Another sorted Stereo 20

[myles]

Hmmm, I rather like the original Bulgins so wouldn't change them.

I suppose the real magic is that the chassis hasn't been amended so it can be returned to Bulgin setup before selling.

 

[rabski]

Sorry Henry, but I really don't like Bulgins. I'm not convinced they give the best surface contact for pins, but the serious issue is that the plugs don't have any strain relief and it's way too easy for the cable to come loose. Either way, as Myles says, it's a non-destructive fix, so can be easily reversed.

On to more important things...

I've just done the backbreaking bit of pulling the 845 out to stick the little grey beastie in the system. Bloody hell it's good. It's the bass that's a real surprise. It's probably a touch tighter and cleaner than the SET. It doesn't quite have the 'liquid' realistic mids of the 845, but it's not in a different league by a long stretch and the top end is excellent.

A bit of a revelation really. I'm normally in the camp that says push pull is bad and feeback is worse, but this just goes to show that done right, it can work well. Young Mr Leak was very good at design though, and the component specs in the feedback loop are very, very carefully thought out.

 

[toprepairman]

Definitely take your point with the strain relief.
I'm gentle with my leads, including the 2 pin Bulgins for Quads.

 

[Bogart]

It's not as cosmetically good as the picture makes it. There are a fair few marks and small paint flakes, but it's not too bad and I don't like the 'brand new' look when they've been repainted. It wears its scars with pride, but then it's what's underneath that counts.

Patina is the word required here.

 

[Jules_S]

Patina Knackered is the word required here.

FTFY

Joking aside, I think we all know that by the time Richard has finished with the refurb it will both look and sound as close to ideal for a vintage Leak as it's ever likely to get. Clever so-and-so.

 

[rabski]

To revisit this... work has got in the way, but I finally managed to put in some hours on the second refurb and it's about done now. Far from being a bin job

The casework cleaned up really nicely, apart from the transformer ends. I managed to spray those in a colour that's close enough to look decent. The board went in the ultrasonic tank for a while and came up really nicely. For this one, I also managed to spray the original caps so it looks near standard externally, but they're dead, so I added modern ones under the chassis.

Jantzen Z-Caps for this one, but like the last, I've kept the standard circuit with the later reliability and stability changes. Just modern, higher tolerance and lower noise components (and proper earthing as well). On soak with a dummy load at the moment, but a 'scope trace suggests all is well. I'll see what it sounds like later.

On to the next one. Managed to paint the chassis yesterday, but I've got the hateful job of doing the waterslide lettering, which takes forever.

 

[rabski]

The outside...

 

[Tony_J]

Very nice Richard.

 

[Idlewithnodrive]

The outside...

That looks lovely

 

[bencat]

Sadly we are all different and i still find it hard to like that colour it is a sort of dirty gold which just does not appeal . The work as has been said looks superb but give me a black one anytime . Stupid really as it will still sound the same but that colour would just annoy me every time i saw it . I know pathetic .

 

[antonio66]

@bencat Shows we are all different Andrew, I like the colour, change from black or silver giving a classic look, well done Richard.

 

[rabski]

The grey metallic is better to my eyes as well to be honest, but I'd only change the colour if the paint couldn't be salvaged. Externally, I'd much rather keep it original.

 

[audio_PHIL_e]

Hmmm, I rather like the original Bulgins so wouldn't change them.

I thought the Bulgins became illegal because it was too easy to get a schock by putting your fingers on the pins but the IEC plug also has pins you could put your fingers on ?

 

[rabski]

I thought the Bulgins became illegal because it was too easy to get a schock by putting your fingers on the pins but the IEC plug also has pins you could put your fingers on ?

AFAIK it's that the Bulgin plugs (3 pin and 2 pin) don't have any cable relief, so it's too easy to pull the wires out. Also, the pin spacing I think means that if the grooved part wears, it's possible to insert a Bulgin the wrong way round. Bulgin and IEC both have 'concealed' pins, so I don't think there's any safety issue in that aspect.

As much as anything, I use IECs because you can fit them without modifying the casework, and the cables are way easier to get hold of.

 

[rabski]

Bulgin and IEC aspects notwithstanding, with anything I repair, build or modify, safety comes above any other aspect. If it's a question of safety or originality, then IMHO there is no question. On all the Leak rebuilds, I'm committing the cardinal sin of drilling a small extra hole in the casework adjacent to the mains socket. This is for a single, standalone earthing connection. On the original, the case earth uses a thin wire that runs through the loom and goes to a multiple ground connection via one of the self-tapping screws for one of the valve sockets. Not only does that not meet correct CE standards, but it offers at least three possible failure points.

 

[bigrod]

The grey metallic is better to my eyes as well to be honest, but I'd only change the colour if the paint couldn't be salvaged. Externally, I'd much rather keep it original.

Always worth more if it’s original colour

 

[bigrod]

Sadly we are all different and i still find it hard to like that colour it is a sort of dirty gold which just does not appeal . The work as has been said looks superb but give me a black one anytime . Stupid really as it will still sound the same but that colour would just annoy me every time i saw it . I know pathetic .

Anything but black

 

[rabski]

Satin black has its benefits of course. It's (very) easy to spray with a rattle can and get a decent finish, and it fits in with most things.

Anyway, it seems the 'scope does not lie. The gold one is currently in the system and sounding very decent indeed. I imagine all the bits will need a little bedding in, so I'll leave it playing for this evening before I massacre my spine getting the 845 back on the rack.

The Jantzens from new seem to have a little more of the 'lucid mids' than the Audyns in the grey one. Experience with Audyns though is that they take a bit longer to bed in but end up equally good. Both of them so far are a stark reminder that a good circuit in the 1950s is still a damned good circuit 70 years later. I have no doubt that using modern (and high quality) parts doesn't do any harm, but I've stuck rigidly to the original circuit. Why not? The main problems with the Stereo 20 originally were more than anything down to component tolerances and quality, and sims and valve specs suggest that apart from a bit too much gain, there's nothing wrong with it at all. Anyway, regardless of the gain, a bit of care with grounding and layout and both of them are dead quiet.

Oddly, the one criticism a few people level at the ST20 (and EL84 amps in general) is somewhat soggy and loose bass. Could have fooled me. It's not megawatt solid state, but it's tight and quite 'dry and fast'.

 

[Chiily]

Incidentally, for anyone with stuff that has the dreaded Bulgin sockets, the IECs are available from Mullard Magic: linky

They do need a fair bit of filing on the corners to get them to fit, but it's plastic, so not too tedious. If you use the original mounting screws/holes they also end up sideways, but again that's hardly the end of the world (though the painted earth marking is wrong) and it means you can use proper cables and connectors.

The Bulgin round ones are dire and don't meet any modern safety standards, so it's a very sensible mod.

Doing a fabulous job there, really great work. And they sound lovely when sorted out.

I notice that the switch on the above picture is shiny and looking new. Is it one you bought to fit? If it is could post a link to it online please as I'm after a switch for the back of my ST20.

Ta.

 

[rabski]

Doing a fabulous job there, really great work. And they sound lovely when sorted out.

I notice that the switch on the above picture is shiny and looking new. Is it one you bought to fit? If it is could post a link to it online please as I'm after a switch for the back of my ST20.

Ta.

No idea, it was just one out of the spares box. Anything rated 5A or above (at AC mains) will do the job. I just pulled one out of the pile that fitted the original 'switch cable' hole without needing to drill it out. There will be literally hundreds on RS that will do the job.