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Old 20th February 2004, 02:09 PM   #91
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Default Alluinium

Quote:
where does one get 6mm and 10mm thick flat sheets of aluminium in small quantities?
Tarun, I use Alluminium Trays availble at crockery shops,as heatsinks and enclosures for my projects. GUess you can use them too. They are also available in 4 X 8 ft sheets of the thickness you mentioned <8mm at hardware stores!!

Good luck!!

Patrick
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Old 22nd February 2004, 12:47 PM   #92
tcpip is offline tcpip  India
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Default Got my first PCBs made

Got the PCBs for my preamp circuit (which I had discussed in another thread in the Solid State forum). They have been made with the services of Image for the films followed by the fabrication by Mr.Subramaniam's workshop. They're lovely.

I have bought PCBs from Rod Elliott. I can confidently say my preamp PCBs are better than those. For one thing, mine have a solder mask. For another, the tinning seems more even. And I paid Rs.250 for the pair of PCBs. (I have yet to pay for the films... that'll be another Rs.250 or so, I guess. But that's one-time stuff, not incremental.) In fact, even the PCB making costs are not really Rs.125 times two. Mr.Subramaniam's just charged me what he charges for ad hoc small-quantities of prototype PCBs.

The process of fabrication of single-sided PCBs which he uses is quite laborious and goes like this (sorry if I've misunderstood any of it):
  • He first coats a silk screen with a photosensitive chemical, and uses my track-side film to expose the screen. Then, after developing the screen, he gets the design ready for printing.
  • He then prints the solder-side image onto a blank PCB using this screen and an etch-resist ink. This print is then manually examined and touched up for cracks if needed. I visited his shop and saw that the print quality is really excellent... I should think he'll safely be able to deliver 8mil tracks with that kind of sharpness.
  • He then etches the PCB to remove the extra copper, and uses an alkaline solution to remove the etch-resist ink.
  • He then does a similar process with another silk screen and the inverse of the solder mask image. He prints the solder mask onto track-side, removes the etch-resist ink, and then bakes the PCB in an oven. Apparently this heat treatment is needed for the solder mask chemical to harden. It's apparently some kind of resin, a bit like Araldite.
  • He then does the drilling of the holes. For single sided PCBs, he prefers to get it done manually, "by eye", not by CNC drilling. The results, as far as I can see, are beautiful.
  • He then does a third round of silk-screen preparation and printing, this time for the legend printing. No etching is done this time.
  • At some point in the process, he does tinning of the exposed copper. This is done by roller tinning, which is apparently superior to what other small workshops do. An experienced friend who has seen Rod Elliott's PCBs said that the tinning on those are quite uneven, probably done using a soldering iron, not roller tinned.
As is obvious, there are issues of skill and quality control in such a process, and based on the PCBs he's made for me, and the other jobs I saw in his workshop, I'd trust him with whatever my amateur needs will be.

One more very interesting thing that I discovered is that one does not need to get films made professionally for each PCB (thus saving money). One can take a printout on polyester sheet and give it to him, one sheet for each image. (For single-sided stuff, he'll need three images: (i) solder side tracks, (ii) solder mask, and (iii) component side legend.) I know I'd reported earlier in this thread that such printouts won't do, but he explained that they'll do, provided I'm willing to write off the printouts after each job, i.e. the printouts wil not be reusable. He explained that he uses some oily compound to make the film stick to the copper-clad board during exposing, to avoid air gaps, and this oily substance spoils the printout. He also said that if I am considering giving him printouts, it's better to print on translucent tracing sheet instead of pure transparent polyester sheet, because the translucent sheet absorbs ink more, and gives a higher contrast image. In fact, it is possible that a good inkjet printer (with 600dpi resolution) will give a deeper, richer film for his purposes than most laser printers.

I'm thrilled to see that I've been able to set in place at least one part of the supply chain for my diy audio activities. PCBs should not be a problem for me now onwards.

And guys, this information is not for Bombayites alone. Mr.Subramaniam and Mr.Desai (of Image) are both very comfortable on the phone and over email, and I am sure they will entertain any orders coming in remotely. Personal visits are not needed. And these two firms work very well with each other, and trust each other's competence.
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Old 22nd February 2004, 02:22 PM   #93
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Default About the PCBs

Hi Tarun,

Great writeup about the PCBs there for your preamp and helpful indeed for all of us. Sounds impressive. I am so very excited after reading your writeup there. By the way I'd like to have the 'Image' ad,email and phone numbers and yes details of their website if any .. and details of the recipient in whose favor the demand will be written.

By the way, while we're on the subject, Tarun.. could you ask them how much they would charge for all the PCBs for the Titan 2000?? I would appreciate that a lot!!


