Found a closer schematic the Hohner 1040 with uses m18-325 outputs. Still no luck getting a clean sound out of it. Can't find the m18-325's either. Hate to give up on this one but have 40 customers in line and have to move on. Must be Germanium transistors. Anybody have any ideas?
Platefire
Platefire
As stated many times before, those are SILICON transistors, and humble 2N3055 should work very well there.
The 1040 schematic provides bias adjustment from 0V>~1V and on the schematic 0.7V bias is clearly written both for the upper and the lower transistor.
The fine tuning is implied in "25mV across emitter resistors".
It confirms Silicon, neither Germanium nor Darlingtons.
So if with fresh and properly biased 2N3055 or MJ1502x there, the amp still does not work, then I guess "there still are some other unresolved problems there".
As a starter, check collector, base and emitter voltages at earlier stages, referred to ground, and all B-E voltages too.
The schematic is chock full of voltages.
The 1040 schematic provides bias adjustment from 0V>~1V and on the schematic 0.7V bias is clearly written both for the upper and the lower transistor.
The fine tuning is implied in "25mV across emitter resistors".
It confirms Silicon, neither Germanium nor Darlingtons.
So if with fresh and properly biased 2N3055 or MJ1502x there, the amp still does not work, then I guess "there still are some other unresolved problems there".
As a starter, check collector, base and emitter voltages at earlier stages, referred to ground, and all B-E voltages too.
The schematic is chock full of voltages.
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The m18 numbers are most likely "house" numbers not actual part numbers. You stated previously that the bias adjust only went from .2-.6 volts. This tells me the resistors in the bias string are suspect. The 1040 schematic values equate to a bias range of 0-1volt with a minimum 14mA through the bias string. Some real measurements and parts values are needed from you before anyone can actually help more than just throwing guesses around.
You can not state such things just by ear, please post some scope waveform pictures.
As of Hohner models, most are basically the same, specially the power amp.
Armed with one schematic (any of the variations), compare it to the PCB and pencil differences, which are minor, then post the corrected schematic.
Parts numbers may differ, so correct those too.
Without that, we are trying to hit a very small piñata, blindfolded of course.
Hi platefire,
You have normal junction voltage drops. So at this point, assume you have not replaced or tested anything. Really, go blank. Approach this amplifier and make a list of the things you actually observe. No conclusions allowed, direct observation only. Don't replace anything until you have a set of observations you know to be true.
Nothing will make a good technician stuck better than a false assumption. This exercise will get you out of trouble if you follow it properly. I strongly suggest that if other normal TO-3 NPN silicon transistors don't work, but the originals do, then something has been overlooked or an assumption is incorrect.
-Chris
Edit: Is it possible those transistors have a built in flyback diode? You can check this by tacking in reverse biased diodes from the emitter to collector on both parts.
I'm sorry, but I don't. But look at this from a component standpoint. Those will not be special transistors, they come from a common transistor number that have been remarked for the manufacturer. These could be special in ways that would not make this difference. They can run special transistors that were picked for high Hfe, high breakdown voltage or other factors. Things that would not cause the 2N3055 to not function. They might act poorly at higher currents, but not to the extent you are describing. I think you are chasing the wrong problem.
You have normal junction voltage drops. So at this point, assume you have not replaced or tested anything. Really, go blank. Approach this amplifier and make a list of the things you actually observe. No conclusions allowed, direct observation only. Don't replace anything until you have a set of observations you know to be true.
Nothing will make a good technician stuck better than a false assumption. This exercise will get you out of trouble if you follow it properly. I strongly suggest that if other normal TO-3 NPN silicon transistors don't work, but the originals do, then something has been overlooked or an assumption is incorrect.
-Chris
Edit: Is it possible those transistors have a built in flyback diode? You can check this by tacking in reverse biased diodes from the emitter to collector on both parts.
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