Bhom Digital Drums EPROM & Sync questions

[Sebo]

Hi:
I recently bought a Dr. Bohm Digital-Drums drum machine in Berlin. It sounds great. I have the Operation Manual and the Assembly Manual (the machine was originally sold as a kit) with schematics and layouts, but they are in german (and I don't understand a word of it). I scanned the Operation Manual, and I used a translator, but the result is not very good. I going to scan the Assembly Manual too.

At this point I'm having problems with the internal battery, at first I tough it needs to be changed, but I discovered that the problem is a bad connection (the original battery leaked acid over the PCB, and it was replaced, but the guy didn't do a good the job cleaning and repairing the damaged tracks). I hope I can solve this soon.

In the other hand I would like to replace some of the sounds. All of them are stored in 2 EPROMs, I need to read them to know how the sounds are organized, and write my own EPROMs, the original ones are Fujitsu MB83256 (32K x 8 bits), and I think I can use standard 27C256 to replace them (correct me if I'm wrong). My problem is how to read the original EPROMs, as my burner don't have it listed as a valid device, and I don't want to ruin the original EPROMs. So, can I read them as 27C256? I have a Willem 4.5 burner. My concern is about voltages.

Also I want to add some kind of sync-in to it. The machine already have FSK sync, but I have to figure it out how is the best way to synthesize the signal inside the computer (may be some VSTi generating pure square wave, and playing 2 notes corresponding to 1200Hz and 2400Hz). Also I'm thinking to generate a clock signal from MIDI MTC using a PIC. I will experiment a bit with that too. Also my concern is that most chips are TTL and I never worked with them, I'm afraid to burn something.

Any help, or extra info on this machine will be very welcome.
Thank you.

[Sebo]

Just an update:
I solved the battery problem, it was a bad repaired PCB track.

I read the EPROMs (as 27C256), the data is 8 bit linear. The samples have different lenght, also there are some kind of header at the beginning of the data. The ride cymbal (the longest sample) have some regular glitches on it, I don't know how to interpret this. Also some samples are clipped. I will try to replace some sounds and burn a 27C256.

[sneakthief]

Wow, what a funny coincidence - yesterday my friend gave me a partly-broken Digital Drums here in Berlin. Or at least, I'm not sure yet

Can you post or send me the manual? I don't have it and I can help you translate some parts to English.

Sometime mine locks up with certain button combinations then I have to wait a few minutes before I can turn it on again.

Not to mention, selecting the different patterns sometimes yields very strange and unpredictable results, often with flamming, weirdly repeated drums or speeds that are way too high, despite the tempo knob being all the way down.

Here are pics of mine - mine has the Accompaniment section but I'm not sure what it does yet, especially since I don't think it has the voice board with the bass or solo synth sounds.







The battery leaked everywhere and I removed it this morning. I cleaned all the corrosion as best as I could.

My Cymbal 1 is a bit glitchy, so maybe all of the samples are like that?

[Sebo]

Hi:
The Bohm sounds great!!!
I'm pretty sure that the problem about the strange behaviour of the sequencer is the battery. Mine does the same before I fixed (as I said it wasn't the battery itself, but a bad reapiring job). The thing is that some parameters of the preset rythms are stored in RAM (tempo, instrument levels).
Try this: turn off the machine, press the four variation buttons and hold them, turn on the machine. This will reset the machine and clear the RAM,
the machine will work without problems until you turn it off.

The samples on mine don't sound glitchy, what I mean is that the ride cymbal seems glitchy when I open the EPROM in my audio editor, I think that the EPROM stores more than the samples, may be some kind of sample lenght informations, or markers, I don't know.

Yeap, yours didn't seems to have the synth board, and for sure don't have the EPROMs for the Accompaniment rythms. Mine have a piece of plastic covering the Accompaniment controls at the inside. Also yours don't have the cassette interface (it adds cassette storage of the memory and FSK sync).

I have the operation manual in 3 formats, a pdf with the scans, a pdf with the OCRed text in german, and a rtf with the translation to english (made with a software, plus some little corrections I did). Also I have the 2 EPROMs.
I will scan the assembly manual and the assembly manual for the cassette interface soon.
I will upload what I have to YouSendit, or something like that and post it here.

