Ive sent pictures to Brad to post for me
Regards
Brian

I have only had to deal with it about twice since the early sixties but that rather sounds like "Squegging" which will happen in the injection from the oscillator circuit. Most likely caused by replacing something one should not have replaced, or mis wired it.

It is always a good idea to take photo's of the inside of the pan before it is interfered with. That way you know where things were before you put it where it wasn't.

The tuning gang and the coils are a matched set. If you interfere with a Mica capacitor on one of these coils, which are often unmarked, you can really upset things.

Modern caps can also wreak havoc around the detector first Audio Frequency valve (6B8)

Marc

Photos uploaded to Post 4.

Thanks Brad, that's better. Those resistors look like originals from 1940 when the radio was made, and at that advanced age I wouldn't trust any of them. Hopefully you've measured them all, to make sure they are still intact.

To read those old resistors, I quote from Wikipedia:

Body-end-dot system
The "body-end-dot" or "body-tip-spot" system was used for cylindrical composition resistors sometimes still found in very old equipment (built before the Second World War); the first band was given by the body colour, the second band by the colour of one end of the resistor, and the multiplier by a dot or band around the middle of the resistor.

There is one thing that needs doing: Check voltages. The -16V tells us if the set is working properly. That is back bias & all of the cathode current goes through it. If is wrong the set is notworking properly.

There is a 25V 25μF Cap on the "Candohm" NB that it is positive to chassis and that's the way it has to be. The grids are negative relative to cathode.

That is like a few NZ sets I have seen. That long bar chain of resistances is an American style "Candohm" resistor. Albeit that I have not replaced one of that type. They are noted on the American forum as being not overly reliable & the local long tapped round ones aren't much better & I have seen a lot failed. Normal fail is open circuit.

The resistors on the grid (500K) of the output Valves have an attrition rate, rarely are many of them, & 50K good.

You may find that coloured markers mates useful. I normally go over every joint and like Kriesler for one; Put a dob of colour on the joint once its been inspected. Every now and again you get one that the factory forgot to solder.

If the set has been sitting a long time the valve pins can corrode and lose contact: Clean (No steel wool ever). Do not pull valves out via the envelope. Hold them via the envelope: Lever them out.

MBVC

Thanks guys. Re replacing things that shouldn't be. I have not replaced any mica caps only the paper was and electrolytic. A couple of the paper ones were in real bad shape broken and was everywhere. Before removing a cap I drew what it was connected to recorded the value so I new were to replace it and only ever do one at a time

Resistors. To be honest I'm yet to learn about those but will spend time this weekend having a go at determining colour codes and testing them. I understand one end has to be disconnected to test them
The same goes for checking voltages, I understand and respect the fact that theres very high voltages in these radios so am I correct in when testing for voltage you use an alligator clip to the chassis the other end to the negative test probe and with your left hand in your pocket use your right hand with the positive probe to check for voltage
Could someone please post a picture of the schematic you are referring to
Thanks again
Regards
Brian

Here is a link for the Courier EC (Radio (1936) Ltd) schematic.

https://nzvrshome.files.wordpress.com/2018/12/RL-EC-5V-BC-AC-1940-41.pdf

Steve Dunford's site also has information on these two models that use the same chassis:

https://www.vintageradio.co.nz/model/golden_knight/ec

https://www.vintageradio.co.nz/model/skyscraper/ec

Some resistors like plate & grid can be measured in circuit. The generalisation being if its higher than spec. it needs further attention. I would expect the ones with green bodies & orange or yellow bands or dots to be out of spec.

As I fix commercially 10% or worse is a dud.

Several parts purveyors have downloadable colour codes but do not always cover the older types. Like this one:-

https://www.teachengineering.org/content/duk_/activities/duk_amradio_tech_act/duk_amradio_tech_act_handout_v1_dwc.pdf

I usually buy 1Watt as that gives a better voltage rating & keeps the inventory down. For monitoring voltage I use IC clips. Beware of probes with long bare metal ends and ones with screws in the side.

All multi-meters are not created equal. Many modern instruments are not designed for valve radio and are barely fit for Low Voltage. You may need to go Industrial, or look at something with a Class III rating.

The Golden Knight EC Photos do not comply with one of those circuits. https://nzvrshome.files.wordpress.com/2018/12/RL-EC-5V-BC-AC-1940-41.pdf is showing metal valves. OP valve & rectifier can be glass.

Need some conformation of what's in it, as that can have / cause shielding issues.

I haven't had a chance to look at the resistors but have asked Brad to post a couple of pictures off the top of the chassis
. Re shielding the 6k7 is a metal tube
Regards
Brian

The metal tube circuit then, may be the right one?

On most (not all) of the metal tubes, pin 1 is their body & shield: That pin should ground. It is never unusual to find odd things on those pins like (B+) which then causes nasty things to happen; alternatively a glass tube goes in, then there is no shielding & all hell breaks loose.


Marc

Thanks marc
Can you help me understand the multiplier part of resistor values please

There is a resistor with the following values A green body -5 a black end -0 and a yellow dot as the multiplier - 4 how does the multiplier work ? What I'm thinking is to establish the value of the resistors and replace them at the same time as trying to learn hoe to test them

There are 2 other resistors which are all brown in body colour with a black mark on the end what would they be ?
Thanks again
Brian

The code has changed over the years, However the value assigned to the colours is fairly constant. In the style of the resistor mentioned a green body represents five. The black represents zero (0) and orange dot (4) as a multiply becomes 10 to the power of four. 5 0 0000 five hundred Kilo Ohms. with a green body, black end and an orange dot it would be 50K.

The solid coloured ones may have a dot but those need to be referenced to the circuit as they represent an obsolete system Brown is 1 black zero so we have and its 10 to the power of one.

The newer resistors Have colour Bands

https://www.codrey.com/tools/resistor-colour-code-calculator/

Marc

Multiplier is simply how many extra noughts you add on the value.

So 5 0 0000 = 500k

We should consider this in powers of ten as that also applies to capacitors.

one: is ten to the power of zero
ten: one (deca) (Brown)
one hundred: two (hecto) (Red)
one thousand: three (kilo) (Orange)
ten thousand: four (Yellow)
one hundred thousand five (Green)
one million six (Mega) (Blue)

In the case of capacitors we go negative

Micro Farad is 10 to the minus 6
Pico Farad is 10 to the minus 12

So we add the zero's after the decimal point an it gets smaller.

One of the many annoying things about most Australian & US circuits is the scant info and tendency to save ink by failing to put in leading on decimal zero's on many.

If you have a copy of the current Silicon Chip. The Amplifier Clipping project has a row of resistors showing their colour bands. Even if you are not interested in building it. That is useful info.

Marc

In Future restorations if you have a 80 or 5y3 rectifier valve you need the main filter caps to be rated at 600 volts! They are available and they do surge to 650 volts. Quite often the 80/5y3 will surge past 500 volts on warm up and most of the 450 volt electros dont surge much past 450 volts.