ARP 2600: Nothing But Problems (HELP!)

[sarmeast]

I've been "permanently loaned" an ARP 2600. It's been in a basement for years, and has been causing nothing but problems.

The first problem is that I think the ADSR is broken. When i press a note, it sustains forever. Could this be the keyboard? It's a 3620 keyboard.

Secondly: I can't get the VCF signal to patch through the ADSR and VCA. I'm not sure if I'm doing anything wrong, I haven't quite figured out how to fully program it.

Thirdly: Depending on the octave you play, the synth does random things. In one octave, the pitch is perfect. In another, it's slightly off. In another, it rapidly dives in pitch. I think this might be the keyboard, as you need to wiggle around the keyboard cable in order to work.

The worst problem is that the keyboard doesn't even work half the time. I have to wiggle around the cable to get it to work. Could this be the synth or the keyboard?

Thanks!

[hfinn]

The cables are notoriously bad.

[Automatic Gainsay]

First of all: with age comes jack wonkiness. The more you use the jacks, the more you'll see functionality do what it should. Just keep plugging 1/8th inch cables into the jacks until the module starts to work right.

Second of all: Oscillator tracking is likely to go after time. You'll get different oscillator pitch relationships in various octaves as a result... you'll need to range and scale the oscillators.

Lastly: I don't know what to tell you about the keyboard except that I know that the cable contacts can lead to behaviors like those you're describing. You might try cleaning the contacts.

[Murderhausen]

I'll give you $1500 for it.

[guitarsandsynths]

I'll give you $1500 for it.

I'll give you 1550!

[schmidtc]

Trying to fix these problems would take some knowledge of electronics. The free service manual and all parts you will are readily available for both the 2600 and 3620, including new keyboard cables/plugs and 1/8 jacks. The release time is probably not a problem with the 3620 and if it's a problem with an encapsulated 4020 module, this is potentially a difficult repair. Calibrating the oscillators for logarithmic Volt/octave response is covered in the manual and takes just a few minutes, you can get it here:

http://www.guitarfool.com/ARP2600.html

If you don't have any knowledge of electronics, let us know what part of the world you're in. Chances are there is a good technician nearby.

[shaft9000]

i don't know what year or Rev yours is, but mine is a Rev2 Tonus from ~'72/'73

I bought it in original condition, and it had several issues.
-1st, and worst: the filter section would completely die after about 30-60 minutes. Required a complete 4012 replacement/rebuild and the transistor-ladder circuit rematched by my tech.
-3604 keyboard bushings and resistors were dead or dying - contact and hitting correct intervals were a bit shaky, at best. Chaos at worst. The low-note priority is a bit disturbing even when it DOES work correctly.
-oscillators out of calibration
-PSU needed new capacitors after 35+ yrs - almost totally dried-out!
-preamp was kaput
-keyboard cable replaced
-some faulty jacks replaced/fixed

all in all it cost me around 800 USD to get these issues repaired.
I also had some mods done, but that's optional....i do highly recommend hardwiring PWM from osc2 to the other oscs to replace the hardwired 'noise' PWmod routing (wtf was ARP thinking??). Also, I had the saw output jack of osc1 changed to a sine for more flexible LFO capabilities.

The first problem is that I think the ADSR is broken. When i press a note, it sustains forever. Could this be the keyboard? It's a 3620 keyboard.

It's different from hardwired synths - the note will sustain forever unless the 'intial gain' slider is at zero.
Also, the interaction between the ADSR slider in the filter section and the ADSR settings themselves are crucial.

Secondly: I can't get the VCF signal to patch through the ADSR and VCA. I'm not sure if I'm doing anything wrong, I haven't quite figured out how to fully program it.

Respectfully, nothing "goes through" the ADSR - it's a modulator.
Unlike a filter, (audio) osc or amplifier, it just controls other things, like 'invisible hands' moving sliders for you over time.
As for the VCA, it should be directly hardwired to the output of the Filter, so it seems like there may be a problem. Try patching the filter output into the VCA manually w/ a cable. Then see if it takes audio patched via cable from an Osc to determine which section may be faulty.

Thirdly: Depending on the octave you play, the synth does random things. In one octave, the pitch is perfect. In another, it's slightly off. In another, it rapidly dives in pitch. I think this might be the keyboard, as you need to wiggle around the keyboard cable in order to work.

I'm not a tech, but I suspect it's the Osc, the keyboard or likely both.

Best of luck !

[I12]

a "permanently loaned" or even a loaned bit of temperamental gear is a pita!!

do you plow money into it or not?