Gainclone building contest details (from BrianGT group order)

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Re: Hey Sherman & Tor M...

JazzzSpazzz said:
Sherman---Where did the aluminum tape come from & does it conduct electricity--e.g. is it real aluminum?

TIA,
Bret Morrow

Bret,
The aluminum tape came from American Science and Surplus. They do have a web site you can order from but I don't know if the tape is available there. I got it from a retail location near Chicago. :D

It is real aluminum and it does conduct electricity. It is about three times thicker than household aluminum foil (maybe even four or five times, it is hard to tell). The roll cost me $7 and it appears to have enough to cover the inside of about five to eight boxes of the size I used.

The only issue with the conductivity is that since the back is covered with adhesive it doesn't conduct through the back. So if you put down a piece and then cross another piece over it there won't be continuity between the two pieces but electricity will flow through each piece separately. If you press it into place with a tool like a screw driver handle sometimes the adhesive separates a little and then there is conductivity between layers.

It seems to provide very good RFI shielding and I've used it in a couple of projects now.
 
I buy similiar al tape at a local hardware store, it is used to seal ducts. I have also used it to shield equipment cases. I butt each strip against the other then add another layer staggered to cover the seams of the first layer...sort of like the way bricks are laid out in a wall. Works well. For thick copper foil I head to an arts and crafts supply, they have large rolls of thick copper foil for embossing at a decent price.
 
Re: Hey Sherman & Tor M...

JazzzSpazzz said:

Tor M--What is lining that box--is it copper flashing used in house construction? & where does it come from?

Please don't say Chicago & Norway, respectively.;)

TIA,
Bret Morrow


Hi!

I just used 0,1mm thin copper sheets i bought in a local hardware store for shielding. The chips are mounted on a 1 cm thick and 7 cm wide copper plate wich is normally used as grounding bars in electric coupling "boxes" for industry use. Bought them from a local manufactor of such "boxes" (Don`t know the right english word for it..)

:) Tor Martin
 
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Joined 2001
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Here's American Science & Surplus
http://www.sciplus.com/index.cfm

Man, after I got my pair of 15" JBL woofers for $130 INCLUDING SHIPPING I love these guys (The supply lasted 3 days)
Most stuff isn't as fancy as that though-just an anomaly.

The hobby store copper works great - AND you can solder it together and solder a ground wire on it so you know you are getting a good connection. Bad ground connections cause all kinds of mischief.
 
Re: Gainclouds with copper lining

bzdang said:
For copper sheet go to www.mcmaster.com - they are the digikey of the mechanical universe. Fast - for example I ordered some spindle oil for my lathe at 3pm and it was at my door at noon the next day.
FYI you can also cut up un-etched copper-clad printed circuit board and solder it together to make box liners and other structures.

Or you could also try Metal Supermarkets they have offices all over North America.

www.metalsupermarkets.com

Anthony
 
3M makes a wide selection of metal foil tapes suitable for many uses.


Go here:

http://tinyurl.com/275mh


and here:

http://tinyurl.com/3a9wv

There is a bricks & mortar 3M dealer/distributor in every major city around the globe and in many smaller cities and towns also, not to mention numerous dealers/distributors with e-commerce.

And now for a question. I just completed my GC and found to my dismay that the output is at supply rail voltage. All PS connections were checked, double and triple before connecting to the v+ and v- on the amp board. PS voltage tested right on at +/- 22volts. I suspect that both chips are cooked. But why? How did this happen? With no carpet in sight and 80-90% RH to boot, static seems unlikely.

Thoughts?

Jimbo
 
Retired diyAudio Moderator
Joined 2002
still taking submissions for my gallery

Don't forget to submit your pictures to me for my gallery. I am mailing out the free pcbs soon to all submissions. Submit your pictures in the next week, and I will mail you a free pcb set.

If you already submitted pictures of your amp, feel free to submit more to me!

For the pictures, keep them to 800x600, and zip them up. You can submit up to 10 pictures to me.

--
Brian
 
It seems to me there are a few people having rail voltage on the output. It happened to me too. In my case the output was at negative rail.

At first i thought it was a faulty chip but it turned out to be a short between two of the chip pins. Check for soldering-flux residues on the pcb between the power supply pins (pin 1&4)and the output pin (pin 3).

I solved my problem by cleaning the pcb *really good* after soldering. with some really aggressive stuff (2-methoxy-1-mehtylacetate, had it laying around, normally used for cleaning epoxy/polyester). Of course you could use something like aceton or alcohol too ;)

/matti
 
matjans said:
I solved my problem by cleaning the pcb *really good* after soldering. with some really aggressive stuff (2-methoxy-1-mehtylacetate, had it laying around, normally used for cleaning epoxy/polyester). Of course you could use something like aceton or alcohol too ;)

/matti


After some experience with flux residue I too have taken to vigorously cleaning the soldered boards. I've been using alcohol and a soft bristle toothbrush. It seems to work though it is necessary to do the cleaning where the stuff flicked off by the toothbrush doesn't get all over. I hold the boards inside a plastic tub.
 
When I realized a group order for knobs wasn't going to happen soon enough, I went ahead and made my own volume knob. It took three knobs before everything fit and turned properly. I'm not sure I like the feet, they are just some old porcelain drawer pulls. They'll work until I find something better.
 

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