I opened it up to clean it and realised this wasnt its original colour.
It really was taupe gray before, but the years had the plastic chassis yellowing
I decided to restore it to its original colour (or as close as i could…)
After 5 months of great fun, I had to open it up because the output went silent.
Gutshots of the Hohner Basset!
Lets start with the DIN jack that connects it to the bass amp..
Circuit board and caps jungle:
Inside the white enclosure there’s a lamp and a ldr.. the lamp is a 10v Valvo branded item. It doesnt light up so that may be a clue..good luck trying to find a replacement.. but my guess is the transistors..could they be the culprit?!
Ahem this means the caps have been doing their job for 50 long years! Only one of the capacitors has failed, please note- the blue valvo 100uF cap now measures 1uF!
I do not think it is a difficult nor long build – i spent a couple of hours at every day off on it, for about a month.
The excitement of being able to own an 808 drove me, and gave me the needed focus and patience boost.
When building the Yocto, it is very important to measure every component before soldering it.
I decided to buy the resistors needed each time I was going to start a new section. This relieved me from measuring hundreds of resistors in one tiring session, put them in order all at once, etc.
I bought a paper note book on which I would tape, writing down their value and position the components, as I prepared them for each part. This helped me double check them before and while soldering them to the boards.
I decided to socket all the IC’s and the noise section transistor.
The germanium diodes provided in the half kit are rare, treat them with care. I cut the curvy terminals to have a straight lead as per picture here.
Check the pictures I enclose here to clarify certain ic’s position.
I made the mistake of putting all the pots at the end, do not do it, it is a mess. Just follow the build guide-do it as recommended, at the end of each section.
Remove the encoders’ tabs before you solder them in!
Please note that you do not have to cut the lead cables at the end of the build (i did it!), what Vincent meant in the last paragraph of the build guide is, you can make them shorter.
I had some issues with the flat cables, aka they broke, so i socketed them too. It is advisable to have a suitable enclosure ready before you get to link the two pcbs with flat cable, otherwise having the boards moving around will cause them to break.
Usually the boards sit a bit shallow in the enclosures, do not use led covers and cut them about the height of the sequencer’s coloured buttons.
Use 5mm spacers to lift the board up and have it sit properly, the keys will stick out properly through the holes.. More on that further down..
(see pic at the top of the post)
A few more tips to build the yocto, not a mod guide by any means, more like a ‘watch out for’ list, for instance where to look if you would like to change the value of some resistors to change the tuning of the instruments.. and other useful things to know as you go along.
A lot of these ideas are to be found in the yocto forum, but here is whatever I found essential to complete the build without headaches.
For a more in depth mods’ list, google dsl-man yocto mods.
THE NOISE SECTION
As opposed to the building guide, a more effective functionality of the noise generator can be achieved with this mod, as per the official Roland service manual (page 15):
R 129 use a jumper instead of the resistor listed
R 131 100k
R 127 10uF electrolytic: see this pic for correct orientation (positive side left)
R 130 22pF in parallel with resistor 130 (it means on top of the resistor, using the same soldering points – check the pic, i soldered it on the other side of the board)
I socketed Q35 as it is a very substantial part of the noise generator.
C 27 1n2 for 1ms pulse, needed for an effective accent
R 165 tuning resistor
R 234 47k (positioned in the Low Tom section)
R 188 check its position carefully
R 195 tuning resistor 1
R 196 tuning resistor 2
R 202 noise filter resistor
R 231 to lower pitch, use a 4k7 resistor (or increase value to lower pitch)
R 257 tuning resistor
R 284 tuning resistor
R 312 tuning resistor
R 315 tuning resistor
R 334 and
R 373 are part of the Hand Clap circuit, although they are to be found here
R 342 and
C 137 may have a solder bridge, it is ok
Do not rush to solder the BA6110 ic, it is better to socket it and add it at a later time, please check the picture here to have it positioned correctly.
R 63 decay resistor 1
R 65 decay resistor 2
Look at this section before trying to find the position of the components. It is L shaped.
R 56 noise filter resistor 1
R 58 noise filter resistor 2 (this is in common with the HiHat)
C 6 and
C 42 and
C 44 and
C 46 I did not have any 22nF caps in my stash so I used, 27nF instead.
INPUT OUTPUT BOARD
Please note the position of this IC
Before you put the keys in, make sure your enclosure will let them stick out properly (as stated before, they sit a bit shallow), and use spacers the right height to suit your eclosure.. As described here..
Before you put it in the enclosure
Prep the enclosure by screwing the spacers in the front panel- i used 5mm spacers but 10mm spacers’ screws (aka the ones that came with the mouser order) that go in for like 3/4 of the spacer’s lenght. Screw the top panel side all the way in through the spacer.
Please note there are two sides to the spacer, one is hollow and the other flat. You want to have the hollow part as receptacle to screw the pcb side in (aka at the back of the front panel) as much as you can (it is not much, a few mm’s but that will suffice to have the pcb steady in place). This means, flat side of the spacer on top.
Look at the picture:
Nuts of the two encoders will have to be placed on top of the front panel not below.
My Yocto fired properly first off.
I made all the trimmer’s adjustment upon finishing it.
I am very satisfied by the result. Vincent has been very helpful too, and the YOCTO forum is an invaluable resource.
Thanks Pawluk for the sturdy enclosure!
Also, if you feel inclined, i would suggest you add a little daughterboard to fine tune the noise generator, to allow for correct voicing of the snare, hats and cymbal (check out the relevant resistors above and swap them with trimmers)..
I arranged them on a small veroboard and i am very happy with the results!