Roberts M5A mystery wires? - UK Vintage Radio Repair and Restoration Discussion Forum

12jslater · 8th Dec 2018, 8:13 pm

I have just started work on a Roberts m5a and there are three leads which should connect to a component but what? On the data sheet it doesn't show a component in its place?

Thank you

ms660 · 8th Dec 2018, 9:04 pm

Are the red (?) and yellow wires connected to anything? If so where about in the circuit.

Lawrence.

12jslater · 8th Dec 2018, 10:19 pm

Both wires go to a tab on the chassis

ms660 · 9th Dec 2018, 12:37 pm

What valves are fitted in your receiver?

Lawrence.

12jslater · 9th Dec 2018, 2:31 pm

The valves are 6f6g, unknown, vr55, Ech 35, vr55

ms660 · 9th Dec 2018, 2:37 pm

Yes, I thought they might be octals, the service data shows side contact types.

EDIT: That valve line up doesn't make sense to me.

Lawrence.

12jslater · 9th Dec 2018, 2:44 pm

Any hope of me finding any data on this set?

ms660 · 9th Dec 2018, 3:50 pm

This receiver gives me the feeling that it might have been got at, the mystery wires might have gone to the HT reservoir and filter electrolytics, so far as I can make out from the Trader sheet data that tag strip in your photo is a connecting point for the HT choke to the rest of the circuit, the tag the yellow is connected to I'm guessing is the feed from the rectifier, the tag that the red is connected to being the fully filtered output, one of the wires from the audio output transformer would be connected to the tag the red wire is connected to and the other wire from the audio output transformer would be connected to the anode of the audio output valve via the 100 ohm anode stopper resistor.

Lawrence.

music-centre · 9th Dec 2018, 4:32 pm

In case you haven't seen it there was this earlier post from a member with an M5A with the later P5A valve line up
Steve.

https://www.vintage-radio.net/forum/...ad.php?t=55816

AC/HL · 9th Dec 2018, 5:25 pm

It looks like someone has cut into the wiring harness, added something, then removed it again. You'll need to trace the wires and reinstate them. There doesn't appear to be anything missing.

PJL · 9th Dec 2018, 5:54 pm

i suggest you post some much better pictures so we can give some advice. The pictures need to cover all of the underside wiring.

12jslater · 9th Dec 2018, 11:02 pm

Here are the wires and the tags they are connected too.

8th Dec 2018, 8:13 pm	#1
12jslater Pentode Join Date: Nov 2016 Location: Wolverhampton, West Midlands, UK. Posts: 117	Roberts M5A mystery wires? I have just started work on a Roberts m5a and there are three leads which should connect to a component but what? On the data sheet it doesn't show a component in its place? Thank you Attached Thumbnails

8th Dec 2018, 9:04 pm	#2
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Roberts M5A mystery wires? Are the red (?) and yellow wires connected to anything? If so where about in the circuit. Lawrence.

8th Dec 2018, 10:19 pm	#3
12jslater Pentode Join Date: Nov 2016 Location: Wolverhampton, West Midlands, UK. Posts: 117	Re: Roberts M5A mystery wires? Both wires go to a tab on the chassis Attached Thumbnails

9th Dec 2018, 12:37 pm	#4
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Roberts M5A mystery wires? What valves are fitted in your receiver? Lawrence.

9th Dec 2018, 2:31 pm	#5
12jslater Pentode Join Date: Nov 2016 Location: Wolverhampton, West Midlands, UK. Posts: 117	Re: Roberts M5A mystery wires? The valves are 6f6g, unknown, vr55, Ech 35, vr55

9th Dec 2018, 2:37 pm	#6
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Roberts M5A mystery wires? Yes, I thought they might be octals, the service data shows side contact types. EDIT: That valve line up doesn't make sense to me. Lawrence. Last edited by ms660; 9th Dec 2018 at 3:00 pm.

9th Dec 2018, 2:44 pm	#7
12jslater Pentode Join Date: Nov 2016 Location: Wolverhampton, West Midlands, UK. Posts: 117	Re: Roberts M5A mystery wires? Any hope of me finding any data on this set?

9th Dec 2018, 3:50 pm	#8
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Roberts M5A mystery wires? This receiver gives me the feeling that it might have been got at, the mystery wires might have gone to the HT reservoir and filter electrolytics, so far as I can make out from the Trader sheet data that tag strip in your photo is a connecting point for the HT choke to the rest of the circuit, the tag the yellow is connected to I'm guessing is the feed from the rectifier, the tag that the red is connected to being the fully filtered output, one of the wires from the audio output transformer would be connected to the tag the red wire is connected to and the other wire from the audio output transformer would be connected to the anode of the audio output valve via the 100 ohm anode stopper resistor. Lawrence.

9th Dec 2018, 4:32 pm	#9
music-centre Heptode Join Date: Sep 2007 Location: Brentwood, Essex, UK. Posts: 687	Re: Roberts M5A mystery wires? In case you haven't seen it there was this earlier post from a member with an M5A with the later P5A valve line up Steve. https://www.vintage-radio.net/forum/...ad.php?t=55816

9th Dec 2018, 5:25 pm	#10
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Roberts M5A mystery wires? It looks like someone has cut into the wiring harness, added something, then removed it again. You'll need to trace the wires and reinstate them. There doesn't appear to be anything missing.

9th Dec 2018, 5:54 pm	#11
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Roberts M5A mystery wires? i suggest you post some much better pictures so we can give some advice. The pictures need to cover all of the underside wiring.

9th Dec 2018, 11:02 pm	#12
12jslater Pentode Join Date: Nov 2016 Location: Wolverhampton, West Midlands, UK. Posts: 117	Re: Roberts M5A mystery wires? Here are the wires and the tags they are connected too. Attached Thumbnails