Obsolete UA759 chip needed...

[maximee]

Hey fellas...
I finally got to start the repair on my old old 70's Crumar DS-2 synth...
Now the good thing is: I found the problem to be the UA759 op amp IC sitting on the main board...
the bad thing: this IC is long gone from what I found out...I can't get it through my local retailers and Ebay didn't have it either. So maybe one of you guys possibly has it?

Of course I'm willing to pay, trade or cook you a nice, healthy and yummy vegan meal
or I write you a song...Basically I'd do pretty much anything to bring that synth back to life!  
Thanks for reading...
Flo

[nelson]

Would you do a charity walk? across hot coals, for 6 miles before going for a swim in a live volcano?

[Rob Strand]

I think the national semi version LM759 is still around.  I used these not too long ago.  I got them from Farnell.

The only thing I would be careful of is the package type - make sure you get all the suffix letter right.

I *have not* check the LM759 is a match.

[maximee]

Yes, sir!

But only if I get to wear my see-through shorts...  :idea:

[David]

Would you do a charity walk? across hot coals, for 6 miles before going for a swim in a live volcano?

Naahhh...  I've got a better idea.  He has to buy up all the available SAD-4096 and CA3080 chips and donate them to Aron!

[nelson]

Naahhh... I've got a better idea. He has to buy up all the available SAD-4096 and CA3080 chips and donate them to Aron!

For a competitive price ofcourse    

[puretube]

http://64.233.183.104/search?q=cache:FPNNd-9ThFEJ:www.ersatzteil24.com/bauteile15.htm+ua759&hl=de

no guarantee...

[maximee]

http://64.233.183.104/search?q=cache:FPNNd-9ThFEJ:www.ersatzteil24.com/bauteile15.htm+ua759&hl=de

no guarantee...

thanls for looking, I already called them and they don't have it anymore.

[Ge_Whiz]

Anything special about the UA759?

Tried http://members.aol.com/fibraintern/?

[Paul Perry (Frostwave)]

Anything special about the UA759?

Tragically, my Fairchild 1973 data book has it as an improved version of the 741, with input common mode includign negative supply, and a whopping output current of 325mA. Comes in a metal can or a VERY unorthodox 4 pin not quite TO-220.

What is it doing in the synth? might be easily replaced by another unit.
There are circuits for converting some ordinary op amps to high current devices with a transistor pair on the output, for example.

[Paul Perry (Frostwave)]

LM759 *IS* a match!!!
and, they have it at Rochester Electronics (USA).

[maximee]

Thanks everybody and thanks Paul! I will try to get a hold of the LM759 and let you know how it works out  

[maximee]

WHAAAT?


LM 759 CP (38169)
*   IC
   1 Stück 77.81 EUR   

http://www.hinkel-elektronik.de/shop/2800.html

80 bucks for an IC? They are crazy...
I'll try Rochester Electronics...

[Paul Perry (Frostwave)]

Maximee, please let me know how you get on with Rochester!
I havn't bought from them myself.
I suspect you might be making that chip yourself :cry:

[toneman]

After googling,
all i come up with for a LM759 is this...

http://www.alldatasheet.net/datasheet/LM-6.html
[scroll down for LM759....]

it's a power opamp;
kinda reminds me of the LM380 &  LM386.
Is this, by chance, the headphone output of your Crumar??
If U have a schematic, U probably can sub something in.
While not pin-4-pin, U certainly can make something work.
If not a "power" OA, mayB a simple LM709 or LM741 would work.
Do U have a schematic??
stayrebuilt
tone

[Paul Perry (Frostwave)]

home.versatel.nl/manualswarehouse/man/mantypec.htm
say they have a manual (prob a copy!) for sale for 10 Euro.

I've found an unconfirmed hint that the bad chip is in the power supply.
if it is, there is always the option of an alternative supply.

The worst possible scenario, would be that it is used as a thermostatically controlled stable oscillator (using the power section to heat up the separate transistors, themselves forming part of an exponential converter for the main oscillator). I havn't checked, but I think Jim Williams designed an oscillator like this many years ago..

[Vsat]

SGS-Thomson makes the L165 - a very nice power op amp (up to 3 amps output) in a 5-pin power tab package. Pretty good specs for audio too. uA759 uA798 etc are very ancient designs.
Cheers, Mike

[maximee]

First off, I want to thank everybody who's helping me with this.
Now hold on to your seat, gentlemen...
Look what I received from Rochester Electronics via mail:

Good morning, Florian!

            After doing some checking, I am pleased to offer the following:

REI    LM759MH  - 1 piece @ $153.51

REI    LM759CP  - 1 piece -these parts are built-to-order and we can't manufacture them for less than 100-pieces at a time.

WTF? Seriously... $153.51 ain't funny anymore. Besides, I would need the CP version anyways...Oh and yes, as you can ready they'd make 100 for me, but I only need one  :?
I don't even dare to think about what the price of a 100 of them would be!

I have the schematics for the synth here, some nice guy emailed them to me some time ago, but I can't find the file, I only have it printed out.
The UA759 is sitting right on the main board - it ain't got nothing to do with the power supply, because that one works after fixing it

Unfortunately the schematic of the main board looks weird. Actually it is not a real schematic, it is just the positions of the transistors and ICs, no other stuff and no connections between them. Looks like some sort of "circuit copy protection" from Crumar. All other modules are well documented. I'll see if I can get a scan of it, then you will know what I'm talking about.

I'm still awaiting some other quotes from some different obsolete part suplliers, although I'm not too confident that they will be much lower in $$$ !

So, for now I'm kind of stuck with this project...I'll see if I can work something out by replacing it with another IC. Too bad that's the first time I'm doing such a big thing like this...
We'll see how I get along. Thanks for reading  

[Paul Perry (Frostwave)]

Maximee, perhaps it is time to join analog heaven, details at:
http://code404.com/faq/
they are dedicated to keeping old synths going.
Also, synth-diy, see http://www.oldcrows.net/~patchell/sdiyfaq.html

Someone there will know what to do!
As for the prices iof some of these old parts.. they are still sitting in some industrial controllers (including nuclear reactors, I wouldn't be suprised) & when one goes, people are pretty happy to pay $00000s, let alone $150 or so.. I guess it is in a way nice that you CAN get them custom made, ifyou were a billionaire!

[DiyFreaque]

Have you tried this?

http://www.electronicplus.com/search-return.asp?search=759&Submit=Search

$7.50 apiece

and keep yer fingers crossed......

Cheers,
Scott