UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)

Notices

Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

Closed Thread
 
Thread Tools
Old 11th May 2011, 10:01 am   #41
sonata149
Tetrode
 
Join Date: Oct 2006
Location: Malta
Posts: 62
Default Re: A Stereo decoder for Leak Troughline 3

OK I'm getting signals from both channel now. Problem was with the rca plug -somehow the two wires were shorting - defective plug. The remaining problem now is that the decoder is not working. (I'm using a battery to operate it.) I can't tune to a fixed broadcast. I'm getting a lot of noise from various stations wherever I move the tuning dial. Is there a way to test the decoder or perhaps the IC? With the decoder disconnected the tuner was OK yesterday.
sonata149 is offline  
Old 11th May 2011, 11:07 am   #42
G8HQP Dave
Dekatron
 
Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 4,870
Default Re: A Stereo decoder for Leak Troughline 3

You will get noise between stations, as this is a feature of FM - the tuner does not have any squelch to silence this. The easiest way to test the decoder is to feed it a stereo signal and check that it decodes it! Tune to a known stereo station (if necessary, via the tuner output rather than the decoder). Adjust the decoder preset until the stereo LED lights. You should then be getting L and R outputs. You may need to check that the input to the decoder is not too small or too large. Too small will mean that it stays in mono mode, but it should otherwise be OK. Too large will cause distortion. Check the DC current draw of the decoder against the data sheet, bearing in mind that the LED may be a significant fraction of this.
G8HQP Dave is offline  
Old 11th May 2011, 7:38 pm   #43
sonata149
Tetrode
 
Join Date: Oct 2006
Location: Malta
Posts: 62
Default Re: A Stereo decoder for Leak Troughline 3

Hi friends. Problem solved.

I can't say why or how. After a lot of trial and error changes I decided to take voltage readings again. First thing I noticed was that R13 was blackened. I changed it and started taking the readings. Voltages around V4 (EF80) didn't seem right, so I changed it. I eliminated the decoder to make sure I had signals coming in right, then connected the decoder and this time I was getting a clear sound and could adjust the LED. From then on things got a lot easier and it's playing right now.

So, thanks a lot to both of you because you gave me the courage to keep on trying until the end. Besides, it was a very worthwhile learning experience as I had never worked on tuners before.

Warm regards and best wishes,
Joe A
sonata149 is offline  
Old 11th May 2011, 8:53 pm   #44
G8HQP Dave
Dekatron
 
Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 4,870
Default Re: A Stereo decoder for Leak Troughline 3

Glad it's sorted. Moral of the story: old equipment often has more than one fault (but they don't all appear at once), and fixing faults can accidentally introduce new ones.
G8HQP Dave is offline  
Old 12th May 2011, 4:02 pm   #45
MrElectronicman
Heptode
 
MrElectronicman's Avatar
 
Join Date: Feb 2011
Location: Washington DC, USA
Posts: 612
Default Re: A Stereo decoder for Leak Troughline 3

That's great I knew you could you it, sometimes just takes a little time and patience
MrElectronicman is offline  
Old 12th May 2011, 7:42 pm   #46
sonata149
Tetrode
 
Join Date: Oct 2006
Location: Malta
Posts: 62
Default Re: A Stereo decoder for Leak Troughline 3

Thank YOU guys; you've been a great help. Your continuous comments and suggestions kept me struggling to succeed. I even found a way to operate the decoder from the 6.3V taps on the tuner's transformer. The problem seems to have been caused by the fact that the original voltage doubler was full-wave. I changed this to half-wave with a common earth. This is good enough to accept a 12V voltage regulator.

I've being listening to it for a few hours and to my ear the Trough line is sounding better by the hour. This wasn't my impression at first, thinking that the mono version sounded better. Maybe my ears are slowly getting accustomed to the new sound.

Best regards,
Joe A
sonata149 is offline  
Old 12th May 2011, 9:49 pm   #47
MrElectronicman
Heptode
 
MrElectronicman's Avatar
 
Join Date: Feb 2011
Location: Washington DC, USA
Posts: 612
Default Re: A Stereo decoder for Leak Troughline 3

The DC power was a potential problem, which is why I asked about it. You cannot use a full wave supply from the 6.3 VAC heater source since it is already grounded at one side.

I used a very small independent 6.3 VAC transformer for my set with FW rectification which gave me 12 VDC.

The original design from Leak used the HT via a dropping resistor with a 250 uF capacitor, however, this idea was was not good since if you disconnected the decoder, the 250uF 25VDC capacitor would end up with full HT on it. BANG!

The stereo sound does "sound" different, and as mentioned earlier can be more noisy if the signal is a bit weak, so you need a better aerial.
MrElectronicman is offline  
Old 24th Jun 2012, 8:25 pm   #48
layumhs
Diode
 
Join Date: Jun 2012
Location: Lund, Swden
Posts: 1
Default Re: A Stereo decoder for Leak Troughline 3

Hi, I'm new here and just found this thread on a decoder for trough line stereo. I just got this tuner in original form and I'm after upgrading the decoder. my electronics knowledge is basic, but I'm willing to learn. whats the best way of getting a new decoder for this tuner? many thanks. M
layumhs is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 9:02 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.