If you didn’t touch the switch, nor the LED and you have sound in bypass mode the only thing I think of is that the 9V is not getting to the board.
Check the battery snap and if you have a multimeter check if the LED gets its 9V.
Make sure you have a guitar cable inserted into the input jack of the pedal when testing because that input switches the battery on/off when a jack is inserted/pulled.

It’s always best to take pictures of the stock unit and then do the repair according to that.
You are referring to a schematic. Which schematic and on what site?
If you’re using the schematics from Kitrae’s site, then that could be the cause for it not working. Some of his schematics are fundamentally wrong. IIRC especially the one for the Black Russian(s).
I have several Black Russian Big Muff Pi’s. I can take some pictures if you like. Maybe you can find some pictures of the wiring online as well.

• This reply was modified 2 years, 6 months ago by j_flanders.

Awesome! Great news and big achievement!

I have a question:

For every Deluxe Memory Man, Big Box, XO and now Nano I read:
– Up to 550ms of vibrant echo
– Maximum delay time of 550mS

In reality, what users report is a maximum delay time of around 400ms.
The way the clock is set up: 5.6k + 100k pot + 240pF timing cap results in a maximum clock frequency of 100µs (as stated in the factory schematics) which results in 409.6ms of maximum delay time.
No amount of reasonable component tolerances could get it anywhere near 550ms. The factory schematic lists 5% for the cap by the way.

So…my question: will the nano version actually do 550ms as stated, or, being the same circuit, do around 400ms just like all of its predecessors?

I’m fine with 400ms and love my Memory Men (Mans?), but do wonder where that ‘550ms’ comes from.

• This reply was modified 2 years, 7 months ago by j_flanders.

The slider switch is a power switch, it turns the battery on or off.
The foot switch turns the effect on or off. It bypasses the effect. But even when bypassed, the effect is still powered up ‘in the background’.

To avoid having to remove the battery every time you’re done playing there’s the on/off slider power switch.
When the footswitch is in bypass mode you should have sound whether the power switch is on or off.

On other battery-only pedals, like a Fuzz Face for example, the power switch is incorporated into the input jack. To preserve the battery when your done, you have to unplug your guitar cable from the pedal, thereby also disconnecting the battery.
I find a power switch more convenient than having to unplug the input jack from every battery-only pedal.

I have two of these LPB2 pedals. I installed a power jack so I don’t have to worry about the battery.

I have 4 of these. I think I have all revisions (A, B and C).

I have never had any hum (50/60Hz) problems with them. I’m not daisy chaining and using the original PSU.

Two of them had a very audible whining issue though. The whine frequency was 666Hz and its multiples: 1,33 kHz , 2 kHz, 2,66 kHz, 3,33 kHz, 4 kHz…
Although on a scope I could see whine in all of them, in the two non-problematic ones the whine was so low in volume that it was impossible to hear over the white noise.

As for the problematic ones:

In a rev A pedal all 5 electrolytic caps were bad. They read in the pF range instead of the µF range.
Judging from some oxidation around opamp U5 right above an E-cap I guess that one leaked while the others seemed to have dried up.
After replacing them the audible whine was gone.
Since these caps are all grounded you can measure them in circuit. They are smd though, so not very easy to replace.

In another one, I think rev C, I tracked down the audible whine with an audio probe and it originated right after the output buffer.
This could indicate an instability (oscillation) of the unity gain output buffer due to capacitive loading.
Depending on what pedal or amp came after it, the whine would disappear or be less audible.

Adding additional series resistance at the output removes the audible whining.
There’s already a 150 Ohm resistor at the output. It’s R35 in the rev B factory schematic which you can find on the internet.
Somewhere between 1k and 2k was enough to make the whine so low in volume that it became inaudible.
You can try some different (Boss) pedals after your Holy Grail. It needs to be a pedal which has some series resistance at its input.
Or you can unsolder the lead going from the pcb to the bypass switch in your Holy Grail and try some additional resistance there.
I used a 1k or 5k pot and dialed in additional resistance until I could no longer hear the whine.
Then measured the pot to see what resistance was needed.
You can read about other, slightly more involved solutions here:
https://www.analog.com/en/analog-dialogue/articles/techniques-to-avoid-instability-capacitive-loading.html

It looks like a modified original.

– modded for Boss style DC jack
– stompswitch was replacd I think, as the originals don’t have the white plastic washer
– knobs are non-original
– maybe a new battery lid
– maybe new rubber feet but could be original

I have both the nano and the old sheet metal box version but I have only modded the old big box version.
So, the info below applies to the old circuit, but the newer nano version might be very similar in operation (even though it uses a different chip)

The info below explains how the switch works:

* fsb forum post explaining how the switch changes the reverb mode electronically: https://www.freestompboxes.org/viewtopic.php?f=11&t=1138#p194980

* block diagram: reverb mode/preset switch: https://i.postimg.cc/xCDCVV2P/Screen-Shot004.jpg

* holy grail big box schematic: reverb mode/preset switch: https://i.postimg.cc/s2ZXLDtX/Screen-Shot003.jpg

As I never use the flerb setting, I changed that setting to something that seems to be large room or different type of hall reverb.
With 3 binary options there are 8 different reverb modes.
The 3 way switch gives you 3 of them
You could use dipswitches to have access to all 8.
On my big box I only found 4 of them worthwhile.

The factory demonstration board for the chip that was used in the big box had these 8 effects, but in the Holy grail pedals those are not the ones you’ll find when ‘unlocking’ the remaining 5 modes, as EHX implemented them differently. That spring reverb+tremolo mode would have been great though.
https://i.postimg.cc/q7Q5dCgL/Screen-Shot005.jpg

Thanks, but that photo is not really helping a lot:

By clear photo, I actually meant something like this: (just an example photo of my ehx Worm)
https://i.postimg.cc/zzjcM6RR/DSC06906.jpg%5Dexample photo

That way, we can zoom in on the components, like this: