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Old 11th May 2018, 11:50 am   #1
victor54
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Default Restaurare Leak III ST Refurbishing

Hi everyboady,

This is my first Thread on that forum. I have just boght a Leak Throughline 3 Stereo in pristine condition. I think I was fortunate, this is like a sleaping beauty. Outside as well as inside, no trace of human action, rust or dust. No component was replaced and valves are the original ones. My intention is restauration/refurbishing as much as can be.
So, for the beginning I had revival the PSU with low voltage as 110 volt getting 230 volt after some hours. I checked the multy section el-cap an was OK also checked some voltage poins and seamed OK also.
After providing a decent aerial and conection with my sistem (Nagra PLL preamp and DIY OTL Tim Mellow power amp) I stared listening.
The audition was much under my expectations. The sound was dull and absent of dinamic even on mono as stereo I was allready not expecting too much from the modest inside decoder.
That's why I am asking some hepl, where to start and what to do next.
By the way I own allready a nice valve decoder from Fischer, the MPX-100 which I intend to refurbish too and cope with the Leak tuner.

Thanks in advance.
Victor

PS. I have some elementary skils in valve AF electronics an I have some equipment like af generator, doble beam scope, wim bridge and multimeter.
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Old 12th May 2018, 6:19 am   #2
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Default Re: Restaurare Leak III ST Refurbishing

Check and replace coupling caps in the AF section for a start as well as any cathode bypass caps etc. Also check resistors for spec; these old R's are long in the tooth and are probably way out of spec.

Andy.
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Old 12th May 2018, 9:33 am   #3
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Default Re: Restaurare Leak III ST Refurbishing

By the way, it's a good ideea to modify the tuner as Leak III mono as I intend to use my Fisher MPX-100 ?
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Old 12th May 2018, 1:58 pm   #4
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Default Re: Restaurare Leak III ST Refurbishing

Quote:
Originally Posted by Diabolical Artificer View Post
Check and replace coupling caps in the AF section for a start as well as any cathode bypass caps etc. Also check resistors for spec; these old R's are long in the tooth and are probably way out of spec.
The PSU capacitor already changed with a new multisection F&T 4x50uF/500V
I wonder if cathode bypass caps has to be changed as they are almost ceramic
As I intend get rid of the modest decoder, I don't see any ther coupling caps. I shall go strait from the multiplex out to my Fisher MPX-100.
What do you think?
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Old 12th May 2018, 4:13 pm   #5
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Default Re: Restaurare Leak III ST Refurbishing

Ceramic cathode bypass capacitors are very unlikely to be faulty, only electrolytic and paper dielectric types. See this thread for more information on “likely to be faulty” capacitors: https://www.vintage-radio.net/forum/...ad.php?t=98964
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Old 12th May 2018, 4:35 pm   #6
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Default Re: Restaurare Leak III ST Refurbishing

Thanks, very interesting thread. What do you sugest about resistors?
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Old 12th May 2018, 6:18 pm   #7
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Default Re: Restaurare Leak III ST Refurbishing

Check the resistors for being out their tolerance ranges (5%, 10%, and so on). These old “carbon composition” type resistors are obsolete technology (for most modern applications) and have probably drifted way out of specification with the passing of many years.

Unless they are shunted by a parallel conducting path, you can measure their values without unsoldering one end. Be careful with those in the radio frequency stages (from aerial input to the first IF amplifier stage) and keep their positions and lead lengths unchanged, or alignment may suffer!
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Old 13th May 2018, 6:44 am   #8
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Default Re: Restaurare Leak III ST Refurbishing

Thanks, I just start doing this.
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Old 14th May 2018, 12:10 pm   #9
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Default Re: Restaurare Leak III ST Refurbishing

Shall I change configuration to the previeus Leak 3 (not stereo) as I ntend to use a Fisher MPX-100?
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Old 14th May 2018, 12:12 pm   #10
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Default Re: Restaurare Leak III ST Refurbishing

Here you are my MPX-100. Any opinion?
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Old 14th May 2018, 8:34 pm   #11
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Default Re: Restaurare Leak III ST Refurbishing

