Luckiestmanalive Posted July 21, 2023 Posted July 21, 2023 Hiya. I have an old Luxman A3600 power amplifier running KT120 tubes and it has a relatively simple, single layer PCB for the first two amplification stages (preamp and phase inverter). The amp (and the PCB) is over 40 years old and there are some quite dark areas in the bits that get very warm (over 80C) when it has been on for more than 15min, and this happens a lot because it makes beautiful music and I love listening to it! I love my amplifier so much I would like to replicate the PCB so I could replace it some time and wonder how easy and time-consuming it might be to do it. Has anyone here done this themselves and have any tips on how to do it?
rockeater Posted July 21, 2023 Posted July 21, 2023 I tried to replicate a relatively simple Wadia input / output board. I met a guy who designs boards for a living and makes some Ethernet switches that sell for tens of thousands and are 4 layer jobs. He said that it would take 15 minutes and asked for all the parts, board dimensions and photographs. I even had an original layout from Wadia 16 manual but no CCT diagram. All in all, 4 ICs, and maybe 20 or 30 passive components. After I sent it all to him, he went silent and never replied to any message. It would appear that reverse engineering even of a simple circuit is not that trivial, even though you could probably sell these boards at $1000 each and upgrade base model Wadias to the top ones. 1
bob_m_54 Posted July 23, 2023 Posted July 23, 2023 The easiest way is to remove components from the PCB, and scan it. Use photo editing software like GIMP with the various filters to turn the scanned image into a black and white image. Once you have a good black and white image with solid traces, print it onto a transparent sheet to make a mask. Depending on whether you get positive etch resist, or negative etch resist, you will either need a positive or negative image. Coat your blank board with the etch resist, and once it's dry you can expose it with sunlight (UV) for the required time, with the mask overlayed. Then you etch the masked board with etching fluid... That's the very basic steps. There are a lot of variations that you can use as far as types of photo resist, etching fluid, exposure methods etc to enable a very good quality end product. But in the olden days I have done it by photocopying a fully populated ADC board, touching up by hand then photocopying to a transparency. Exposing with sunlight and etching with ferric chloride. 3
rockeater Posted July 23, 2023 Posted July 23, 2023 19 hours ago, bob_m_54 said: The easiest way is to remove components from the PCB, and scan it. Hm... On the Wadia input / output PCB, there is close to 60 components. On the Luxman Amp, there would be probably many more. Not a trivial task. 2
bob_m_54 Posted July 24, 2023 Posted July 24, 2023 4 hours ago, rockeater said: Hm... On the Wadia input / output PCB, there is close to 60 components. On the Luxman Amp, there would be probably many more. Not a trivial task. Well I did say it was the easiest way to make the board. So you have a choice, depopulate, or go for the more difficult way.. Cad, dedicated PCB software etc.. 2
Luckiestmanalive Posted July 25, 2023 Author Posted July 25, 2023 Thanks, guys. I've seen youtube videos where they use sprint layout over a scanned copy of a PCB. It looks easy enough, if a little time consuming. My PCB (see below) doesn't have a lot of components. However, I don't really want to have to unsolder them all and go the etching route. I have seen a used board for sale on Yahoo auctions Japan but I didn't bid - perhaps, I should have... 1
rockeater Posted July 25, 2023 Posted July 25, 2023 4 minutes ago, Luckiestmanalive said: I've seen youtube videos where they use sprint layout over a scanned copy of a PCB. It looks easy enough, if a little time consuming. Could you post some links please? 1
Luckiestmanalive Posted July 27, 2023 Author Posted July 27, 2023 This is the webpage with a youtube video on it that got me interested... 1
Luckiestmanalive Posted March 19, 2024 Author Posted March 19, 2024 (edited) Update! I found a website called fiverr with people who you can task with cloning a PCB for not much money for my job (under $100). I signed up and commissioned the job with one of them and provided pics of the top and bottom of the board (populated) plus pics of the naked board from the assembly manual. This seemed to be enough and now I have Gerber files that I've checked the product on the PCBway website. This is what it looks like: I've run out of my splurge money this month so I'll let you know how they turn out once I pay for the finished boards and receive and populate one! Edited March 19, 2024 by Luckiestmanalive 1 1
stereo coffee Posted March 21, 2024 Posted March 21, 2024 (edited) On 19/03/2024 at 6:20 PM, Luckiestmanalive said: Update! I found a website called fiverr with people who you can task with cloning a PCB for not much money for my job (under $100). I signed up and commissioned the job with one of them and provided pics of the top and bottom of the board (populated) plus pics of the naked board from the assembly manual. This seemed to be enough and now I have Gerber files that I've checked the product on the PCBway website. This is what it looks like: I've run out of my splurge money this month so I'll let you know how they turn out once I pay for the finished boards and receive and populate one! If you begin with a schematic, in your case doing so from the existing PCB , by tracing each part and its connection to the next part, you can then use a free program called Easy EDA to replicate that schematic. Once you have that you can populate a pcb with best layout, and generate a Gerber File. it looks like you have had success, but keep Easy EDA in mind if it might be useful in future. All of our pcb's other than one using Fritzing , were designed and made by ourselves using Easy EDA https://easyeda.com/ One really nice aspect of this is ability to have layers , so pcb size ( the costly part of board production ) can be heavily reduced. You also get expertise unexpected sometimes advising about layers. One of our boards as example was a challenge for the pcb manufacturer by having 5 layers , they took it all in stride , and were proud of what they achieved, as were we. Edited March 21, 2024 by stereo coffee 1 1
Luckiestmanalive Posted March 21, 2024 Author Posted March 21, 2024 That's great advice, thanks, SC! I'll take a look at Easy EDA and import my gerber file and have a play!
