Another area where things can go awry: Note that there are two earth symbols: These are not the same. You will often see these in hot chassis sets especially in America.

The one like an arrow head will signify that the actual ground, or negative is a rail (wires) that traverses the body of the set, but is not grounded to it, this may be a series of wires terminating at the same node.

The brush one that looks like rain from a cloud (with no cloud) from a weather map is the one that indicates parts actually connecting to the chassis. like C33 goes to chassis C34 goes to the common negative rail.

Well

I had a wire come of what Marc is describing as a common, but it is an initial power supply wire. Bad solder. Also, I sat down last night and had a good look at the schematic, after reading Marc. I am sure it is very different from what I have. Even though the suggestion is a 604A ( I think thats right).

And not long back someone here mentioned the shielding of components. I remember the days when old cars would go past home, and the static would drive neighbours mad as their home radios would crackle. This was from memory because the car parts were not able to shield the static made from the dizzy, the leads and un-suppressed generators and later alternators.

So, the earth based sheilding in this radio is more about keeping the static out, and not I think related to reception. From memory.

Perhaps it is not possible to fix this the way we are working. I'm a mechy, not a sparky. So plan C might be to bring it to town, and trade some goods for a repair job. I offer the gizmo, and some other things.

One must sometimes diversify. I started secondary education in a trade school, and we learnt the basics of woodworking, turning & fitting, sheet metal work, and of course physics & chemistry. It is the latter that I found my self working in. Although I did spend a few months working in a sheet metal factory making air-conditioning ducts. All very handy skills. Although other qualifications like Cert IV in TAA were done over the years.

Despite this physics was good for radio & I was fixing them before I left. Being on a Farm & Grandad being a Chippy, I really think I was into a building apprenticeship before I left state school. Turning & fitting I still do & the lathe here was used Thursday to make a new dial pulley for the KM

Don't mind Motor mechanics, I have a 1958 Ute, the young ones would not be able to fix. I have to re-do my tractor engine after 33 years since the last time & I did do a top overhaul on one last July: Diesels are dirty. Mechanical things like that: No stress, just fix.

Good news people.

I found a bloke who can help me. I brought it to him and he got stuck into the power supply and did several repairs and replaces. It turns out the main issue was the two EC's identified by Marc. So the power supply was unable to clean the signal from the vibrator, which was overdriving the speaker ( I think thats right). I am now doing some good restorations with some modern bits out of the shed. Soon I will turn it on. I will be back for an update when I do.

Secondly, is there a way to identify vavles needed from a machine without having chassis markings or drawings.

Reason I ask is obvious, plus I just saw a cool radio that is European in nature, possibly English made. It is I think their version of an SW radio with FM included. I'm guessing 1960s. Its missing valves.

I haven't got it, but do you think I should? I have a photo, hopefully I can get it here. It is highly likely someone here will know what it is, so I could get help. Should I ?

Back soon.

What this guy showed me, is that I could have sorted this problem myself.

It may not be necessary to understand the wizardry behind it, so long as I take my time, study and try, I might be relatively successful with a bit of expert help. The biggest things are the language barrier (like calling a barrel a cap, or a common rail a plate) and abstract stuff like that. I tend to understand electrics in terms of hydrology. I dont know if this really applies to electronics, but the basic principle works for me. If only I could dig out what I new when I was a kid, I could do these radios easy I'm sure.

But what I need now is a meter that measures the values of the parts; measurements like mF & pF and etc. I could try to find what I need on the net. What would someone recommend for a basic repairman (er repairinatorpersonage) like myself?

ends

Ok
So, two things, one is further dating of this radio, the other is a diagnosis session.

Date?
AWA E30020, Chassis No E0050020.
I explored the VR site, and found information about valve types and the licencing labels from the era. The label for this radio is a small green one produced in the 1950s era. It doesn’t contain the words ‘and Television’. It is a No6, 128784. So I am going to say that it is prior to 1951. So the radio can be dated to between 1941 and 1951. In addition, the valves are Base models, also prior to 1952. The only thing left is the chassis No, this would give a pretty precise date, if it could be dug up.

Diagnosis?
It isn’t speaking.
Thanks to MTV for supplying the schematic.
After the initial repairs old mate did, the radio was a good deal quieter at the speaker. Just the normal warm up hum. No channel sweep now. So I spent some time with the multimeter, and here are the results from the power supply only:
At the 200 ohm setting:
R10 = 002, R7 = 001, R11 = 012, R12 = 205, R8 & R9 don’t exist, L8 = 010 ohms.
The two wire heavy wire wound things aren’t part of the radio power, but are for the auxiliary external power supply plug. I don’t think they are in the drawing. They are run from the vibrator and measure 002 ea, and are hooked up to the newer 30 ohm, 3wat add-on. These three can be seen together in the photos.

So I think a couple of resistors are bung.

And I am looking into getting a ESR meter so we can do the capacitors. I also need to find some PDF that has an explanation of the objects in valve radios, and some basic explanation, and terminology of the day (I think this could do with an upgrade at the scholastic level. Particularly if we look at the hydrological aspect, and Ohms law). Not the maths though, because for me 2x2 equals about 7.

Am I right in needing to replace the resistors, and if so what is the advice on modern types, or can I just go get.

