Vintage Synth Repair

Hi,
I'm new to this board. I have a totally original Arp 2600 rev2 with
3620 kb (never been worked on). It's been put away for many years, and
I decided to set it up yesterday to check everything out. The exterior
is pretty rough but it still sounds great. I think my wife is more
concerned about the exterior than I am...(!)

Although I haven't checked out the patch jacks yet, all the electronic
components seem to be ok. I'm hoping all I'll have to do is calibrate
the VCO's (something I've never done before) and clean the sliders.
I've been reading through the archives and found a couple of threads
on slider maintenance. I was ROTFLMAO when I read about submerging the
unit in a DeOxit bath (msg 657) :-))

Now for my question. My 3620 keyboard has always had a problem with
erroneous (multiple) triggers. I haven't opened it to look at the
mechanics, but many years ago a local tech told me this is a common
problem and the fix isn't a big deal. Some keys are worse than others,
but four or five are bad enough that spurious triggers occur during
normal playing. 

Can anyone tell me what's involved to resolve this problem?

David

On Thursday 18 August 2005 11:52 am, David wrote:
> Hi,
> I'm new to this board. I have a totally original Arp 2600 rev2 with
> 3620 kb (never been worked on).

Not ever?  :-)

> It's been put away for many years,

What a waste...

> and I decided to set it up yesterday to check everything out. The exterior
> is pretty rough but it still sounds great. I think my wife is more concerned
> about the exterior than I am...(!)
>
> Although I haven't checked out the patch jacks yet, all the electronic
> components seem to be ok. I'm hoping all I'll have to do is calibrate
> the VCO's (something I've never done before) and clean the sliders.

Personally I wouldn't mess with the sliders if you don't have to for some 
reason.  If you're gonna calibrate anything at all,  do the power supplies 
first!

> I've been reading through the archives and found a couple of threads
> on slider maintenance. I was ROTFLMAO when I read about submerging the
> unit in a DeOxit bath (msg 657) :-))

There's archives?  :-)

> Now for my question. My 3620 keyboard has always had a problem with
> erroneous (multiple) triggers. I haven't opened it to look at the
> mechanics, but many years ago a local tech told me this is a common
> problem and the fix isn't a big deal. Some keys are worse than others,
> but four or five are bad enough that spurious triggers occur during
> normal playing.
>
> Can anyone tell me what's involved to resolve this problem?

I don't remember running into this,  but although I've worked on a LOT of 
those units it's been a while.

I'll be looking forward to seeing other responses to your post as well.

And,  anybody have any old ARP junk they don't want,  send it to me!  :-)

--- In vintagesynthrepair@yahoogroups.com, "Tom Remi Flygel" wrote:
> I don't know if it will help, but here is a link to the ARP2600
manual in PDF form (open in Acrobat Reader), where there is a whole
chapter about VCO calibration. Users are meant to be able to do it
themselves. 
> 
> http://www.oldschool-sound.com/index.php?rub=3
> 
> They have both the 3620 service manual and user manual for download.
Plus the entire patch manual :)

THANKS TOM! This is just what I needed. I had located a site that
sells the service manuals, so you just saved me some $!

The 3620 service manual mentions the trigger problem, but all it says
is that the trigger contact is meeting the bus too late. There are no
diagrams of the keyboard/bus mechanicals. Hopefully it will be obvious
when I open her up.

David

--- In vintagesynthrepair@yahoogroups.com, "Roy J. Tellason" wrote:

> On Thursday 18 August 2005 11:52 am, David wrote:
> > It's been put away for many years,

> What a waste...

Out of sight, out of mind... I've gotten involved in other hobbies
over the years (amateur astronomy is my latest money pit) but I'm
looking forward to spending some quality time with the old 2600. I
also have a Korg 10 analog sequencer, a Sequential Circuits 800
digitial sequencer, Tascam 3440 and 8x4 mix board with DBX 155 noise
reduction system and digital delay line. My first synth was the Arp
Odyssey. I also had a Polymoog but sold it.

