Leak amplifier restoration questions - UK Vintage Radio Repair and Restoration Discussion Forum

cjwhoishe · 15th Oct 2017, 4:19 pm

Hi all, sorry for a bit of a long post.
Over a year ago I became the unexpected owner of a couple of Leak TL12+ amps and a varislope stereo pre-amplifier.
These have had 2 effects since I acquired them, I have started to look at repairing other bits of old electronics I have, and I have re-found vinyl media.
They were almost literally a barn find. A friend of my mothers was clearing a shed at the bottom of her garden. In that shed were these units and they had been in there for at least 30 years, before that were in the attic of the house.
They were a failed attempt of her late husband setting up an hi-fi system in the 60s and got 'dark-holed' when he couldn't get it working.
One of the amplifiers (gold one) and the pre-amplifier survived reasonably well as they were in original boxes. The boxes though didn't and were covered in mould.
The black one was in a much worse state (the photos are after cleaning) as it was un-boxed and had everything on it.
Early on I decided I would like to get these going again, but there was no way I was going to power them up immediately.
I left them for 4 months in a dry environment, to ensure any damp within the transformers had gone.
I then re-formed the capacitors in each unit and changed the important capacitors (that capacitor). I powered them up slowly and they seemed to hold out (very surprising for the black one).
I then replaced the rest of the capacitors, one of the rectifiers and have been listening to the trio for the last 6 months or so.
They are still working fine with nothing getting excessively hot and so have proven themselves and I am confident to fully restore them.

After this little story I know get to the main reason for the post.
I intend to get these 3 units to an up to date state and use them as my main system.
As you can see the black one is in a real state internally and I think I have 2 options.
1. Strip it down and turn it gold like the other.
2. Strip it down, clean up the inside and the outside as much as possible but leave original black.

If I choose option 1 does anybody know how to get the Leak logo back on?
I have looked into waterslide decal paper but printing white on these is a problem.

Another question is whether I should replace the main power capacitors as part of the final update, I have some but the ones in place seem to be fine?
To do them justice I would need to re-stuff them in the original cans.
I do intend to replace all the other components.

On the black unit the speaker impedance selection sockets are badly corroded and I soldered the connection I need.
Are these socket connections readily available or will I have to keep this hard link and blank the plate off?
I already have more of the plugs.

GrimJosef · 15th Oct 2017, 5:41 pm

As far as the Leak logo is concerned, I'm afraid there is no very easy answer to this. The original was, presumably, screen printed. So the best solution would be to repeat that process. But that would involve scanning the logo, investing in a screen print kit and finding a suitable ink to get as close as possible to the original look. It wouldn't be a trivial exercise.

Your reformed HT capacitors have proven to be reliable. Have you measured their capacitance ? If that is OK then the only remaining performance issue is their ESR (equivalent series resistance). This can sometimes go high which can make the capacitors less effective at doing their job (reducing 100Hz ripple on the HT supply). The effect of this is to raise the level of backgound hum, although it's worth noting that that level of hum can also be raised by other things (e.g. mismatch between the output valves). If you're happy with the hum level then personally I'd leave the capacitors as they are.

Cheers,

GJ

Nickthedentist · 15th Oct 2017, 7:10 pm

It's very sad to think that the original owner (apparently) never got to hear these amps working as they were meant to.

bikerhifinut · 15th Oct 2017, 8:07 pm

Try this link for some information.

http://www.44bx.com/leak/

The site owner Steven Spicer is an authority on the Leak products, and if you can get hold a of a copy of his book "Firsts in high Fidelity" you will find not only a definitive history of Leak and HJL himself, but probably the most accurate resource in one place of reference material, not just circuit diagrams but histories of major updates to the amps.

There's also a Yahoo group dedicated to Leak stuff, I am not sure how active these days as I haven't visited myself for a while. There's more than a couple of members of that group who frequent these hallowed pages so you'll get some good pointers.

Grim Josef's advice is very sound, he knows his onions on these amps.

The charcoal grey amp does look very tired, and if you do feel that you want to renovate it, I see no issue with repainting it to match its mate. There are people who have made new slide transfers as I remember so you might be able to dig around for a bit of info there.

