roman 245/246 happiness

Discussing some incredible modules that don't quite fit into the other forum categories.

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levelhead3
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roman 245/246 happiness

Post by levelhead3 » Fri Aug 23, 2019 1:03 am

So there have been numerous threads here and on emcloned discussing the two main problems with the roman 245 and 246 - first that there is a "null" zone on the CV pots' travel from about 3:00 on, where the output voltage maxes out at around 9.4v and after that no additional voltage gain occurs, and second that adjacent stage outputs "blend" together and do not independently trigger a 281r.

I'm happy to say the Dave Brown has come to the rescue and successfully addressed both issues. The CV null zone required the replacement of the CV banks' summing opamps, and a reduction in the the sustained voltage level on the stage pulse output waveforms allowed the 281r to "see" the independent pulses.

He also looked into the pulser & reference waveforms and the clock. These modules are now 100% operational as far as I can test.

As usual complete details of these mods are posted on his website, and I just want to repeat the sentiment of an earlier thread and express my gratitude for his continued support of our community.

Thanks Dave!

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Peake
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Post by Peake » Fri Aug 23, 2019 3:47 am

:sb: :sb: :sb:
This is not the place I'd imagined it to be.

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diophantine
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Post by diophantine » Fri Aug 23, 2019 12:40 pm

Nice!

Do you know if this was this a problem with the first 245 PCBs that were made available on emcloned? (Not made by Roman, but another user.) I have two, but haven't built them yet...

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davebr
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Post by davebr » Fri Aug 23, 2019 1:54 pm

diophantine wrote:Nice!

Do you know if this was this a problem with the first 245 PCBs that were made available on emcloned? (Not made by Roman, but another user.) I have two, but haven't built them yet...
I am aware of another 245 PCB but I don't know if it what you are referring to. Is there any nomenclature on PCB2? You can either post or send a photo to me of PCB2 component side, and a BOM would help.

If it doesn't use 24V or have a DC-DC converter to generate 24V there should be a dead zone, but with the right resistor values, can be pretty minimal. That was my "better" solution on my website.

Dave

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diophantine
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Post by diophantine » Fri Aug 23, 2019 7:59 pm

davebr wrote:I am aware of another 245 PCB but I don't know if it what you are referring to. Is there any nomenclature on PCB2? You can either post or send a photo to me of PCB2 component side, and a BOM would help.

If it doesn't use 24V or have a DC-DC converter to generate 24V there should be a dead zone, but with the right resistor values, can be pretty minimal. That was my "better" solution on my website.
Thanks Dave - it has cj3000 written on it. I only see a +5V regulator, with a jumper for internal/external +5V. The BOM is around here somewhere...

Will try to take a look at your mod notes this weekend!

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davebr
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Post by davebr » Fri Aug 23, 2019 10:41 pm

diophantine wrote:
davebr wrote:I am aware of another 245 PCB but I don't know if it what you are referring to. Is there any nomenclature on PCB2? You can either post or send a photo to me of PCB2 component side, and a BOM would help.

If it doesn't use 24V or have a DC-DC converter to generate 24V there should be a dead zone, but with the right resistor values, can be pretty minimal. That was my "better" solution on my website.
Thanks Dave - it has cj3000 written on it. I only see a +5V regulator, with a jumper for internal/external +5V. The BOM is around here somewhere...

Will try to take a look at your mod notes this weekend!
I am familiar with that and can post the reference numbers on my website. You'll have to double check them as I have no way of doing that. Some of the mods are already done. The stage CV outputs are dual op-amps so I'll have to find an affordable rail to rail dual. There aren't many available in DIP.

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davebr
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Post by davebr » Fri Aug 23, 2019 10:49 pm

diophantine wrote:It has cj3000 written on it. I only see a +5V regulator, with a jumper for internal/external +5V. The BOM is around here somewhere...

Will try to take a look at your mod notes this weekend!
I do not have a BOM nor reference diagram for this PCB. If you find the BOM please send it to me. I would also appreciate you scanning your unpopulated PCBs, both sides, and send them to me so I have traces and can make reference diagrams. Scanning works better than photos as the distortion is minimized.

Dave

kashmir
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Post by kashmir » Fri Aug 30, 2019 1:27 am

diophantine wrote:
davebr wrote:I am aware of another 245 PCB but I don't know if it what you are referring to. Is there any nomenclature on PCB2? You can either post or send a photo to me of PCB2 component side, and a BOM would help.

If it doesn't use 24V or have a DC-DC converter to generate 24V there should be a dead zone, but with the right resistor values, can be pretty minimal. That was my "better" solution on my website.
Thanks Dave - it has cj3000 written on it. I only see a +5V regulator, with a jumper for internal/external +5V. The BOM is around here somewhere...

Will try to take a look at your mod notes this weekend!
I have the same set of PCBs, there are still unpopulated so I can scan them if yours are already built. I also have BOM and schematics in case you didn't find them yet.

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davebr
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Post by davebr » Fri Aug 30, 2019 4:10 pm

kashmir wrote:I have the same set of PCBs, there are still unpopulated so I can scan them if yours are already built. I also have BOM and schematics in case you didn't find them yet.
Please do. PM sent.

Dave

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