Substituting tantalum capacitors

[Gus]

Off topic about changing caps in effects.

Take an effect like the RAT. The interesting thing is if one changes the caps on the two - input to ground legs. I have measured the caps value and removed Als and installed tants of very close to the same value not ESR in a friends Rat. Out of a lot of the parts changing(web calls it modding) in effects changing the two caps in a rat does seem to be an audible change. The 560 ohm leg 4.7uf and 47 ohm leg 2.2 uf. the other electros don't seem to make much difference.

http://www.diystompboxes.com/pedals/PCRAT1.GIF

Now I realize the ESR is different between Als and tants and maybe the 2.2 uf Al ESR is a good % of the 47 ohm resistor. Maybe it is the 2.2uf that some people seem to be able to hear when changed maybe it might be a change in the highpass.

It might be interesting to run distortion of matched under 10uf Al and tant cap values in non inverting amp with a low value - to ground resistor like the RAT has

 

[burdij]

Not sure where the info on tantalum sources came from but the largest tantalum mines are located in Australia. Australia produces about 30% of the world consumption. The largest deposits of tantalum and niobium in the world are located in Saudi Arabia and are currently under development. Tantalum is produced as a byproduct of tin smelting and a significant amount of the world consumption is produced by tin mining in Thailand, Malasia and other areas.

 

[thermionic]

I don't think the C4 documentary was inferring all supplies of tantalum are from immoral sources, just some of those in the war torn parts of Africa.

Wikipedia isn't always accurate, but it seems to correlate with the C4 doc: http://en.wikipedia.org/wiki/Coltan

BTW - C4 news is by far the best news on UK tv - by a large margin. A one-off C4 news special is unprecedented, so I would tend to suspect they did their homework before broadcasting the coltan special.


Justin

 

[Swedish Chef]

I recently had a Neve 33609 on the bench that just didn't want to go away.
I spoke to Wayne K about it in a few emails and he advised me of this thread, so here I am, sharing my experiences.

Firstly the ref schematic is here.
Page 18

The unit first came in when the Power Tx went open circuit on the primary so I replaced it with an over-spec torroid and soaked it for a couple of days. After I was satisfied that it would not go wrong, I returned it to the client.

He didn't try it for a month but had it turned on for most of that time.
When he came to try it, both channels' compressor sections had given up.
So it returned to me.
On tracing the signal through the compressor side-chain, I seemed to be getting what I would have expected up until the junction of C7 and R59, after which it all disappeared.
I checked he caps with my Cecil Bateman Tan-Delta meter (excellent!!!) which showed all caps seemed to be behaving as one might expect, and then moved on to transistors that I thought could have taken a hit when the PT blew. No dice.
After lots of head-scratching I went back to that C7 eventually, removed it and measured it with an ohm-meter.
50Ohms.
Eh?
Replaced those on both channels and all is still going swimmingly a couple of weeks later...

TANTs: Grrrrrrr

chef

 

[gar381]

tants...not if I can help it

They do love to turn into pieces of wire in the
nicest of gear!!

GARY

 

[plumsolly]

Just thought I would add some recent information regarding the moral questions about Coltan/Tantalum. From Amnesty International:

"A small window of opportunity just opened this week that could finally break the cycle of weapons freely flowing in to the Democratic Republic of Congo (DRC) and conflict minerals irresponsibly being mined out.

Right now, the House of Representatives is weighing a piece of legislation that would make it easier to identify imports into the United States that contain minerals such as coltan, cassiterite, wolframite - commonly found in cell phones, laptops and other electronic devices - used to fund the activities of armed groups operating in the DRC.

If Congress required companies to disclose the origins of the minerals used in their products, then we, as consumers, could be assured that the electronics and products we purchase do not directly finance conflict or fuel human rights abuses."

According to Wikipedia:
"In central Africa the colloquial term coltan is used to refer to niobium (COLumbium)-containing and TANtalum-containing minerals. The United States Geological Survey reports in its 2006 yearbook that this region produced a little less than 1% of the world's tantalum output for the past four years."

So it sounds like not a lot of tantalum comes from minerals mined in Central Africa, but they are still able to mine and sell enough of it to help finance these tragic wars. I would suspect that, of this tantalum, the diy community consumes VERY little. But, even so, I feel more directly connected, being a purchaser of tantalum capacitors. So, here is a link to a letter you can send encouraging the U.S. Congress to address the issue of transparency as to the origin of these minerals when they are imported into the U.S. http://takeaction.amnestyusa.org/siteapps/advocacy/ActionItem.aspx?c=jhKPIXPCIoE&b=2590179&aid=13740&ICID=S1004A02&tr=y&auid=6239771

and here is a link to other Amnesty International issues that you can support if you want: http://www.amnestyusa.org/take-action-online/page.do?id=1031043

Sorry this ended up in the Drawing Board, it sort of morphed into a Brewery thread.

Best, Ben

 

[12volts]

Not audio, but relevant to the comments made so far. Years ago, I ran a Lab. that used a lot of CAMAC gear. Very high spec.
gear used predominantly in the nuclear industry. One single circuit board could cost £2000+ , each rack would carry 12 boards.
Virtually all early faults were tantalum caps. Obvious when they had burnt a hole in the pcb !! ALL tants. were changed to electrolytics
- no more problems. As far as I am concerned, and as a solution, I have not used them for 25 years+ whatever the application.