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Old 25th August 2013, 12:36 AM   #271
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Great thread.

I'm happy to delve into a tube amp but the SS stuff makes me apprehensive. Less so after just reading all 270 posts here.

I think it would be worth making this thread a sticky for SS newbies (and not so newbies)?

I consider the advice given freely and persistently from Enzo, Juan, & Nigel - & others - is pure gold.

Last edited by djgibson51; 25th August 2013 at 12:47 AM. Reason: Credit where due.
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Old 25th August 2013, 10:24 AM   #272
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Quote:
Originally Posted by djgibson51 View Post
I'm happy to delve into a tube amp but the SS stuff makes me apprehensive. Less so after just reading all 270 posts here.
Valve/tube amps are far simpler and cruder - so far easier to repair - the sort of gear you can mend with a hammer and a pair of pliers. Transistor gear is more a tweezers and magnifying glass job, with the ever present danger of a "row of dominoes".

But modern repair agents seem to have little or no clue about valve/tube amps, I get various ones for repair which have been round many shops and couldn't be mended, yet all have simple common faults (but I date back to the latter end of the valve/tube days - they were mentioned ONE DAY at college, and that was when the normal lecturer was off).
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Old 26th August 2013, 07:02 AM   #273
Enzo is offline Enzo  United States
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And the sad thing is, troubleshooting is troubleshooting. The technologies have specific details, but the approach is still the same: isolate the problem.

I agree with Nigel, tube are much cruder and simpler. Vacuum tubes was a mature technology 50 years ago, there is pretty much a way to make tube amplifiers and everyone did it that way. Detail are the main variations.

SOlid state amps, power amps anyway, are massively fed back on themselves. They are one big loop. That does require attention. And Nigel is right about the row of dominoes. All those transistors connected together, one can blow and take down a bunch more.

But still, when they blow fuses, we look for shorted outputs, then shorted rectifiers, maybe shorted caps... just like a tube amp problem. A signal path problem is still a matter of tracing a signal stage by stage. Voltages may be different but the rule is still the same: no circuit will work right if it doesn;t have good power supply.


As to the 270 posts, keep in mind that we are trying to fix this with the hands of someone else, someone who really doesn't know what he is doing. And we are doing it one voltage reading or one question at a time. That takes a long time and many posts. Something that takes a month to fix this way is probably fixed in under an hour in my shop if it is in front of me. SOmetimes the same point is made by multiple people, if for no other reason than to state the point in various ways so it becomes clearer. The posts add up.
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Old 26th August 2013, 07:36 AM   #274
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Quote:
Originally Posted by Enzo View Post
As to the 270 posts, keep in mind that we are trying to fix this with the hands of someone else, someone who really doesn't know what he is doing. And we are doing it one voltage reading or one question at a time. That takes a long time and many posts. Something that takes a month to fix this way is probably fixed in under an hour in my shop if it is in front of me. SOmetimes the same point is made by multiple people, if for no other reason than to state the point in various ways so it becomes clearer. The posts add up.
And that is why I found this thread such a great learning tool

Thanks everyone.
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Old 22nd July 2014, 05:21 PM   #275
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Default fender 212 / 2n 4003 transistor

I'm new and realize this is an old post.don't know if you ever solved the fender 212 transistor problem but, a little late with the info maybe but that is a mis-print on the schematic.absolutely 100% for sure.the number on the actual component Q6 and Q7 is 2N4403 which crosses to a ECG 159 PNP audio class preamp transistor
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Old 22nd July 2014, 05:41 PM   #276
Enzo is offline Enzo  United States
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And also Q16,17 would be 2N4401 and 2N4403.


But no need to cross to NTE, 2N440x transistors are common and cheap. Mouser sells them for 20 some cents each or about 15 cents if you buy 10.

I found NTE159 at Newark for $2 each, $1.49 at jameco, and as low as $1.09 elsewhere.
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