Leak Stereo 70 - UK Vintage Radio Repair and Restoration Discussion Forum

Whaam68 · 22nd May 2016, 10:41 pm

I got this amp a few years ago free with a set of sandwich 15 ohm speakers. After messing about with valves for some time I thought it was about time to give the leak a new lease of life so I can taste the glory of early transistor sound. I managed to blow the driver and output transistors fitting new trimmer resistors and not checking they were not fully on. In the end I went for a do it all once approach and did a full re cap and all the metal tube carbon resistors. It's now working very well indeed, has great drive and a surprisingly good phono. I've re capped the sandwiches so it's retro for me for now. One thing that everyone cautions about are the edge contacts and switches and pots but with a bit of servisol these were all fine. For some reason these seem to be going up in value which is not a good thing in my book but if you have one they are well worth an overhaul.
Mike

HamishBoxer · 23rd May 2016, 11:07 am

One thing to watch for is the high value resistors as they can go higher and loose you a channel.

Whaam68 · 23rd May 2016, 1:11 pm

I did change any out of spec resistors on the power amp boards. The bias on both channels is stable around 30ma. What I did notice is the Carbon comps in the power supply at R1 (1K) and R2 & R3 (390R) all ran hot to the point of their outer wax shell was softening. I'm sure they account for some of the leak amp smell when you open one up! I replaced these with 3W parts and they run much cooler.

HamishBoxer · 23rd May 2016, 1:15 pm

Sounds good, time I got mine out and sorted .Also got a couple of Leak speakers (not the sandwhich type I am afraid).

nutteronthebus · 23rd May 2016, 1:57 pm

HI this is a link to the cct diagram

http://www.44bx.com/leak/Leak/Circuits/cctStereo70.gif

Dave L

greg_simons · 23rd May 2016, 3:56 pm

Very underrated transistor amps these, grab one while they're still relatively cheap, just restored a stereo thirty and it's surprisingly good for it's age with excellent build quality.
Greg.

Whaam68 · 23rd May 2016, 4:07 pm

I have a couple of cheap 30's I picked up but both are non running & need work. I do like the understated looks of Leak amp & tuners from this era.

Whaam68 · 23rd May 2016, 5:40 pm

Here is the outside.

Bob_Moss · 23rd May 2016, 8:47 pm

I rescued a Leak Delta 70 that was destined for the tip last month, not tried it yet but looks in VGC.
It was sitting on an old fridge-freezer, outside, waiting for the scrap wagon.
I will pair it with my Leak 3020 speakers as a second system.

22nd May 2016, 10:41 pm	#1
Whaam68 Hexode Join Date: Feb 2007 Location: Luton, Bedfordshire, UK. Posts: 457	Leak Stereo 70 I got this amp a few years ago free with a set of sandwich 15 ohm speakers. After messing about with valves for some time I thought it was about time to give the leak a new lease of life so I can taste the glory of early transistor sound. I managed to blow the driver and output transistors fitting new trimmer resistors and not checking they were not fully on. In the end I went for a do it all once approach and did a full re cap and all the metal tube carbon resistors. It's now working very well indeed, has great drive and a surprisingly good phono. I've re capped the sandwiches so it's retro for me for now. One thing that everyone cautions about are the edge contacts and switches and pots but with a bit of servisol these were all fine. For some reason these seem to be going up in value which is not a good thing in my book but if you have one they are well worth an overhaul. Mike Attached Thumbnails

23rd May 2016, 11:07 am	#2
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: Leak Stereo 70 One thing to watch for is the high value resistors as they can go higher and loose you a channel. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

23rd May 2016, 1:11 pm	#3
Whaam68 Hexode Join Date: Feb 2007 Location: Luton, Bedfordshire, UK. Posts: 457	Re: Leak Stereo 70 I did change any out of spec resistors on the power amp boards. The bias on both channels is stable around 30ma. What I did notice is the Carbon comps in the power supply at R1 (1K) and R2 & R3 (390R) all ran hot to the point of their outer wax shell was softening. I'm sure they account for some of the leak amp smell when you open one up! I replaced these with 3W parts and they run much cooler.

23rd May 2016, 1:15 pm	#4
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: Leak Stereo 70 Sounds good, time I got mine out and sorted .Also got a couple of Leak speakers (not the sandwhich type I am afraid). __________________ G8JET BVWS Archivist and Member V.M.A.R.S

23rd May 2016, 1:57 pm	#5
nutteronthebus Hexode Join Date: Jun 2011 Location: Glossop, Derbyshire, UK. Posts: 487	Re: Leak Stereo 70 HI this is a link to the cct diagram http://www.44bx.com/leak/Leak/Circuits/cctStereo70.gif Dave L __________________ Any tool can be used as a hammer but a screwdriver makes the best chisel

23rd May 2016, 3:56 pm	#6
greg_simons Octode Join Date: Jul 2004 Location: Evesham, Worcestershire, UK. Posts: 1,423	Re: Leak Stereo 70 Very underrated transistor amps these, grab one while they're still relatively cheap, just restored a stereo thirty and it's surprisingly good for it's age with excellent build quality. Greg.

23rd May 2016, 4:07 pm	#7
Whaam68 Hexode Join Date: Feb 2007 Location: Luton, Bedfordshire, UK. Posts: 457	Re: Leak Stereo 70 I have a couple of cheap 30's I picked up but both are non running & need work. I do like the understated looks of Leak amp & tuners from this era.

23rd May 2016, 5:40 pm	#8
Whaam68 Hexode Join Date: Feb 2007 Location: Luton, Bedfordshire, UK. Posts: 457	Re: Leak Stereo 70 Here is the outside. Attached Thumbnails

23rd May 2016, 8:47 pm	#9
Bob_Moss Pentode Join Date: Mar 2003 Location: Mansfield Woodhouse, Nottinghamshire, UK. Posts: 216	Re: Leak Stereo 70 I rescued a Leak Delta 70 that was destined for the tip last month, not tried it yet but looks in VGC. It was sitting on an old fridge-freezer, outside, waiting for the scrap wagon. I will pair it with my Leak 3020 speakers as a second system. __________________ I was so upset that I cried all the way to the chip shop.