Looking under the amps, I see the original paper in oil coupling caps are still present. In my book these are a "replace on sight" item as invariably they will be leaky both electrically and physically, neither of which is good for the amp or possibly you. I would happily use something like the Vishay 630V rated plastic film capacitors as sold in the BVWS magazine. (other sources are available). Avoid using fancy expensive capacitors, just make sure it's working. If the voltages at the important points are within tolerance I'd be inclined to leave the resistors as they are although the carbon types used in the era of these amps can drift off spec quite a lot.

Lovely amps, enjoy them. I have a TL2+ that I need to restore to as near as original layout etc as I can get it and also still regularly use my Stereo 20 that I have had for around 15 years now and it has stayed reliable. They are good amps and with the right loudspeakers modern or period they are lovely.

Finally if, in your research, you come across any advice to alter the original circuit in any fundamental way, such as different valves or circuit design, DON'T DO IT! They will never sound better than they do in their original setup. They can be a bit over sensitive with modern sources and there are relatively simple ways to get round this but I never did with mine and have learned to turn the volume control down! I'm not a fan of the Leak preamps especially on their magnetic cartridge input but if you like what they do, and plenty of folks do, then that's great. Check inside that too, there's a lot of those paper in oil caps in them. Again change them for decent quality plastic films and leave the rest alone unless you are a glutton for punishment.

I hope you do get them running and looking sweet, I'm a real fan of those EL84 power amps and they should be enjoyed and used.

Andy.

bikerhifinut · 15th Oct 2017, 8:12 pm

Could it be possible to print a scan or photo of the original logo on to something like OHP transparency film and then stick them on prior to the spray lacquer final paint coat?

A

cjwhoishe · 15th Oct 2017, 8:30 pm

Hi Bikerhifinut
Thanks for the link but I had already scoured that thoroughly.
As I said I have changed all of the caps, the photos were when I had only changed 'that' cap on the black/grey one and to show how they were originally.
I wouldn't have run them for so long without doing that.
My major worry was long term reliability of the grey ones transformers so I got them working with the least expense (not the optimal replacement capacitors) and just used them.
I think your right about the preamp (there is certainly little need for all the equalization options). This has had most of the capacitors replaced as well and the main PSU capacitor also reformed OK.
My ears are not as good as they were so the preamp sounds fine to me.
The next step now is to rebuild them knowing the transformers are OK.

GrimJosef · 15th Oct 2017, 11:09 pm

Quote:

Originally Posted by bikerhifinut

Could it be possible to print a scan or photo of the original logo on to something like OHP transparency film and then stick them on prior to the spray lacquer final paint coat?

I racked my brains for a while trying to come up with a scheme like this. But the fundamental problem is that Leak's logo is nearly white. When it comes to domestic printers it seems you can have any colour as long as it's not 'nearly white'

.

I'd recommend Stephen Spicer's book too. As well as being a valuable technical resource it's also a jolly interesting read.

Cheers,

GJ

Ted Kendall · 15th Oct 2017, 11:10 pm

Well then, paint it gold and have a black logo?

bikerhifinut · 15th Oct 2017, 11:17 pm

Except the gold units also had white logos so for matching purposes perhaps not ideal. But good thinking Ted!

A.

bikerhifinut · 15th Oct 2017, 11:23 pm

One thing in the original Leak preamps favour is that they have adjustable attenuators on some of the inputs so matching to modern high output sources is easier.

A.

GrimJosef · 15th Oct 2017, 11:27 pm

I think the 'bronze' units had white logos but the 'champagne' ones had black

http://www.44bx.com/leak/Leak/TL12Plus_a1.jpg

Cheers,

GJ

Goldie99 · 16th Oct 2017, 12:39 pm

Maybe also worth reviewing the following thread & discussing it with David G4EBT ?

http://www.vintage-radio.net/forum/s...+knob+markings

cjwhoishe · 17th Oct 2017, 1:40 pm

Thanks Goldie99
I have asked David G4EBT some questions.
I have ordered 2 types of waterslide paper and I am going to do some experiments.
The restoration of these amplifiers is a winter project (and probably into next summer) so I have lots of time to do these experiments.

