Vintage Synth Repair

Hi, the top 5 keys (intermittently) fail to sound on my D5. I can 
always see a time multiplexed signal for each key on the main board and 
can just about see a difference in pulse width when the second velocity 
contacts come in (but not as pronounced as for the working keys). I 
have a paper copy of the service manual but it does not describe the 
keyboard. Does anyone have a description or schematic of the keyboard 
operation please? Thanks in advance, Andrew.

Andrew, The D5 has a membrane style plastic film for key contacts. Have 
you checked for dirt and/or corrosion between the film layers? I can 
look at the D5 in my shop if you need more details. It's been a while 
since I was inside it.
Let me know, Fran

--- In vintagesynthrepair@yahoogroups.com, "aent440" <andrew@...> wrote:
>
> Hi, the top 5 keys (intermittently) fail to sound on my D5. I can 
> always see a time multiplexed signal for each key on the main board 
and 
> can just about see a difference in pulse width when the second 
velocity 

> contacts come in (but not as pronounced as for the working keys). I 
> have a paper copy of the service manual but it does not describe the 
> keyboard. Does anyone have a description or schematic of the keyboard 
> operation please? Thanks in advance, Andrew.
>

Hi Fran,

Thanks for the quick reply. I think I am going to have to bite the 
bullet and strip out those offending keys to check that region out. 

Cheers, 

Andrew.

--- In vintagesynthrepair@yahoogroups.com, "narfman96" 
<narfman96@...> wrote:
>
> Andrew, The D5 has a membrane style plastic film for key contacts. 
Have 
> you checked for dirt and/or corrosion between the film layers? I 
can 
> look at the D5 in my shop if you need more details. It's been a 
while 
> since I was inside it.
> Let me know, Fran
> 
> --- In vintagesynthrepair@yahoogroups.com, "aent440" <andrew@> 
wrote:
> >
> > Hi, the top 5 keys (intermittently) fail to sound on my D5. I can 
> > always see a time multiplexed signal for each key on the main 
board 
> and 
> > can just about see a difference in pulse width when the second 
> velocity 
> > contacts come in (but not as pronounced as for the working keys). 
I 
> > have a paper copy of the service manual but it does not describe 
the 
> > keyboard. Does anyone have a description or schematic of the 
keyboard 

> > operation please? Thanks in advance, Andrew.
> >
>

Hi, the mystery is over, the keyboard flexible PCB (and much of the 
galvanised chassis) had been corroded by cat urine! I was able to 
bypass the corroded region by scraping off the top plastic layer of 
the PCB with a scalpel to reveal the silver paint below, gluing a 
very flexible wire to the PCB for strain relief, then quickly 
soldering the wire to the paint.

Cheers,

Andrew.

--- In vintagesynthrepair@yahoogroups.com, "aent440" <andrew@...> 
wrote:
>
> Hi Fran,
> 
> Thanks for the quick reply. I think I am going to have to bite the 
> bullet and strip out those offending keys to check that region out. 
> 
> Cheers, 
> 
> Andrew.
> 
> --- In vintagesynthrepair@yahoogroups.com, "narfman96" 
> <narfman96@> wrote:
> >
> > Andrew, The D5 has a membrane style plastic film for key 
contacts. 
> Have 
> > you checked for dirt and/or corrosion between the film layers? I 
> can 
> > look at the D5 in my shop if you need more details. It's been a 
> while 
> > since I was inside it.
> > Let me know, Fran
> > 
> > --- In vintagesynthrepair@yahoogroups.com, "aent440" <andrew@> 
> wrote:
> > >
> > > Hi, the top 5 keys (intermittently) fail to sound on my D5. I 
can 
> > > always see a time multiplexed signal for each key on the main 
> board 
> > and 
> > > can just about see a difference in pulse width when the second 
> > velocity 
> > > contacts come in (but not as pronounced as for the working 
keys). 
> I 
> > > have a paper copy of the service manual but it does not 
describe 

> the 
> > > keyboard. Does anyone have a description or schematic of the 
> keyboard 
> > > operation please? Thanks in advance, Andrew.
> > >
> >
>

> Hi, the mystery is over, the keyboard flexible PCB (and much of
> the galvanised chassis) had been corroded by cat urine!  

Aw, and I was going to guess it was beer...