Content Comparison

1

CPU mounting

As you can see you also need to do a jumper wire between the solder point marked A on the pixie cpu and pin 10 (!WE pin) of *any* of IC 7,8,9 or 10 (they’re all connected to the same signal)
Please note:
* This is on the back of the 808
* you solder the pins on the cpu on the “wrong“ side
* the jumper wire can be soldered directly as it’s just one wire, I use a pin header and patch cable here mainly during development as I can easily remove the cpu without having to desolder anything
* as the cpu is upside down, make sure you connect the midi wires the correct way!
* as always - pin 1 and 42 is unused and can be left unconnected (pin 1 is the hole with a square pad)

01/2022

2

PSU 

Do not fit the DC jack on the PSU circuit board. Its not used and it is not wired correctly.

use a cable for the jack as shown for example

01/2022

3

Tactiles /caps install

heres a tip about the installation of the tactile caps:

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i prefer this process:

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01/2022

4

MIDI WIRING

Image Modified  credits to a FB User..

11/2022

5

Silkscreen wrong 

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11/2022

6

Mainboard resistors

- handclap 

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in case you have the trimmer on solder side (recommended)

Add the R200 (10K) as shown in the left picture above at the 2 red dots.

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11/2022

7

guide /tip

for the voice board: 

first install all 1/8watt resistors on bottom of the pcb R1-9 are 1/8w or the switchboard do not fit

use MLCC caps there and no IC socket. for IC1.

when you have a solder frame: install the flat Trannys and ic sockets before you install the other parts

for the mainboard

use for the noise transistor and muting trannys - ic socket pins to swap/change the trannys

install good trimmers from nearside instead cheap trimmers from component side - better calibration possible

11/2022

8

Transistors - sequencer failure

use sockets for the muting transistors.

some users reported issues in combination with the pixie CPU, boot/start problems.

the muting Transistors affect this  - you can remove this.

1.Dec.2022

9

Power Pinout

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credits by Martin.J.K  - Thank you

02.Jan.2023

10

general

install good trimmers on back side (solder side) - for easier calibration

install the BA662 clone on solder side - in this was you can use a socket

install the muting JFETS and noise Transitor on solder side for easier swapping

install R333 on solder side to give you the opportunity to replace this with a trimmer (50k) to change the handclap sound..

02.Jan.2023

11

bugfix

install a jumper as shown to get your 808 working as designed

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03. Jan.2023

12

capacitor on Sync jack

install a 10nF polyester cap or bipolar electrolyte cap at the sync jack or on the pcb

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13

clock calibration fix

remove C203 on mainboard (39nF) or your clock can't be calibrated

in case you can't reach 120hz by trimmer end, install a 2M2 resistor in parallel on R43

04.Jan.2023

14

calibration/mod

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Hi tom noise level = R273
Middle tom noise level = R245
Low Tom noise level = R216

BassDrum Endless/Extended Decay -- replaced R170 (470k) with 370k resistor in series with a 100k potentiometer. then i set the potentiometer to the 'sweet spot', where the extra decay sounded best to me, and measured the resistance of the 370k resistor plus the resistance of the potentiometer setting. on my Yocto, 445k was the nicest value for self-oscillating/extreme decay Image Added. then i removed the 370k resistor and potentiometer from R170, and finally replaced R170 with an SPDT switch that selects between a 470k resistor (the original value/normal setting) and 445k (the 'sweet spot' for extra decay i measured, using a few resistors to achieve the 445k value).

BassDrum Tuning -- replaced R165 (47k) with SPDT switch that selects between original value (47k) and a 100k potentiometer (audio/log preferably)

BassDrum Tuning Envelope -- replaced R166 (6.8k) with SPDT switch that selects between original value (6.8k) and a 5k potentiometer in series with a 2k resistor. (in combination with the tuning mod, this mod enables some nice extra-punchy bass drums!)

Clap Noise Offset -- replaced the 10k trimpot in the clap section with 10k potentiometer..

Closed Hihat filter -- replaced R147* (2.7k) with an SPDT switch that selects between original value (2.7k) and a 10k potentiometer in series with a 1k resistor

Open Hihat filter -- replaced R153* (2.7k) with an SPDT switch that selects between original value (2.7k) and a 10k potentiometer in series with a 1k resistor

source: https://www.e-licktronic.com/forum/viewtopic.php?f=18&t=143

02.April 2023

15

wiring

 found on FB - bad quality of the picture...

you find on bottom pictures of my builds which can be more helpful - especially for the sync switch wiring

new 07/2023 - HD quality : 808-wiring.png

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16

wiring

new 07/2023 cable length and color code !

