diyAudio

diyAudio (http://www.diyaudio.com/forums/)
-   Parts (http://www.diyaudio.com/forums/parts/)
-   -   [INDIA] Chassis, knobs, PCB makers (http://www.diyaudio.com/forums/parts/28068-india-chassis-knobs-pcb-makers.html)

tcpip 12th February 2004 04:49 AM

[INDIA] Chassis, knobs, PCB makers
 
I am in the process of building one or two amps, among a small group of friends. I have found sources for decent quality professionally made chassis, a sort-of source for good knobs, and silk-screen printing of legends on front and back panels of the boxes. I thought I'd write all this down in case some other Indian DIYer wants to know this. I know how much effort and travelling around in the heat all over the city I had to do... I'd like to believe I can save some of you some of this effort, not to speak of cab fare. :)

For the chassis, we found Dinrack, in Goregaon East, Bombay. I'll give you full access information if anyone wants it. This organisation is quite old, and is headed by an engineer named Mr.Vishwas Deshpande. They have been doing business for many years. They make 19" racks, as well as boxes to go into these racks. I visited their works, and saw that they also make a lot of complex boxes, cabinets, and chassis, for use by various government and private companies. Their clients include the Indian Armed Forces, Bharat Electronics, Midas Electronics (a telecom product company working with Prof.Jhunjhunwala of IIT Madras and creating path-breaking low-cost telecom products), and many others. I saw a line of racks with card cages, full EMI shielding, and ducts for air circulation, which were supposed to go into Indian submarines. They appear to have quite sophisticated computer-controlled tooling facilities to create any custom items in this area.

They have off-the-shelf chassis available, in 2U, 3U, 4U, and 6U height, and 84TE and 42TE width. (1 TE is about 5mm, and 84TE means full 19" rack width. This gives you front panel width of 426mm. 42TE is half-width.) Depths of the boxes are 260mm, 320mm, 380mm, and I guess one or two other sizes are also available. The boxes are constructed by four pieces of Al extruded section for the top and bottom edges of the front and back panels. (There are no Al sections for the side edges.) Onto these extruded sections are screwed on the six sides of the box, as six separate metal plates. The front and back plates are Al sheet, 2.5mm thick. The top and bottom plates are thinner (1-1.5mm) steel sheet. I haven't yet checked whether the side plates are Al or steel. Most of the screws are black anodised and countersunk, so that you can't see them unless you look closely.

In these boxes, they have two ranges, the DR-30 and DR-33. The latter is marginally costlier, and is meant for "table-top" work, i.e. screws etc are more invisible. My friend has bought a DR-30 box, and while it's perfectly acceptable, I think we'll opt for the DR-33 for subsequent boxes, specially since the price difference is marginal.

They are able to cut out holes of the shape and size you want, if you give them a drawing (even a neat hand-drawn drawing) with dimensions and sizes, like any engg drawing done by a draughtsman. (I used XFig on Linux, and my memories of engg drawing, to give them front and back panel diagrams. The drawing was not full size, but the dimensions were clearly marked. They did a perfect job of the cutouts based on that.) They don't seem to charge separately for each hole or cutout... it seemed to be all included in the total price, as far as we could see.

FInishing of the boxes is powder-coating or anodising. They can even do that lovely brushed finish that is in vogue nowadays; they have special equipment for that. We got this box done with brushed black anodised front panel, and powder-coating for all the other surfaces. They can also do legend printing, but they said that they outsource that work, so it'll be easier for us if we talk to a screen printing chap ourselves and get the legend printing done. We agreed, and it's worked out well that way. (More on that later.) The box can come with optional rack-mountable ears and handles. In our case, all these were also full black. Quite slick looking.

The price they quoted for our 2U, 320mm deep box, including the brushed finishing, anodising, powder coating, rack-mount ears, handles and cutouts, was Rs.1360, pre-tax. They applied some 16% excise duty and 15% sales tax on top of it, and we paid Rs.1806 all inclusive. If we had opted for the DR-33, the price difference would have been Rs.200 extra, plus taxes. They apologised about delivery times, saying that they are terribly overbooked till about 31 March because of some huge defence order (we saw signs of work in progress) but they managed to accommodate our request and deliver within a week. And they accepted our cutout drawings as PDF files by email. This email-friendly approach is not to be taken for granted from a company which does not yet have a Website in spite of being in business for more than a decade. :)

How does it look? I am sorry none of us have a digicam, so pics yet. The finish is very good, and is better than anything I've seen on L.Road selling for Rs.80 or so. I suspect that boxes available from Hammond Manufacturing, Lansing Enclosures, or Bud Industries may look as good or bad as this one, and they don't give you this brush finished front plate option. The box is not very heavy (my 26-0-26V, 5A E+I power transformer is heavier), but seems sturdy enough to take the transformer bolted to the bottom plate happily. All in all, I'm happy. I can't imagine any cheaper path by which I'll get a box which looks as good as this one. The work has been executed very professionally. Cutouts are neatly done and cleanly finished; you don't see any burrs. Dimensional tolerances I found were less than 0.5mm for hole sizes.

