It is not a reverb board, it is an echo board.
I would place it after the Uno preamp circuit, you can also try it om the wiper of the treble pot as this is a common place for a volume pot. Just experiment.
I don't think it would work very well as a reverb, but I would be curious if you could mount 3 of them in parallel and set slightly different times, what it would sound like.
Like Joecool85 said, a Belton Brick is 3 PT2399 units running together set at different time intervals.
You should also look up The "Valve Wizard Equinox 2" project, just google it.

Please let know how it works

Sound like your back is the opposite to mine, my vertebrae between my shoulder blades have fused together to one solid lump of bone, and it tries to do that all over the place.
Soft connective tissue like ligaments and tendons start turning into bone, if my hole spine fuses and I fall it will snap.
To be honest I hate taking oxy, but I use it practically every day when I go to bed.
I never get a buzz from the oxy, not even when they fed me 32 tablets in 20 hours in hospital. If it is really needed for pain it does not give you a high, or maybe the pain was just so bad I didn't notice.

I have nearly finished the PCB now, just tidying up, then I will post it here for others to use if they want to.
I will make a different one later a lot smaller, with the sockets off the PCB, and maybe add an effects loop and reverb on the PCB.

But before I make this one smaller I will make one up for the Marshall 12 watt reverb
with an effects loop, I will combine all the 12 watt circuits I can find and add them all on one PCB, then just add the components you need for the one you want to build.
I will also make the power amp a mix of the 12 watt and the 30 watt one, again just use the right components for what you want.

Jimiphoton, you wouldn't have the measurements for the 12 watt amp would you ?
I would be after the spacing of the pots and pots to jacks.

Chers
Michael

It sounds like you need to convince someone to make a Paramix with a reverb circuit built into it, that might be a nice board that can be added to any amp.
I find measuring inches with a metric ruler hard too, always never on the line.
I find a small plastic ruler best that you can see through when I measure PCB's.

I found a nice Inches to mm guide online I downloaded.

Thank you so much for that phatt.
Its joining the build list, might even get nudged towards the top of the list.
:dbtu:

Looking at the circuit again, I would definitely go for the Log pot first, that would give you more control over the volume at lower level.
Another option is to put a resistor in series with the pot, but then you cant turn it up to full any more.
I presume it is a 24mm Alpha Taiwan potentiometer you have in there (RV24AF-22 model) since it is a Marshall.

The very last option if it were my amp, I would get a 16mm pot (log A4k7) with a push pull switch on it, and wire that in.
Wire it so if you pull the switch out you put a resistor in series with the pot, when pushed in it is like it is now.
Being 16mm you would have to run short wires to the PCB as the pot won't reach the PCB.
If the pot is too close just turn it sideways so the terminals point sideways.
I don't know if the capacitor C31 will be in the way for this.

If you have a copy of where you drilled the holes on the chassis I would love to see it, that would confirm the PCB measurements.
If you can measure the PCB from the left side (Input side) to the center of the sockets and center of the pots (pin 2 wiper),
that would make it easier for me to understand.
Sometimes I don't think too clearly, I'm only 61 but have constant chronic pain and have trouble sleeping.
Shitty bone disease as well as arthritis everywhere, at least my doctor gives me drugs I only dreamed of when I was younger.

I get my PCB's from JLCPCB, I just checked and 5 PCB's for this amp would cost me $18 plus shipping ($ 13 to $27 to Australia)
5 PCB's to the US would be $18US for the 5 PCB's and shipping $24US  DHL, $23US FedEx, $11 Airmail.
I think that is fairly good for 5 large PCB's (JLCPCB only do 5 PCB's minimum)

I am a bit wary as well on any stress put on solder points, like pushing plugs in /out.
If I use a jack on a PCB it will always be a stereo switching jack socket with 6 pins for the most strength.
I made up draft 5 of the schematic, we will se how we go this time.
pinkjimiphoton, I am not sure what you meant with the measurements on the Jack Sockets.
I think you left a message on the DIYstompboxes forum that the measurements were to a pin and not the center of the socket.
I am posting a picture with measurements, If you could write on the picture and return it I can get that fixed up as well.
I have the PCB nearly finished apart from moving the Jack Sockets to the final place.
The strange footprint for the Tantalum caps is one I made up when I did the Sunn Beta board for myself.
Its so I could use Electrolytics, Tantalum, WIMA Box caps where the 2uF electrolytics were on the original PCB.

One more thing, the hole for the spacer between the heatsinks, do we want that in the same location as the original ?
I would need the measurements for that as well.
The only tracks on the top of the PCB are on the TO-3 transistor, the original did not have any, they relied on the power going through the screws.
There are also tracks on the fuse holders on the top, but they can be on the bottom, it's just the way I made the footprints.
You can make it a one sided board if someone wants to etch one, just leave out the tracks between the screws on the TO-3's like Marshall did.

