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Leak Stereo 20

Should not make any difference.
Pull the interconnects out.
If you get noise from the speakers, short the inputs to ground, i.e. put the inter connects back in and short the outer rings to the central pins of the RCAs.
 
toprepairman said:
The 270 R resistors normally have about 12 Volts across them which equates to 44mA. This results in 528mW or just over half a watt. Therefore a 1W resistor is fine. A bigger one will last forever. However in a fault situation it would be best if the resistor burnt out before anything else (expensive transformers) so 1W is better than 5 in this instance.
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That's good to know. I'll order some 1W Takmans and get those 5 Watters out then.

@Tony L - Did you use 5W Mills in the same position in your TL12+ ?
 
John_73 said:
@Tony L - Did you use 5W Mills in the same position in your TL12+ ?
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Yes. I think I over-spec’d absolutely everything to be honest! I do have a valve tester (the little Orange) though, but how much I trust it is yet to be defined. Maybe I should change them, but I want to deal with the ‘buzz’ fault first. No idea what rating the big red resistors in my S20 are!
 
Personally I would not worry about the wattage value too much.
I asked John_73 because they looked a different colour to the ones next door (470kΩ) and wondered if they were under extra un-wanted stress. I understand they are a different make now.
In reality as you both have replaced the 0.22uF coupling caps (C4 and C6) with Russian PIOs there is very little risk of leakage (which is the prime culprit for 'burning up' the valves and resistors.)
And you see un-restored ST20s and TL12+s with the resistors badly cooked, because the output vales are drawing far too much current from leaky coupling caps, but still intact. (More often the associated bypass cap has let go first...)
A fuse in the HT line, like Will of Radford Revival implemented, is possibly better all round protection.
 
Have run those tests Alan, and placed the EL84 valves where you said to. The results are:

1. 9.8V (this is the valve with the faintest flashing).

2. 10.5V

3. 10.9V

4. 10.1V

5. 321V

6. 305V.
 
That's fine.
I would be happy to run it for an hour and then check the mains transformer temperature and so on. Just do not leave it unattended for a few sessions...
 
That's good to know, thank you. Looking at those voltages for the EL84s I could probably just order a single used Mullard of similar vintage (mine are '67) just to ensure they're all safely around 10V or over to tide me over until the Russian ones arrive. Might put a wanted ad here later.

Must admit for a few seconds I thought something was going badly wrong as I could smell something heating up. Forgot that new components often give off a bit of a whiff at first! Had a careful look and nothing was discolouring. That 100R is NOS and I know that one gets hot, so likely that was the whiffy culprit.
 
Ummm,
I wouldn't bother with another Mullard. Either wait for the Russian valves to turn up and retire the set you have, so they stay with the amp if you sell it. Or buy a couple of JJ EL84s from a reputable seller to tide you over.
 
It used to belong to my Great Uncle, who passed on last year alas, so this one is here to stay, and I restored it as a sort of homage to him.

Have powered it up again and touch wood sounding mighty fine, though will only power it on an hour at a time, though the temptation is to enjoy it all evening it really does sound fantastic. Exactly the kind of sound I love, full bodied mids, crisp treble, surprisingly dynamic bass. Very impressed.
 
They really are fabulous amps!

PS The mains transformer does get pretty hot on the Stereo 20, around 50C after a couple of hours in a typical ambient temperature IIRC. Made me a bit nervous at the start. Leak had real issues exporting to nice hot climates such as Australia, South Africa etc as the wax regularly melted! I guess yours may well run noticeably cooler than mine as IIRC the reduction of transformer voltage was partly to combat this.
 
Really am extremely chuffed - and surprised as I wasn’t expecting it to sound quite this good (though slightly on edge waiting for that valve to suddenly make an underpants changing type noise should it meet its maker!).

We’re in a 247V-ish (last time I measured it) area so might well run hotter as a result. I’ll be far happier when those valves arrive, though tempted to look out for a single ‘67 (or thereabouts) Mullard for piece of mind.
 
Always worth having more than a quad of power valves IMO. Where possible I try to buy eight identical valves and alternate the sets now and again. That way it should be a very long time until I’m down to only four of that set that measure good. I’ve done this a fair bit with various 6p14p types and by pure fluke actually have some pretty similar Mullards to supplement the yellow print ‘64 set that came with the grey S20. I’ve got two which are the same type number, but different date-codes, plus another two earlier square getter ones (came with my first TL12 Plus), and a pair of ‘made in Holland’ Mullards which have a different plate style that came with the second TL. All currently measure ‘good’ on the Orange tester.
 
@John_73 Your rebuilt Leak Stereo 20 looks magnificent. I'd be interested to hear your own thoughts on how the Leak compares to a well rebuilt Quad 303, as I know that you've got experience of those! :)
 
dommydops said:
@John_73 Your rebuilt Leak Stereo 20 looks magnificent. I'd be interested to hear your own thoughts on how the Leak compares to a well rebuilt Quad 303, as I know that you've got experience of those! :)
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Hello there! Hope your 303 is still providing lots of enjoyment.

