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

[TimDude]

You’re a scholar and a gentleman. Thanks!

[Matt J]

#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.

I know this is an older thread, but I'm curious if anyone who has built #124 with the original 1984 Classic tone stack configuration shown here could chime in with what they thought about it. Especially if they have built the later Skyliner version and can compare the two.
I ask because I'm working on a #102 high plate Skyliner right now and am considering building #124 alongside it in the low plate Classic configuration to have more variety.
Thanks!
Matt J.

[lgehrig4]

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

Small note for anyone using this BOM. The Mid Boost switch (line 134) should actually be an on-on type so it will not be the same switch as the Rock-Jazz.

Screenshot 2025-04-10 at 10.46.38 AM.png

[jazzbass]

Hi everyone, sorry to bother you sometimes.

I'd like to ask for clarification or suggestions. I'm building a #124 Low Plate Classic following the Manning & Albany 1984 layout, and I've noticed some discrepancies with the wiring diagram I found on TAG. I don't know the author, but the label says: #124 Original 1984 version (rel.) 1.7.
I thought that in the wiring diagram, the switch and relay diagram showed the center contact with the toggle switch. For example, the midrange switch has 270kΩ resistors attached to the two center contacts. If I follow the layout, however, the 270kΩ resistors are connected to the bottom terminals of the switch (deep switch/mid switch). Who's right?

Thanks and hugs.
Franco

[martin manning]

The layout drawing reflects the 1986 update to Skyliner preamp, which replaces the Deep function with PAB. The 1984 schematic is an educated guess at how it was originally built. Which version are you building?

[jazzbass]

Good morning Martin,

Thanks for your reply. I'm (attempting) to build the 1984 Low Plate #124 original 1984 (rel.) 1.7 version of the schematic and was comparing it with your layout of the 1984 "OVERDRIVE SPECIAL #0124" version in its original form, A Low Plate Classic MFG 1984.

Thanks

Franco

[martin manning]

Ok, got it.

For example, the midrange switch has 270kΩ resistors attached to the two center contacts. If I follow the layout, however, the 270kΩ resistors are connected to the bottom terminals of the switch (deep switch/mid switch). Who's right?

Both are right. Electrically the same either way.

[jazzbass]

Dear Martin,

Thank you. I'll definitely bother you again before I finish this build.

Hugs.
Franco

[Richard1001]

Although i guess no one knows how the trimpot was modified from 500k to 345,5k i wanted to try and replicate it.

My thought was that there is a 1M resistor across the trimpot and since these pots have quite some tolerance a 528k pot and 1M resistor would make 345,5k.

I first tried it with a normal resistor parallel to a 500k pot. With the 1M resistor the voltage drop over the 220k resistor feeding it is higher, so there is less signal voltage across the trimpot. With the 1m resistor installed over the trimpot, the trimpot is actually is set to 108k to measure 100k. Set like this the signal voltage to the grid of v2a is 12,5% (1/8) of the voltage feeding the 220k resistor. (Output of v1b)

Next i installed a smd resistor inside of the trimpot using a normal soldering iron. This works well using a little flux. Inside, the legs of the pot are folded over the carbon track and can be soldered on.

Ofcourse i don't know if this method is how the trimpot was modified, but it works.

I took some pictures for those interested.

IMG_20260311_181324~2.jpg

IMG_20260311_191739.jpg

[The Quadratus]

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

Just signed up to this forum.
Thank you, for this. Had no idea where to search to find something like this.
To the Mods, maybe it would be useful to all here if there was a thread where all the BOMs on this website are found?
Just a thought.

[nuke]

I've seen this done a couple of ways.

One easy way is to put a dab of conductive silver paint (or copper, nickel since silver has gotten so expensive) on one end, (or both ends) of the carbon track to lower the resistance. It won't hold up to repeated running the wiper over the paint and the rotation gets shortened. It is up to you which end to paint.

To increase resistance, the carbon track can be thinned by sanding the edges.