808 wire sizes.pdf

17

MIDI connection MOD

the 3D printed part is available in my shop https://www.diysynth.de/spezial-re-808-parts/re-808-midi-anschluss-3d-druck.html

or print it myself (Resin preferred) 

just use 2 screws to mount this at the typenumber plate holes at the rear and drill a small for the MIDI cables.

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18

3D Print tool rotary switch

this tool make things easier.

just drop the rotary switch inside and its easy to saw the switch, but you should need file the length 1-2mm shorter (depends on your knobs and if you want the knob as close as possible against the case)

available in my shop :

https://www.diysynth.de/spezial-re-808-parts/re808-schaltersaegehilfe-3druck-teil.html

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19

Tip Rotary Switches

for much easier rotary switch assembling, use this knowledge PLUS the ALPS assembly guide, my infos are a additional tip how to remove and bend the tabs.

you need in total 3 rotary switches 2x 6Positions, 1x12positions endless all 3 switches must have a knurled shaft and the length must be

since we can't buy this from stock we have two buy in total 6 rotary switches and make from this 3 rotary switches.

you can follow the alps rotary switch guide which is attached at top of this page but you should read my improved tips how to remove/bend the switch..

Background:

we dont need the upper part of the D shaft switches (we need knurled shaft for the 808 knobs)

and we don't need the lower part of the mouser/digikey knurled switches.

that's how you prepare the switches:

for the D shaft switches you can bend the tabs at the bottom for removal as close you can - because we dont need the upper part - put the upper part (metal) in the trash bin, we only need the base(bottom part incl. blue plastic)

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for the assembled knurled switches you can cut the pcb on bottom to remove the bottom part without bending the tabs, after you have removed the pcb - you can much easier bend the tabs !!! we only need the top metal part of this switch.

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after you proceed the other steps as described in the alps rotary switch guide , you have to bend back the pins which hold the bottom part and upper part.

I used here 2 tools and a hammer.

in first step I punched with the smaller hex. and the hammer and later with the bigger hex. and a hammer.

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In case your switches wobbles, you can add 2K glue from the sides of the switches (metal to pcb) but doublecheck that no glue comes in contact with the blue/green plastic part.

furthermore, you have to use a nut and washer to mount the switches on the case

20

recommend Mods for Clap and Snare

remove R333 and install a 50K trimmer from solder side - this adds the opportunity of changing the Clap frequency/bandpass

Install a header for the Noise Tranny of the PCB Solderside - you can try different Noise transistors of your choice (less white noise at the snare, gain stage between handclap and Snare, a loud Handclap is wrong, too much white noise at the snare is wrong)

forget the 133mV AC measurement of the noise Tranny - the important thing is the spectrum of the noise.

use a transistor tester (peak tech for example to get the correct polarity or use the datatsheets)

Furthermore: (highly recommend)

you change c51 from 0.47uF to 0.68uF (or up to 1uF) to get more reverb/room on the Snare.

use milled pins on the solderside for testing the value.

Only do this mod when you are lucky with the snare sound except the reverb part is too small (personal choice)

its not recommend to do this mod until you have found a good noise transistor otherwise you have too many variables.

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02.April 2023

21

Cowbell bugfixing

in case your cowbell is out of the trimmer range while calibration 800hz/540hz install in parallel to R44 a 10K resistor and the same for R55 (add a 10K in parallel)

since we connect a scope there, let enough space to clip the probe there.

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in case you have failures in the cowbell, here's a good page:

visit http://frisnit.com/roland-tr-808-cowbell-rebuild/

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02.April 2023

22

Grounding /wiring

Connect the "Chassis GND" from the safety PSU directly into the Jacks A "Chassis GND". Do not wire it thru the chassis. 

Connect Jacks A to Jacks B.

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02.April 2023

23

Cymbal Mod

source:

https://www.modwiggler.com/forum/viewtopic.php?t=264016

change: The modification involves changing C40 (in the middle branch next to the 33k resistor) from 1µF to 100nF

Raising C41 gives a longer decay- (not tested by me)

Technical paper:

tr_808_cymbal_a_physically_informed_circuit_bendable_digital.pdf

04.April 2023

24

general tip

mount the DIN jack from inside of the Case - don´t install the DIN socket thru the metal case, in case of trouble shooting its much easier with the wiring - otherwise you have to disconnect/desolder some cables.