The decoder schematic looks very nice
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Old 14th May 2018, 8:57 pm   #12
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Default Re: Restaurare Leak III ST Refurbishing

Do you think I have to do some improovments?
At least de-emphasis modiffication from 75 to 50 uS and the PSU components...
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Old 14th May 2018, 9:53 pm   #13
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Default Re: Restaurare Leak III ST Refurbishing

Yes you should do the de-emphasis mod but try it first
Do not expect much in the way of selectivity with the leak tuner as these were designed in an era when the FM band was far less crowded
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Old 15th May 2018, 9:27 am   #14
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Default Re: Restaurare Leak III ST Refurbishing

As My target in Bucharest is one or two stations which are still transmiting live classic an jazz concerts, I am not too much concerned about selectivity.
Bouth stations transmits from the same Emitter-tower so I shall use a prity directive yaggy aerial.
For the rest of chanels I intend to use a Denon internet tuner which I shall lamizite...or not.
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Old 17th May 2018, 2:57 pm   #15
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Default Re: Restaurare Leak III ST Refurbishing

Hi again,
Does anyone restoration on this tuner and has any tips?
Truly I think there is planty of Leak fans in UK that did it or sent it in a dedicated service shop. Unfortunately I can't aford that from Romania so I have to do all the job by myself on my banch after office hours. So I still waiting for your help, ideea, ecorage...
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Old 17th May 2018, 5:11 pm   #16
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Default Re: Restaurare Leak III ST Refurbishing

Quote:
Does anyone restoration on this tuner and has any tips?
This webpage looks quite helpful: http://www.keith-snook.info/leak-troughline-stereo.html

I'd start by following the advice already given, by testing all those carbon composition resistors and replacing any that are significantly out of tolerance. I'd also replace any small electrolytic capacitors fitted, with new ones. If there are any paper dielectric capacitors like the ones pictured in the "capacitors black museum" link I mentioned in an earlier post, I'd definitely replaced them.

Whilst you're at it, look for suspect (that is, bad high resistance) soldered joints and poor chassis connections (as per the "Keith Snook" webpage). Anything that is obviously not original should be treated with suspicion and checked against the official Leak issued schematic diagram.
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Old 17th May 2018, 7:18 pm   #17
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Default Re: Restaurare Leak III ST Refurbishing

Do not attempt to adjust any if coils unless you have the correct tools while we are talking about if the leak uses a non standard frequency of about 12 mghz
Change the electrolytic's and any out of spec resistors that you find other than that it should work

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Old 17th May 2018, 7:52 pm   #18
victor54
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Default Re: Restaurare Leak III ST Refurbishing

Quote:
Originally Posted by dazzlevision View Post
This webpage looks quite helpful: http://www.keith-snook.info/leak-troughline-stereo.html

I'd start by following the advice already given, by testing all those carbon composition resistors and replacing any that are significantly out of tolerance. I'd also replace any small electrolytic capacitors fitted, with new ones. If there are any paper dielectric capacitors like the ones pictured in the "capacitors black museum" link I mentioned in an earlier post, I'd definitely replaced them.

Whilst you're at it, look for suspect (that is, bad high resistance) soldered joints and poor chassis connections (as per the "Keith Snook" webpage). Anything that is obviously not original should be treated with suspicion and checked against the official Leak issued schematic diagram.
I know by hart the article of Keith-snook. Its a shame the secound part was not available.
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Old 20th May 2018, 7:29 am   #19
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Default Re: Restaurare Leak III ST Refurbishing

Do anyone knows about Neville Roberts restauration kit? Does it works ?
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Old 20th May 2018, 10:59 am   #20
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Default Re: Restaurare Leak III ST Refurbishing

I used that article about four years ago and the hardest part was making the cutout for the large capacitor. I used a fretsaw with a blade suitable for metal.

I use my leak troughline ll every day and have had almost no trouble with it apart from a couple of resistors going high.

The case is pine with routed corners to match the curve of the facia.

Pictures to follow.
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