Clarke and Smith 8812 FM problem - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

qualityten · 11th May 2018, 11:24 pm

Thanks Ron. You are quite right about the 500pF cap!

qualityten · 12th May 2018, 10:33 pm

I opened the LM1179 module today and replaced the two BF195 transistors with BF595 ones, as these were the only ones to hand. It did not resolve the problem. In the Sets and Parts Wanted section, a member has suggested that the problem sometimes lies with the capacitors.

I attach a picture of the opened unit. I am not familiar with the capacitor types here. Which of them should I suspect first...?

Thanks to all who have offered advice here or in the other section.

qualityten · 20th May 2018, 10:44 pm

I have not had any success repairing the LP1179 module, nor buying a replacement. In the meantime, I picked up the Velleman digitally controlled FM radio kit, at the remains of Maplins. I quickly assembled it this afternoon, and have located the circuit diagram, which I attach.

Please could anyone advise on whether I can connect this to the Clarke and Smith radio circuit? It seems I have a 5v supply and could take the signal from before the LM386 amplifier. Is this likely to work?

bc312 · 21st May 2018, 4:46 pm

Some LP1179/2 modules available from here:

http://markhindes.easywebstore.co.uk...9-2_AC200.aspx

I think it would be hard to integrate the Maplin unit into the 8812 without losing the functionality of the capacitor tuning. My own 8812 has a valve FM tuner, so no experience with the LP1179 arrangement. Have you tried powering the LP1179 as a stand alone unit and measuring the current drawn - should be around 4.5mA. From your image of the module internals, I think most of the capacitors look to be ceramic, so unlikely to cause a problem. The high current problem on FM suggests something other than the LP1179 being at fault.

General question to all - I have never been able to find a schematic for a LP1179 module; does one exist anywhere?

qualityten · 21st May 2018, 7:10 pm

Thank you for the information about availability from Mark Hindes, and the advice on the Maplin unit, bc312. Also helpful to be advised to do more systematic fault tracing.

I've not seen a schematic of the LP1179 anywhere myself.

Nuvistor · 22nd May 2018, 3:40 pm

Not the circuit but the specifications for the 1179, supply 6.8v 4.5ma, three version, just different mounting.
https://www.vintage-radio.info/download.php?id=432

11th May 2018, 11:24 pm	#21
qualityten Octode Join Date: Feb 2009 Location: Wallasey, UK. Posts: 1,311	Re: Clarke and Smith 8812 FM problem Thanks Ron. You are quite right about the 500pF cap!

12th May 2018, 10:33 pm	#22
qualityten Octode Join Date: Feb 2009 Location: Wallasey, UK. Posts: 1,311	Re: Clarke and Smith 8812 FM problem I opened the LM1179 module today and replaced the two BF195 transistors with BF595 ones, as these were the only ones to hand. It did not resolve the problem. In the Sets and Parts Wanted section, a member has suggested that the problem sometimes lies with the capacitors. I attach a picture of the opened unit. I am not familiar with the capacitor types here. Which of them should I suspect first...? Thanks to all who have offered advice here or in the other section. Attached Thumbnails

20th May 2018, 10:44 pm	#23
qualityten Octode Join Date: Feb 2009 Location: Wallasey, UK. Posts: 1,311	Re: Clarke and Smith 8812 FM problem I have not had any success repairing the LP1179 module, nor buying a replacement. In the meantime, I picked up the Velleman digitally controlled FM radio kit, at the remains of Maplins. I quickly assembled it this afternoon, and have located the circuit diagram, which I attach. Please could anyone advise on whether I can connect this to the Clarke and Smith radio circuit? It seems I have a 5v supply and could take the signal from before the LM386 amplifier. Is this likely to work? Attached Thumbnails

21st May 2018, 4:46 pm	#24
bc312 Pentode Join Date: Feb 2005 Location: Longfield, Kent, UK. Posts: 240	Re: Clarke and Smith 8812 FM problem Some LP1179/2 modules available from here: http://markhindes.easywebstore.co.uk...9-2_AC200.aspx I think it would be hard to integrate the Maplin unit into the 8812 without losing the functionality of the capacitor tuning. My own 8812 has a valve FM tuner, so no experience with the LP1179 arrangement. Have you tried powering the LP1179 as a stand alone unit and measuring the current drawn - should be around 4.5mA. From your image of the module internals, I think most of the capacitors look to be ceramic, so unlikely to cause a problem. The high current problem on FM suggests something other than the LP1179 being at fault. General question to all - I have never been able to find a schematic for a LP1179 module; does one exist anywhere? __________________ Leave me alone - I know what I'm doing. BVWS member, EUG, G-QRP Radio Bygones/Radiophile

21st May 2018, 7:10 pm	#25
qualityten Octode Join Date: Feb 2009 Location: Wallasey, UK. Posts: 1,311	Re: Clarke and Smith 8812 FM problem Thank you for the information about availability from Mark Hindes, and the advice on the Maplin unit, bc312. Also helpful to be advised to do more systematic fault tracing. I've not seen a schematic of the LP1179 anywhere myself.

22nd May 2018, 3:40 pm	#26
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: Clarke and Smith 8812 FM problem Not the circuit but the specifications for the 1179, supply 6.8v 4.5ma, three version, just different mounting. https://www.vintage-radio.info/download.php?id=432 __________________ Frank