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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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12th Dec 2017, 10:17 pm | #61 | |
Pentode
Join Date: Aug 2017
Location: North London, UK.
Posts: 114
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
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Agreed just for myself i want to know whats in there, i want it neat and all similar. |
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14th Dec 2017, 6:59 pm | #62 | |
Tetrode
Join Date: Aug 2007
Location: Sheffield, South Yorkshire, UK.
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
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I don't know if anti-surge fuses were available when these amps were new, but maybe if you do fit a fuse then choose an anti-surge type??
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14th Dec 2017, 8:22 pm | #63 | |
Dekatron
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Location: Oxfordshire, UK.
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
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A few years ago there was a thread here somewhere where Stephen Spicer and I discussed the use of this resistor as a protection device. I and others have seen Stereo20s where the tags on the board are not cut, so in the event of the solder melting the resistor wouldn't drop out. My best guess is that actually Leak found that it didn't offer much protection in practice so they simply stopped bothering to cut the tags. The reason Leak didn't fit a fuse would have been some combination of cost (he was running a business and very few of his competitors were paying for an HT fuse) and practicality. The output transformer primary windings are a bit marginal. So a protective fuse would have had to have been rated at a current quite close to the normal operating level . That would have resulted in some degree of 'nuisance blowing' which would have upset the customers. As far as the look of the resistors goes, we shouldn't forget that Leak didn't pay for a baseplate for this amp either. So we can see the resistors whenever we lift the amp and look. Leak set a lot of store by appearance (it was a selling point that they were proud of). So in much the same way that while your E-type will drive just as well on solid wheels, you really want it to have the lovely looking wire ones don't you ? VB
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14th Dec 2017, 9:07 pm | #64 | |
Rest in Peace
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
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During the soak check afterwards, one of the amps cut out, because it had overheated and R21 had dropped out. The reason, I suspect, was that up to that time I had been running the amps on their sides so that I could monitor voltages etc. During the soak check I had this amp standing on its base - there were no feet fitted, so there was no circulation of air under the amp contributing, I suspect, to the build up of enough heat to desolder the resistor. After refitting it and fitting feet, it was fine. Cheers, Frank |
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14th Dec 2017, 11:09 pm | #65 |
Pentode
Join Date: Aug 2017
Location: North London, UK.
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
It took most me of the day, but I was able to finish fitting the components today, keeping what was in range and replace where it was needed.
I found the input/preamp area fiddly and a real pain especially since the resistors were hooked around the terminals and so close together. I didn't have small 32uf caps for the power supply, so just to get it tested I used the black replacements as you see, I carefully took the original ones out to change back at a later stage. Once everything was double checked, it was switched on without any valves and transformer voltages checked again. Then one by one each valve, starting with the rectifier, was inserted and the voltages and current drawn was checked around the circuit. So far everything is as it should be! Next will be to actually put some test tones through it and check it all on the oscilloscope, do a soak test, play some music through it and make sure it runs sweetly. Any tips here would be appreciated, Once I get to that stage I'll start tidying it all up. So far very happy. |
14th Dec 2017, 11:21 pm | #66 | ||
Pentode
Join Date: Aug 2017
Location: North London, UK.
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
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14th Dec 2017, 11:23 pm | #67 | ||
Pentode
Join Date: Aug 2017
Location: North London, UK.
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
Quote:
Quote:
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15th Dec 2017, 12:08 am | #68 | |
Rest in Peace
Join Date: Jan 2015
Location: Cottesmore, East Midlands, UK.
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
Quote:
I've probably got some smallish rubber feet I can let you have. Cheers, Frank |
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15th Dec 2017, 3:40 pm | #69 |
Pentode
Join Date: Aug 2017
Location: North London, UK.
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
Post man came today with some more gifts.
Russian PIO capacitors and a full component kit to repair the TL12 plus, thanks to Paul at Classic Sounds Leicester. |
16th Dec 2017, 12:22 am | #70 |
Pentode
Join Date: Aug 2017
Location: North London, UK.
Posts: 114
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
Thought i would do a parts list for the TL12 plus. Taken from the circuit diagram supplied in Stephen Spicer's book.
only thing which was confusing was C13 (smoothing cap) it has at 200uf, so far i've seen three different circuit diagrams with different values for C13 - 32uf,100uf and 200uf. C14 - 32uf, 60uf,8uf Like seriously which one is it? I downloaded circuit diagrams from well known websites and each one is different. Unfortunately my original caps are finished and need changing so not sure which i should use. Thinking stick the the Stephen Spicer Diagram C13 being 200uf and C14 8uf Please have a look and let me know if i made any mistakes! Trying to provide help for other future enthusiasts. LEAK TL12 PLUS Resistors Qty Designator Original Value R1 1M, 1/2W R2 22K,1/2W R3 2K2, 1/2W R4 100R, 1/2W R5 82K 1/2W R6 1M ,1/2W R7 100K, 1W R8 3.3M R9 91K R10 1K R11 22K,1/2W R12 12K or 1M ,1/2W R13 100K, 1W R14 3.3M R15 10K, 1/2W R16 470k R17 470k R18 10K, 1/2W R19 270K R20 270K R21 10K R22 100R, 3W R23 4.7K Capacitors Qty Designator Original Value C1 1000pf C2 50uF electrolytic,12v C3 1uf 450v C4 0.1uf 350v C5 16uf C6 8uf C7 200pf C8 0.025uf 350v C9 0.1 uf 450v C10 0.025uf 350v C11 50uf C12 50uf 12v C13 200uf C14 60 uf C15 200pf Last edited by vishalk; 16th Dec 2017 at 12:30 am. |
16th Dec 2017, 10:23 am | #71 |
Dekatron
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Location: Leominster, Herefordshire, UK.
