A Collection of #124 Information (Schematics, Layout, etc.)

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Joost
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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by Joost »

Great forum! Incredible resources. I downloaded three layout files for the 124 in this thread.

Dumble Overdrive special Complete Layout 52010
Dumble Overdrive special Complete Layout3
Dumble Overdrive special Complete Layout revised

Which is correct?

Also, is there no Bill of Materials anywhere for 124?

Final question. Is there information on the actual values of the caps, pots and resistors as opposed to their nominal value? a few percent's difference on each part due to tolerance can make a big difference in the end.
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Structo
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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by Structo »

#124 was built in 1984 then updated by Dumble in 1988.

So there are differences between the two.

The 1988 has Mid boost instead of Deep, has Skyline tone stack, etc.

This layout here is supposedly the 1984 layout.
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Tom

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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by Joost »

Structo wrote:#124 was built in 1984 then updated by Dumble in 1988.

So there are differences between the two.

The 1988 has Mid boost instead of Deep, has Skyline tone stack, etc.

This layout here is supposedly the 1984 layout.
Great thanks! And which is the 1988 update? Looking for the skyline tone stack
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Structo
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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by Structo »

The Skyline stack is the one shown on the latest #124 layout, with the 250K mid pot and the .01 mid cap.
Tom

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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by Joost »

Ok, I'm working on a 124 BOM and I think I've found an error/inconsistency between the layout and the schematic.

The grid resistor attached to pin 7 on V1 is 33k in the schematic and 22k in the layouts.... or am I missing something obvious
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Structo
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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by Structo »

From the pictures of #124 it shows a 33K grid stopper but the layout has a 22K.
In reality I don't think anybody could tell the difference between the two.

The larger will attenuate more highs and allow less signal in theory but as I said, if you can tell the difference between the two you have far better ears.

I would say the majority of people here use the 22K if that helps.
Tom

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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by Joost »

Still chipping away at the 124 BOM. There are quite a few differences with other BOMs. Now i am stumped. On those other BOMs they say the 4,7uF caps on the fet board (FET output coupler and FET 'cathode' bypass caps) are electrolytic. When I look at the layout and this pic of the actual 124, I am very sure they are the blue caps and those aren't Elcos. What are they? Ceramic?


Image

BTW, those other BOMs also claim the 100pf FET input coupler is Mica 100pF, when this picture and the layout clearly shows a ceramic disk and the schematic claims a ceramic temperature coefficient X5F
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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by jborders5 »

Joost wrote:Still chipping away at the 124 BOM. There are quite a few differences with other BOMs. Now i am stumped. On those other BOMs they say the 4,7uF caps on the fet board (FET output coupler and FET 'cathode' bypass caps) are electrolytic. When I look at the layout and this pic of the actual 124, I am very sure they are the blue caps and those aren't Elcos. What are they? Ceramic?
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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by Joost »

great thanks! I assume 10v is enough?
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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by talbany »

From the pictures of #124 it shows a 33K grid stopper but the layout has a 22K.
Tom
Are you 100% sure of that..I know sometimes it's hard to decipher red from orange on those resistors since the resistor coating is yellow which makes the red look more orange to me!.. FWIW I have yet to see a 33k in any later ODS classic/skyline amp..

joost
Although a BOM for 124 would be of some use I am sure ..Most of the parts used in this build things like Sprague Filter caps,Tepco bypass CTS pots Sprague Q-line resistors/precision MF Bypass resistors, seasoned Fender power and output transformers to name a few are all HUGE tone generators in 124 and these are next to impossible to find even as NOS..
Good Luck and looking forward to the BOM..

Tony

Tony
" The psychics on my bench is the same as Dumble'"
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Structo
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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by Structo »

Well I suppose the photo could make the colors look different but, to me it looks like orange, orange, orange with the red 2% band.

I also noticed the schematic shows 33K as well.

It probably doesn't amount to much either way because I doubt if most people could hear the difference.

There are only two photos I have found that show that resistor.

Image

Image
Tom

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talbany
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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by talbany »

Tom
I agree it's hard to tell and doubt you would notice as well.. still curious to know for sure what it is.

All The Best!!

T
" The psychics on my bench is the same as Dumble'"
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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by Joost »

Several people posted on this thread asking for a 124 BOM. Here it is. Every part is accounted for, and I've added descriptions of its function. You'll also find parts numbers and in many cases a link to the part in a store.
This should provide a solid base. There are also versions on the Ampgarage I did with the parts for a built-in Dumbleator, but to keep things clean, this version is just for the 124 build. BTW, it calls for a 12V transformer for the relays, but in the original 124 HAD used a 6.3V, hence the voltage doubler in the schematic
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musicmaddness2011
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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by musicmaddness2011 »

Thanks Joost!!
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Re: A Collection of #124 Information (Schematics, Layout, etc.)

Post by Joost »

I have two questions:
1) on the layout I don't see the shield of the coax from input connected anywhere. On the schematic it is connected. Do I connect it or not? If so, how do I do that without shorting anything

2) aren't connections 1 and 5 on the footswitch connector reversed? doesn't matter, but the orange cable is 5 on one end and and 1 on the other end
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