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Author Topic: Hohner 1250 Question  (Read 173 times)

lovatomi

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Hohner 1250 Question
« on: February 15, 2021, 02:45:05 PM »
Hello All, first post here, but I have been lurking for a while. Was able to sort out a Lab Series L5 with some good information I found on this forum. I know my way around tube amps pretty well, but am still a bit of a novice at solid state stuff. I was recently trying to sort an old hohner 1250 I ended up with. It seems like it's supposed to have a clean and dirty mode which is actuated by a pull switch on the preamp volume pot. When i got the amp it seemed to be in dirty mode permanently with the pull switch doing nothing. I believe the circuitry for this boost is all on a little circuit board attached to the volume pot. I found a schematic for a 1040 and I believe that is what my 1250 should look like as well. I attached that schematic. The little board attached to the pot is outlined in red. The weird thing is that my amp had all the same parts as the 1040 in the red outline, but they were wired up completely differently. My question is, does this schematic make sense? Is that bundle of 4 diodes coming off T101 supposed to go that direction? it was reversed in real life, which makes a little more sense to me. Either the original wiring was wrong, or this schematic is wrong. Or it could be a little of both. Thoughts on the schematic? Should that work? When i wired mine to match the schematic it was pretty quiet and had no switching capability. Thanks!

image_21488
« Last Edit: February 23, 2021, 08:37:56 AM by lovatomi »

lovatomi

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Re: Hohner 1250 Question
« Reply #1 on: February 23, 2021, 08:47:38 AM »
Apologies. I think perhaps the schematic hadn't been visible. Should be fixed now

Jazz P Bass

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Re: Hohner 1250 Question
« Reply #2 on: February 23, 2021, 11:34:51 AM »
It appears to me that the diode string is what makes it a distortion circuit.
With the string removed you should have a clean signal.
If you do not, then you have other issues that need to be addressed first.

lovatomi

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Re: Hohner 1250 Question
« Reply #3 on: February 23, 2021, 12:40:57 PM »
Thanks Jazz, other issues are entirely possible. Pardon my ignorance, transistors are quite new to me, but how does the diode bundle work to make the signal distorted?

mandu

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Re: Hohner 1250 Question
« Reply #4 on: February 23, 2021, 01:26:45 PM »
Sorry wrong post
« Last Edit: February 23, 2021, 01:31:53 PM by mandu »