(Bare in mind it’s only been working for a couple days, and I’m not using it regularly yet until one of the valves is replaced) I’d describe the Stereo 20 so far as a fantastic blend of the full-bodied and smooth (as in lacking any grain, not lacking for detail) midrange and presence of the 303, with the excitement, and pace/rhythm of a NAP160. Surprising bass kick to it too - 10W??! So far, very impressed!
 
Tony L said:
Always worth having more than a quad of power valves IMO. Where possible I try to buy eight identical valves and alternate the sets now and again. That way it should be a very long time until I’m down to only four of that set that measure good. I’ve done this a fair bit with various 6p14p types and by pure fluke actually have some pretty similar Mullards to supplement the yellow print ‘64 set that came with the grey S20. I’ve got two which are the same type number, but different date-codes, plus another two earlier square getter ones (came with my first TL12 Plus), and a pair of ‘made in Holland’ Mullards which have a different plate style that came with the second TL. All currently measure ‘good’ on the Orange tester.
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Ordered a single used Mullard EL84 of similar construction vintage (‘68) from ‘Mullard Magic’ for £22. Of course postage then bumped it upto £28! Doh... Oh well, it’ll be worth it to run a full set of Mullards until those Russian valves arrive from Romania, without worrying about that one with the faint flashing suddenly going South and taking a capacitor with it.
 
John_73 said:
Hello there! Hope your 303 is still providing lots of enjoyment.

(Bare in mind it’s only been working for a couple days, and I’m not using it regularly yet until one of the valves is replaced) I’d describe the Stereo 20 so far as a fantastic blend of the full-bodied and smooth (as in lacking any grain, not lacking for detail) midrange and presence of the 303, with the excitement, and pace/rhythm of a NAP160. Surprising bass kick to it too - 10W??! So far, very impressed!
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The 303 is doing sterling service, thanks! Very glad that the Stereo 20 is working out so well. I had to look up the NAP160, but what you say fits with my own experience of the Leak - I've never had any concerns about the St20's bass. Look forward to following your revival of your St20 to its final stage. There are some very good tips throughout this thread for St20 owners, by the look of it; I need to wade through earlier pages...
 
dommydops said:
The 303 is doing sterling service, thanks! Very glad that the Stereo 20 is working out so well. I had to look up the NAP160, but what you say fits with my own experience of the Leak - I've never had any concerns about the St20's bass. Look forward to following your revival of your St20 to its final stage. There are some very good tips throughout this thread for St20 owners, by the look of it; I need to wade through earlier pages...
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Almost there with it really. I just need to get those two new F&T dual 32uF caps painted (though I’m rather warming to the bare aluminium look!), plus get an aluminium plate cut and painted to fit the on/off switch I’ll be using, which will fit in place of the unused twin mains output connectors which have been carefully removed and stored. Will need to add a switch suppressor to the on/off switch too. Other than those things, just waiting on two sets of new valves (ordered another from Harma to get me going sooner than the Russian 6P14P-ER valves I’m waiting on). Might get a couple of right angle phono plug adapters too so the interconnects don’t look quite so awkward sticking up like they do. There’ve been a few mods, but just in terms of use-ability with new phono and speaker sockets. The originals were carefully removed and are stored away too.

Heard a single crackle (the first!) from the channel those worn valves are on, so have taken no chances and turned it off. Will leave it now until the Harma Retro valves turn up. Already missing it, though the Quad 606 is still a firm favourite :)
 
Inspired by this thread I've been listening to my ST20 today for the 1st time in a couple of months having been distracted recently by my newly acquired Quad 33/303.
The amp was rebuilt & serviced in Nov 2018 by Graeme at AmpRegen, all the caps & resistors on the main board were replaced using polypropylene & polystyrene caps & carbon film resistors. The smoothing caps were left alone, Graeme checked them & found them to be OK so on the basis of "if it ain't broke" we decided to leave them in place.
The amp is still sounding superb hooked up to my JR149s but a problem has cropped up. When I powered the amp on I noticed the usual start up hum was louder than usual & didn't subside completely as it it used to. It quietened down a bit but still remained a steady hum that can just about be heard from my listening seat (fairly nearfield 1.5m triangle). This remains steady regardless of volume setting or source selected. The rest of the set up is my Khozmo passive pre being fed by either an Rpi with Allo Piano 2.1 DAC hat & Kali Reclocker streaming Spotify & my Rotel RCD-965BX.
Any ideas?

PS, I had been thinking about selling the amp recently. A couple of hours listening this afternoon has completely knocked those foolish thoughts out of my head despite the hum!

Thanks

TS
 
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