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wolf1419 · 10-09-2008, 11:14 AM

Isolate is probably too general. I should say "rule out" certain parts of the circuit(by audio test) so that I can work my way toward isolating any issues that may exist, which may be more than 1, from what I've found so far.

Is there any difference between TL072S, which this amp calls
for, and TL072, which I also found in another amp/schematic of mine.....VS100, VS265R, if I remember correctly
The actual IC's on the 8100's board are JRC 072BD......what gives on all this....?
I can only find TL072ACP IC Dual J-FET Op-Amp 8 Pin DIP
from a supplier, without having to order by the hundreds.....
are they equivalent replacements for one an other..any issues using one or another, or is it just MFG, #'s...072 being the key?

Some of my other confusion is in the fact that voltage is the "potential push available" and current is the actual flow/quantity of electrons passing a given point at a defined time(Amps). Ohm's law defines the relationship of these 2 factors relative to resistance, but I can't picture it at work in these amplifiers and schematic circuitry yet, despite continued research, but I'll keep plugging at it.

You may be able to "jog my mind" into the proper way to comprehend this. I've read stats and descriptions for all the components you mentioned, but the "big picture", making the relationships of the components is not coming through. How do the terms "signal flow" itself, differ and relate to Voltage, Current, and Resistance, from the output of the guitar through the preamp & power amp to the output to the speakers. Please try to paint me an image that will make this all start to click, even if just in a very general way, and then I may do better with my actual curcuitry and components research, and make the connection to how these components relate to the changes required to alter and amplify sounds through an amplifier. I apologize for mosty writing and less hands on, but a lot of this is done from my bed, and needs to work in my head, which is the most difficult part - acquiring the practical knowledge!

10-09-2008, 11:14 AM	#100 (permalink)
wolf1419 Senior Member Join Date: May 2008 Location: Taunton, Ma. Posts: 101	Re: Marshall 8100 valvestate blows fuses!!! Isolate is probably too general. I should say "rule out" certain parts of the circuit(by audio test) so that I can work my way toward isolating any issues that may exist, which may be more than 1, from what I've found so far. Is there any difference between TL072S, which this amp calls for, and TL072, which I also found in another amp/schematic of mine.....VS100, VS265R, if I remember correctly The actual IC's on the 8100's board are JRC 072BD......what gives on all this....? I can only find TL072ACP IC Dual J-FET Op-Amp 8 Pin DIP from a supplier, without having to order by the hundreds..... are they equivalent replacements for one an other..any issues using one or another, or is it just MFG, #'s...072 being the key? Some of my other confusion is in the fact that voltage is the "potential push available" and current is the actual flow/quantity of electrons passing a given point at a defined time(Amps). Ohm's law defines the relationship of these 2 factors relative to resistance, but I can't picture it at work in these amplifiers and schematic circuitry yet, despite continued research, but I'll keep plugging at it. You may be able to "jog my mind" into the proper way to comprehend this. I've read stats and descriptions for all the components you mentioned, but the "big picture", making the relationships of the components is not coming through. How do the terms "signal flow" itself, differ and relate to Voltage, Current, and Resistance, from the output of the guitar through the preamp & power amp to the output to the speakers. Please try to paint me an image that will make this all start to click, even if just in a very general way, and then I may do better with my actual curcuitry and components research, and make the connection to how these components relate to the changes required to alter and amplify sounds through an amplifier. I apologize for mosty writing and less hands on, but a lot of this is done from my bed, and needs to work in my head, which is the most difficult part - acquiring the practical knowledge! Last edited by wolf1419; 10-09-2008 at 01:43 PM.