Vintage Synth Repair

Hi Folks,

I have a Roland SDE 1000 Digital Delay that I used 20 years ago in my 
studio -- now it doesn't work.  Digital Delay flashes as delay knob 
is turned, but the output is pretty garbled, and the number panel 
doesn't show any info (except when turned from on to off)

I took it apart and pulled all the connectors and cleaned.  Seemed to 
help a bit, but not much.

I was wondering if it might be the battery, as the manual says to 
replace every 5 years.

any thoughts on this one?  I'm guessing I could probably find the 
battery on ebay and replace if somebody thought this would solve the 
problem

If not, I'll probably just sell it as nonworking.

Thanks!

Fred

>>I have a Roland SDE 1000 Digital Delay that I used 20 years ago in my 
> studio -- now it doesn't work.  Digital Delay flashes as delay knob 
> is turned, but the output is pretty garbled, and the number panel 
> doesn't show any info (except when turned from on to off)<<

more likely to be a power supply problem- can you check (or get
someone to check) the power supply rails inside the thing? there
should be 12s & 5s in some combination, same as in 99% of digital kit.
+12, -12, +5, -5, & maybe some more of the same for analogue circuits... 

look at the big capacitors around the power supply- prob'ly one of
them has leaked a bit or otherwise failed. or it could be a rectifier
bridge that's failed. 
are any of the chips socketed? you could try "crunching" them home
gently...
if it's not this, you may discover some combination of key-presses
that re-initialises the box, if it is a dead memory battery. this too
should be checked for terminal voltage (with the box off) & leakage-
many of these batteries can damage circuit boards if they are badly
sited & have leaked. poly-6 owners know all about this!

hth-
duncan.

Thanks for the tips Duncan.  I'm experienced enough to check the 
voltages, and come away with 3 brands, 4.37, 11.87 and 26.  Does that 
sound ok?  Is the 26 for professional operation?  

Anyway, voltages seem ok, fuses ok, no leaks from any components...

I'm beginning to think it's beyond me.  No chips in sockets (like my 
kurz 1000px -- that was the problem there)

If it worked, then I'd chase after the battery, but it doesn't seem 
to work very well at this point.

What do you think...beyond me?

Thanks,

Fred



--- In vintagesynthrepair@yahoogroups.com, "ferrograph632" 
<ferrograph@...> wrote:
>
> >>I have a Roland SDE 1000 Digital Delay that I used 20 years ago 
in my 
> > studio -- now it doesn't work.  Digital Delay flashes as delay 
knob 
> > is turned, but the output is pretty garbled, and the number panel 
> > doesn't show any info (except when turned from on to off)<<
> 
> more likely to be a power supply problem- can you check (or get
> someone to check) the power supply rails inside the thing? there
> should be 12s & 5s in some combination, same as in 99% of digital 
kit.
> +12, -12, +5, -5, & maybe some more of the same for analogue 
circuits... 
> 
> look at the big capacitors around the power supply- prob'ly one of
> them has leaked a bit or otherwise failed. or it could be a 
rectifier
> bridge that's failed. 
> are any of the chips socketed? you could try "crunching" them home
> gently...
> if it's not this, you may discover some combination of key-presses
> that re-initialises the box, if it is a dead memory battery. this 
too

> should be checked for terminal voltage (with the box off) & leakage-
> many of these batteries can damage circuit boards if they are badly
> sited & have leaked. poly-6 owners know all about this!
> 
> hth-
> duncan.
>

>>I'm experienced enough to check the voltages, and come away with 3
brands, 4.37, 11.87 and 26.  Does that sound ok?  Is the 26 for
professional operation?<<

I wouldn't expect a 26V rail anywhere in a hybrid digital/analogue
circuit, but then they aren't all the same.  please bear in mind that
I'm writing this with no knowledge of this particular box or it's
schemos :-) I have a similar korg box here though, the sdd3300.

there may be a higher voltage for the display backlight but this would
probably be quite a bit higher (80V or so) & probably there'd be an
inverter to generate this close to the display itself.
again, I can't be certain on any of this, but it would be typical. for
all I know, the backlight could be a bunch of LEDs like in my old
cheetah sampler, or a fluorescent job with an inverter like in my emu
samplers.
 
so the 26V- you might be measuring across the whole of a +12 to -12,
of course.... no obvious negative voltages? 
& the 5 & 12 seem to be low, especially the 5. this might prevent the
CPU operating properly.

if you can read any of the chip numbers, especially things like audio
op-amps (5532, 4558, that sort of thing) then check their pin-outs on
a datasheet, you may discover more. 
the digital chips are where the problem probably is though, since the
box has scrambled brains, so you'd need to identify any of the logic
ICs & check those locally (i.e. instead of at the power supply); it
could be a cracked track on the back of the board, or a single bad
chip dragging a whole rail down. again, you might see familiar chip
numbers, 74xx or 474xx or even 4000-series stuff, 12 or 14 pins on
them, used as latches, gates & buffers. there are bound to be some of
these around the control panel.

thinking about that- you might want to dismantle the control panel &
check for contaminant ingress causing a shorted button- devices like
this can behave in a peculiar way sometimes if a button is "held down"
while they boot.

do you know what sort of power supply it is? is it a linear psu, with
a big mains transformer, bridges, big electrolytic caps & series
regulators? or a compact switched-mode device? the latter are easily
identified since they are so much smaller, & usually the host device
will work on any voltage from about 80 to 300, 50 or 60 Hz.
switched-mode psu's generally fail completely too.
if it's a linear power supply, it would usually have obvious output
regulators, either 78xx/79xx three-pin devices on heat sinks, or power
transistors performing the same function.

if you can find these devices & measure something "traditional" (12s &
5s, I mean) then the problem is probably with the CPU or the
associated ram. I had a juno 106 once that wouldn't start up because
the CPU ram was damaged; the memory battery was fine on that occasion,
but I had to replace the combined CPU & memory (with a revised design
comprising two separate devices that came separately by boat from
japan!)  

