Re: 2600 mods/repairs

From Bad MoFo
Sent Wed, Mar 22nd 1995, 22:01

On Wed, 22 Mar 1995, Transistor Rhythm wrote:

> i'm extremely happy about my 2600 score this weekend,

I should hope so!

> but have already blown the keyboard op amp.  

OOPS!  Don't plug it into the wall next time! %-}

> my service tech here says that the 6 pin 
> rectangular plug was bad news, as it didn't like the irregularities in 
> voltages and would blow out frequently.  he suggests that i replace both 
> end plugs with 5 pin din connectors 

Hmmm.  Don't understand the irregularities in voltages part, BUT, if your 
keyboard cable looks anything like mine, it's seen better days & is ready 
for replacement.  A 5 pin DIN is okay, as long as you don't try plugging 
your 303 into it!  You might need a Radio Slack DIN Cable instead of a 
MIDI cable - they have more conductors in them.

> along with replacing all the op amps.

This will definitely help...I'd recommend either LF411's or TL061's (you 
can spend a bundle more on AD711's, but I don't think you'll hear the 
difference).  This goes for ALL the op amps, not just the ones in the 
keyboard.  Make sure he knows to clip the compensating caps between pins 
1 & 8 - those aren't needed w/ quality op amps.

While you're at it, have him solder in 1uF, .1uF, .047uF, and.01uF poly 
capacitors into the power supply between the + & - outputs & ground.  He 
can solder them across the 8uF caps that are already there.  This should 
help smooth things out a bit - he should do it before calibration, though.
I did it yesterday - took me 15 minutes & $1 in parts.
> ARP would pay him for an additional 2 1/2 hours of labor to laboriously 
> go through and service every 2600 patch point.  this was on top of how 
> long it took for the initial "problem".  it sounds like ARP wanted their 
> 2600 customers to be taken care of.

You might want to consider doing this yourself.  I don't know how 
comfortable you are poking around inside of things these days Psi.

Can you ask this guy if he has any of the little black pointers that fit 
on each of the sliders?  Mine came missing 3, and I'd like to score some 

> also i have a line on a roland mc-4b micro composer.  what can be said 
> about this piece?  value? function?  it's supposed to be the father of 
> the mc-8.

No, it's the son of the mc-8.  4 channel CV sequencer - it might come in 
handy for controlling the 2600 or System100m, unless you'd rather go out 
& buy a really good MIDI-CV convertor.  Hmmm, not sure what they're worth 
- ask Ric Miller.  You'd better enjoy punching on calculators, though.

Hey man, I need to get your Orb video back to you.  Maybe I should drop 
it off in person?  (When you have the 100m & 2600 back from the shop %-} )

Happy Tweakin'