06.April 2023

25

general

Here are few pictures, how I installed LED resistors on sockets, to change easily the brightness of the LEDs.

recommended: 680R instead of 68R for the step led brightness and 1k or more for the 4 other LEDs.

I used in one of my builds flathat LEDs for the variable/pattern LEDs with 1K resistor and there's no issue that other leds are still on/glow.

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2023

26

wiring

few users requested some pictures of the wiring..

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2023

27

MIDI

Midi In Mode: (Sync)

1.turn the Pattern write switch to "Manual Play"

2. hold the Pattern Clear Pushbutton and Press Step16 - the Step16 LED must be off

3. turn the Pattern write switch to "1 st PART"

4. move the Sync Switch on the rear side of the 808 to Input

5. now the 808 reacts on incoming Midi Sync Signals

MIDI Out Mode (Sync)

by default the 808 sends MIDI Out Sync Signals.

otherwise check this:

The Rear Sync Switch must be to Out

1. turn the Pattern write switch to "Manual Play"

2. hold the Pattern Clear Pushbutton  - the Step16 LED must be ON

in case its still not working, check the MIDI OUT wiring (MIDI In Wiring must be ok, since you flashed the Pixie CPU in this way)

2023

28

Switchboard

the Switchboard is green, which can be seen thru the slots of the Stepswitches in some circumstances.

on the original TR-808 is a felt cover installed on all parts (Instrument switches, basic variation switch, I/F Variation )

For the RE-808 switchboard is a solution to use black paint/spray for the pcb, or use a Edding pen or black tape, or nail paint.

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2024

29

General

DO NOT INSTALL the Knobs before everything is 100% working and calibrated. The Knobs at the 3 Rotary switches can't be easily removed.

Do not installed the Side panels and don't close the case too.

10/2024

30

General

in case everything is working and calibrated, use nuts at the screws which is at both bare steel rails (which holds the pcbs) Furthermore use lock washers (check that no trace is too close there) at the pcbs and use Screwpaint, to avoid loose screws over the years or while transportation.

10/2024

internal Clock TP2 and TP3 isn't correct

as above described - the C203 is a additional cap and isn't required for all IC Versions.

The most CD40106 doesn't need the 39nF cap. But require a 2.2M resistor in parallel at R43 to reach 8.33mV.

Check all resistors and capacitors, Trimmer values in the clock section. Especially IC10 must be 3.3nF.

Remove the CPU. in case of a CPU failure or soldering, the CPU affect the Clock. (which was happen by me due to a solder bridge)

do not trust infos from Facebook to change C10 from 3.3nF to a other value, thats only a workaround and affect the clock circuit at all.

Instrument failures and basic troubleshooting

in case that only one instrument isn't working or partial working.

Start in this order:

check your external gear (hi vs low output, panorama at your mixer)

Check from solderside all solder points. check the wiring to the jack board. Use a scope - use the jackpcb ground for your scope ground.

Check with the scope a working instrument at the jack pcb, to have a reference for Volt and timing of your scope. The same step for other sections like envelope, VCA, OSCs..

now start from rear: is the output signal at the 4558 IC available ? compare it to a working instrument.

Then we have to check the trigger inputs of the envelope which is must have.

The most reasons is faulty soldering, wrong part installed, IC Orientation. In case of rare ICs, swap the part with an other section IC - Crosstest .

nothing is working on a fresh build

the device is powered from a external PSU.

Test with a Voltmeter at the DC input, then at the power switch and at the DC_DC PSU PCB.

measure the output of the DC-DC PSU 15/-15/5V. -pay attention the 5V must be checked with the other GND. Don't forget the fuse…

in case the input of the PSU is fine, but the outputs do not. Remove power cable from the 808 mainboard and measure again. in case of a massive failure on the mainboard, the PSU will fail to work and the Power rails can crash. ( too much current draw ends in shutdown of the voltages. The root cause is often a wrong installed IC or fake ICs. Solderbridges. wrong power wiring.

lets say the fresh built 808 isn't working at all, do not try to flash the Pixie CPU. The internal clock works without the CPU. So you should measure with a scope as described in the build guide the TP2 and TP3. The Clock is the most important thing in the 808. if the clock isn't working at all, check the wiring to the DIN port and sync switch.