'd choose EL84, but you may want more than the 2-4W this will put out), not because it sounds better or worse than the Williamsom Bernhard suggested, but because it is simplier. The deciding factor may well be what iron is available.

dave
 
#29
Frag,
Most every audio amp built using a pair of power tubes in a Push/Pull configuration is based on the Williamson Circuit. So you have a large advantage as to used tranformers. Like Dave I also suggest a Single Ended instead of a Push Pull simply because of it uses fewer pieces, less soldering and might work with well with speaker you own now if they are efficient enough. I would suggest the Eico AF 4 as a good starting project since getting a manual on it shouldn't be too hard. Better transformers that the kit had are advised(especially the power supply) but the design is a good one and getting a complete how to build it manual is a great help with 1st projects.
Thatch
 
#31
Rick,

I would be interested in three of the types of tubes you listed. I recently acquired a tube amp and am interested in laying in a supply of tubes for future years when they may not be so available. The amp I have uses 6L6GC, 12AX7 and 6SN7 tubes. If you have any interest in peeling off 10 or so of each of those tube types for individual sale, please email me at: jnliu@pacbell.net I would be happy to pay the going rate, though I also would have to do a little digging to find current values, as I am also new to all this. If you don't want to deal with small volumes and would rather unload all of them through someone like Welbourne Labs, I understand. Let me know.

Norm
 
#33
Heath kit AA-40 found

Still finding stuff! How exciting!

I looked in the bottom of a 19 inch rack located in audio/video projection room in the original building constructed in 1956 and what did I find? Heath kit AA-40 in perfect condition (well, perhaps some pencil marks on back panel). Nothing burned or suspicious. One of the small tubes is labeled "heath tube". The other is RCA...someone changed it out?

The two big tubes are EL 34's.

I read through threads and believe this is next course of action for found old eqt going back into service, based on Thatch Ear and others' advice.

1. Don't plug it in, yet.
2. Bake for 2 hours at 200 F.
3. Power up with Variac.
4. Hook up speakers first, then power up and listen.

Is this correct? I find it hard to resist simply hooking up speakers and plugging it in!

Any advice would be greatly appreciated.

By the way, thank you all for being such a great resource and board!

Rick
 
#34
Re: Heath kit AA-40 found

Here is an extract from a post on the JoeList by a fellow who does this alot:

Here is the procedure I use to bring up an unknown amplifier. First, check the tubes to make sure all are good and none are shorted. Look things over for any indications of anything burned, then with a variable B+ supply, gradually bring up the B+ while monitoring the current drain, until the filter caps are reformed and leakage is not more than a few ma (with the filaments off). If the current is high, locate and replace any bad/leaky filter cap(s). If there is a bleeder, you might want to temporarily disconnect it so you can assess the filter cap leakage more accurately. Ignore large value bleeders, like 100k, or so. Then check the voltage across all grid resistors (with the B+ on, filaments off) to determine whether there are any leaky coupling capacitors. Use a high impedance voltmeter for this. There should be very little voltage across any grid resistor. If so, replace the coupling cap. By this time you should have found most of the problems, and quickly, at least those that could be catastrophic. You might want to measure the resistors to see if any are grossly out of spec. Then power it up and see whether it hums, or smokes, whatever. You should check the power tube(s) bias, whether fixed or cathode bias, immediately upon powering it up, which preferably should be done with a variac. If it hums, locate the bad filter caps and replace as required. Here is a good way to determine whether a filter cap still has its rated capacity. While observing the magnitude of the ripple on the scope under load (or perhaps with an ac voltmeter) parallel a known good cap of the same value across the cap under test. If it has full capacity the ripple will be reduced to half it former value. Precharging the cap with a series resistor is advisable. If you are equipment-challenged, to be PC, then with a speaker connected see if the hum is decreased appreciably when the cap is paralleled by a known good cap. There will be some hum reduction even if you are paralleling a good cap, when there is a bad cap elsewhere, but not neaarly as much as when the bad cap is paralleled, anyway, measuring the ripple reduction is preferable. If the power trannie is bad, you will find out soon enough. If bad, it will blow fuses, smoke, smell bad, overheat, or some combination thereof. You should have eliminated a bad rectifier tube, bad filter cap (or other short) and bad coupling caps before ever turning it on. A variable B+ supply can easily be made using a surplus power transformer, rectifer, filter cap and a variac, which every bench should have. It should be fused. After assuring normal operation, have a listen, then upgrade components as desired.
Click to expand...

dave
 
#35
old eqt.

Thanks a bunch, Planet10!

I am still deciphering those instructions but will implement ASAP!

As I am still very green to this field and board, I can't help but wonder if this organization or an individual has thought about compiling and indexing all of the great information (instructions) provided on this site for future (easy) reference.

Just a thought,

Rick
 
#36
Fragman56,

As you can see from the botom of my page, I make amps. I also collect and restore antique radios. The short of it... I would like to purchase some of those tubes you already listed. In particular:

1L6
EL84
12AX7

I will pay what you ask within reason, like $8-$10 each for the EL84, but not over $15 for the 1L6. I do know what they are worth, but not willing to pay what some overprice them at.

email me at gabevee@yahoo.com

Thanks!
Gabe
 
#38
fragman -

I know several companies will buy NOS tubes. I sold Richardson Electronics 35 6LF6's about a decade ago for a good price, for instance. You can make up a list of tubes you are interested in selling and distribute them to many companies that advertise NOS tubes for sale.

As far as the tubes that are currently most popular for audio e.g. 12ax7, etc. you may want to hang on to those and sort them by manufacturer and certain construction details. Some of them may command premium prices on Ebay, for instance.
 
#40
still got the tubes

I have thought about selling the whole lot and even got a quote but just haven't.

I will probably just hang on to them all. Currently pulling all the tubes out of some old, found o-scopes. Those have lots of tubes inside!

Rick
 
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