Let me know please fellas.

https://www.kevinchant.com/uploads/7/1/0/8/7108231/902a-903a-904a-905a-906a.pdf

First advice I can give you:
Measure voltages with the radio running. Compare to the circuit. You should be able to follow the path of the electricity and discover where it stops. Usually that will pinpoint the bad component.

Remember that a resistor will pass DC electricity, a capacitor should not.

The big benefit of this method is you don't need to cut anything.
A golden rule to follow when faultfinding is to disturb as little as possible.

Second advice:
Don't get fixated on testing individual components.
When you do need to check a component an ordinary multimeter is all you will need.

Third advice:
A quick way to cut your faultfinding in half is to turn the volume control half-way, hold your finger on the metal blade of a screwdriver and, without touching anything else, touch the middle pin of the volume control pot with the tip. If you get a noise ("burp"), the audio amplifier (i.e. after the volume control) is OK. Concentrate on the section before the volume control.
No burp, your fault is AFTER the volume control.

Remember that even though it is running from a battery a vibrator radio develops potentially lethal voltages so don't put yourself in the circuit. Keep one hand in your pocket!

Ok

We have reception but it is very faint. I didnt put the meter in it yet.

I had another good look at the schematic, and it just gets weirder everytime I look at it. Like where are the volume and channel pots. And what is the lonseome object on the far left? I'm guessing it is the brass can which I think is a small transformer type thing. Its not listed. And then there is the 'plate' (I'm guessing), which is not marked and I'm guessing is live and positive and a part of the chassis. And the 'filament connection' which may or may not be the heater circuit of the valves. And L2 which is listed as an aerial coil, using the same prefix as the chokes- L. Not sure if I'm confused or not.

Anyway, after taking my time I noticed c33, and that is connected to the shield circuit not earth as such. Then I realised I was operating the two units separate and without the shield/earth link along the connecting line. So I clipped a lead inbetween. And then thought I should check my battery, which showed about 20A, but 10.5V. So I switched it out with a weak 12.5V 20A supply and hey presto, reception. It looks like it would be happy with 12.5V or more.I shoved a long piece of wire hanging from the light into the aerial plug. But it is weak, and it has the 'pop' on the volume as IR said to test for.

I remember this test, I remember seeing people doing it in the workshop. Think I did it too, and did the follow through, which is logically simple. Must have been basic radios. I accidentally hooked the speaker the wrong way and the vibrator shut down. I thought oh no. But it was ok.

Anyway, she is a goer, but not right yet.

Marc is in their for a credit.

Please see diagram in Post 58.

Nominal voltage is 13.8V. Post a photo of the strange bit. some had spark plates to kill the 200 or so volts back EMF from the Kettering type ignition.

There were for Robbbert valves of all eras. There is one here with six pin series.

Bit concerned with that original current? Most of those were fused at 5A. Pull the vibrator out & have a look at the heater train for a start.

Could be a shorted cap? Check 6X5 despite being designed for car radios, some designs of it were notorious for heater cathode shorts.

If its a dead short test valve out, pin 8 should not have any resistance to pins 2 or 7 (or any other) All valves can do that trick as well.

Beware of that cloth rubber wire its doing the same as the Monarch I am working on and is common: The insulation creeps back & that can short. Shrink tube helps.

The "plate" is what was called a "hash plate" in car radios, It is a large flat piece of sheet metal rivetted to the inside of the case but insulated from it with a sheet of material like thick varnished paper, to form a capacitor with a very low impedance to the case. Its purpose is to trap ignition and generator noise entering the radio via the battery cable. The battery cable is generally connected to one end of the plate and the radio draws its power from the opposite end.

OK, you can hear a signal. It is quiet. Does reducing the antenna length by half make it significantly quieter? If so you have low gain in the RF section.
If not, you have pow gain in the audio amplifier.

Photo uploaded to Post 53.

One thing I have just for car radio's on the repair bench is a car radio antenna.

One of the first things I do (needs equipment) is to attempt to do an IF alignment. That tells me if the IF & Audio is actually working as signal can bypass the IF via the AGC.

Whilst I did actually test two caps today in a light & one was shorted (Junk wrong cap type) Obsession with equipment does not always fix radio's. Generally if the Electrolytic caps are really old & unused in that sort of radio, they and any wax paper & some oil filled ones, these will be duds.

Physically it looks like the volume is the small shaft inside the hollow tuning shaft: Does it work? In most radios with 6V6 the potentiometer was in the grid circuit or fed it from the first AF valve.

So

this is a first draft drawing. But I saw this morning I got the 6x5 wrong.

One thing I found was the earth to case coming from the audio -top LH corner- was bad. So I redid it with a red hot screwdriver. And now there is no reception. I still have not put a meter in it, but I think I will get the capacitor meter. That would make what we are trying to acheive much quicker and easier.

Anyway, I think most of the drawing is right.

Photo uploaded to Post 58.

Could someone please help me here.


In the above, c21 & c22 have been replaced with new> 350v, 22μF 645KO (M) x 2 caps. The line voltage in is 141dc, out = .03v.

The original old electrolytics were> 16 MFD. 525 P.V, type 51-126-3 x 2.

What are the correct caps here please? Also, the earth at c21, should that be there? It seems wrong to me.

Thanks ...