15th Oct 2017, 4:19 pm	#1
cjwhoishe Triode Join Date: Jun 2016 Location: Grantham, Lincolnshire, UK. Posts: 27	Leak amplifier restoration questions Hi all, sorry for a bit of a long post. Over a year ago I became the unexpected owner of a couple of Leak TL12+ amps and a varislope stereo pre-amplifier. These have had 2 effects since I acquired them, I have started to look at repairing other bits of old electronics I have, and I have re-found vinyl media. They were almost literally a barn find. A friend of my mothers was clearing a shed at the bottom of her garden. In that shed were these units and they had been in there for at least 30 years, before that were in the attic of the house. They were a failed attempt of her late husband setting up an hi-fi system in the 60s and got 'dark-holed' when he couldn't get it working. One of the amplifiers (gold one) and the pre-amplifier survived reasonably well as they were in original boxes. The boxes though didn't and were covered in mould. The black one was in a much worse state (the photos are after cleaning) as it was un-boxed and had everything on it. Early on I decided I would like to get these going again, but there was no way I was going to power them up immediately. I left them for 4 months in a dry environment, to ensure any damp within the transformers had gone. I then re-formed the capacitors in each unit and changed the important capacitors (that capacitor). I powered them up slowly and they seemed to hold out (very surprising for the black one). I then replaced the rest of the capacitors, one of the rectifiers and have been listening to the trio for the last 6 months or so. They are still working fine with nothing getting excessively hot and so have proven themselves and I am confident to fully restore them. After this little story I know get to the main reason for the post. I intend to get these 3 units to an up to date state and use them as my main system. As you can see the black one is in a real state internally and I think I have 2 options. 1. Strip it down and turn it gold like the other. 2. Strip it down, clean up the inside and the outside as much as possible but leave original black. If I choose option 1 does anybody know how to get the Leak logo back on? I have looked into waterslide decal paper but printing white on these is a problem. Another question is whether I should replace the main power capacitors as part of the final update, I have some but the ones in place seem to be fine? To do them justice I would need to re-stuff them in the original cans. I do intend to replace all the other components. On the black unit the speaker impedance selection sockets are badly corroded and I soldered the connection I need. Are these socket connections readily available or will I have to keep this hard link and blank the plate off? I already have more of the plugs. Attached Thumbnails

15th Oct 2017, 5:41 pm	#2
GrimJosef Dekatron Join Date: Sep 2007 Location: Oxfordshire, UK. Posts: 4,311	Re: Leak amplifier restoration questions As far as the Leak logo is concerned, I'm afraid there is no very easy answer to this. The original was, presumably, screen printed. So the best solution would be to repeat that process. But that would involve scanning the logo, investing in a screen print kit and finding a suitable ink to get as close as possible to the original look. It wouldn't be a trivial exercise. Your reformed HT capacitors have proven to be reliable. Have you measured their capacitance ? If that is OK then the only remaining performance issue is their ESR (equivalent series resistance). This can sometimes go high which can make the capacitors less effective at doing their job (reducing 100Hz ripple on the HT supply). The effect of this is to raise the level of backgound hum, although it's worth noting that that level of hum can also be raised by other things (e.g. mismatch between the output valves). If you're happy with the hum level then personally I'd leave the capacitors as they are. Cheers, GJ __________________ http://www.ampregen.com

15th Oct 2017, 7:10 pm	#3
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,846	Re: Leak amplifier restoration questions It's very sad to think that the original owner (apparently) never got to hear these amps working as they were meant to.

15th Oct 2017, 8:07 pm	#4
bikerhifinut Octode Join Date: Nov 2013 Location: Penrith, Cumbria, UK Posts: 1,993	Re: Leak amplifier restoration questions Try this link for some information. http://www.44bx.com/leak/ The site owner Steven Spicer is an authority on the Leak products, and if you can get hold a of a copy of his book "Firsts in high Fidelity" you will find not only a definitive history of Leak and HJL himself, but probably the most accurate resource in one place of reference material, not just circuit diagrams but histories of major updates to the amps. There's also a Yahoo group dedicated to Leak stuff, I am not sure how active these days as I haven't visited myself for a while. There's more than a couple of members of that group who frequent these hallowed pages so you'll get some good pointers. Grim Josef's advice is very sound, he knows his onions on these amps. The charcoal grey amp does look very tired, and if you do feel that you want to renovate it, I see no issue with repainting it to match its mate. There are people who have made new slide transfers as I remember so you might be able to dig around for a bit of info there. Looking under the amps, I see the original paper in oil coupling caps are still present. In my book these are a "replace on sight" item as invariably they will be leaky both electrically and physically, neither of which is good for the amp or possibly you. I would happily use something like the Vishay 630V rated plastic film capacitors as sold in the BVWS magazine. (other sources are available). Avoid using fancy expensive capacitors, just make sure it's working. If the voltages at the important points are within tolerance I'd be inclined to leave the resistors as they are although the carbon types used in the era of these amps can drift off spec quite a lot. Lovely amps, enjoy them. I have a TL2+ that I need to restore to as near as original layout etc as I can get it and also still regularly use my Stereo 20 that I have had for around 15 years now and it has stayed reliable. They are good amps and with the right loudspeakers modern or period they are lovely. Finally if, in your research, you come across any advice to alter the original circuit in any fundamental way, such as different valves or circuit design, DON'T DO IT! They will never sound better than they do in their original setup. They can be a bit over sensitive with modern sources and there are relatively simple ways to get round this but I never did with mine and have learned to turn the volume control down! I'm not a fan of the Leak preamps especially on their magnetic cartridge input but if you like what they do, and plenty of folks do, then that's great. Check inside that too, there's a lot of those paper in oil caps in them. Again change them for decent quality plastic films and leave the rest alone unless you are a glutton for punishment. I hope you do get them running and looking sweet, I'm a real fan of those EL84 power amps and they should be enjoyed and used. Andy. Last edited by Station X; 15th Oct 2017 at 9:42 pm. Reason: Readability.

