I know this will sound stupid but are the mica caps inside the can or are they normally mounted underneath the chassis. My Skraider has started to fade away very quickly after switching on . When I keep switching it on and off it just comes on strong then fades. IF the radio is cold it will come on and stay on untill it warms up and then fades. I know the valves are ok and the on off volume switch is ok. The problem is not in the audio stage either. Suggestions please

In my experience, they are usually inside the can (sometimes covered in wax or tar), and can contribute to the symptoms you describe.

So my next question is do I just remove the outer shell of the IF can or do I need to remove the entire assembly from the chassis.

It depends on the particular transformer design. Some are easier to deal with than others.

Have to say that the two items I like least about radio repairs are: (1) dial strings and (2) IF transformers.

If the can is screwed to the chassis, undo the screws then if you're lucky, the can might just lift off, leaving the coils in view. But more likely, you will have to unsolder the wires underneath, then remove the transformer (still in the can), and then extract the coils. Sometimes it can be difficult to get it out.

Once done, you'll see the caps soldered across the pins at the bottom, one for each winding. Of course, not all transformers are conventional, there's a few really weird ones out there.

After replacement, it shouldn't be too hard to get it back in. You just need to make sure that it's the right way around and the wires are soldered onto the exact terminals they were on before.

Nice to know what we are dealing with? Some IFT's have trimmers inside, more common on top but I have had an EMMCO with them in the base. Outside is rare. The IFT's with inductive tuning will have fixed caps.

Also rare in my experience with Australian radio's is their failure. I have had about two go in abt 50 years & they were mechanical clean breaks. These normally have a lot of volts on them, not across them.

It would be the last place I would look;. They tend to hiss & crackle, in fail mode.

Monitor B+ & see what it does, If it rises something is loosing conduction & the bigger the rise the more likely it is the output. It looks more like a charging type, or a thermal fault, like a heater going out, or a dry joint.

Charging fault: It can be a cathode resistor going open & it dies when the bypass cap is charged, a coupling cap, or bad grid resistor, even one in HT.

Lets not get to the stress level to "shotgunning" that method rarely works. Tedious as it may seem methodology will win.

What test equipment is available (for later voltmeter first)

Ok firstly the IF Cans in question are on the Skyraider of which there are a heap of photos in general discussion. I do have all the nessasary test equipment at my disposal as my mate who restored the old girl for me isnt far away and is always willing to help. I tell you guys I feel pretty lucky to have such a decent friend to help me out and teach me . I also am pretty impressed with the level of help that I get here. I spend twelve hours a night doing guard duty with access to the net hence I have a lot of time to learn so any suggestions are warmly welcomed.

If you have a lot of time available to browse the web, I would suggest sites such as this:

http://www.vintage-radio.com/repair-restore-information/

In the end, most learning comes from doing, but having the knowledge of correct technique is very important, as alluded to by Marc.

Thanks for That GTC

GTC is rather confirming my comment. The greatest amount of learning is from sets that do not play ball.

Its like a modern mechanic looking at my ute & me saying under my breath, that you are not getting your hands on it. It has grease nipples, unlikely he knew what they were for, or had a grease gun. It's got points, not taught how to set them, or the mechanical timing.

Worse still he can't plug it into a computer & have it tell him whats wrong and the similarity here is that in order to fix it, an understanding of how it works, gives a greater understanding of why it won't.

With the radio the first thing is to look at the Power supply, then the Audio & then the RF. This is why I say start with the voltmeter after you look at the valves. With most of the heater valves & filament types like 5Y3 /80 & globes you can see the glow & if it extinguishes you have a problem.

You can pull the rectifier & watch whats left, that way you don't fry the transformer if its a HT fault. Why I say that is that valves like some 6X5 are notorious for going short, an 80 /5Y3 can go short run sideways. I have had cut wires flash over as soon as the rectifier produced enough "B" voltage reversed & dodgy & underrated electrolyics can do the same and they do not have to be old. bits of solder & debris can do similar.

For monitoring B+ on startup IC clips are useful as they cling to the wire(cap lead). I have a kill switch on the isolation transformer. If the B+ goes feral on the way up like a recent new (500v) cap going short at 470V its easy to work than a switch. (especially if your hand is on it).

So lets check heaters & for shorts, then the PSU, before the next move, if there needs to be one.

I notice a photo has appeared in your 2nd post, showing some random components and an electrolytic filter capacitor, but nothing related to IF cans. What is the photo for?

Possibly to show that the red cap that probably should have been replaced looks like it could be shorting to the chassis.

No I think Brad may have had a drink or two tonight lol that photo is for another post. It's supposed to be in the Hotpoint version of the AWA 573MA post in Techtalk lol.

Ah, it all makes sense now :P

Despite the senior moment, I would still look at that cap & not power it.

Back to plan A & the salt mine.