Complete 124 Schematic

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LooseChange
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Re: Complete 124 Schematic

Post by LooseChange »

Interesting to me is the totally standard (Fender) plate and cathode resistor values. After looking at so many schematics of these amps and implementing the circuit this appears to be unusual. (?)
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Structo
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Re: Complete 124 Schematic

Post by Structo »

From what I remember a typical Fender bypass was 25uf/1K5 and 100K plate loads.
Don't see much of that in Dumbles unless I misunderstood your meaning. :wink:
Tom

Don't let that smoke out!
LooseChange
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Re: Complete 124 Schematic

Post by LooseChange »

Structo wrote:From what I remember a typical Fender bypass was 25uf/1K5 and 100K plate loads.
Don't see much of that in Dumbles unless I misunderstood your meaning. :wink:
Okay, darn close.. 5uf bypass cap cuts off a bit higher (~40hz) than the 25uf (~9hz) but most guitar speakers don't reach that low anyway.
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heisthl
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Re: Complete 124 Schematic

Post by heisthl »

Believe me you can hear a big difference increasing a value by 5uf makes in a bypass cap, even though on paper you shouldn't hear much of a difference. Pick a stage and try the 5,10 and 25uf's on clipleads
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Zippy
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Re: Double Boards

Post by Zippy »

sst4270 wrote:I was just perusing the photos of #124 today for the Nth time, and I'm curious...

What's the story with the double boards. In all the threads I've read (and I've spent hours and hours lurking in here and over on the other TW side) no one's ever mentioned the fact that most of the boards are double stacked. (Would it be out of character for Mr. Dumble to have components in between these boards? Along the vein of gooping up everything)

What's going on in between them? The boards weren't removed during the photo shoot (at least as far as the photo record shows), so how are "we" confident about the wiring underneath?

I've never seen anyone recreate the double stacked boards in any posts either...
Search on "backing boards"...

http://ampgarage.com/forum/viewtopic.ph ... king+board

http://ampgarage.com/forum/viewtopic.ph ... king+board
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ic-racer
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Re: Complete 124 Schematic

Post by ic-racer »

I was just checking this again to get the latest version with the send/return jack update and I noticed you had touched up the power light circuit. Though I think the lamp comes off between the resistor and the diode. Not that it makes any functional difference.
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ampdoc1
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Re: Complete 124 Schematic

Post by ampdoc1 »

Odourboy

Nice job on pulling all this together. I checked out the schematic I made of this amp back in 10/06 (attached) to see if I was close, and I don't see any major component differences (I may have mis-labled the bass pot value), but I didn't try to nail down all the details. Good to have more info and verification!

One thing,.. I don't know that I ever looked at the pics well enough to distinguish, but I see you have the channel relay normally closed for the "clean" channel. This may be correct, but most switching amps put the "OD" on the NC side of the relay, so that the relay is not operating when in a higher gain mode.

ampdoc
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odourboy
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Re: Complete 124 Schematic

Post by odourboy »

Thanks Ampdoc!

To the best of my knowledge, the schematic I did captures the way the 124 relays were wired. The intent of this thread was to document 124 as accurately and completely as possible - not to try to improve on HADs practices or make 'corrections'. There's a couple of other weird bits in the implementation as well. I think it's important to discuss these so people understand that if they were to build exactly to that schematic, there's going to be a few quirks. Your post adds to that understanding.

Cheers mate!
"Let's face it, the non HRMs are easier to play, there, I've said it." - Gil Ayan... AND HE"S IN GOOD COMPANY!

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