ARP Omni Repair

  • Thread starter Thread starter peritus
  • Start date Start date
peritus

peritus

The not fountain head
Trying to repair this synth... Lots of problems with it.. I'm looking to replace all the major components...

Here's a good link on the subject:
http://people.umass.edu/brownp/arp/techinfo.html

Anyways... I want to start with the CD40xxx chips, as described at the link...

PART ARP/MFG NUMBER DESCRIPTION QUANTITY REPLACE
1404201 CD4007AE IC, C MOS PAIR PLUS INVERTER 1 x
1400601 CD4011AE IC, GATE, 4 X 21, NAND 3 x
1404401 CD4013AE IC, DUAL `D' FF, SET/RESET 4 x
1404501 CD4016AE IC, QUAD BILATERAL SWITCH 7 x
1404601 CD4025AE IC, GATE 3 X 31,NOR 7 x
1405801 CD4069BE IC, HEX INVERTER 11 x
1405101 CD4071BE IC, GATE, 4 X 21, OR 5 x
1405201 CD4520BE IC, DUAL BINARY UP COUNTER 6 x

Here's the problem.. I want to make sure that I obtain the proper parts before beginning the project... When I search for CD4007AE at digikey, I get no results.. If I search for CD4007, I get CD4007UB and CD4007UBM

http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=296&M=CD4007UBE
http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=296&M=CD4007UBM

Will these work? Should I order, without regard to the suffix?

It would be awesome if someone could help me get a parts list going using digikey parts... I'm paranoid that I'll buy the wrong thing and it'll explode.. :D
 
the letters after generally indicate an upgrade (like a mil spec/etc) or packaging change (like surface mount) so you may need to go to the manufacturers site to check it out for sure...
 
dementedchord said:
the letters after generally indicate an upgrade (like a mil spec/etc) or packaging change (like surface mount) so you may need to go to the manufacturers site to check it out for sure...
Click to expand...


Now I'm really confused...

So digikey has the two listed above...

I'm physically looking at the CD4007AE... Its packaging is 14 pins with straight arms (not the surface mounted folded arm type)...

So according to the datasheet CD4007UBE (diagram N) has straight arms but 16 pins...

And the CD4007UBM (diagram d) has folded arms and 14 pins...

Even more confusing is that the digikey listing for both is 14 pins...

Would it be reasonable to say that the digikey part 296-3501-ND (their CD4007UBE) is a 14 pin straight armed version (aka exactly what I need)?

Thanks... There really must be an art to reading datasheets...
 
Why are you starting by replacing a bunch of chips? Unless it got struck by lightning or something, I doubt any of your problems are caused by defective silicon. In gear that old the most likely problems are:

  • Dirty chip contacts
  • Dirty jacks for patch cables
  • Worn out jacks for patch cables
  • Dirty interconnect plugs between boards
  • Dried out electrolytic or paper capacitors resulting in unstable supply voltage

The chips would be somewhere around dead last, so unless you're replacing things like op amps in the signal path to try to get better sound quality or something, I wouldn't start with that....

In my experience, when dealing with the guts of vintage analog synths, electronic organs, etc., the best thing you can do for it is disconnect every single connector, hose it down with contact cleaner (e.g. DeOxIt), then repeatedly plug and unplug it several times before you plug it back in permanently. It's amazing how often bizarre problems are just caused by some corroded contact.

If that doesn't fix it, sit down with the schematic and check power supply voltages at all the test points, then slap a scope on each point and make sure the power is clean.

If you've already done all that, then never mind.
 
dgatwood said:
Why are you starting by replacing a bunch of chips? Unless it got struck by lightning or something, I doubt any of your problems are caused by defective silicon.
If you've already done all that, then never mind.
Click to expand...

actually i could'nt agree more ... he just sounded like he was already in progress...
 
Will do... I've been chatting with the author of the page linked to above, via email. For the sake of detail.. Here are the problems I'm having...

The synth section is completely silent.

On the strings side, the release control does nothing.

The violin button is permanently on.

The cello button does nothing.

The bass and viola section come on intermittently.

Anytime a note is pressed on the string section, it produces a long sustaining "un-pitched" note (which I believe to be coming from the violin section). The note it produced doesn't change when a different key is played. However, if bass or viola are working, their properly-pitched note is produced in addition to the non-pitched violin note.

The synth bass 16' and 8' led's intermittently light up (upon hitting the buttons), but pressing the synth 8' and 4' buttons does nothing.

Since the synth and synth bass sections aren't producing any sound at all, I'm pretty sure there are multiple things wrong there.

Pressing waveform enhancement doesn't light the led or change the sound.

A couple keys on the keyboard are sitting at different heights. This is minor, but pretty annoying.

I'm pretty sure I'm forgetting a couple details, but that's the main overview of problems. Please keep in mind that I bought this synth at a garage sale (for $50) and it has been gigged extensively (so said the seller).

Given all these problems, systematically replacing things seemed to be a good idea. Hopefully I can do something for it.

I'll be disconnecting the p/s from the rest and doing some multimetering... Wish me luck.. :)

Thanks
 
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