However, it is possible that you may be able to get a custom-built box actually built and power-coated as per your drawing, if you talk to any of the smaller sheet metal workshops all over the city. Such boxes, made to standard sizes (none of which remotely resemble a rack-mountable amp chassis) are available in L.Road for Rs.50 to Rs.100. I have bought one such box of size 8"x8"x6", for Rs.80; the amount of metal which will go into an amp chassis will be somewhat more, but not much. These boxes are made of sheet steel (perhaps 1mm thick), accurately bent to shape, and two C-shaped pieces bolt together to make the box. Each C-shape forms three sides of the box. The outer surface is powder coated black, the inner surface is painted grey. It will be a little less sturdy than the Dinrack box, but it will be enormously less expensive. Of course, you'll have to add separate metal plates front and back just so that you can give those plates to a screen printer for printing legends. And the metalworking workshop will make cutouts for you as per your drawing if you want. I am told lots of such metalworking shops exist who will do one-off custom jobs for you, maybe not to as much accuracy as Dinrack. But the prices of such one-off pieces will not be more than Rs.400 for a 2U amp chassis, I'm certain. So, the Dinrack route is not the most economical; we took that route because we couldn't find any of the low-cost metal working workshops.

Tarun

PS: For non-Indian readers, INR (i.e. Rs.) 45 is roughly USD 1.00, and INR 27 is roughly SGD 1.00. I believe INR 35 is about AUD 1.00.

tcpip 12th February 2004 04:57 AM

Screen-printing of legends on panels
 
We needed to print legends like "volume", "power", etc, on the front and back panels; the cutouts had already been done by Dinrack. So we approached a screen printer close to our office. He turned out to be a really competent chap, running a small shop, who was quite computer savvy, and had an A3 printer.

The front and back panel sizes for 84TE width of chassis, is 426.7mm. A3 paper is 420mm long. Therefore, if I do a drawing for the panels at 1:1 scale, I was losing 6.7mm. That was not a problem for the guy, because there was no legend to print near the edges of the panels; I had left a healthy inch on either side. So I created the panel master layouts using XFig on my computer, and gave him PDF files. He printed the artwork on his A3 printer, matched them with the physical panel to ensure that they were indeed to scale, and printed them. This was a one-off job, i.e. just one copy of each artwork. So his fixed costs were quite high. He charged us Rs.300 per panel, or Rs.600 for both panels. He said that if I'd given him ten copies of each panel to print, his total charges would have gone up from Rs.600 to Rs.650.

The screen printing has been done very well... I can actually see details of the typefaces I've used (Postscript Helvetica), including the precise shapes of the ends of the strokes of the characters (Helvetica characters have slanting ends at the tops of the strokes). We asked for off-white printing, which looks good on the pitch-black metal. The job was done in one day.

It is possible that you may be able to find a less expensive screen printer. However, remember to check that the guy seems technically competent and confident. You cannot afford to have him botch up or smudge the print; spare panels will cost you more than anything you save with a cheap printer.

Tarun

tcpip 12th February 2004 05:37 AM

Uncle Harry's knobs
 
We looked at knobs easily available on L.Road, and we found that most shops stocked metal knobs from probably the same source... they all looked the same. These knobs come in either black or plain aluminium finish. I presume they're anodised. The black anodised knobs have a 1mm-wide aluminium "edge" marked all round the edge of the knob. They come in various diameters, typical ones being 19mm, 25mm, 38mm. We have also seen one knob in one shop, only in plain aluminium finish, of 50mm. (I love the idea of outsized volume control knobs. :) )

When we look online, we don't find too many choices of good-looking large black metal knobs abroad either. Knobs seem to be a universal problem area for DIY audio, as are good looking flat-metal-paddle toggle switches.

We heard of this gentleman, Mr.Behari Valecha, who calls himself Harry, and has been building knobs for forty years. He does not keep a retail inventory, and has no product brochure. He makes knobs only to order. I visited the office cum factory of Harry Electronics in the second floor of Unique Industrial Estate, in a lane opposite Siddhi Vinayak Temple in Dadar West, Bombay. Harry turned out to be a very friendly, unassuming, middle-aged guy, who showed me his boxes full of knobs he has made for customers in the past. His minimum order quantity is in the hundreds. He fashions knobs from cylindrical aluminium bars, and each knob is first cut from the bar and then shaped in a sequence of sometimes complex shaping and finishing operations. His machines can handle bars of up to 100mm diameter, and the largest knobs he's made are of 50mm diameter so far. His minimum order quantity is one or two bars of aluminium, and each bar is 12 feet long.

