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Removing coating from all voice and wave chips from Juno 106

PostPosted: Thu Jan 11, 2018 11:43 pm
by NCChao1268
I recently purchased a very nice condition Juno 106 nearly mint and thought of removing the epoxy coating from all the six voice chips and three wave chips before they fail. I know many sites that teach one how to remove the coating and restore the chips, but anyone know of a very good site? Would this be a good idea to remove the coating before the chips fail? Any advice on this process is appreciated.

-Nathan

Re: Removing coating from all voice and wave chips from Juno

PostPosted: Fri Jan 12, 2018 2:37 pm
by HideawayStudio
NCChao1268 wrote:I recently purchased a very nice condition Juno 106 nearly mint and thought of removing the epoxy coating from all the six voice chips and three wave chips before they fail. I know many sites that teach one how to remove the coating and restore the chips, but anyone know of a very good site? Would this be a good idea to remove the coating before the chips fail? Any advice on this process is appreciated.

-Nathan

Hi Nathan,

I think there might be some confusion about the potting on the 80017A VCA/VCF modules which is being perpetuated across the internet.

Epoxy potted ceramic subtrate modules are somewhat notorious for long term reliability issues and not just limited to those found in the 106. In many cases it is not the potting that causes the issue but bad solder joints on the components and in some cases failed components. With the correct tools although removing the potting may allow the module to be repaired (and in some cases even appear to magically fix it!) it often doesn't for very long.

Stripping off the epoxy is in itself a risky task to do properly and involves the use of copious amounts of hydrogen peroxide based solvents which is a really messy job. Before this can even be undertaken the modules need to be removed from the voice board which requires considerable care because the tracks and pads on the 106's pressed paper/resin pcbs are rather fragile compared to modern FR4 plated-thru pcbs.

But frankly by the time you've done all of that - you might as well replace them.

My stance with the 106 et al is simply to wait until a module fails and then replace it with one of the better clones such as the Analogue Renaissance modules. It only takes an hour or so for a good tech to remove the old module, fit a clone and recalibrate. The 106 in my studio has suffered from 2/6 failed 80017A VCA/VCF and 1/3 failed D5534A wave gen over the past 20 years.

BTW.. being pedantic - people keep calling these things chips.. strictly speaking they are ceramic hybrid modules which contain several chips.

Re: Removing coating from all voice and wave chips from Juno

PostPosted: Fri Jan 12, 2018 11:08 pm
by NCChao1268
HideawayStudio wrote:I think there might be some confusion about the potting on the 80017A VCA/VCF modules which is being perpetuated across the internet.

Epoxy potted ceramic subtrate modules are somewhat notorious for long term reliability issues and not just limited to those found in the 106. In many cases it is not the potting that causes the issue but bad solder joints on the components and in some cases failed components. With the correct tools although removing the potting may allow the module to be repaired (and in some cases even appear to magically fix it!) it often doesn't for very long.

Stripping off the epoxy is in itself a risky task to do properly and involves the use of copious amounts of hydrogen peroxide based solvents which is a really messy job. Before this can even be undertaken the modules need to be removed from the voice board which requires considerable care because the tracks and pads on the 106's pressed paper/resin pcbs are rather fragile compared to modern FR4 plated-thru pcbs.

But frankly by the time you've done all of that - you might as well replace the them.

My stance with the 106 et al is simply to wait until a module fails and then replace it with one of the better clones such as the Analogue Renaissance modules. It only takes an hour or so for a good tech to remove the old module, fit a clone and recalibrate. The 106 in my studio has suffered from 2/6 failed 80017A VCA/VCF and 1/3 failed D5534A wave gen over the past 20 years.

BTW.. being pedantic - people keep calling these things chips.. strictly speaking they are ceramic hybrid modules which contain several chips.


Hey HideawayStudio,

The reason I wanted to do this overhaul of the chips is to ensure a long life for my Juno 106 and an increased investment price, many people use acetone to remove the coating as well as buying better pins to make remounting the chips more efficient and long lasting with much success in either two just described. The way I am thinking of going is a least costly method that still preserves the original parts in it without any calibration needed.

I personally don't like service techs too much as of now because they ended up being very expensive in the end, and the job needed to be accomplished is something someone can do if they have experience with PCB's and electronics.

-Nathan

Re: Removing coating from all voice and wave chips from Juno

PostPosted: Tue Jan 16, 2018 11:49 am
by HideawayStudio
NCChao1268 wrote:
HideawayStudio wrote:I think there might be some confusion about the potting on the 80017A VCA/VCF modules which is being perpetuated across the internet.

Epoxy potted ceramic subtrate modules are somewhat notorious for long term reliability issues and not just limited to those found in the 106. In many cases it is not the potting that causes the issue but bad solder joints on the components and in some cases failed components. With the correct tools although removing the potting may allow the module to be repaired (and in some cases even appear to magically fix it!) it often doesn't for very long.

Stripping off the epoxy is in itself a risky task to do properly and involves the use of copious amounts of hydrogen peroxide based solvents which is a really messy job. Before this can even be undertaken the modules need to be removed from the voice board which requires considerable care because the tracks and pads on the 106's pressed paper/resin pcbs are rather fragile compared to modern FR4 plated-thru pcbs.

But frankly by the time you've done all of that - you might as well replace the them.

My stance with the 106 et al is simply to wait until a module fails and then replace it with one of the better clones such as the Analogue Renaissance modules. It only takes an hour or so for a good tech to remove the old module, fit a clone and recalibrate. The 106 in my studio has suffered from 2/6 failed 80017A VCA/VCF and 1/3 failed D5534A wave gen over the past 20 years.

BTW.. being pedantic - people keep calling these things chips.. strictly speaking they are ceramic hybrid modules which contain several chips.


Hey HideawayStudio,

The reason I wanted to do this overhaul of the chips is to ensure a long life for my Juno 106 and an increased investment price, many people use acetone to remove the coating as well as buying better pins to make remounting the chips more efficient and long lasting with much success in either two just described. The way I am thinking of going is a least costly method that still preserves the original parts in it without any calibration needed.

I personally don't like service techs too much as of now because they ended up being very expensive in the end, and the job needed to be accomplished is something someone can do if they have experience with PCB's and electronics.

-Nathan

I agree that any electronics tech/eng could undertake this task but its perhaps a little unfair to say a synth tech will be more expensive unless the engineer is a friend who is doing a favor for you.

I'm also far from convinced anyone would pay more for a 106 with its original filter modules in place. The bulk of the labour to change the modules is the very same labour you'd undertake to remove the originals prior to removing the epoxy resin. There really is no special voodoo about these modules - its not like the infamous KORG35 filters (which are extremely sensitive to component selection due to their remarkably minimal design) - the components on the 106's modules are a mixture of bread and butter parts and the same Roland OTAs used in the previous Juno models.

As for calibration - ideally it is periodically needed regardless of what modules are in there - especially if using self-resonant filters as a second oscillator is important.

I still think the safest/more inexpensive route is to replace them as and when.