Marconi T69DA no power

[condense]

Please forgive me if this is a really stupid question - I am still a beginner.
I have replaced the caps and got ready for a lamp limiter start up.
Unfortunately the set is dead.
I am cautious about fiddling around while the power is on at this stage so with the power off I thought I would look at the on/off tone switch. With no power I don’t get anything from any of the 5 outputs when I connect the other end to the Neutral or live inputs. I assume that means the switch is a problem ? If so is this something that can be repaired or will I need to find a new one ? If it’s the latter does anyone have any idea where I can get one ?

[Station X]

3 Amp fuse in mains plug OK?

Please confirm that the set is absolutely dead ie no sound whatever from the speaker.

Do the valves light up? If not check for continuity from mains pin live to mains pin neutral via the heater chain, dropper and voltage selector. You can do this without applying power.

[condense]

The fuse is fine
And yes there is no power anywhere - no sound at all and no lamps / heaters lit.
There seems to be continuity in the heater circuit. The black and green wires from this switch seem to be that circuit and there is some low resistance between these and the heaters.

There is no measurement between the power cable (N and L) and either the green or black wires

[condense]

Better photo I hope

[Station X]

That's the mains switch ie S2 and S3 on the circuit diagram. I assume it's set to ON? Does the green wire go from the lower right tag to the PCB or is there no wire on that tag?

Either way you need to find out where the break in the chain is by starting at one pin of the mains plug and working your way round to the other using you meter on a low resistance range.

Most likely fault is a faulty mains switch. Once you've proved this temporarily bridge it.

[condense]

Yes the green wire is attached to the tag and goes to the PCB and on to R38 and the pilot lights. The black one goes to V4 amongst other places (-ves of 3 large electrolytics)

[condense]

I think my problem is that there is no connection from the mains lead to either the green or black wires

[Station X]

Originally Posted by condense

Yes the green wire is attached to the tag and goes to the PCB and on to R38 and the pilot lights. The black one goes to V4 amongst other places (-ves of 3 large electrolytics)

That's good. We're not concerned with electrolytic caps at this time.

If the fuse in the mains plug is good you'll have continuity from the live pin to the brown wire on the back of the mains switch. Check that with the mains switch on this continuity extends to the green wire, then through X1, X2, R40 etc.

[Station X]

Originally Posted by condense

I think my problem is that there is no connection from the mains lead to either the green or black wires

Check for continuity through the mains switch having made sure it's turned ON.

[Station X]

If the mains switch is faulty you may be able to repair it as described here:-

https://www.vintage-radio.net/forum/...0&postcount=36

[condense]

Thank you for your help
It must be the switch. It has 3 other legs on it which I think are the tone control so I am not convinced it will be an easy fix. I will give it a try though

[Station X]

Have you actually tested the switch for continuity? If not please do so.

If it is indeed faulty, then temporarily bridge it with one or two pieces of wire, depending on whether one or both poles are faulty. Then you can carry on testing.

The three other tags probably are the tone control pot, but they have nothing to do with getting the valves to light up.

[condense]

The way I have tested the switch is to measure the resistance between the brown live power lead and both the green and black leads - I get nothing ( the switch is on).
I’ve tried the same with the neutral wire and get nothing too.
Seems strange to me that both aren’t connecting ?

[condense]

So if I clip the brown and green together & the blue and black together - would this essentially bypass the switch and be a safe way to try it out?

[Station X]

Yes. Not sure what you mean by clip. Use two pieces of wire.

[condense]

I meant some crocodile clips - sorry
Yes that worked - thank you so much
I’ve got lights and a hum. I didn’t fiddle around too much as clearly my next job is to sort that switch!

[Station X]

I'd leave the switch bridged for the moment and continue testing. There may be other show stopping problems.

[condense]

Thank you that sounded like a very sensible idea so that's what I have done and I've got clear stations on at least 2 bands so am really pleased.
Thank you so much for your help.
It looks like this evening's job will be attempting to repair that switch. I've been looking on eBay and can't see one the same so I'm hoping the repair will be successful.

thanks again

[condense]

Just to update and conclude this thread. The set is now working although haven’t picked up stations on LW yet.
The switch was stuck just like described in the link above, although there is a crack in the bit which moves (top left of photo) However once I freed it up and added some lubricant it still seems to work ok - time will tell I suspect

Thank you for all of your help - this forum is amazing