> If you're gonna calibrate anything at all, do the power
> supplies first!

Yes, that makes sense! But I bet I'll still need to calibarate the
volts per octave on all three VCO's and VCF. 

BTW, the pages Service Manual at the link posted by Tom are not
numbered and out of order =:-o  Hopefully I can figure out the correct
sequence using the section numbers and inferring from split sentences.

> There's archives?  :-)

surely you jest...?!

David

Hi

I use the Original Syn by DSTec and was wondering if
anyone else in this group uses one? I'm feeling a bit
lonely as there's not much on the Web about them!

Thanks

David.M


	
	
		
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--- In vintagesynthrepair@yahoogroups.com, "David" <Ginahoy@a...> wrote:

> Although I haven't checked out the patch jacks yet, all the electronic
> components seem to be ok. I'm hoping all I'll have to do is calibrate
> the VCO's (something I've never done before) and clean the sliders.

The tuning procedures can be found here:

http://www.synthfool.com/openresources/
ARP2600_1973_Tuning_Procedure_(handwritten)_1of2.jpg
http://www.synthfool.com/openresources/
ARP2600_1973_Tuning_Procedure_(handwritten)_2of2.jpg

> I've been reading through the archives and found a couple of threads
> on slider maintenance. I was ROTFLMAO when I read about submerging the
> unit in a DeOxit bath (msg 657) :-))

*checks archives*  Yeah, that's funny. :-)
I've personally seen 2600 sliders that have had DeOxit sprayed in them.  Yuck.

I've cleaned 2600 sliders before, but I forgot what solvent(s) I used.  I do remember using 
LOTS of q-tips.

> Now for my question. My 3620 keyboard has always had a problem with
> erroneous (multiple) triggers. I haven't opened it to look at the
> mechanics, but many years ago a local tech told me this is a common
> problem and the fix isn't a big deal. Some keys are worse than others,
> but four or five are bad enough that spurious triggers occur during
> normal playing. 
> 
> Can anyone tell me what's involved to resolve this problem?

My guess is to check the keyboard contacts.

--- In vintagesynthrepair@yahoogroups.com, "arp2600fan" wrote:
[snip]
> > Now for my question. My 3620 keyboard has always had
> > a problem with erroneous (multiple) triggers. I haven't
> > opened it to look at the mechanics, but many years ago
> > a local tech told me this is a common problem and the
> > fix isn't a big deal. Some keys are worse than others,
> > but four or five are bad enough that spurious triggers
> > occur during normal playing. 
> > 
> > Can anyone tell me what's involved to resolve this
> > problem?
> 
> My guess is to check the keyboard contacts.

Well, I got into the keyboard this weekend and removed all the plastic
key covers to clean them. Now they look great! As for the multiple
triggering problem, this turned out to be dirty contacts (control
voltage contact bus and spring), just as you suggested. Q-tips and
alcohol did the trick. In a few cases, the bus "appeared" to be clean
after the initial cleaning, but required some extra rubbing before the
multi-trigger problem was resolved. Fortunately, none of the contact
springs required adjusting.

On another note, the rubber bushings are seriously deteriorated. This
not only affects the 'feel' of the keyboard but the little "Y" on the
top of the bushing is spread apart, creating drag on the inside walls
of the plastic key covers. This makes many of the keys feel like
they're sticky. I have to use slightly more pressure to begin the down
stroke, and in some case, they drag on the way back up. Fortunately, I
found a source for a set of replacements. If they work as advertised,
the keyboard should feel just like a new!

BTW, I decided to sell my 2600. It may be a few weeks before I get it
ready. Prices on eBay have been out of sight lately. I just can't
justify holding onto it any longer. I'm also going to let go of my two
sequencers (Korg SQ-10 and Sequential Circuits Model 800). Sniff, Sniff.

David