The finishes I saw on his knobs were out of this world. I can confidently say that he can make, and has made, knobs identical to the best-looking knobs I have ever seen on any of the world's most expensive and good-looking audio equipment I've ever seen anywhere. I won't go into the details of all the different finishing options he can do, but suffice to say, the better looking ones are breathtaking.

After my conversation with him, I was all prepared to ride the highway to Heartbreak High, since he didn't seem at all prepared to handle small orders. But Uncle Harry came to my rescue. He said that he had some regular bulk customers for whom he was already busy making knobs. If I was willing to accept whatever he was already making, and I could place an order for small quantities before his batch got completed, then he would be able to sell some knobs to me. I saw his work-in-progress set, for a Delhi-based amp maker. Those knobs were nice black ones with a brushed finish, similar to the brushed black front panel Dinrack had done for me. The largest of the knobs was a mere 35mm in dia, and the rest were 19mm. But they looked better than anything I've seen on L.Road, so I happily accepted. He also told me the diameters of the shaft holes for each of the knobs, and I realised that they would work with off-the-shelf Indian pots and rotary switches. So that was settled.

One of the knobs he showed me haunts me still. This one was out of 25mm dia stock, and was longer than its diameter... it was probably 40mm tall. It was plain aluminium colour, and had a matte finish. It tapered in soft curves from 25mm at the rear to, say, 20mm in front. There were no sharp edges or totally flat surfaces anywhere... it was all organic curves. No doubt, knobs of such shape and size have a "strong personality", and must be matched to the rest of the panel with care. However, I feel that anyone wanting to go for a brushed aluminium front panel with a plain anodized finish would be able to make a show-stopper piece by combining with these knobs. The interesting story behind these knobs was that they were made for an order placed by a gentleman who later died before he could take delivery of the knobs. So this stock is lying with Harry, and he doesn't know what to do with them. They are also not of the size and shape where they'll be picked up by the roadside shops, so they've remained. But ever since I saw them, I've been wondering how to use them on a plain aluminium panel. Those knobs deserve to have an amp designed around them. The only thing that's missing is a larger knob of that same style, for the volume control. So, one will either have to use a 50mm L.Road aluminium knob of a different styling, or build a panel where all knobs have the same size.

One thing I haven't understood is why Harry doesn't export. I am sure that with the right business tie-ups, he can become one of the most interesting sources of knobs anywhere.

I haven't yet got the knobs I ordered; they're still being made. I'm picking up enough to last me for a few amps. I've already got the cutouts on my first chassis done as per the dimensions of these knobs. Hope it all turns out well.

I can pass on access information for Harry Electronics if you want it. Let me know.

Tarun

sangram 12th February 2004 05:52 AM

Tarun, you are Zeee Man!!!!

Really an awesome effort, what with finding people from Goregaon to Dadar to Lamington who give you what you want. And I want, as well.

What amps are you building? I'm at 9 8 1 9 3 2 4 8 5 2. Call me!!!

tcpip 12th February 2004 05:59 AM

PCB makers
 
It appears that there are plenty of small PCB makers in Bombay. One party which I was given a lead to, by a professor at the IIT, makes PCBs from Gerber files and couriers them to you. He even accepts Gerber files by email. (I presume the demand draft or cash will have to reach him by non-electronic channels.) He operates under the name of "Image", and works out of an industrial estate in Chakala. The person who gave me this lead said that they seem to screw up with thin tracks of 8mil or less. I asked whether I could safely take one track between two legs of a DIP IC (that would be about 16mil, I think), and he said that that will not be any problem at all.

Rates were quite low, from what I was told. Minimum order quantities are apparently 3 PCBs, though that is probably negotiable. The price of making a 6"x4" single-sided FR4 PCB with solder masking and legend-printing on the component side, was about Rs.200 per PCB. I am going to place my first order today, for the preamp with tone controls which I've discussed on another thread (Solid-State forum). Let's see what comes out of it. I'll keep you posted.

If any of you live in the Western suburbs of Bombay and want to check out this "Image" fellow, let me know, I'll pass on contact info.

Visha Electronics on L.Road is well-known to hobbyists and students for prototyping and retail sales and services. They too undertake to make PCBs. In the past, I have always seen that their PCB making is quite coarse. There's absolutely no chance that they'll let you take a track through two pins of a DIP IC... they always land up shorting the tracks, and then they'll manually take a file and cut the short to fix it. I have decided it's no point getting any but the simplest PCBs made at Visha.

