Author Topic: Building a Douglas Self power amplifier!  (Read 752 times)

Online Zilch

Building a Douglas Self power amplifier!
« on: February 22, 2021, 08:52:30 PM »
Yep, I'm actually building a power amp.

Starting this thread very early.  Still need to get the components.  Need to get proper replacement transistors for the discontinued Toshiba ones.

I'm also moving soon, so hopefully at the new place I can set up a proper soldering station!

Here are some pics for your pleasure...
If you don't understand the difference between "their", " there", and "they're", then your an idiot.

Online Zilch

Re: Building a Douglas Self power amplifier!
« Reply #1 on: February 22, 2021, 08:53:04 PM »
Here's the PCB...




If you don't understand the difference between "their", " there", and "they're", then your an idiot.

Online Zilch

Re: Building a Douglas Self power amplifier!
« Reply #2 on: February 22, 2021, 08:59:02 PM »
The package was shipped around mid Sept. 2020.  Before today I'd completely forgot about about it.  Until I found a lovely little paper in the mailbox from the SAPO.  Surprisingly the package was intact!

It came all the way from the U.K, from George Todd.  Who I met on Reddit, of all places :pleasant:

Really excited to get started on this project!  Should be a great sounding piece of kit :groovy:
If you don't understand the difference between "their", " there", and "they're", then your an idiot.

Online Zilch

Re: Building a Douglas Self power amplifier!
« Reply #3 on: February 22, 2021, 09:03:20 PM »
And here are some scans of the B.O.M, PCB layout, and schematic diagram!

I've cut out his email address, for obvious reasons.

The inductor appears to be a homemade one, being wrapped around the resistor next to it (on the schematics).

Some holes were too small for some components he purchased.  When my order comes in I'll check, hopefully they fit as is :pray:
If you don't understand the difference between "their", " there", and "they're", then your an idiot.

Online Family_Dog

Re: Building a Douglas Self power amplifier!
« Reply #4 on: February 22, 2021, 09:06:55 PM »
You can purchase a small 1mm drill bit, just put it in a loose chuck and turn by hand if necessary. Or use a Dremel drill if you have one.

Try Rabtron for any semiconductors you might require.

This looks like a load of fun!


-F_D



-Eric

That Guy in South Africa...
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Online Shonver

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Re: Building a Douglas Self power amplifier!
« Reply #5 on: February 22, 2021, 09:17:32 PM »
Good amp. Enjoy!
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Offline Camy1zn

Re: Building a Douglas Self power amplifier!
« Reply #6 on: February 22, 2021, 09:35:38 PM »
All the best on this build zilch. Great project.

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Online Zilch

Re: Building a Douglas Self power amplifier!
« Reply #7 on: February 23, 2021, 02:34:03 PM »
Thanks everyone!

F_D I'll try them!  Looks like they may have some in stock!

Sorry for deleting the images.  Missed something I needed to cut out.  Will upload later.

Can a mod please delete the Imgur links in Reply #2?
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Re: Building a Douglas Self power amplifier!
« Reply #8 on: February 23, 2021, 02:36:24 PM »
Where are you buying your power transistors from? Beware of fakes, especially with obsolete devices.

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Online Zilch

If you don't understand the difference between "their", " there", and "they're", then your an idiot.

Offline DACMan1

Re: Building a Douglas Self power amplifier!
« Reply #10 on: February 23, 2021, 03:01:32 PM »
Where are you buying your power transistors from? Beware of fakes, especially with obsolete devices.

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Yup these devices are VERY rare. I would buy an extra pair and bust them open to check - the likelihood of being fakes is higher than not...

Online Zilch

Re: Building a Douglas Self power amplifier!
« Reply #11 on: February 23, 2021, 03:20:57 PM »
pwatts recommended I have a look at the MJ21193 & MJ21194 as replacements.  They look like pretty good devices!
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Re: Building a Douglas Self power amplifier!
« Reply #12 on: February 23, 2021, 03:24:50 PM »
You got good advice there.
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Re: Building a Douglas Self power amplifier!
« Reply #13 on: February 23, 2021, 03:40:45 PM »
Just check that they come in the package that you want. The data first sheet that came up was TO-3 style. You will find other recommendations for current replacements on DIYAudio.com.
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Online Zilch

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