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September 4, 2013 / billo44

Trio W-38

This was a very lucky find in a junk shop in early 2011. Face

1,500 Yen or about 15 US Dollars these days.  Dates from 1961 or 62 which makes it older than me…

I set about trying to restore this one and was helped out by various folk; Bob, just outside Boston, was very helpful, and various folks on the UK Vintage Radio Repair and Restoration forum (link at the bottom), Andrew G. who had painstakingly built an excellent amp from the amplifier stage of his W-38.  He compared the sound favourably with the legendary Quad 2 amplifiers which got me thinking!  (Cant comment on that  since I have still never heard a Quad 2…).

When I started work on the amp/receiver there was very little output.

Here is the top side after cleaning…

ND3_9587

And here is the underside with a lot of electrolytic capacitors in need of replacement.

ND3_9329-2

Not a circuit board in sight, all wired point-to-point.

ND3_9585

And after replacing 98% of the capacitors…

Still sounded terrible!

My friend Bob suggested I try the headphone output, and it was OK so I worked through the signal with an oscilloscope and found a dirty speaker phase switch  I cleaned all the signal path slide switches and replaced the final 2% of the leaky electrolytic capacitors and the thing woke up and sounded lovely playing through the aux input.

After about three weeks of re-listening to favourite albums I then got around to fitting a direct input to the amp stage.

Trio W38 direct in (4)

Connects to pin 1 of the front two of the 6BM8 valves.

ND3_9720

This is a pretty inconspicuous and fully reversible modification, mounted using existing screws… but leaves the volume control on the back of the unit.  This is OK by me…!

The volume control on the front doesn’t do anything! ….. I hate it when people turn down the music while I am listening to something inspired!

The switch selects from direct input or input via the original pre-amp stage.

Its very discreet with the lid back on….

ND3_9723

Had to listen to all my favourite recordings again for three weeks….

Still one of my favourite sounding amps to date… I am looking for another W-38 which is cosmetically bad enough to cannibalise for a nice sounding 10 Watt  power amp.

Note also the obligatory upgrade to the AC mains lead including the addition of a safety ground for the chassis.

And here are the links…

http://www.vintage-radio.net/forum/showthread.php?t=57768

and

http://85.92.85.233/forum/forum/showthread.php?t=67837

Bored you now!…

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3 Comments

Leave a Comment
  1. Neelesh / Jun 30 2014 2:48 am

    Awesome build. I recently acquired one – and it’s in need of a total cap replacement. Do you have a list of all the caps you replaced?
    So far my list is:
    0.01uf 600wv x 4
    0.02uf 600wv x 1
    0.05uf 600wv x 15
    25uf 10wv x 6

    Also what caps did you use?

  2. Bill O'Connor / Jun 30 2014 8:50 am

    Thanks Neelesh, I sent you an e-mail with the cap list.

    • Neelesh / Jul 2 2014 5:02 am

      Thank you! Your information kicked off my refurb into high gear. I replaced all the signal path caps already and the sound has already improved quite nicely!! She is definitely low on power though and I’m hoping that a change in the PSU caps would resolve this.

      Again thank you for your assistance on this matter. It’s awesome seeing something this old – jump into life again.

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