Tarun

tcpip 12th February 2004 06:08 AM

The effort.... the effort...
 
Quote:

Originally posted by sangram
Really an awesome effort, what with finding people from Goregaon to Dadar to Lamington who give you what you want. And I want, as well.
The effort is quite considerable. Luckily, I have a couple of friends who share some of the load, but the sheer leg-work of finding just a good-looking well-constructed toggle switch which you don't feel like hiding behind a burqa, is awesome. It involves entire days spent walking around in L.Road, and if you've done it, in the heat, you know what I mean. :)

I remember a line from Professor Leach's Web pages, where he has tried to answer the FAQ "How long does it take to build one of his amps?" He has said that typical student experiences show that it takes a few months just to obtain all components, and a few more months to build and test the amp. I am beginning to live the truth of that statement.

Let's get in touch. :) What are your usual haunts in Bombay? I live and work in New Bombay.

Tarun

corbato 12th February 2004 06:29 AM

Hi Tarun
Your findings are just sinking in. Does that cab maker have thing suitable for Valve projects?
You indeed are the most valuable trump card for us folks.

tcpip 12th February 2004 07:43 AM

Quote:

Originally posted by corbato
Your findings are just sinking in. Does that cab maker have thing suitable for Valve projects?
I don't know what's needed for tube amps. But what he basically has are boxes. Think ordinary, well-constructed, well-finished boxes, with six flat surfaces. That's all you get. All else is extra. Of course, if you want to do a custom job, he can pretty much fabricate whatever anyone else anywhere else can, so there's no limit really. For instance, he has special machinery to do some countersinking and actually fix a bolt or a nut on the inner wall of one of the sides of his chassis, without making any through-hole. So, from the outside, you see a plain surface, but from the inside, you see a very firmly fixed bolt or hex-nut fixed on the plate, which can probably take half a kilo or more of force. So, custom jobs can be quite hep.

Quote:

You indeed are the most valuable trump card for us folks.
Flattery, sir, will get you anywhere with me. Just keep it comin' :D And jokes apart, I feel that a repository of such knowledge, of switches, chassis, knobs, transformers (remember www.toroidal.com?) are really the DIYers' trump cards.

Tarun

sangram 13th February 2004 04:27 AM

Re: The effort.... the effort...
 
Quote:

Originally posted by tcpip

The effort is quite considerable. Luckily, I have a couple of friends who share some of the load, but the sheer leg-work of finding just a good-looking well-constructed toggle switch which you don't feel like hiding behind a burqa, is awesome. It involves entire days spent walking around in L.Road, and if you've done it, in the heat, you know what I mean. :)

I remember a line from Professor Leach's Web pages, where he has tried to answer the FAQ "How long does it take to build one of his amps?" He has said that typical student experiences show that it takes a few months just to obtain all components, and a few more months to build and test the amp. I am beginning to live the truth of that statement.

Let's get in touch. :) What are your usual haunts in Bombay? I live and work in New Bombay.

Tarun

I have yet to see summer in Bombay - I moved in in September. I live in Bandra and work in Worli, but I am changing jobs and I may move further out towards western suburbs though I hate to.

My usual haunt is my home, as I am in the middle of setting up a little studio in my living room. The living room is really small, which is why I need to move. I am looking at building a set of monoblocks for my soon-to-arrive Yorkville Studio monitors, and though I have a large percentage of my parts with me, there are miles to go.

I still need chassis, heatsinks, PCB (I haven't yet decided between P2P/PCB) etc. no knobs - the control will be with my mixing console. Just two monoblocks in small cases with separate power supply and umbilicals. Balanced outputs from my soundcard means I can drive bridge amps with no hassle at all.

My email id is below and I've already given you my cell number. Let's touch base.

tcpip 13th February 2004 07:08 AM

Re: Re: The effort.... the effort...
 
Quote:

Originally posted by sangram
I still need chassis, heatsinks, PCB (I haven't yet decided between P2P/PCB) etc. no knobs - the control will be with my mixing console. Just two monoblocks in small cases with separate power supply and umbilicals. Balanced outputs from my soundcard means I can drive bridge amps with no hassle at all.
Sounds interesting. :) You could try out the DR-33 half-width chassis from Dinrack, of 2U or 3U height. I felt those boxes would be very suitable for monoblocks. And heatsinks are available quite easily of arbitrary length, in a variety of cross-sections, on L.Road, made to order.

Will get in touch with you as soon as I get some breathing time.

Tarun


All times are GMT. The time now is 01:27 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio


Content Relevant URLs by vBSEO 3.3.2