Problem with inputs A2, A3, B2, B3, C2, C3, D2, D3

Hi there,

I’m looking for some help with a problem I am having with inputs A2, A3, B2, B3, C2, C3, D2, D3. I turned the synth on last night and the LEDs of these inputs appear to have lit up red with nothing patched. Looking at the scope their levels are at the lowest CV input value. When I patch an LFO in to these inputs there is no change in the value. When I patch a dummy cable in the values remain the same too. Inputs A1, B1, C1 and D1 are all working normally.

I’ve recently updated to the latest stable firmware but didn’t notice any problem at the time. To test I downgraded to my previously installed version but no change.

It is connected via i2c to a few other modules. Everything else in my case looks to be ok.

Any help would be greatly appreciated


This looks like your CPU board has been damaged. Here is how to replace it:

Maintenance and Repair - docs @ O|D

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Thank you for the quick reply Brian. Gutting! But thanks for the detailed instructions - I’ll look into this

Thanks again,

I just wanted to give you an update (also for those in the UK reading this thread who run into similar problems).

Unfortunately, due to Brexit, it is impossible to order the part mentioned without a minimum order of £200 (the part is €37). And the only place I could find it for delivery to the UK was eBay at a vastly inflated price.

There’s no way round this of course, and certainly not your problem!!!

Thank you once again. Looking forward to getting things working again.


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Hi David, I am in Greece at the moment coming back to the UK at the end of October. If you haven’t found a solution till then, I can probably get it for you. Cheers

how did this happen?

Hi Terry,

This is really really kind, thank you. There is no need as I have done the impatient thing and just bought the part.

Thank you again though!

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I’m not really sure. I had to turn the synth on and off a couple of times to test something else I was doing so perhaps that had something to do with it.

I really have no idea

Was the er-301 connected together with other modules on a busboard attached to Teletype?

Yes it is, though I haven’t had any major problems with my setup for the last 18 months since I put it together (apart from the usual i2c setup tribulations).

It is a rather i2c heavy setup with:
ansible x2
txb (bus board)
jf x2
w/ x2

There is also a 16n faderbank, which I recently swapped for a sweet sixteen (both in follower mode).

I can’t quite remember the exact configuration of the i2c cables behind the panels. It is mostly in series, though I think the er-301 may have its own branch from the txb.

Do you think the bus board could be part of the problem?

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I had something similar lately, ended up with my JF and txO being not functional anymore. Also the i2c communication disappeared. ER-301 is not recieving any i2C, other functions are perfectly working. We swapped the microcontroller on teletype with a new one, I will still need to test if it does work now.
It’s a strange issue, seems more people had problems with.

That’s interesting, but rubbish you’ve had the go the effort of replacing the tt microcontroller. I hope it works!

After my er-301 stopped working the first thing I did was to remove the i2c connection. Everything else in the setup works fine until I reconnect the er-301 again and then all ii communication stops. I’ve left it disconnected for now.

These modules are available here (uk) if anybody is in need

I’m getting a banner saying they dont sell to individual UK customers for the time being because Brexit…

Which is a shame. Theres things I’ve not been able to find in the past except from TME.

I saw that banner too. It says ‘temporary suspension’ so hopefully this means sales to UK will resume at some point. Even a Brexit administration charge would be preferable to complete cessation of sales.

This has worked, thank you again for your help!