Luckiestmanalive Posted October 20, 2024 Author Posted October 20, 2024 I know its been a while but I paid for and received the PCBs and ordered all the components. This took a while and then we moved house so I've only just managed to get started on populating the first board! Here is the board with the three 9-pin tube sockets and all the resistors soldered in place. The tube sockets were a bit tough - the holes for the pins and the centre ground were too small so I used a 1.5mm and 4mm drill bit to widen them enough so they fit snugly. Everything else went smoothly and I've checked the values and continuity and all looks good! I just have to solder the caps and the heater wire jumpers and its done! Unfortunately, I may not have time to finish until next weekend and then it will be ready to replace the old one!
rockeater Posted October 20, 2024 Posted October 20, 2024 (edited) Greg, this is a bit off topic, but the soldering on this board is rather poor, with some through holes not even fully covered. It appears that the issue is in either: - too low iron temperature used - poor soldering technique (you should apply the heat to the joint to heat both the land and component leg while feeding the solder until it flows over the entire joint). - poor eyesight, for which I recommend a magnifying lamp, which I myself use. I have a friend whose work is of similar standard and who keeps telling me he cannot see properly (yet refuses to buy a maggi-lamp). Most of the solder joints on this board require re-flowing but I have highlighted the 3 which are most suspect. If you were in Perth, i would invite you over for a quick, 5 minute soldering course after which you would never have a dry joint. I am sure that someone in Sydney will help too. Cheers Roman Edited October 20, 2024 by rockeater 1
bob_m_54 Posted October 20, 2024 Posted October 20, 2024 I agree with @rockeater Also, along with the points he made, you need to firstly make sure the solder pads are clean, by giving them a good rub with a lint free wipe, moistened with Isopropyl Alcohol. I use Kimwipes 4103, which are labeled as delicate task wipes, but they are more aggressive than ordinary tissues. Another point is that even though solder designed for electronics is rosin flux cored, it is prudent to use additional flux to assist in better wetting of the joint. I use the old school brown liquid Rosin Flux, because I have heaps that I acquired years ago, but even something like a flux pen like this one would help. https://www.altronics.com.au/p/t1927-no-clean-solder-flux-pen-12ml/ When cleaning flux, as in the 3 main socket anchors, don't use metal tools to scrape the flux off. Use a toothbrush or other similar stiff bristle brush, and Isopropyl Alcohol. I use a flat fitch brush with cut down bristles like this. But if the flux residue is still not able to be easily removed with the brush and alcohol, you can use a bamboo skewer, with the end cut at an angle, and soaked with Isopropyl Alcohol 1
thatmetalman Posted October 20, 2024 Posted October 20, 2024 (edited) @Luckiestmanalive Hi, Greg. These are extracts from an excellent article published many, many moons ago but still very much relevant. I agree with previous comments, the solder joints on your board need attention. I hope these extracts help. Also, a variable temp soldering station is a wise investment, although I suspect for you this project is a once off? Flux remover spray is very effective too. Available from Jaycar, Altronics, etc. Edited October 20, 2024 by thatmetalman
Luckiestmanalive Posted October 30, 2024 Author Posted October 30, 2024 (edited) Thanks, guys, for the tips and material to help my soldering technique. I agree, the soldering looks bad. I wasn't sure why as the PCB is new. I was applying the right technique and the solder is OK (I had some bad solder in the past), but I didn't know the board had some coating on it that needed cleaning off with isopropyl. Since that photo was taken, I sprayed and cleaned the board thoroughly and reflowed or removed and reapplied solder and it looks much better! Edited November 1, 2024 by Luckiestmanalive 2
Luckiestmanalive Posted November 1, 2024 Author Posted November 1, 2024 (edited) So I unsoldered the wires to the old board, unscrewed the 6 bolts and removed it. Then I put my new board in place. Then I had to remove it and make a few adjustments to the holes (my measurements were off because I took them off the old board while it was in place). After that was done, I bolted it in place and resoldered the wires back in place. Then I plugged it in and turned it on while monitoring voltages and temps. It works perfectly and I’m stoked! Here is what it looks like installed in my amp. I just need to make a few adjustments to my file: align mounting holes better, make the test points vias suitable for DMM probes, make soldering points bigger (diameter of the holes and more copper showing). Edited November 1, 2024 by Luckiestmanalive 1
Recommended Posts