Work In Progress... Leach Based Amplifier

[John Wu]

Now, rotate them 180 degrees.

Gajanan Phadte

Good idea, thanks a lot!


John

 

[John Wu]

I use TO3 for driver, the circled TO3s on the small plate are the drivers. It according the initial design that M. Leach published in 1975.
The reversion layout in M. Leach current website use TO-220 for driver and locate on main PCB.
I think this may be the reason makes you confused.

There are 8 output TO3s located on the plate that you marked with red vertical bar, there is a 10mm thick plate between it and main heat sinker.



John

I hope this photograph can help for you to figure out my build.


John

 

[TonyTecson]

i hope someone can come up with gerbers of the Super Leach original lay-outs...

 

[John Wu]

i hope someone can come up with gerbers of the Super Leach original lay-outs...

The PCB of my build was by manual with black tape and compact than Leach's original.




John

 

[TonyTecson]

The PCB of my build was by manual with black tape and compact than Leach's original.




John

very good John, what i have in mind also is the incorporation of the 4 TO-3 drivers into the boards...

John, are those yellow tubes ceramic or plastic? how much will a 1000pcs cost?

 

[John Wu]

very good John, what i have in mind also is the incorporation of the 4 TO-3 drivers into the boards...

John, are those yellow tubes ceramic or plastic? how much will a 1000pcs cost?

They are Teflon, cut off from Teflon packaged copper wire.


John

 

[Jay]

The PCB of my build was by manual with black tape and compact than Leach's original.

What kind of tape?? Is it really possible or strong enough?? I'd like to find different approach to etch a PCB (quickly)

 

[djk]

I've used black electrical tape as a resist for a one-off.

Just roll it flat to get good adhesion or the trace will be undercut during etch.

I used a paintbrush during the etch phase to remove most of the copper quickly (and I didn't have enough etchant for a tank anyway).

 

[gmphadte]

What kind of tape?? Is it really possible or strong enough?? I'd like to find different approach to etch a PCB (quickly)

The tape is of the old method. It is some type of paper tape and may not be available now. This tape was used when PC methods were not available. This artwork would be done on a pvc(?) paper and later used for UV exposure.

Gajanan Phadte

 

[TonyTecson]

i used masking tapes for one off's...

nowadays, i use the flat-iron method....

also nowadays, it is very cheap to have boards fabbed in china...a 2 inch x 3.5inch double sided board with vias costs me about U$1 each for a 50 board run...

 

[John Wu]

The tape is of the old method. It is some type of paper tape and may not be available now. This tape was used when PC methods were not available. This artwork would be done on a pvc(?) paper and later used for UV exposure.

Gajanan Phadte

Hello Gajanan,

Thanks a lot for your kind description.
I can tell that Jay should be much younger than me. 🙂


John

 

[Jay]

I've used black electrical tape as a resist for a one-off.
Just roll it flat to get good adhesion or the trace will be undercut during etch.

Hmmm... hard to believe it is strong enough, but I will try that sometime...

Hello Gajanan,
Thanks a lot for your kind description.
I can tell that Jay should be much younger than me. 🙂

Hehehe 😀 Before internet era (we used 386 in university) I have no idea about schematics. Have done flip flop but in bread board(?) tho. Incredible what the internet can bring to the third world community 😀

 

[jwilhelm]

There are loads of different etch resist schemes. In high school we used layout dye and scatched out where we wanted the copper gone. There are also many different ways to etch. I threw away my etch tank years ago. On one ounce copper boards I use a sponge soaked in warm etchant. It works faster than the tank because the corroded copper is constantly being wiped off and uses little etchant. On half ounce boards I put them in a ziplock bag with a small amount of etchant. Immerse it in warm water and rub the suface of the board. Clean up is really simple that way.