Patrick
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Old 22nd February 2004, 06:58 PM   #94
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Default Re: About the PCBs

Quote:
Originally posted by peterpan73
By the way I'd like to have the 'Image' ad,email and phone numbers and yes details of their website if any .. and details of the recipient in whose favor the demand will be written.
Since you will be getting things done remotely, it's best if you talk only to one contact point, which is Mr.Charu Desai of Image. His email address is cdimage at vsnl dot com. He doesn't know me by name; my friend has done all the dealings with him. But you don't have to give him any reference; just write to him. Tell him clearly that you want him not just to make films but also to get the PCBs made, in prototype quantities. He'll contact Balaji Hertz and get the fabrication done; they work very well in a team. You'll have to settle accounts with just Image in that case, and Mr.Subramaniam will be totally transparent to you. I believe Image will happily courier the finished PCBs to you.

Quote:
By the way, while we're on the subject, Tarun.. could you ask them how much they would charge for all the PCBs for the Titan 2000??
There are too many attributes to be decided in the making of a PCB for me to be able to make those choices for someone else. Therefore, please can you contact Mr.Desai directly?

One tip I can give you: you'll have to send him clean high-contrast hardcopies of the PCBs which you want him to make. He cannot print from PDF file. His office is very computer savvy, but he does not have a good office printer. His Gerber plotter can only print Gerber files, not PDF or Postscript. So, in such cases, Mr.Desai usually wants the customer to supply a very good hardcopy of the PCB layout.

Tarun
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Old 23rd February 2004, 02:12 AM   #95
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Default About lost emails

I am not sure if the email i sent you via the forum link was recived by you so I am sending it again here as George is yet to reply !! Guys please bear with me!!

Helo Tarun,

OK please try sending the 2nd Part of the Titan 2000 to patrick_pugh2000@yahoo.com and with a CC also to peterpan73@mickeyevents.com

By the way I use alluminium trays for making water cooled heatsinks for my amps not the fanned ones. Fanned heatsinks are difficult to come by in where I stay and.
At the moment I am also developing heat sink molds for alluminium alloy casting to make fanned heat sinks cheaply for smaller amp projects from scrap alluminium and copper.


Patrick
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Old 23rd February 2004, 02:36 AM   #96
gjo is offline gjo  India
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Patrick

What was your question?

If it was about the toroids, I asked you to email Miracle directly, they will reply. If it was about something else, I dont recall it, though I recall asking you to email me offlist. I am a bit busy this week with some other matters, so I may not have time to wade through the various posts and reply promptly.

George
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Old 24th February 2004, 11:03 AM   #97
tcpip is offline tcpip  India
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Default My first PCB from the Image+Balaji combine

Got my PCBs from the fab. Here is the track side image.

Mr.Subramaniam cribbed when I met him, about the small size of the solder pads. From now on, I'm increasing the sizes in Eagle. You can see how small the sizes are, but you can also see how accurate their fab process is, to get absolutely straight track edges, neat circles for the pads, and in most cases, holes precisely in the centre (done with manual drilling).
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File Type: jpg pcb-tracks-150dpi.jpg (51.6 KB, 463 views)
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Old 24th February 2004, 11:05 AM   #98
tcpip is offline tcpip  India
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Default ... and the legend-printing

Here is the legend printed side. For this particular PCB, assembly would have been very difficult without legend printing, I feel, because there's a haphazard distribution of all sorts of small resistors and caps, in all sorts of orientations.
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File Type: jpeg pcb-top-150dpi.jpeg (68.8 KB, 441 views)
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Old 24th February 2004, 12:29 PM   #99
tcpip is offline tcpip  India
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Default PCB: total damages

Just got the figure that Image has charged for the films. Rs.300. This means the total damages come to Rs.550 for two PCBs. I suspect if I'd made three, the total would probably have remained at the same figure. All in all, even at Rs.280 per PCB, I'm totally satisfied. It's USD 6.00 per PCB.
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Old 24th February 2004, 01:30 PM   #100
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Default PCBs

Hey Tarun,

Those PCBs look fab..... and I am impressed...and excited too. By the way, I still don't know wyy I haven't received the Titan 2000 part two and three. I guess my mailbox is not allowing it. Tarun have you tried. I need to print those Titan 2000 boards from the pdf file and send it to Image.

George,

Hell... thanxs a lot.... I got the Torodal quote today by snail mail. I was expecting an email. Hey Toroidal prices are very reasonable they charge the price of an E-I made here, even less. TYheyu charge rs.2835 for my 35 amp tranny. I am so excited. I love these guys. I'm ordering from them right away. George, I've sent you an email vide the email link from this forum. I hope it arrived.

I'm in good spirits today (not to be mistaken for a hangover)! Well You know why!

Another thing. I am looking for heatsinks. Those long large ones with large fins. I asked Visha and Gala but no replies. Size and type - well large enuf for the Titan 2000. Can anyone here give me a ballpark figure to help me fix a budget for these amps.

Patrick
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