Draft 4 and maybe final if ok with everyone.
I do have a few questions for pinkjimiphoton:
Are you happy with the numbering on the 2200uF Electrolytics ?
You had them as C23, C24, but to me it looked like C22, C23. (Not very clear though)
I marked the transformer as 14v = 14v secondary, close enough ?
I used the same Transformer number as the other 5010 schematic
Do you know what the Jack sockets are ? Cliff, Neutrik (I want the right footprint for the PCB)
Can't think of anything else right now.

I messed around with the PCB just for fun with your measurements.
This is what i came up with so far, but will change for what we want.
This is just mucking around a bit.
Are you after a very close copy of the original, or a better suited one for making a new layout ?
I could make the board 215mm (8-1/2") wide instead of 324mm (12-3/4") wide, just wide enough for the pots to fit.
Jacks would be connected with wires, It would make the PCB cheaper to buy, and still work as a replacement.
On the mock-up I added fuses for the transformer secondary wires, I prefer that.
I made a quick footprint for the pots so you can use Alpha 16mm or 24mm ones, just 2 extra holes is all.

I stand corrected on the trace at C1 and R4, I could not make that out on the pictures I was looking at.
I don't have much experience with audio circuits as I always worked in heave industry as an electrician.
I could repair 50kW DC drives for DC motors no problem, but never worked with audio circuits.

Anyway, here is Marshall 5010 PCB78-2 Draft 3 Schematic, please ignore the stereo input jacks.
I put stereo input jacks so I could start on the PCB in KiCad, I like the added strength of 50% more solder points.

pinkjimiphoton, If I was to make up a PCB in KiCad, what changes would you like to see ?
Is there a better or modern Darlington that you would prefer ? TIP142 / TIP147 ??
I prefer a TO220, TO247 or similar at the end of the board, I could put a heatsink there or run wires to TO-3's
I always use stereo sockets for all jack sockets on PCB's, I like all the soldering points for mechanical strength.
I use Alpha 16mm pots on my projects, but it would put the alignment out with the Jack sockets (Height).
I might make up a footprint for 16mm and 24mm Alpha pots together, use what you like.
I like to use Moles KK254 and KK396 sockets for wiring off the PCB, but I usually solder the wires in anyway (No Sockets)

Here is an example of a board I'm working on, 12W / 12W reverb / 12W Mk1 / 12watt to 30watt amp (5010 poweramp)

I can not see anything wrong around C1, C2, R4, but the photo is not very clear to me.
Perhaps we could get another photo around that area that is a bit closer / clearer ?

I don't understand why Rob thinks it is wrong when he has not traced the tracks himself.
Comparing this circuit to another version of the amp is not possible when they are different.

I did find he inputs wired wrong, also R18 was connected wrong, the MIDDLE pot was reversed.
I have updated the faults and have now got Draft 2 ready.
I did enlarge and sharpen the image around C1, C2 R4 but I just cant make it out perfectly.
I really need a better photo of the tracks around C1, C2, R4, to make sure I got it right

I found a couple of mistakes on the picture of the trackside I had marked components on.
I fixed the picture and put the good one up.
I cant see the part numbers for the main capacitors, the 2200uF ones.
I had to rename R22, I had it as R32.
I have a draft of the circuit made up in KiCad, still a bit messy but I think it is correct.
Please let me know if you see any mistakes.

Could you tell me what the measurements are between the Jacks, and between pots.
I could make up a PCB in KiCad if I know the component spacing on the front panel.
The Gain pot on the schematic should be Preamp Volume, I will fix it later.

I might give you a hand with this one, its late down here now so it will have to be another day.
well,  later today maybe as it's 2.30am here now.
I did find another photo of the track side of a 78-2 PCB so I mirrored it and marked out the components quickly.
On the picture the inputs are on the left.

My fault, I should have looked at the schematic closer.
You want to reduce the signal between the pre-amp to the power amp.
It looks like the place to insert the patch lead is between jS4 on the pre-amp schematic and JS1 on the amplifier schematic.
I think that means the Master Post socket is the pre-amp out. I think Marshall did not install JS1 on the power amp circuit on the back panel.
If you really wanted to you could remove the shielded wire on the power amp PCB and put the resistors there.
Or you could install JS1 on the power amp schematic on the back yourself, but it means drilling a hole.
If you did drill a hole, a switch would be simpler to add / remove the resistors.
A power amp in jack would make it simple.
If you can provide a photo of the bottom of the PCB the rear jacks are on we could check to make sure, just have to look at the tracks.