Can anyone tell me the resistance of this resistor?

[Luxman1050]

I got this across the output transformer but have no idea of resistance. Anyone have any idea? The body is red the ends are violet and gold cannot find a dot.

Cheers Chris

[Bazz4CQJ]

Tricky, so red and violet tell us the number 27 but we need the spot on the body to tell us where the decimal place needs to be. What would be your best guess as to the colour the spot was?

Could you trace the connection back a valve, perhaps the anode of the output valve?
B

[Luxman1050]

Had another look and the spot appears to be black.

[G.Castle]

2.7k. Red violet red.

Edit*
Won't be black as it would signify 27 ohms

[Luxman1050]

Cheers guys

[Station X]

I'm a bit puzzled as to why a resistor would be connected across an output transformer. A tone correction capacitor would be more likely.

[Luxman1050]

Well I thought that as on the schematic it has a 0.02uf cap but this has a resistor. For a murphy AD94.

[Bazz4CQJ]

Originally Posted by Station X

I'm a bit puzzled as to why a resistor would be connected across an output transformer. A tone correction capacitor would be more likely.

I think you sometimes see unused tags on transformers and I suspect the R is not across the winding but only connected at one end, The other tag just offers an anchoring point for the large and hot component. I wondered if it could be a screen grid resistor?
(written before seeing the last post, but anyway, that looks like a resistor to me).
B

[Station X]

According to the manufacturer's service sheet the tone correction capacitor is C31 which is mounted UNDER the chassis. The only resistor with initial digits 27 is R15 270k in series with the volume control wiper. This is mounted near, but not on the output transformer. I think the OP needs to check where this resistor is actually connected to. The fact he's asked for the value suggests it's open circuit or out of tolerance?

[Station X]

Something's not right here. The service sheets show the output transformer as being mounted on the chassis, not on the speaker frame. Looks like the set may have been modified.

Coincidentally the resistance of the transformer's primary winding is shown as 270R. Could the primary be open circuit and someone has tried to simulate the DC conditions for testing purposes?

[Luxman1050]

Further investigation needed

[Luxman1050]

There is one end connected via wire which goes to a transformer whilst the other end is just soldered to a blank tag on the other transformer.

[Station X]

If the resistor goes to a "blank" tag with no connection to the transformer windings then it can't have any function. Is there a hole/s in the chassis where the output transformer should be?

[Station X]

I think the first picture in post #12 is the original output transformer. This is an AC/DC set with no mains transformer.

[Robert Gribnau]

I think the original loudspeaker has a field excitation coil (besides the usual voice coil).

In the service documentation coil L13 is not to be found on the bottom and top view of the chassis. In the list of components it says that is can be found at "Square L.S.F.". This could stand for "Loudspeaker frame". The value of 900 for coil L13 could represent the dc-resistance of this coil.

This does not explain why the mystery resistor is connected parallel to L13. Perhaps someone wanted B+ for the valves to be a bit higher?

Addition: Or perhaps the loudspeaker is not the original one and L13 was changed for a choke, which went open at some point? So, the mystery resistor is a substitute for this choke? Or the replacement choke needed extra resistance in series with it so as to come closer to the value of 900 for coil L13?

[Station X]

I agree. What we see in the picture in post #1 is not the output transformer T1, it's the smoothing choke L13.

Some wire tracing/continuity testing is needed.

[Mark the Spark]

Hi,

Out on Interest what is the Current Resistance

Thanks

Mark

[Luxman1050]

Wow lots of info to take in there. I have not had a good look at yet. But appears to need lots of work done including the majority of wiring as that has perished. The speaker appears to be original although it is badly damaged. Makes you wonder how it got damaged in the first place unless removed at some point! No mains transformer. Not been able to get a reading off the resistor.
So it looks like many moons ago bits have been changed? I wouldn't know.

Thanks for the input.
Chris

[Luxman1050]

There's no room on the chasis for the transformer.

[Station X]

That's because it's already there. I mistakenly thought the inductor shown in post #1 was the output transformer.