Transistor amp from scratch

[MidnightArrakis]

The IEC rectangular hole can be made very simple. Just Drill some holes and the rest can be excavated using a file or rasp. In aluminum, it just needs fifteen minutes to do so. You don't need a special instrument for all, just use own skills and your done with standard instruments which everyone has at home.

[Just Drill some holes and the rest can be excavated using a file or rasp] -- I just let a sheet-metal shop punch it out for me, along with all of the other holes and cutouts and inserting the necessary PEM-hardware. Works excellently EVERYTIME!!!

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[DaveP]

I have been adding components and have passed the halfwaypoint.
This is the board as of today:-



The BC107's are tight fitted between the output transistors to sense and compensate for heating of the heatsink, the are secured with araldite on the other side.


The back of the board looks like this:-


The wiring is with 20 gauge tinned wire and held in place by "staples" of the same wire. It feels like a very solid construction, we shall see.

Best
DaveP

 

[Chandra]

That is fine if you are young and fit but if like me you are old and have arthritis in your hands it is not much fun at all.

Cheers

Ian

There are snippers available, looks like a small pliers. Drill a 6 mm hole in the marked area and you can snip by 3 mm by 3 mm square. Can use on sheet metal up to 1.5 mm or Aluminium 3 mm thick.
Using file is time consuming and pain (for me).
Regards.

 

[JohnRoberts]

Hand "nibbling" tools are useful for cutting odd shaped holes in sheet metal.

JR

 

[Chandra]

Have to say it seems you've been very unlucky with your pcb experiences.

• Fragility - no they aren't. At least if you use standard 1.6mm FR4.
• foil lifting - need better quality fabrication
• copper corrosion - if this is a problem then you need environmental protection in the form of some sort of conformal coating or 'varnish'.
• With point to point you can cut a component out and replace it without making too much mess. - same with pcb really. And with SMT.

For cars under new design, the sheet metal body is joined using only rivets until it passed a track test.
Regards.

 

[Chandra]

Hand "nibbling" tools are useful for cutting odd shaped holes in sheet metal.

JR

Yessss... I have the same one. The name Nibbler is correct, not exactly snippers.

 

[ruffrecords]

Cool. Never seen those before. Excellent tip.

Cheers

Ian

 

[MidnightArrakis]

I have been adding components and have passed the halfwaypoint.
This is the board as of today:-



The BC107's are tight fitted between the output transistors to sense and compensate for heating of the heatsink, the are secured with araldite on the other side.


The back of the board looks like this:-


The wiring is with 20 gauge tinned wire and held in place by "staples" of the same wire. It feels like a very solid construction, we shall see.

Best
DaveP

With what the low-cost of even prototype PCBs are these days, I cannot imagine going through the hassle of creating a PCB like this anymore.....-- UNLESS -- you just had to have a PCB by this afternoon!!!

/

 

[ruffrecords]

With what the low-cost of even prototype PCBs are these days, I cannot imagine going through the hassle of creating a PCB like this anymore.....-- UNLESS -- you just had to have a PCB by this afternoon!!!

/

I think it is worth remembering that Dave comes from a tube based point to point wiring background. For his first transistor build it is natural for him to build it in a fashion he is familiar with. He does not need to acquire and learn to use a PCB CAD program or source a suitable PCB manufacturer, probably make a few mistakes and take several PCB iterations and wait for each one to arrive. Instead he uses his tried and tested prototype techniques, He can just sit down and get on with it.

Cheers

Ian

 

[MidnightArrakis]

I think it is worth remembering that Dave comes from a tube based point to point wiring background. For his first transistor build it is natural for him to build it in a fashion he is familiar with. He does not need to acquire and learn to use a PCB CAD program or source a suitable PCB manufacturer, probably make a few mistakes and take several PCB iterations and wait for each one to arrive. Instead he uses his tried and tested prototype techniques, He can just sit down and get on with it.

Cheers

Ian

[Dave comes from a tube based point to point wiring background] -- OK.....with my now knowing that, I can better understand -- why he is doing what he is doing -- with his layout. "To each their own".....I guess.

[Never seen those before] -- I am surprised that you have never seen a "Nibbler" before!!! I used to use one back in the 70s when I was creating custom snake-boxes and cutting out holes in 1U and 2U rack chassis front- and rear-panels when I was packaging custom electronics for bands when they went on tours.

I never found them to be all that "great" to use, but they did eventually get the job done. Now, as I have made mention of before, I just let a sheet-metal shop take care of my sheet-metal needs. It's much easier.

>> P.S. -- You never got back to me about your sourcing a "Galvanneal" supplier there in the UK. I have been waiting for a response from you about that ever since!!!

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[KIDVOX]

I have been adding components and have passed the halfwaypoint.
This is the board as of today:-



The BC107's are tight fitted between the output transistors to sense and compensate for heating of the heatsink, the are secured with araldite on the other side.


The back of the board looks like this:-


The wiring is with 20 gauge tinned wire and held in place by "staples" of the same wire. It feels like a very solid construction, we shall see.

Best
DaveP

i like the look of this. real old school do it as you see it. please keep the photos coming

 

[KIDVOX]

Cool. Never seen those before. Excellent tip.

