Vintage Synth Repair

I have an ARP Odyssey 2 that only outputs a faint clicking/thumping. The audio signals disappear across R1-R3 in the Audio Switcher/Mixer Section on Board C-II. I'm guessing the problem lies within the 4075 submodule but I'm not sure how to proceed.

Any thoughts?

The string section doesn't go through the filter module.


Sent from my Apple ][e

On 17/05/2012, at 12:40 PM, "Alexis V. Rogers" <alexis.v.rogers@gmail.com> wrote:

> I have an ARP Odyssey 2 that only outputs a faint clicking/thumping. The audio signals disappear across R1-R3 in the Audio Switcher/Mixer Section on Board C-II. I'm guessing the problem lies within the 4075 submodule but I'm not sure how to proceed.
> 
> Any thoughts?
> 
>

At 15:54 Uhr +1000 17.05.2012, Mike wrote:
> The string section doesn't go through the filter module.

He wrote "Odyssey"! Since when does the Odyssey have a string section?

At 2:40 Uhr +0000 17.05.2012, Alexis V. Rogers wrote:
> I have an ARP Odyssey 2 that only outputs a faint clicking/thumping. The
>audio
> signals disappear across R1-R3 in the Audio Switcher/Mixer Section on Board
> C-II. I'm guessing the problem lies within the 4075 submodule but I'm not
>sure
> how to proceed.

You could try to run a wire across input and output of the filter module
(pin 1 and 10) to short it out temporarily. This will at least show if the
problem is with the filter or with the amp section.

Oops. My bad.

I was reading another post about an omni. Sorry.

Sent from my Apple ][e

On 17/05/2012, at 5:31 PM, Malte Rogacki <gacki@...> wrote:

> At 15:54 Uhr +1000 17.05.2012, Mike wrote:
> > The string section doesn't go through the filter module.
> 
> He wrote "Odyssey"! Since when does the Odyssey have a string section?
> 
>

Okay, so I jumpered the input and output of the sub module and nothing changed. The filter is ruled out. 

Sent from my iPhone

Does the "VCA Gain" control do anything?

It should result in a kind of drone regardless if a key is pressed or not.

Had the same issue on mine (model 2800). Fixed by changing the LM301 (ref A1) on board C. Needs recaping however (luckily far less tants in an Odyssey compared to an Omni)..

--- In vintagesynthrepair@yahoogroups.com, Terje Winther <terje.winther@...> wrote:

>
> In my experience it is more likely that something in the VCA section  
> has failed.
> Quite often the CA3080 in the VCA fails.
> Second to that, caps fails. You could try to desolder caps in order to  
> isolate various parts of the signal chain that might short out the  
> signal.
> The clicking/thumping probably means that the envelopes are still  
> working.
> 
> Den 17. mai. 2012 kl. 04.40 skrev Alexis V. Rogers:
> 
> > I have an ARP Odyssey 2 that only outputs a faint clicking/thumping.  
> > The audio signals disappear across R1-R3 in the Audio Switcher/Mixer  
> > Section on Board C-II. I'm guessing the problem lies within the 4075  
> > submodule but I'm not sure how to proceed.
> >
> > Any thoughts?
> >
> > 
> 
> Terje Winther
> terje.winther@...
> http://www.wintherstormer.no/
>

The VCA Gain slider only increases hiss. There is no drone. The AR and ADSR all affect the thumping/clicking sound which is just barely audible. With a scope, I can trace the audio signal into Board C-II, through the Audio Switches and Mixer Sliders. But the signal suddenly disappears at the junction of R1-R3 and C1 and C13, just before the input of the 4075.

I completely removed the submodule and jumpered over it. There is now sound. So the problem is within the submodule. 

--- In vintagesynthrepair@yahoogroups.com, "Alexis V. Rogers" <alexis.v.rogers@...> wrote:

>
> The VCA Gain slider only increases hiss. There is no drone. The AR and ADSR all affect the thumping/clicking sound which is just barely audible. With a scope, I can trace the audio signal into Board C-II, through the Audio Switches and Mixer Sliders. But the signal suddenly disappears at the junction of R1-R3 and C1 and C13, just before the input of the 4075.
>

Feel under your bridging board to see if any of the pins are one out on the
sockets underneath?    I have taken to using touch to verify each one is
properly lined up.

Couldn't duplicate anything like this problem on two 2800s with different
combo settings of envelope and slider.

 

Lorne.

From: vintagesynthrepair@yahoogroups.com
[mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of Alexis V. Rogers
Sent: Friday, May 18, 2012 9:46 AM
To: vintagesynthrepair@yahoogroups.com
Subject: [vintagesynthrepair] Re: ARP Odyssey II no sound

 

  

The VCA Gain slider only increases hiss. There is no drone. The AR and ADSR
all affect the thumping/clicking sound which is just barely audible. With a
scope, I can trace the audio signal into Board C-II, through the Audio
Switches and Mixer Sliders. But the signal suddenly disappears at the
junction of R1-R3 and C1 and C13, just before the input of the 4075.

The pins are all in the proper sockets.

See my posting above. I have verified that the issue is within the VCF submodule. I tried jumpering the input and output of the VCF with no result, but with the submodule completely removed and a jumper across, I get output.

I've recapped the VCF, but haven't found what is shorting the audio signal.

--- In vintagesynthrepair@yahoogroups.com, "Lorne Hammond" <lhammond@...> wrote:

>
> Feel under your bridging board to see if any of the pins are one out on the
> sockets underneath?    I have taken to using touch to verify each one is
> properly lined up.
> 
> Couldn't duplicate anything like this problem on two 2800s with different
> combo settings of envelope and slider.
> 
>  
> 
> Lorne.
> 
> From: vintagesynthrepair@yahoogroups.com
> [mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of Alexis V. Rogers
> Sent: Friday, May 18, 2012 9:46 AM
> To: vintagesynthrepair@yahoogroups.com
> Subject: [vintagesynthrepair] Re: ARP Odyssey II no sound
> 
>  
> 
>   
> 
> The VCA Gain slider only increases hiss. There is no drone. The AR and ADSR
> all affect the thumping/clicking sound which is just barely audible. With a
> scope, I can trace the audio signal into Board C-II, through the Audio
> Switches and Mixer Sliders. But the signal suddenly disappears at the
> junction of R1-R3 and C1 and C13, just before the input of the 4075.
>

Tants or transitor failed?  The 4075 is around an a good hot substitute if
needed.  It is often scrounged out of lesser arps.  JL put one in my oddy
rev II and it is hotter and nastier than my oddy rev III side by side.

Lorne

 

From: vintagesynthrepair@yahoogroups.com
[mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of jammie
Sent: Monday, May 21, 2012 10:44 AM
To: vintagesynthrepair@yahoogroups.com
Subject: Re: [vintagesynthrepair] Re: ARP Odyssey II no sound

 

  

what revision vcf as theres a few different models of the submodule

 

check the transistor pairs

----- Original Message ----- 

From: Alexis V. Rogers <mailto:alexis.v.rogers@...>  

To: vintagesynthrepair@yahoogroups.com 

Sent: Monday, May 21, 2012 6:30 PM

Subject: [vintagesynthrepair] Re: ARP Odyssey II no sound

 

  

The pins are all in the proper sockets.

See my posting above. I have verified that the issue is within the VCF
submodule. I tried jumpering the input and output of the VCF with no result,
but with the submodule completely removed and a jumper across, I get output.

I've recapped the VCF, but haven't found what is shorting the audio signal.

--- In vintagesynthrepair@yahoogroups.com, "Lorne Hammond" <lhammond@...>
wrote:
>
> Feel under your bridging board to see if any of the pins are one out on
the
> sockets underneath? I have taken to using touch to verify each one is
> properly lined up.
> 
> Couldn't duplicate anything like this problem on two 2800s with different
> combo settings of envelope and slider.
> 
> 
> 
> Lorne.
> 
> From: vintagesynthrepair@yahoogroups.com
<mailto:vintagesynthrepair%40yahoogroups.com> 
> [mailto:vintagesynthrepair@yahoogroups.com
<mailto:vintagesynthrepair%40yahoogroups.com> ] On Behalf Of Alexis V.
Rogers
> Sent: Friday, May 18, 2012 9:46 AM
> To: vintagesynthrepair@yahoogroups.com
<mailto:vintagesynthrepair%40yahoogroups.com> 
> Subject: [vintagesynthrepair] Re: ARP Odyssey II no sound
> 
> 
> 
> 
> 
> The VCA Gain slider only increases hiss. There is no drone. The AR and
ADSR
> all affect the thumping/clicking sound which is just barely audible. With
a

> scope, I can trace the audio signal into Board C-II, through the Audio
> Switches and Mixer Sliders. But the signal suddenly disappears at the
> junction of R1-R3 and C1 and C13, just before the input of the 4075.
>

Thanks. That did it. There was a short in Q1.

--- In vintagesynthrepair@yahoogroups.com, "jammie" <jammie.emma@...> wrote:
> check the transistor pairs