15th Oct 2017, 8:12 pm	#5
bikerhifinut Octode Join Date: Nov 2013 Location: Penrith, Cumbria, UK Posts: 1,993	Re: Leak amplifier restoration questions Could it be possible to print a scan or photo of the original logo on to something like OHP transparency film and then stick them on prior to the spray lacquer final paint coat? A

15th Oct 2017, 8:30 pm	#6
cjwhoishe Triode Join Date: Jun 2016 Location: Grantham, Lincolnshire, UK. Posts: 27	Re: Leak amplifier restoration questions Hi Bikerhifinut Thanks for the link but I had already scoured that thoroughly. As I said I have changed all of the caps, the photos were when I had only changed 'that' cap on the black/grey one and to show how they were originally. I wouldn't have run them for so long without doing that. My major worry was long term reliability of the grey ones transformers so I got them working with the least expense (not the optimal replacement capacitors) and just used them. I think your right about the preamp (there is certainly little need for all the equalization options). This has had most of the capacitors replaced as well and the main PSU capacitor also reformed OK. My ears are not as good as they were so the preamp sounds fine to me. The next step now is to rebuild them knowing the transformers are OK.

15th Oct 2017, 11:10 pm	#8
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,670	Re: Leak amplifier restoration questions Well then, paint it gold and have a black logo?

15th Oct 2017, 11:17 pm	#9
bikerhifinut Octode Join Date: Nov 2013 Location: Penrith, Cumbria, UK Posts: 1,993	Re: Leak amplifier restoration questions Except the gold units also had white logos so for matching purposes perhaps not ideal. But good thinking Ted! A.

15th Oct 2017, 11:23 pm	#10
bikerhifinut Octode Join Date: Nov 2013 Location: Penrith, Cumbria, UK Posts: 1,993	Re: Leak amplifier restoration questions One thing in the original Leak preamps favour is that they have adjustable attenuators on some of the inputs so matching to modern high output sources is easier. A.

15th Oct 2017, 11:27 pm	#11
GrimJosef Dekatron Join Date: Sep 2007 Location: Oxfordshire, UK. Posts: 4,311	Re: Leak amplifier restoration questions I think the 'bronze' units had white logos but the 'champagne' ones had black http://www.44bx.com/leak/Leak/TL12Plus_a1.jpg Cheers, GJ __________________ http://www.ampregen.com

16th Oct 2017, 12:39 pm	#12
Goldie99 Heptode Join Date: Jul 2014 Location: Boston, Lincolnshire, UK. Posts: 995	Re: Leak amplifier restoration questions Maybe also worth reviewing the following thread & discussing it with David G4EBT ? http://www.vintage-radio.net/forum/s...+knob+markings

17th Oct 2017, 1:40 pm	#13
cjwhoishe Triode Join Date: Jun 2016 Location: Grantham, Lincolnshire, UK. Posts: 27	Re: Leak amplifier restoration questions Thanks Goldie99 I have asked David G4EBT some questions. I have ordered 2 types of waterslide paper and I am going to do some experiments. The restoration of these amplifiers is a winter project (and probably into next summer) so I have lots of time to do these experiments.