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Another Leak Stereo 20 restoration

Rug Doc said:
Yes the first one. Aha! Glad it’s gone back to original.

my second question - would you restore to a custom colour??
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I like the original colours myself but yes I could do it, provided I can get the paint mixed. For example if you wanted a specific car colour that'd be easy to do.

Earlier this year I visited English Acoustics and saw their Stereo 21C painted in all sorts of colours and to a very high standard too.
 
Alex S said:
There’s no stopping you, or stopping me enjoying mine.
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This.

A seriously impressive amp. Not just beautiful to look at, but it sounds it too. Mike's done a top job restoring mine, so the owner of the newly restored one is in for a treat.

@myles ...would suit your Tannoys perfectly.
 
Possibly daft question but I'll ask anyway! Replacing the the speaker terminals seems standard practice, as is fitting a power switch, both of which makes sense. Is there a reason why no one ever replaces the bulgin power connector with a standard IEC job?
 
paulfromcamden said:
Possibly daft question but I'll ask anyway! Replacing the the speaker terminals seems standard practice, as is fitting a power switch, both of which makes sense. Is there a reason why no one ever replaces the bulgin power connector with a standard IEC job?
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Some people do replace it and some people seem to think it is a step too far away from originality for the amp.

For me it was a step too far when the Bulgin plug works fine, just have to be careful of the lack of cable grip in the plug; don't tug the mains wire.
 
paulfromcamden said:
Is there a reason why no one ever replaces the bulgin power connector with a standard IEC job?
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Some people do, but it usually involves chassis butchery which obviously devalues the amp from a collector perspective. The speaker terminals and switch can be done in a reversible way, as can the RCA inputs.

Bulgin connectors really aren’t great, but assuming you find and use a good tight-fitting cable gland (I found some NOS for mine) they can be made safe. Remember people gigged all over the place with them as they were standard on all the classic Marshall and Vox amps plus loads of keyboards, PAs, mixers etc. I got my first shock from one as a teenager (PA amp), so that has made me make and check them *very* carefully!

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Here are my pair for my TL12 Plus. Notice the rubber cable gland/strain-relief. It is a very tight fit over the cable and has a fat washer-like end that won’t pull through the bakelite hole. This is as safe as this plug design can possibly be. I’d still not want to gig Bulgins and if I was a touring muso I’d replace them with IECs, but for home audio wired like this they are absolutely fine.
 
@Tony L I didn't realise they were once used on sound gear - interesting.

Those power cables look really like a very sensible approach. If I start using my ST20 again I may have to do something similar to mine.
 
paulfromcamden said:
@Tony L I didn't realise they were once used on sound gear - interesting.
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Military and heavy industry too. They were the UK standard before IEC. You’ll find them all over the place on any kit that needed a detachable mains lead. They are only rare and expensive now as gigging musos keep breaking the ones on the back of their amps. Bakelite does not bounce off a hard stage! The one I got a shock off all those decades ago just came apart in my hand. I guess it was already badly cracked.

I really have mixed feelings about them as, when in perfect condition and wired properly, they are a beautiful item. I’m a big fan of Bakelite, and I think they look really cool, all part of the vintage aesthetic. That said, from a logical design perspective they are just batshit crazy. Truly stupid. If you actually sat down with the design brief to create a mains connector that could fail in multiple ways, all of which were potentially fatal to the end user, there’s a very good chance you’d come up with something remarkably close to a Bulgin plug.
 
Tony L said:
You’ll find them all over the place on any kit that needed a detachable mains lead. They are only rare and expensive now as gigging musos keep breaking the ones on the back of their amps. Bakelite does not bounce off a hard stage!
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I'm surprised I've never run into one in the wild even on stuff like Lesley cabinets, Fender Rhodes, etc. Makes me wonder if hire firms like John Henrys just fit a captive cable so they're not constantly replacing bulgin plugs. Or dealing with electrocuted musicians!

edit: and apologies to Mike for the slight thread detour.
 
paulfromcamden said:
I'm surprised I've never run into one in the wild even on stuff like Lesley cabinets, Fender Rhodes, etc. Makes me wonder if hire firms like John Henrys just fit a captive cable so they're not constantly replacing bulgin plugs. Or dealing with electrocuted musicians!
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It was very much a UK standard, American stuff like Fenders, Hammonds etc tended to have captive mains leads. You’ll find a Bulgin on the back of a Mellotron, Vox Continental, VCS3 (I think a mini here like a Quad 303) etc.
 
And here I go again with another ST20 restoration. I think that makes this one my sixth?

Much of the process has already been covered multiple times in other threads so I'll try to only post about anything that's different or not been covered already.

My latest ST20 is a 1963 example with an 8162R mains transformer. The chassis is needs some repairs, so it'll be getting a full strip down and repaint.

Here's the nastiest bit. At the rear of the chassis someone has fitted an extra socket of some sort and in order to do it they've crudely cut a hole in the chassis.

ST20 rear showing chassis damage by Michael Pickwell, on Flickr

There are also two holes drilled on the side of the chassis.

ST20 screw holes on side of chassis by Michael Pickwell, on Flickr

And there are multiple dents to deal with too.

I began by stripping down the amp to it's constituent parts so that I could then take the chassis and transformer cover off to be sand blasted.

Chassis blasted by Michael Pickwell, on Flickr

One side of the chassis was bent inwards along the bottom edge and had to be bent back out.

ST20 chassis dent by Michael Pickwell, on Flickr

I use a hammer and dolly to get the smaller dents out and get it all nice and tidy again whilst checking in good light against a straight edge.

Hammer and dolly by Michael Pickwell, on Flickr
 
To repair the hole in the chassis I first tidied the hole up with a file to make nice and square. I then scribed around the hole to make its shape onto to a piece of sheet steel of the same thickness as the rest of the chassis. The patch was then shaped so that it fitted nice and snuggly in the hole ready to be welded/soldered in.

To repair the screw holes I drilled and tapped the holes to accept normal metric machine screws.

ST20 hole filled ready for solder by Michael Pickwell, on Flickr

The screws were then silver soldered in before being cut off flush to the chassis and the square patch was similarly silver soldered in place. To be honest the sensible thing would've been to MIG weld it in place but since I already had the oxyacetylene torch out I just did it with silver solder.

Once everything had been carefully ground back and sanded smooth the repair is smooth and will be completely invisible when painted. And it's an all metal repair with no filler.

ST20 chassis repair by Michael Pickwell, on Flickr

What screw holes?

ST20 screw holes filled by Michael Pickwell, on Flickr
 
toprepairman said:
That's a lovely restoration you're doing there.
Were you able to find replacement 0.8mm solid core wire?
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Thanks. I was able to find some 0.8mm solid core hookup wire in mist of the original colours on ebay. It was only pink I couldn't get.
 
All finished and another one saved.

I'm just about to sit down with a coffee and have my first proper listen to it.

ST20 6 angle by Michael Pickwell, on Flickr

ST20 6 top by Michael Pickwell, on Flickr

ST20 6 underside by Michael Pickwell, on Flickr

St20 6 rear by Michael Pickwell, on Flickr

ST20 6 board side view by Michael Pickwell, on Flickr

I'm going to be concentrating on my bike frame build for a while now but after that I've got yet another ST20 in the 'to do' pile that is a real horror show!
 
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