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
Your list has redundant "Qty" headings in it!
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16th Dec 2017, 12:05 pm | #72 |
Pentode
Join Date: Aug 2017
Location: North London, UK.
Posts: 114
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
Did it late last night, eyes were tired so missed it when I copied and pasted it!
Either way the list is there, I'll correct and repost. |
17th Dec 2017, 11:03 pm | #73 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,637
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
One off topic post deleted.
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18th Dec 2017, 10:54 pm | #74 |
Pentode
Join Date: Aug 2017
Location: North London, UK.
Posts: 114
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
As I write this the stereo 20 is in the background playing Michael Buble Christmas songs (wife's choice of music)
Its been playing for 4 hours with no issues and I must say it's a joy to listen to. Beautiful warmth to it and not fatiguing to listen to. I'm running through a valve preamp with no issues at all, so I have no problem with the input gain. Using the function generator and oscilloscope I managed to get 10wrms per channel, everything was as it should be! Next is the pair of TL12 + although these will have a few slight modifications. |
18th Dec 2017, 11:23 pm | #75 |
Pentode
Join Date: Aug 2017
Location: North London, UK.
Posts: 114
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
Guys do any of you have some spare leak power bulgin connectors i can purchase, please PM me if you do!
Thanks |
18th Dec 2017, 11:28 pm | #76 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,637
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A pair of Leak TL12s
To avoid confusion, please start a new thread for the TL12s
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26th Dec 2017, 8:54 pm | #77 |
Pentode
Join Date: Aug 2017
Location: North London, UK.
Posts: 114
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
Hi All
I hope you are enjoying the Xmas festivities, for me it started off with my leak amplifier dying on me. My wife on Xmas day switched the system on, although didn't wait for the amplifier to warm up before playing music. She tells me one of the EL84 valves flashed and glowed brightly, at which point she saw smoke and smelt burning! This is where she switched it all off (I was in the shower when all this happened). Please see attached pictures, resistor R15 burnt out taking the associated EL84 valve with it. Now I'm not sure why as it's been working beautifully, upset as it took out one of the quad matched Mullards . Could it be that the valve just became faulty? Or is it one of the components? Means I have to recheck all the component values and retest the voltages. Anything else I should look out for? |
26th Dec 2017, 10:41 pm | #78 |
Octode
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,993
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
OK, replace the resistor (obviously) and then check that no DC can be measured on the grid of the burnt out valve. Do this with no output valves plugged in or even with no valves except GZ34, this will eliminate a leaky coupling capacitor which could cause the valve to pass more current than its rated for and cause it to fail. Make sure no short circuits anywhere. then check all the voltages at the various key points with a set of known good valves in. I am assuming that you did replace all the coupling caps with new plastic film jobs of a suitably high DC voltage rating?
As I remember you are using the Mullards that the amp came with? It's quite possible that it simply died of old age and unfortunately failed in a manner that took out the cathode resistor. I'd put the other 3 Mullards to one side once sure the amps ok and replace the lot with decent new ones. And flog the other 3 on Ebay, you'll likely cover the cost of a new quad of Russian or Chinese etc etc that way. A. Last edited by bikerhifinut; 26th Dec 2017 at 10:45 pm. Reason: clarification |
26th Dec 2017, 11:13 pm | #79 |
Rest in Peace
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Location: Cottesmore, East Midlands, UK.
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
Hi, Vishal,
I had exactly the same problem on one of the ST20s I did back in March or so. All the surrounding components checked in spec and the voltages looked good. In the end I decided that the resistor was was simply not man eneough for it's supposed wattage and replaced all 4 main cathode resistors with higher wattage items (IIRC 3W) When I fitted the new ones, I stood them away from the board by about 6-8 mm or so to allow better circulation. If all else looks good, you might try that. And remember that you can't have the amp sitting right down on to its chassis - you need some sort of feet to raise it enough to allow cool air to get in under the chassis. Cheers, Frank Last edited by frankmcvey; 26th Dec 2017 at 11:19 pm. |
26th Dec 2017, 11:30 pm | #80 |
Octode
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,993
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Re: Leak Stereo 20 and TL12 Plus in need of recommissioning. Help and Guidance needed
Well spotted Frank. Yes I'd replace all 4 270R cathode resistors and as frank says, stand them off to let air get round. 2W should be well man enough though. I used the bog standard 2W metal films from uncle Maplin and they are still there some 13 years later! They will be dissipating around 0.6W so 2W should be plenty of headroom. Those 2W Maplin jobs are a similar size to the originals which I think might have only been 1W jobs all those years ago.
Otherwise totally in agreement with you frank Andy. |