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I am just a little perplexed with recapping this baby . I have not done any thing wrong yet so I thought I better ask about the electrolytic cans. one of them has three connections of which one is earth. Does this mean that it actually contains two capacitors. I know it may seem obvious to you guys but I am just being careful. By the way it is the one that is connected to V4. Thanks guys I hope to hear from you soon. I am waiting on parts so time really is no issue.

I assume you are talking about C25, close to the transformer? It connects between the rectifier (6X4) cathode, and the back-bias supply (provides the grid bias to V4 output valve), positive end to the cathode. The back-bias end has a small 470K resistor connected to it. A measurement should show 150 ohms to earth (the value of R17).

The only other electro is C23, about halfway along the radio, which is a standard can with the outside earthed, and the centre pin filtering the HT supply.

This is a standard configuration for a back-bias power supply.

Yes thats correct. I am just wondering if it's got two capacitors or what because I am not going to replace the can. I just wish to put the new caps underneath.

It should be a single capacitor, according to both the manual and my experience with those radios, unless someone has done something....

I have sent some pics but I will take a real close up for a better look.

Because of the back bias, that cap is isolated from the chassis. There are two twist-lugs that attach it to the insulator - then 100 ohms or 150 ohms to ground.

Those Ducon cans were normally pretty good. I'd consider reforming them rather than replacement. Replacing them would look ugly. Only replace them if you have too much hum.

Do you know how to reform electrolytics? There are a few easy tricks.

Bearing in mind that I often fix commercially. There are a few things I would not do to that set.

Leave the paper caps in there
Leave that cable on it. Knots are now illegal. Buy a pre- made three wire cable & plug seek advice on how to anchor it eg gland, or clamp to rail.

Don't replace the electrolytics with cheap 450V ones they don't last.

I will not reform old caps like those. You may have to add a tag strip & make absolutely sure that the first filter cannot ground. I only use the reformer for new caps that have been sitting a while, or I suspect are duds. The technology of the new caps is not the same as those.

Make sure that you check the resistors as you change caps. Some cannot be reliably measured unless one end is out of circuit, but if its high in circuit, it has failed, I work on 10%

Ok guys this has set me on the correct path. I am grateful for your input. I have a few nights off this week so I might get stuck into it. And I can Assure you I never leave those old power cables in situ, it is cut and I leave it there till everything else is done and then I put the new cable on.

Now what I have done to replace this cap (CAN) is to cut the resistor and the red wires away . I joined the red wires and the yellow cap ( which is out of this picture ) together. then I rerouted the resistor to the far end of the red wire (on the valve socket) then connected the positive end of the new 22μF electro and the negative end to where the old cap is earthed. I do believe that this is ok. any thoughts?. . I will send new pics. Oh and dont panic I will be replacing the power cable before I power it up. It's just that Jaycar are not open at 00.30 am which is quite thoughtless of them lol.

Now there are cheap cables out there & more than one source. I hope one lot have mended their ways since I had a face to face with one of there sales team & pointed out that cost is one thing & quality is another & like the recall of all that house electrical wire. Might be why that mob is in trouble. Reducing the expensive plasticiser that makes it flexible will have ramifications.

Middy's & a few others sell those "suicide cables". But do not over look computer cables, the ones with IEC ends get tossed by the dozen & I grab them. 99.9% are perfect, new in packet even.

If you get a male & female you can use them to replace things like mains turntable connections and if you cut the IEC end off, you have a new cheap, suicide cable for your radio.

Marc

Powered it up successfully. Got noise. Lots of interference. Then just noise. Set about and replaced all of the resistors near the valves. (some were definetly not factory). Still have intermittent interference and distortion which goes to nothing. Started tapping the valves with no response untill I tapped the IF CANS. Yep they made heaps of noise so I'm guessing I may have to do surgery on them. Looks like I will replace all the micas any way or could be some dry joints. Thoughts please.

Right guys this baby had a meltdown a few days back ie stuffed rectifier valve and possibly transformer as well . But I am thinking because the chassis is so neat and clean I am going to do a total rebuild . ie wire for wire and component for comnponent. once I test the tranny I will work ou if I need to rewind it ( which will be done ) or or not but I am not going to give up with out a fight lol.

That's sad, sounds like you shorted out the rectified HT.

First thing to do is to check out the transformer.

Unplug the power cord.
Unplug all the valves (but remember which went where),
Remove dial lamps.

Do a measurement on all the windings for continuity, especially the primary as that is the one that usually lets go first.

Measure across the power plug pins for continuity when the radio's on/off switch is set to on.

If all measurements are ok, put dial lamps back in, then plug the radio into the power point and measure the output voltages of each winding. If the heater winding is ok the dial light will come on. The voltage on each leg of the HT winding should be approximately the same as each other, maybe 20-30 volt difference at most. You can take the measurement at the rectifier valve's socket.

Leave on for a while and make sure the transformer stays cool and doesn't start to stink or issue smoke. If it passes all those tests it's probably ok.

Unplug radio from power point. I assume you already fixed the short that caused the problem.

Check also pins 1 &7 of the 6AQ5 both of those pins are grid 1 and its not unusual for some hacker to use one as a tag strip.

I always power up after rework with an analogue meter on B+. If it has not started to develop volts in the time expected, then the kill switch gets hit.

This is not good-- Make sure you did not reverse the filters

Marc

Marcc pin 7 is where the electro connects ( +) then the (-) goes to the transformer and then to ground via the resistor you can see on the transformer. That doesnt sound right to
me.