Cheers

Ian

they are available as air tools aswell but are never as good as you would expect for air tools. often the brute force ones are better

 

[DaveP]

I think it is worth remembering that Dave comes from a tube based point to point wiring background. For his first transistor build it is natural for him to build it in a fashion he is familiar with. He does not need to acquire and learn to use a PCB CAD program or source a suitable PCB manufacturer, probably make a few mistakes and take several PCB iterations and wait for each one to arrive. Instead he uses his tried and tested prototype techniques, He can just sit down and get on with it.

Thanks Ian, I could not have put it better myself!
best
DaveP

 

[JohnRoberts]

With what the low-cost of even prototype PCBs are these days, I cannot imagine going through the hassle of creating a PCB like this anymore.....-- UNLESS -- you just had to have a PCB by this afternoon!!!

/

Back in the early 70s when I was working as a technician at MIT Instrumentation Lab, the engineer I was supporting needed a PCB as quickly as possible. I took a piece of copper clad, and painted a simple PCB pattern of traces on it with dykem blue tooling ink. I etched off the unpainted copper.

It worked and he had his simple PCB within a couple hours.

JR

 

[abbey road d enfer]

Back in the early 70s when I was working as a technician at MIT Instrumentation Lab, the engineer I was supporting needed a PCB as quickly as possible. I took a piece of copper clad, and painted a simple PCB pattern of traces on it with dykem blue tooling ink. I etched off the unpainted copper.

I made my first PCB's in 1962. The only method available for a pennyless kid was a specific paint that smelled of naphta, dried in about 30 minutes. This paint was advertised in all the "radio" magazines.. It came with a rapidograph (actually not the real Rötring but a cheap copy).
Did that until the early 70'S, where photoresist became available to amateurs. Actually they may have been earlier, but I was not in a very technology-oriented country in the late 60's.

 

[JohnRoberts]

Back when I was writing kit articles (1970s-80s), it was standard practice to publish PCB foil patterns so readers to replicate the PCBs using photographic transfers.

JR

PS: It may be instructive but those engineers never asked me to do another crude hand drawn PCB... But I did not stay in that job more than a few months.

 

[ruffrecords]

When I retired in 2000 and decided to design some tube circuits I had never laid out a PCB in my life. As an engineer I had had lots of PCBs laid out for me and I supervised the layout of many more but I had never done one myself. So, before going down the bottomless pit of selecting an ECAD package, learning how to drive it and then creating the extensive library of special footprints you need for pro audio tube circuits, I decided to do something much simpler. I got some Eurocard sized single sided copper clad PCBs and using a small hand drill I removed the copper between tracks for valve bases and components. Everything was just soldered direct to the copper. No need to drill any holes.

Cheers

Ian

 

[Newmarket]

When I retired in 2000 and decided to design some tube circuits I had never laid out a PCB in my life. As an engineer I had had lots of PCBs laid out for me and I supervised the layout of many more but I had never done one myself. So, before going down the bottomless pit of selecting an ECAD package, learning how to drive it and then creating the extensive library of special footprints you need for pro audio tube circuits, I decided to do something much simpler. I got some Eurocard sized single sided copper clad PCBs and using a small hand drill I removed the copper between tracks for valve bases and components. Everything was just soldered direct to the copper. No need to drill any holes.

Cheers

Ian

Sounds good but I'm not sure I understand no holes - so you "surface mounted" the components / bases ?

 

[ruffrecords]

Sounds good but I'm not sure I understand no holes - so you "surface mounted" the components / bases ?

Yes. Copper side upwards. I might still have one of the early boards around somewhere. If I can find it I will take a pic and post it.

Edit: Found a pic (attached but a little blurry I am afraid) from December 2007.

Cheers

Ian

 

[MidnightArrakis]

Back in the early 70s when I was working as a technician at MIT Instrumentation Lab, the engineer I was supporting needed a PCB as quickly as possible. I took a piece of copper clad, and painted a simple PCB pattern of traces on it with dykem blue tooling ink. I etched off the unpainted copper.

It worked and he had his simple PCB within a couple hours.

JR

Back in 1972 I was stationed at a "secret" military base located literally in the middle of the Utah desert (now known as "Area 52"). There was nothing around the base for nearly 100-miles in every direction. This base primarily conducted tests for chemical and nerve-agent warfare and the mist from these tests, being dispersed from radio antenna structures several hundreds of feet high, would be picked up by thousands upon thousands of sensors placed in ever widening concentric circles out there in the desert. The data-signals from these sensors were all sent back to a "Command Center" that processed the signals using an IBM main-frame computer system.

Unfortunately, lots of the signals from the sensors became corrupted along the way to the IBM main-frame, so the "Group Leader" instructed an electronics engineer to design some type of buffering circuitry to go between the incoming signals and the input feeding the IBM. Then, the "Group Leader" pointed at me saying, "And, you.....Williams.....you design the mechanical enclosure and the Printed Circuit Boards for Dave's circuitry".

Being out there in the middle of the Utah desert, I had ordered chemicals and materials to design the PCBs from some catalog, even though I had never done that before. I converted a large storage locker into a "dark-room" to expose the photo-sensitized laminates and Dave and I built a motorized PCB acid-bath mechanism to etch the boards. It was really exciting watching everything come together from nothing.

In any case.....it was from my designing those first PCBs and also mechanically designing a small edge-card enclosure for the first time that got me into the direction of eventually becoming the "Electronics Packaging Designer" that I am today. After being discharged from the Army, it was also my working with bands, concert sound-reinforcement companies and recording and TV studios that "married" my equipment design work with my audio background.

>> Is this "too much noise", Abbey?

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