free downloads of old tube technology books.

[dragonworks]

Technical books online

if this helps anyone

[redelephant]

Yeah! Fantastic resource. Another one is TDSL Tube search for all the tube data you'd ever need.

[ThermionicScott]

Peter Millett is the man. I've learned so much from the scans on his site.

- Scott

[dragonworks]

I have been trying to learn tube amp repair forever. I have a scope, signal generator, meters etc. Plenty of non working amps to fool with etc. I cannot find anyone who knows how to give me hands on instruction, I am willing to pay. I have tons of books, none of them really good for the subject. I just bought two of Jack Webers books at twenty five each, kind of a waste of money, but some valuable information. Once in awhile I fix something but it is more by luck than anything else. It seems I will electrocute myself before I really get anywheres. There was a course for amp repair being offered for 1800.00 for three months but it was in NYC and I live about 2 hours north and have to work so that was out. I will just keep plugging away until I either get electrocuted or I learn something. I know how power supplies work, preamps, amps etc. I understand the basic math and how the individual components work. Yet, when I open an amp, I just can't seem to make heads or tails out of all the jumbled wires etc. It looks so neat on the schematics, easy to follow, etc, and then it is welcome to the jungle.

[JoeM]

The first book I had on fixing amps was Jack Darr's. Do you have a copy?

Some chapters from Jack Darr's classic book

[dragonworks]

yes I do, one of the originals and the best one I have.

[redelephant]

Dragonworks, what is your level of knowledge in electronics? Do you fully understand Kirschoff's current law and such basics? What do you know about transducers, small signal amplification, noise sources, ground loops, power dissipation, the difference between a source and load, temperature resistance in materials, heat radiation, dialectric properties of insulation, acoustics, etc...

You must have a basic understanding then reading books found on Pete Millet's site will give you all the understanding you'll need.

[dragonworks]

I have read books for years and took basic electronic courses in college. I am not looking to design amplifiers, just work on them. Mechanics are technicians that work on cars, they don't have to understand the physics behind them. I just need a bit of hands on help, someone to ask specific questions to etc, and I think I could learn quickly. I can play a mean guitar, but none of that came from a book. I am a very good machinist and none of that came from a book. I think you might know what I am trying to say here. You do machining long enough and when a problem arises you recognize it immediately. You work on cars all your life and a problem arises you usually can pin it down fairly quickly. All of this came from working with it hands on and working with people who were doing the same thing. There is no one in this area that I can go to for answers, to show me the ins and outs of using the scope, the other instruments, relating the schematics to the actual hardware. I can find the power supply, the preamp stage, the output stages, I know how they work together etc, but when it comes to diagnosing I have no exp. and the same for testing. It can be a scary thing poking around high voltages not really sure of what your'e doing.

[redelephant]

So you are probably one who can get all the help you need here, and probably one who can help me from tmie to time as well as others. It's what this forum is for aint it?
You should be able to do a circuit analysis with what you know already. Draw up the schem if u aint got none, find out where all the quiescent currents go, estimate all plate voltages, cathode voltages, calculate max idle current for the output tubes so you know what the max bias should be, etc. Write all that down on the schematic and have all those values in sight when you fire up the amp. Then measure all nodes on the amp and find out if any values are way off...that's basic analysis of an amp.
If the amp has a gripe, then make a note on the schem what to expect and look for it when it's fired up. Go from there and find the fault...
If servicing an older amp, check electrolytic capacitors, perhaps R&R them even if they seem good, check pots for noisy wipers, perhaps spray some 'fader lube' on them, etc, etc.
I'd be glad to help, the only way I'll ever learn myself, and I am sure most others here feel the same, so no need for a personal mentor, unless you really want one.

[Prairie Dawg]

@dragonworks, problem solving in a technical field obeys certain universal themes. For lack of a better word I've sometimes referred to it as a process of economical thinking. It translates directly to amps-at least relatively simple ones. My background was in aircraft turbine engines. Documentation is very important but not strictly necessary.

My old crew chief used to say "think system! think system!" and what he was saying was this.

Reduce your universe to a manageable size by eliminating extraneous stuff. If you've got an oil pressure problem, no need to worry about the fuel control or the prop governor-unless you've got no oil pressure at all.

With a guitar amp it is worth noting that your problem lies in a relatively small piece of the universe-probably 10 x 24 inches large.

When you take a relatively simple amp like a tweed Deluxe, you can see what the systems are and what they do-understanding where a problem is located is half to 3/4 the battle right there.

It would really help if you had something simple like a Deluxe open on your workbench, hooked up to a load and live. Then, you can get in there and figure out how things work. You don't need a scope or an EE degree, just a reasonably good voltmeter, a soldering station, a strong light and some basic reference works to guide you.

[melvin]

You mean books by Gerald Weber? The first thing you should learn is how NOT to electrocute yourself, like how to drain caps and how to use your voltmeter. The GW books are good for simple mods and common problems. I'm sure he shocked himself a lot learning his trade, by the way. He was a salesman before he built amps. But the OLD tube amps are best to start with. I suggest building a kit of a tweed maybe. Once you get that working, start doing mods to it from GW books. Also, if you know how a power supply works (the simple fender supply) and how a triode voltage amp works, you are on your way. Just ignore the jungle and use the schem. Follow a wire to a node...

[Steve Conner]

With a guitar amp it is worth noting that your problem lies in a relatively small piece of the universe-probably 10 x 24 inches large.

True, but don't forget to include the person trying to repair it in your "universe", who is usually part of the problem as much as the solution. And a far more interesting and complex part than the actual amp itself.

For instance, the subsystems of a piece of electronic equipment, indeed the whole concept of "system", only exist inside the brain of someone with an engineering education. Vintage consumer electronics is hard to analyze from a systems perspective, because things that should be "subsystems" were mashed into each other to save money. The outstanding example for me is the old "reflex" tube radios that used the same tubes as both the RF and the AF amplifier simultaneously.

The original poster said that he couldn't see the link between the schematic on paper, and the wires inside the thing. The ability to identify subsystems surely builds on top of that, so he should work on that first. Start with the simplest piece of equipment in the junk pile that you have a schematic for, and try to get that working, being aware that the schematics for vintage gear aren't always correct. Or build a Champ kit or something.

[kg]

. Or build a Champ kit or something.

i think that's the best way to start to correlate schemos with physical builds.

[mozwell]

Dear All
There are a heap of books here Professional books : Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics
as well as here freestompboxes.org • Index page then click on FSB public library

enjoy

[dragonworks]

Thanx for the responses all,