>>What do you think...beyond me?<<

I couldn't possibly say! :-) the aforementioned 106 was written off by
a professional synth service company & would be scrap but for my
persistence. do you know any decent techs near you? I don't know what
roland are like where you are, but they weren't much help to me; when
I wanted to fix the 106, I ordered a CPU & of course, the CPU turned
up 60 days later with no internal memory... 70 days after that I got
the thing working well enough to deal with it's many other issues.

oh well- hope this helps.

duncan.

Hi Duncan,

Thanks so much for your detailed response!

I did read every word, and I see what you're talking about.  
Ultimately, I'm concluding this is a bit beyond both my abilities and 
the time I want to invest in the unit.  

It does have the compact psu... and I've unplugged/cleaned/replugged 
a number of cables, and whereas there does seem to be a slight 
differenece in performance, there is little improvement.

Everything on the board seems soldered in place so there's no simple 
way to remove/clean/reinstall (which did wonders for my Kurz px1000)

I kind of suspect (based on your post) that the 26v could be where 
the problem is...but then ultimately I don't think it's worth me 
going any further with it.  :(  

After giving it a go, I think it's time to let it loose on ebay.  
Either somebody will want it, or it's time for the electronic 
recycling center.  Hate to do that, but I never use it anyway.

Thanks so much for your detailed responses!  It did help, even if 
I've ultimately given up.

Cheers,

Fred

--- In vintagesynthrepair@yahoogroups.com, "ferrograph632" 
<ferrograph@...> wrote:
>
> >>I'm experienced enough to check the voltages, and come away with 3
> brands, 4.37, 11.87 and 26.  Does that sound ok?  Is the 26 for
> professional operation?<<
> 
> I wouldn't expect a 26V rail anywhere in a hybrid digital/analogue
> circuit, but then they aren't all the same.  please bear in mind 
that
> I'm writing this with no knowledge of this particular box or it's
> schemos :-) I have a similar korg box here though, the sdd3300.
> 
> there may be a higher voltage for the display backlight but this 
would
> probably be quite a bit higher (80V or so) & probably there'd be an
> inverter to generate this close to the display itself.
> again, I can't be certain on any of this, but it would be typical. 
for
> all I know, the backlight could be a bunch of LEDs like in my old
> cheetah sampler, or a fluorescent job with an inverter like in my 
emu
> samplers.
>  
> so the 26V- you might be measuring across the whole of a +12 to -12,
> of course.... no obvious negative voltages? 
> & the 5 & 12 seem to be low, especially the 5. this might prevent 
the
> CPU operating properly.
> 
> if you can read any of the chip numbers, especially things like 
audio
> op-amps (5532, 4558, that sort of thing) then check their pin-outs 
on
> a datasheet, you may discover more. 
> the digital chips are where the problem probably is though, since 
the
> box has scrambled brains, so you'd need to identify any of the logic
> ICs & check those locally (i.e. instead of at the power supply); it
> could be a cracked track on the back of the board, or a single bad
> chip dragging a whole rail down. again, you might see familiar chip
> numbers, 74xx or 474xx or even 4000-series stuff, 12 or 14 pins on
> them, used as latches, gates & buffers. there are bound to be some 
of
> these around the control panel.
> 
> thinking about that- you might want to dismantle the control panel &
> check for contaminant ingress causing a shorted button- devices like
> this can behave in a peculiar way sometimes if a button is "held 
down"
> while they boot.
> 
> do you know what sort of power supply it is? is it a linear psu, 
with
> a big mains transformer, bridges, big electrolytic caps & series
> regulators? or a compact switched-mode device? the latter are easily
> identified since they are so much smaller, & usually the host device
> will work on any voltage from about 80 to 300, 50 or 60 Hz.
> switched-mode psu's generally fail completely too.
> if it's a linear power supply, it would usually have obvious output
> regulators, either 78xx/79xx three-pin devices on heat sinks, or 
power
> transistors performing the same function.
> 
> if you can find these devices & measure something "traditional" 
(12s &
> 5s, I mean) then the problem is probably with the CPU or the
> associated ram. I had a juno 106 once that wouldn't start up because
> the CPU ram was damaged; the memory battery was fine on that 
occasion,
> but I had to replace the combined CPU & memory (with a revised 
design
> comprising two separate devices that came separately by boat from
> japan!)  
> 
> >>What do you think...beyond me?<<
> 
> I couldn't possibly say! :-) the aforementioned 106 was written off 
by
> a professional synth service company & would be scrap but for my
> persistence. do you know any decent techs near you? I don't know 
what
> roland are like where you are, but they weren't much help to me; 
when

> I wanted to fix the 106, I ordered a CPU & of course, the CPU turned
> up 60 days later with no internal memory... 70 days after that I got
> the thing working well enough to deal with it's many other issues.
> 
> oh well- hope this helps.
> 
> duncan.
>