Murphy V230 Cardboard TV - UK Vintage Radio Repair and Restoration Discussion Forum

Murphy Maniac · 26th Dec 2012, 1:54 pm

I am still struggling badly to try and achieve frame hold on my horrible Murphy V230 (Trader Sheet 1302). I am still on a steep learning curve when it comes to TV so please be gentle with me! On first switch on I have a reasonable picture but as the set warms up, it starts to lose lock (only talking a very short time here). Just prior to breaking away fly back lines appear. This can be corrected with the frame hold but then, seconds later, the same happens again. Eventually, I reach the end of the pot and have to switch off and wait. It has been suggested that I change MR1 which is quoted as Q6/1. Could anyone please suggest a modern equivalent which would do as a replacement, I think 1N4007 was suggested to me but I have a head like a seive and have forgotten!
Best Wishes,
Geoff.

Heatercathodeshort · 26th Dec 2012, 9:18 pm

Hello Geoff,
Unlikely to be the interlace filter diode Q6/1. Any diode will do including the 1N4001, ideal. Have you got the circuit and recapped all of the capacitors in the frame oscillator and output stage? This is most important. The fault you describe is typical of aged capacitors that leak when warm causing oscillator drift and poor linearity.
Actually these are nice little receivers that are quite reliable. The hold should be solid, without drift on both line and frame. Regards, John.

Murphy Maniac · 28th Dec 2012, 1:11 am

Hi John,
Thanks for that, I have replaced most of the caps in that area but, once the holiday is over, I will get around to having another look and complete the replacement of any likely culprits now I know I am looking in the right area. As you say, despite the cardboard case, it seems to have the making of quite a good picture.
Very Best Wishes
Geoff.

Heatercathodeshort · 28th Dec 2012, 10:44 am

Work with the circuit Geoff. Highlight each capacitor as you locate it on the chassis and note it's effect when replaced. You may discover that some of the smaller capacitors look a bit like resistors so a circuit is essential to produce a satisfactory conclusion.
Good luck with it. The linearity should be 99%. The aluminised CRM124 CRT certainly does give a very satisfactory picture. John.

richrussell · 28th Dec 2012, 11:07 am

Faults like this, which get worse over a time period are generally down to something charging up or leaking - which pretty much says 'capacitor'. Either that or something getting hot and changing its resistance, but the fact that it clears so quickly after switching off and on again in this case makes that less likely.
It'll be bound to be one of the capacitors you didn't change because it looked all right

26th Dec 2012, 1:54 pm	#1
Murphy Maniac Hexode Join Date: Aug 2009 Location: Liverpool, Merseyside, UK. Posts: 254	Murphy V230 Cardboard TV I am still struggling badly to try and achieve frame hold on my horrible Murphy V230 (Trader Sheet 1302). I am still on a steep learning curve when it comes to TV so please be gentle with me! On first switch on I have a reasonable picture but as the set warms up, it starts to lose lock (only talking a very short time here). Just prior to breaking away fly back lines appear. This can be corrected with the frame hold but then, seconds later, the same happens again. Eventually, I reach the end of the pot and have to switch off and wait. It has been suggested that I change MR1 which is quoted as Q6/1. Could anyone please suggest a modern equivalent which would do as a replacement, I think 1N4007 was suggested to me but I have a head like a seive and have forgotten! Best Wishes, Geoff.

26th Dec 2012, 9:18 pm	#2
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Murphy V230 Cardboard TV Hello Geoff, Unlikely to be the interlace filter diode Q6/1. Any diode will do including the 1N4001, ideal. Have you got the circuit and recapped all of the capacitors in the frame oscillator and output stage? This is most important. The fault you describe is typical of aged capacitors that leak when warm causing oscillator drift and poor linearity. Actually these are nice little receivers that are quite reliable. The hold should be solid, without drift on both line and frame. Regards, John.

28th Dec 2012, 1:11 am	#3
Murphy Maniac Hexode Join Date: Aug 2009 Location: Liverpool, Merseyside, UK. Posts: 254	Re: Murphy V230 Cardboard TV Hi John, Thanks for that, I have replaced most of the caps in that area but, once the holiday is over, I will get around to having another look and complete the replacement of any likely culprits now I know I am looking in the right area. As you say, despite the cardboard case, it seems to have the making of quite a good picture. Very Best Wishes Geoff.

28th Dec 2012, 10:44 am	#4
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Murphy V230 Cardboard TV Work with the circuit Geoff. Highlight each capacitor as you locate it on the chassis and note it's effect when replaced. You may discover that some of the smaller capacitors look a bit like resistors so a circuit is essential to produce a satisfactory conclusion. Good luck with it. The linearity should be 99%. The aluminised CRM124 CRT certainly does give a very satisfactory picture. John.

28th Dec 2012, 11:07 am	#5
richrussell Heptode Join Date: Jul 2008 Location: Selby, North Yorkshire, UK. Posts: 979	Re: Murphy V230 Cardboard TV Faults like this, which get worse over a time period are generally down to something charging up or leaking - which pretty much says 'capacitor'. Either that or something getting hot and changing its resistance, but the fact that it clears so quickly after switching off and on again in this case makes that less likely. It'll be bound to be one of the capacitors you didn't change because it looked all right