[Sebo]

Hi:
Here there are the Digital-Drums Operation Manual Scanned (in German), the OCRed version, a translation to english (made with a translator program, so is full of errors), images of the 2 sound EPROMs, and a txt with the sound list of each EPROM plus the adress an lenght of each sound in samples:
http://www.sendspace.com/file/t58a1p
I will scan the other 2 manuals soon.
If somebody can help translating the manuals will be great. Thanks.

I'm about to burn a new set of EPROMs, and see if works.
MIDI sync is in the pipeline too.

Cheers.

[sneakthief]

[Sebo]

[Plink]

Hello guys,

new to the forum,
was looking to google for any info on the Bohm and found this thread!
I'm so glad it is so recent.

I also have 2 Dr. Bohm digital drums and last week I found the keyboard!
I actually never opened the machine to check for leakages and its nice to hear there is such a problem cause the 1 bohm has sequencer problems!

The other one is working great and also has the synth section, which works with the keyboard, but i'm still trying to figure out how it works...

It would be great if you could share your understandings about the operation of the bohm in general.
I'm not really sure how the sequencer and programmer works...

I'll post some photos of my bohm later...

[Sebo]

Hi:
I've scanned and OCRed the Cassette Interface building manual, I also used the damn translator software to get a bad translation.
I uploaded here:
http://www.sendspace.com/file/puenfk
Also I updated the EPROMs sound list with extra info, and some corrections.

Plink: I uploaded a scan and translation of the Digital-Drums Manual, the link is some posts above. The translation is made with a software translator so is very bad, but with a little patience you will understand the basics.

Also I get the sound expansion working. I used two 27C512 EPROMs and a pair of switches to change between the original samples and my own samples. Note that the original EPROM was a MB83256 (27C256), so I copied the sample data, pasted at the end of the original, then replaced the samples in the second part for my own samples. The 27C512 fits in the MB83256 socket, but I bended the leg 1 up and connected via a 10K resistor to +5V and directly to a switch that is connected to ground. So I can change between the first set of samples and the second one.
Maybe I will draw a schematic, but it is very simple.

I started with the sync, that's why I scanned the cassette interface manual, it have in the same circuit, the FSK sync and the sync out (called trigger in the Bohm).

Also I will start to scan the building manual soon, but is very large. The first half or so, is mostly a course of how to solder, how to bend legs of components, and that kind of stuff. Maybe I will scan only the relevant part of the manual, but as I can't read german, maybe I'm missing something...

[Sebo]

Another update:
I found a easy way of sync the drum machine to my computer.
I tried a VST plugin that generates FSK, but it was for Roland gear and the frequency was wrong (the Bohm loses the sync after one or two measures).
I contacted the guy that coded the plugin (Wim Vanheste), a really nice guy, and he added a mode with the correct frequencies for the Bohm.
Now I use an output of my sound card to send FSK to the Bohm. And syncs
very well (at high tempos sometimes loses the sync a bit).
You can download the plugin here:
http://www.rv0.be/suac.html
Make sure you make an FSK cable as described in the Cassette Interface building manual.
To sync the drum machine to FSK press Clear+Start and the display will show --E--, it waits the FSK signal to start.
Remember to select the Bohm mode in the plugin (second mode).

Sebo

[Sebo]

Hi:
I've scanned the most relevant parts of the Digital-Drums Building Manual, schematics, layouts, etc.
The link is here:
http://www.sendspace.com/file/ep6331
Also I reuploaded previous files:
Operation manual:
http://www.sendspace.com/file/ncvurg
Cassette Interface:
http://www.sendspace.com/file/0fxb7u

I did some more mods: Changed the cuttof frequency of HiHats and Cymbals to a higher frequency, and did a new output stage without the EQ and with the individual outputs switching out of the main mix when plugged in.

[realitychanges]

Hi there
Please can you help ?
I have the assembling manual of this machine … and the machine
I have a problem; it is missing the page showing schematics of PCB 023 the one with the battery and all voice chips
Do you have this schematics ?
I appreciate lots if you could help
Im in Australia and I need to repair this particular PCB
Best Regards
Jul Pe

[sneakthief]

Schematics, as posted on a thread at Synthforum.nl:

http://www.dompselaar.org/Bohm/bohm_digital_drums.rar

[J303]

Hi all,

New to the forum and first post , bought a Bohm Digital Drums in eBay months ago, can't figure out how to record and just can't find the user manual anywhere, I would really appreciate any help about finding the operation manual.

Many thanks
J