The Hundred-Buck Amp Challenge

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MTBF of an electrolytic drops rapidly with temperature. You see ratings like 1000 hour, 5000 hour, etc. That is the average lifetime at maximum temperature. Somewhere there should be a MTBF VS temp curve. Panasonic used to publish one and there was also a lifetime derating for voltage and ripple current. When you realize that 1000 hours isn't very long for a device that sees a lot of use, you try to use 105 degree C rated caps in tube circuits and keep them away from the output tubes.
Panasonic still has some "old appnotes" online about electrolytic caps but I can't find Panasonic's page that links to them. I've saved them, and only found the actual files by googling for one of the (odd and unique) filenames. The links are in post #4 here - this is a bunch of good tech info on electrolytics:
Amp question. - Hydrogenaudio Forums
 
I stripped the board of parts up to the power supply and did the new circuit. Got the sockets and transformer mounted. Sure hope this thing is going to work.

Tabletop04.jpg
 
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Joined 2004
How to screw up a really nice day.

I will tell you. First, break off one of the PT primary pins....do some nasty job with a lighter and a carving knife to fix it up. Boy, that hole sure looks ugly. Now you're not feeling oh so happy so you try to regain your former good mood via illegal ways. OK.... now you're stoned, things are beginning to look better, start the paint job and screw it up again!! By this time I'm really pissed off so I need another smoke.....brain toasted....no more work for today. End of story.
 
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Working out the layout. Did a half baked version last night just to show the build is not that scary. The software I used did not have a four pole three position switch so I sort of made my own.

What software did you use for that layout? I have used OmniGraffle in the past and it seems to work well, but what you're using looks purpose built for electronics.
 
Challenge deadline extensionS

Ok everyone,
now it's my turn to ask for an extension of the deadline.

I just got some mail about a matter that should have been closed and over with years ago that requires my immediate attention, and the state is not going to wait for me to take my time about getting back to them. I'm going to have to go downtown and clear something up which promises to involve time-consuming layers of red tape, and takes priority over everything else.
 
Deadlines come and deadlines go, but the only ones that really matter are the ones that come out of the bosses mouth at +120 db!!!!! I am working on one of those now. Project not finished.....closing report due Nov. 23.

The challenge deadline was issued by BST and changed at least once. it only matters if he chooses to determine a winner and award a prize. In my view the prize isn't important, and would probably be best applied toward the medical bills.

This thread has brought a group of people together to discuss, share, and learn about guitar amps. While we don't always agree on things, we have all learned from this endeavor and it should continue on as long as someone has something useful to contribute. That was the intended effect and it has worked.

I may or may not have an amp finished by the end of this month, and as it seems, I am not the only one who gets sidelined by lifes little interruptions. I guess it's about time to post the BOM and schematics of the amps as they exist on Oct. 31.

At the start of the week it looked like hurricane Rina was going to come to town this weekend and ruin everyones day. Now it looks like we will just have a whole bunch of rain. There definitely won't be any Back Yard Amp Lab this weekend.
 
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Joined 2004
BST is probably busy now as well. That makes three of you with deadline problems. Since there will be about six amps presented for this competition (yes, there will be a winner) that makes it enough for changing the deadline. I'm going to wear BST's robe for a second and say: new deadline is now November 15th and this time is FOR REAL. (no more excuses please :))
 
Good, I have been trying to find time to finish my amp, I doubt I will make the $100 mark but still wanted to get it done to keep the rest company. I am back to square one on my kitchen floor, just got a message two weeks after I should have got it saying the manufacture is having trouble making it and I should pick another. In the mean time, no stove, cabinets are in the living room, pots and kitchen stuff is packed away. As much as I like my microwave...

I was going to buy new appliances once the floor was in as the old ones are shot, Now I have to go through the whole floor shopping thing again. Was hoping to have it all done for Christmas, was going to have the family over. Life is full of fun little surprises.
 
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Joined 2004
We don't need no stinking deadlines

I really need them to keep me functional. If I were immortal I wouldn't get out of bed, ever. Well, maybe just to go to the toilet. Not sure if immortals need to go to the toilet, though.


In my view the prize isn't important

Are you suggesting that BST should raise it to 1000$? :D Yeah, that would bring some motivation. I agree the prize isn't important but we must have a winner and then some losers too. Haha.
 
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Joined 2011
The chassis and the potted torodial PT comes from a power supply bought at a surplus store here in Madrid for 2 euros. BTW, I can't believe the prices, a bag with six axial 100uF/350 volts caps for 1 euro, 20 MKP 400V 2uf caps....yes, another euro. Lots of high voltage Sprague caps ridiculed priced and much much more...I'll stop here before some of you get really upset. Hehe.

Where in Madrid do you find deals like that?

Jaz
 
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Joined 2004
Center of town. Small shop full of electronic goodies is surrounded by pricey hifi stores. Oh the irony. Out of curiosity, I talked with the manager about their silly prices....he told me he has millions of caps stored in a warehouse (WTF?). Wima, Siemens, Sprague, ROE... all good brands he sells no junk. Anyway, now I need bigger drawers. Resistors have silly prices too, I bought four 25W 150 Ohms Dale resistors for 1 euro.