Transistor amp from scratch

[DaveP]

This is probably as good a time as any.......................
This January I was diagnosed with mesothelioma (asbestosis) and I have had 9 doses of chemo since then. I have never knowingly worked with the stuff but it was in everyones home during the 1950's when I grew up. My mothers's ironing board and the pads for bunsen burners at school for example. As this will probably be my last project "from scratch", I decided to keep it simple.

 

[Newmarket]

This is probably as good a time as any.......................
This January I was diagnosed with mesothelioma (asbestosis) and I have had 9 doses of chemo since then. I have never knowingly worked with the stuff but it was in everyones home during the 1950's when I grew up. My mothers's ironing board and the pads for bunsen burners at school for example. As this will probably be my last project "from scratch", I decided to keep it simple.

Very sorry to hear this Dave. The ongoing consequences of widespread asbestos use are terrible.
Let us know how the amp project goes.
Thoughts.

 

[TwentyTrees]

This is probably as good a time as any.......................
This January I was diagnosed with mesothelioma (asbestosis) and I have had 9 doses of chemo since then. I have never knowingly worked with the stuff but it was in everyones home during the 1950's when I grew up. My mothers's ironing board and the pads for bunsen burners at school for example. As this will probably be my last project "from scratch", I decided to keep it simple.

I'm ever so sorry to hear this. I look forward to seeing how this project goes, your build reports are always inspiring stuff.

 

[Migs 31]

This is probably as good a time as any.......................
This January I was diagnosed with mesothelioma (asbestosis) and I have had 9 doses of chemo since then. I have never knowingly worked with the stuff but it was in everyones home during the 1950's when I grew up. My mothers's ironing board and the pads for bunsen burners at school for example. As this will probably be my last project "from scratch", I decided to keep it simple.

Yes Dave,

That stuff is everywhere even now.
My old flat in England, where I used to live for 10 yrs, has it on the ceiling.
They are trying to remove it now (a big mess)...

Good luck with your project. I wish you success.
Post some pics of your progress on the PtP project!

M

 

[sahib]

Very sorry to hear that Dave.

I am hoping that you have not purchased all of your components yet. I have tons of stuff that are removed from pro-audio and/or hi-fi equipment. Perfectly working. So, I insist I supply these as my contribution to the project. The stuff I have includes

IEC with or without fuse/ on-off switch. I can see that you already have the aperture cut out for the IEC and also the fuse holder. In which case give me the aperture dimensions for the IEC. I also have vintage fuse holders.

Front panel on/off switch in case you do not want it at rear.

Matching knobs for switches and potentiometers. Seeing that your case is natural colour. I have metallic ones that would work a treat. I also have the volume potentiometers to match the knobs. We have options here. We can either use a dual potentiometer with single shaft or dual concentric for separate LR control.

Based on your schematics, all of your capacitors and resistors. I have two boxes of high high wattage resistors and I am sure we'll have something in the required values.

I see that the DC supply is 36V. I think I have got a transformer for that.

Hook up and screened signal wires.

 

[DaveP]

I thank all of you for your kind words and support. Groupdiy has allowed me to contact so many wonderful people over the years that I would never had met otherwise. All of my projects have been encouraged and supported by so many people, it is impossible to mention them all, but they know who they are.

Sahib, your offer is typical of the spirit on this forum, but in fact I am in the same position as you with loads of spare parts! This summer I gave away most of my reference books and resistors and caps to those I knew would put them to good use. None of my kids have any interest so everything would have just gone to recycling.

No-one will commit themselves as to how long you have left, so it makes it difficult to make a decision on a final project, above all I want to finish it!

best
DaveP

 

[scott2000]

above all I want to finish it!

Sorry to be selfish but I'm praying God has others planned after this one.

 

[sahib]

Dave,

You are here. Let's do it.

If you change your mind for the parts offer is still on the table. However, here is the transformer. It has the main tap at 34V and then the various auxiliary outputs. But unfortunately judging by the core size it is about 50VA.


However, although you may already have them, to stimulate the project I have photographed various schematics from a Mullard book that I have.

 

[MidnightArrakis]

Sounds good. My "stripboard & wire" things are one off efforts / prototypes. If I were making more then I'd look to go PCB.

[If I were making more then I'd look to go PCB] -- The pricing for PCB's these past few years has become so reasonable, that even the cost of a "one-off" PCB makes more sense and is much easier to do, than the effort it takes to accomplish a "Point-To-Point" stripboard these days!!! Not only that, but.....with all of the resources that I have for PCB-fabricators, I can usually get 3-to-5 PCB's for nearly the same price as a single PCB would cost!!! So.....to me.....it becomes a "Why Not" just design a PCB??? But.....that's just me!!!

/

 

[Mr. Moscode]

I think that amp will sound pretty good. It's not overloaded with negative feedback. The suggestion to use a darlington output circuit is a good one. I would suggest some polypro bybass caps on the lytic output and bootstrap caps and one for an input cap, too.

I'm sorry your're dealing with that disease and I wish you the best. As a baseball announcer who was reading the injured list said, So and so is listed as day to day, as are we all.

Keep us posted.

 

[Matt Syson]

Hi Dave
As with the others I am sorry to hear of your diagnosis. Regarding the amp project, the 25 watt design put up by Sahib using the Darlington configuration will most likely cut the distortion down and you could use more modest 'driver' transistors and limit the power overall to 10 watts which is probably pushing the BD139/140 transistors anyway.
I see you list yourself as living in France. I too am in France, North West (ish) about 40km South of Caen if you would be interested in messaging me. Either DM on this board (if that works) or 'google' my name. The best to you anyway.
Matt

 

[DaveP]

Sahib,
I already have all the parts, the transformer I am using is a 120VA 2x25V toroidal, which will give me a separate supply for each channel.
I have access to all those photos you posted in the original book.
I will keep you posted with the project and thank you once again for your support.

best
DaveP

 

[DaveP]

Scott2000,
Thank you for your video and kind thoughts. I have many Christian friends who have prayed for me during this ordeal. I will let you judge the results of their prayers from these figures. When they first fitted me with a pleurix (to drain the pleura) the nurse took 650ml the first week, then it fell to 450, 350, 250, 175 then 75mls, then they switched to every two weeks as it was so low, the last drainage was 10mls. Obviously the chemo drugs did their part, but as of today, it has not spread anywhere else.

best
DaveP

 

[Ricardus]

This is probably as good a time as any.......................
This January I was diagnosed with mesothelioma (asbestosis) and I have had 9 doses of chemo since then. I have never knowingly worked with the stuff but it was in everyones home during the 1950's when I grew up. My mothers's ironing board and the pads for bunsen burners at school for example. As this will probably be my last project "from scratch", I decided to keep it simple.

I'm so sorry to hear this. Wishing you the best.

 

[DaveP]

Back on topic:

All the major components are now in position on the board. The amps will be mirror images of each other as far as possible.



Starting to arrange the Power Supply.



Best
DaveP

 

[thomasdf]

Another amazing build in the making !
How did you do the IEC hole ? Hole punch ?

Bravo !

 

[Walter66]

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.

 

[DaveP]

Just Drill some holes and the rest can be excavated using a file or rasp

That's how I did it
Best
DaveP

 

[thomasdf]

That’s also how I do it. But I don’t get such clean results.. for now

 

[ruffrecords]

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.

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