Starting to populate the chassis....

[GAStan]

Hi BrianL,

I have built a #124 using Erwin's chassis and boards, and #183 with Taylor's chassis and boards. Both chassis and board sets are great quality and are solid foundations for these amps. Either chassis/boards set can be used to build either amp. Both of the amps work well. Both are documented here on TAG.

The #124 originally was configured as you are talking about with a non-switchable FET. I later converted it to a foot switchable FET and want to second what Franco just stated. I like having it switchable with the adjustment on the front panel, it makes for another easily adjusted layer of tone control. If it is lack of a relay board that is holding you up PM me and I'll send you one, I ordered extras with my chassis.

I have not built one using the layout you posted so cannot say if it will work. From a quick look at it I don't see anything obviously wrong. One would need to compare it wire by wire, component by component, to a proven schematic or layout to determine if it will produce a working amp. Or take a chance and build an amp to prove or disprove it. Where did it come from?

[martin manning]

That layout is posted somewhere on the site. It was drawn by J Borders, who had the original ODS PCB set made ~10 years ago. Note that the switchable FET boost is not wired correctly, since the 1M resistor on the input jack is paralleled with the 3M3 on the FET board when the boost is switched in.

[dbharris]

Hi Brian,

Glad to see you are back. I agree with everyone's comments so far. I just wanted to chime and hopefully not tell you something you already realize, but the layout you posted is not the same circuit as ODS #124. You posted what we call a 2nd Gen Hybrid, because the preamp is largely the same as the 2nd Gen layout while the power section uses the much later Precision Power Supply (as seen in #183 and bluesmaster layouts).

#124 was originally built as a low plate classic, meaning the "classic" tonestack, "traditional OD entrance," and 100K plate resistors. It was later updated to have a "skyline" tonestack.

The 2nd Gen amps also have low plates, but some version of a "pre-classic" tonestack and the "funky OD entrance."

The good news is that pretty much all of these amp variations can be built into any chassis. Best thing to do is choose a layout based on the sound you like most from artists who have recorded with a similar circuit.

I don't think you can go wrong with any variation. I would pick one, build it to the exact layout specs, play it for a couple of weeks and then start tweaking to enhance things you like or rework things you don't like so much. Good luck!

-Dan

[BrianL]

Thank you all for your optimistic opinions. I'm going to give it a try but with the unswitched FET as I already have a two-button footswitch to use and the board is already wired into the chassis.....I know, I know, a couple seconds with the iron and it's not connected anymore........I'll keep it in mind though, I can always change it.
To the Batmobile Robin, quick to the electronics store.......
Thnx, BrianL

[BrianL]

Looking at the footswitchable FET.....
Using this with a footswitch, wouldn't this be like having two on-off switches?
Push/Pull Pot on Faceplate and the footswitch

[erwin_ve]

Looking at the footswitchable FET.....
Using this with a footswitch, wouldn't this be like having two on-off switches?
Push/Pull Pot on Faceplate and the footswitch

Just like the OD and PAB, both switchable by backplate toggle or by Fsw.

[BrianL]

Ok,Thnx. Reason I've asked is because I'm going to use Martin's board and wiring because I've already got them made up. Going to replace this one with Martin's and I just
needed to know how the switches worked, if they were independent of each other or if both needed to be on for the FET to work
Thanks, BrianL

[Raoul Duke]

Glad you’re back at it Brian!
Martin’s compilation of the different layouts and parts haven’t failed me yet; and I’m positive that you will reach your goal in no time. The sense of accomplishment as well as the satisfaction of hearing the amp you made will be worth it in the end! It’ll be great

[jazzbass]

That layout is posted somewhere on the site. It was drawn by J Borders, who had the original ODS PCB set made ~10 years ago. Note that the switchable FET boost is not wired correctly, since the 1M resistor on the input jack is paralleled with the 3M3 on the FET board when the boost is switched in.

Board?


Hi Martin, What is the right scheme you suggest to fix the FET Board error?

Grazie

Franco

[erwin_ve]

Ok,Thnx. Reason I've asked is because I'm going to use Martin's board and wiring because I've already got them made up. Going to replace this one with Martin's and I just
needed to know how the switches worked, if they were independent of each other or if both needed to be on for the FET to work
Thanks, BrianL

Fwiw there are 2 errors in the layout; the 2 wires coming from the PAB board to the middle lugs of the rock/jazz switch must be reversed and lug 3 on the bass pot must be connected to the buss bar with a 10k resistor
And I would suggest to replace the 2 caps on the bass pot to 1 cap, a 0.002 on the outer lugs of the pot. This make your tonestack a bit more responsive.

Erwin

[martin manning]

What is the right scheme you suggest to fix the FET Board error?

Follow the foot switched FET relay layout posted in the files section (copied above), where the 1M input resistor is relocated to the FET relay board.

[BrianL]

Thanks Erwin for pointing out errors and changes to make. I appreciate that.
Here are a couple pics, can't see much but shows what it looks like in person.
I just used a 10K pot, not a push pull as I will only use it on the footswitch.
Yes it's dirty in there, I have to vacuum it out b4 powering it up.
All the loctite I put on the screws and nuts is peeling off, just looks sloppy.
Can just barely see the repositioned 1M resistor that Martin is talking about in pic one, it's under the relay
on the board by the FET board. Slid the FET board down the side towards the back and added the relay board
where the FET board was. Took the trimmer off the FET board and the 10K pot on the faceplate is used instead.
Second pic shows the input jack and 10K pot mounted.
Thanks for looking, BrianL

[BrianL]

Got my third relay board today, should finish this section of the build tonite.
Shout out to "GAStan for sending me the board I needed and parts that go with it.
"Yay, GAStan" thank you
Looking at this layout, there's not so many added caps and resistors like the #124 layout,
I suppose they could/should be added later or needed later to adjust or customize your sound.

All of the front panel pots arn't grounded to the buss bar, should they be? I know they are grounded
through the mounting but why the xtra wire on the buss.

Thanks, BrianL.

[BrianL]

Better pic of the 1meg resistor that gets moved to the FET relay board

[BrianL]

So, dumb decision on my part. I do need to have the "FET" board switchable so I can use it if the footswitch is unavailable.
I do have an extra toggle switch I can squeeze on the back panel by the ODS and PAB switch, add the lettering and good to go.
While comparing wiring diagrams between the Dumble #124 and Jason Borders layout I noticed the wires on the "Presence" pot are switched. Should I switch them correctly or wont it make a differece?
Thanks, BrianL.