eguth
pfm Member
MEMOIRS OF A DIY HI FI NUT- Part XII
LEAK TROUGHLINE TUNER -UPGRADES
By eguth & toaster
LEAK TROUGHLINE TUNER -UPGRADES
By eguth & toaster
PREFACE
We worked on this project jointly. We spent well in excess of 100 hours- not including experiment, listening and correspondence. This was spread over 14 months during 1992-7. We would have liked to thank all who helped. Unfortunately, in the case of Ralph Williams, this is not possible. His tragic death at an early age was a loss to valve hi fi. Ralph held a degree in Electrical Engineering from University College, London. Thanks go to Glen Nicolas, Denys Trickett, Peter Watson, Peter Lewis (the designer of the Mullard decoder), and David Heaton. None of these are in any way responsible for any errors or omissions.
We emphasize that many of the parts specified or used are no longer available. The coil was never available. If you decide to try any of the mods we cannot advise you on any step or procedure. Nor can we advise on parts substitutes or how to wind the coil.
This article is posted as it may be of historical interest. We both still use our modified Troughline tuners and they sound excellent.
Now I can start. Ill do anything for a laugh- if only I had a sense of humour- so when I learned that my friend toaster had just purchased a Leak Troughline MONO tuner I thought to myself why dont we both ATTEMPT to convert our tuners to stereo together? This could turn out to be Very Funny. I had heard about (but not heard) stereo. Some thought it may be better than mono. After all, most of us do have 2 ears.
Toaster liked the idea of stereo. He agreed that it would be a Good Thing to do our conversions together. Two heads are better than one, said he. So he whipped out his RS catalogue and we proceeded to burn up the pages with out joint order. I managed to dig up a couple of old Quad 22 steel cases for the outboard decoder and its power supply. They turned out to be not a quarter of an inch too large for what eventually was put into them. It would have been absolutely impossible to do the conversion to the high standard we set within the Leak tuner case: out of the question.
I
Renovating the Tuner
The following link shows photos and schematics referred to in this thread.Renovating the Tuner
http://redirect.viglink.com/?format...ww.flickr.com/photos/3451470...7612748160694/
1. The Knobs. Nothing on earth would shift the 30 years of ingrained dirt from the white Bakelite. I finally hit upon my tooth brush and the damp scouring powder that I brush my teeth with. That shifted it.
2. The Valveholders. Remove each valve and clean the valves and sockets. The best thing I have found is Deoxit. It comes with a brush to get down into the sockets. Getting it out afterwards calls for some ingenuity. Be sure not to enlarge the socket holes when you do this. Replace V5 valveholder with the type that takes a screening can and fit a can.
3. Sensitivity Switch. Remove the two wires from local/distant sensitivity switch. Clean wires with emery cloth. Solder these together, first slipping a piece of insulated sleeving over one lead to cover the finished joint. The switch is now bypassed. Temporary; only until the entire tuner is rewired.
4. Turn the tuner upside down and remove the bottom cover. Bypass the volume control potentiometer. To do this you remove the wires, clean and solder them together. This mod brings a noticeable reduction in distortion. I installed a new, modern on/off switch in place.
5. Clean MPX phono socket with switch cleaner. Remove flying phono output lead from MONO audio output and install a quality nickel plated phono socket.
6. Spray AFC switch with switch cleaner and work to and fro.
7. Clean the fuse and fuseholder.
8. Oil the bearings at both ends of the tuning capacitor.
http://farm4.static.flickr.com/3494/3208766743_c52953f121_s.jpg
9. Cut a hole in the rear of the case to take an IEC mains socket (the shuttered type, FEMALE with no pins [no, I am not sexist]). A good place for this socket is at the top of the rear panel just left of the voltage selector plug. LIVE is wired from the terminal at the top of the fuseholder. The terminal hole should be drilled out slightly larger to take both wires. NEUTRAL is wired from the voltage selector terminal, which already has a large hold (see Fig. 1). (See below for mains wiring UPGRADE/SCREENING inside tuner).
10. Carefully pull out the voltage selector plug. Clean pins. Reinsert in CORRECT position a few times to clean, using switch cleaner. Double check that the final position indicates the correct voltage.
11. Aerial Connexions. There is a terminal strip at the rear of tuner. If you use balanced twin feeder this should be connected to both outside terminals and not to the centre terminal. If you use normal unbalanced coaxial cable usual in U.K. installations, you have two alternatives- neither of which is very satisfactory. Either remove the plug and connect the coax direct to the CENTRE terminal and the inner wire to EITHER of the outside terminals or, alternatively, you can run a short length of balanced twin feeder to a balun (expensive) and connect the coax to the balun. Using this second method you will lose some of your previous signal from the aerial. To avoid these problems, purchase a chassis- mounting 70-80 ohm (unbalanced) females socket [I am not sexist]. Cut a hole in the rear of the case above the terminal aerial strip. The outer contact is soldered to the centre terminal and inner to EITHER outer terminal. Plug the coaxial cable plug into the new aerial socket.
12. Feet. The original tuner had four rubber feet which were necessary to protect the Perspex front panel lip from damage. Four rubber doorstops glued to the underside of the case do a better job, because they lift the unit clear of lip destroyers. The original feet dont.
13. Trim. The lip on my front panel was chipped in places with paint missing. Using matching pain on the REAR surface did work well; this makes it impossible for light to shine through to the front and the panel then looks undamaged.
Decoder. An inexpensive good one may be a problem to find. We were lucky to get Mullard LP1401 stereo phase- locked modules (1975 vintage) new (see Figs. 2,3,4). This decoder is more advanced than the one used in the Leak Troughline Stereo tuner and, in our upgraded form, quite superb. You can build an upgraded LP1401 from scratch using this article and diagram.
At this point some of you eagle- eyed listeners will ask What happened to MEMOIRS OF A DIY HI FI NUT- Part XI? You already have it in Pink Fish Media- see my Passive Switched Attenuator Thread This should be renamed MEMOIRS OF A DIY HI FI NUT-Part XI
http://www.pinkfishmedia.net/forum/showthread.php?t=29612