bad CA3280 dual OTA's

fonik · Last edited by fonik on Wed Jun 03, 2009 12:09 am; edited 1 time in total

hi all,

i recently built jim patchell's vocal filter. this monster filter unit uses 9 (nine!) CA3280 dual OTA's. i bought mine from futurlec.com, due to their reasonable price.

last weekend i brought the unit to an annual german modular synth meeting (HK2009) and the unit ran from 1200LT to 2000LT without any issues, then one filter died.
i troubleshot the unit and traced the failure down to 2 (two!) CA3280 that went bad.
sometimes it is good to 'burn in' a gear, isn't it?

now i wonder, could this have happened due to low quality ICs? the only other conclusion would be to have a weak design here, what i cannot believe, since jim patchell surely knows his stuff!

neandrewthal · Joined: May 11, 2007 Posts: 672 Location: Canada

That`s balls. I just got a few 3280`s from futurlec for my Teezers. They better work Evil or Very Mad

Funky40 · Posted: Wed Jun 03, 2009 7:54 am Post subject:

there was a thread at Synthesizerforum.de. ( maybe 2 threads )
Tomcat statet that parts from futurelec may vary, i think he was speaking about CA3280 ( or LM 394).
some were pulled, some not etc.

peng

fonik · Posted: Fri Jun 05, 2009 3:52 pm Post subject:

realy good info, peng. very appreciated.

BTW i bought 30(?) LM394 from futurlec in 2007 and they are quite fine, as far as i can tell...

TekniK · Joined: Aug 10, 2008 Posts: 1059

anyone has another source for CA3280?

i did planned to order from future but when i read thit..

peng · Posted: Fri Jun 05, 2009 5:04 pm Post subject:

Strange thing is...I would think more people would have had these problems. Perhaps Fonik and I were just unlucky?

Fonik - can you post the number from your bad 3280s? It could be a case that a batch or specific make are bad/out of spec and others may be fine.

I haven't gone through the full 100 chips yet. Many of them ARE good but you just have to test out a bunch first to find them. Hey, even if half of the 100 are bad, that comes out to $150 for 50 CA3280E. It is still a good deal.
but...I won't be ordering anymore.

It's a shame these chips where discontinued (could care less about the 3080). For any new designs I pretend they don't exist.

I'm saving the good ones for replacements or for pcbs that need them (Neural Ag., Vocal Filter).

I'm also keeping the bad chips. Some of them did really interesting 'bad' things. Could be cool for one-of-a-kind sound fx devices, etc.

p.

fonik · Posted: Sat Jun 06, 2009 3:23 pm Post subject:

here is the markings of the batch of my ICs:

CA3280E
H0011

whomper · Posted: Sat Jun 06, 2009 9:29 pm Post subject:

I've had my fair share of problems with the LM13600 ordered from Futurlec. They did not behave as required and caused me some minor headache till I replaced them.

I have ordered some 13700 to try them out.

fonik · Posted: Sun Jun 07, 2009 10:14 am Post subject:

zthee · Joined: Feb 20, 2008 Posts: 414 Location: Stockholm

etaoin · Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL

numbertalk · Posted: Mon Jun 08, 2009 12:37 pm Post subject:

Same exact thing with me. Seems ok but since the Threeler is an original design I don't have the total frame of reference to say it performs 100% as it should but it seems ok. Not sure of the datecode on the chip offhand can check later.

fonik · Posted: Mon Jun 08, 2009 1:48 pm Post subject:

just for clarification:

at the first power up the vocal filter worked fine, and it worked fine at any occasion i used it from then, unitl the day i run the unit constantly for more than 8 hours. some call that a "burn in", i think!? after these 8 hours two 3280 OTAs went bad. one totally, the 2nd lost one half...

TekniK · Joined: Aug 10, 2008 Posts: 1059

fonik · Posted: Tue Jun 09, 2009 2:02 am Post subject:

etaoin · Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL

Ricko · Posted: Tue Jun 09, 2009 8:22 pm Post subject:

What actual proof (not second hand or speculation) does anyone have that Futurlec supplies pulled parts for their standard catalog? (Either now or ever...)

Ever since I saw that one Asian specialty supplier was slagging off at his business rival (whether fairly or unfairly) I have been worried that the meme of "cheating foreigners" would become the first thing that comes into people's minds rather than the last. (I am sure that was not Fonik's intent, he is just asking AFAICS)

How do you tell a pulled part? (serious question: bent pins?) I have had at least half a dozen orders from them of lots of different things, all good as far as I can tell.

When I Google for comments about Futurlec the comments seem to be either old (did they not have their fulfillment capability in place in 2005?) or irritating (people from a certain country who don't realize that shipping goods from the other side of the globe takes longer than 1 week, apart from order filling time.) There was the recent comment about resistor tolerances, IIRC too (I tend to think that if you want such exact values for resistors, you probably want more than 1% or need a trimmer anyway, but I agree that things should match their description, especially in this age of Six Sigma)

They have a 90 day warranty: I am not sure that it would apply when plugging into a new board with a new board design with a new circuit design though, but you could try. If there is a problem with quality, tell them. How will they know if a supplier is dodgy unless they are told?

frijitz · Posted: Tue Jun 09, 2009 8:36 pm Post subject:

TekniK · Joined: Aug 10, 2008 Posts: 1059

[quote="frijitz"]

frijitz · Posted: Tue Jun 09, 2009 10:14 pm Post subject:

fonik · Posted: Tue Jun 09, 2009 11:23 pm Post subject:

i did not say anything at all about pulled parts - i was just stating that 2 out of 9 CA3280's in my vocal filter went bad after 8 hours of constant operation, due to low quality standards of the manufacturer probably. Very Happy

etaoin · Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL

TekniK · Joined: Aug 10, 2008 Posts: 1059

etaoin · Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL

The only source I know which has been pointed out is Bridechamber, but when I asked a couple of weeks ago Scott only had a few left and was selling close to $20 each. So that's not a real source in my book.