I would not replace any caps, at least until you get it going.
Most if not all look perfectly OK to me, and would only require changing if faulty.
Not to mention the high risk of creating a “ man made” fault when doing so, and the hardest fault to fix.
JJ

OK, so basically replace every single capacitor. That’s a lot, and there are many different ones, so I hope they are all available. I know nothing of the replacement types you describe.
Is there anything else likely to need replacement; would that usually be enough to resurrect an old radio?

NO, read my post #16
JJ

Matt, I strongly agree with Johnny on this issue.

That radio isn't old enough to need the shotgun approach and you do risk creating a fault where none existed previously.

I have several radios in my collection that have redcaps and none of them is bad. One of those radios has survived a flood.

Don't do it!! Measure first. Think with your head, not with your hands.

Actually I have found many 3V electrolytic caps in some of them, underrated & out of spec. I normally use the 100V rectangular types to replace caps like 0.01mfd. Rather than the big caramel 400 & 630V ones.

What destroys them in cars is the heat, cars get very hot in the sun.

OK. Thanks. I hadn’t seen all the posts when I last replied, I didn’t appreciate the conversation had moved onto two pages, apologies Johnny.
I’m up to date now, but not really wiser, being an amateur, about how to basically approach this thing. I need some pointers on what to check and how to test, and where to focus my effort. I can go through every capacitor I suppose, and see if any are bad. I have a capacitor tester.
Is there a recommended guide to radio repair principles for dummies?
What generally goes wrong with old radios like this?

OK, will try again.
Do not change any caps at this stage.
Find any speaker 8 ohms or more. Does not matter whether round or what physical size.
Connect speaker to radio, then connect to a variable DC supply with either current limiting or current monitoring.
Slowly wind up the voltage, up to around 12 volts, monitoring the current.
If it gets to 12 volts without say exceeding 200 or so milliamperes, all good.
Then connect a short piece of wire into the aerial socket.
Turn up the volume and I would not be surprised if it doesn’t burst into life.
If not, report back to the forum and there are plenty of people able to take you to the next step of the repair.
JJ

Johnny, thank you. That’s the advice I need.
It may be very simple to most people here, but when you’ve had no experience of this stuff you don’t even know where to start.
Thanks for your patience.
Matthew

Hello again
I’ve made a bit of amateur progress with the Astor car radio. It’s now operating. The current is around 400mA at 13V.
I bought a new speaker that’s a correct sized repro unit, and rated at 16ohms. However, I thought I’d check it upon arrival, when tested it is only a bit over 10ohms. I contacted the supplier who says the speakers are made intentionally with lower resistance to improve performance and it's fine to use.
I have two questions - is the current level acceptable? And will the 10ohm speaker be alright to use as advised, or should I add a resistor?
Thanks
Matthew

I do not know how you managed to measure the speaker at 10 ohms.
Must have some fancy, expensive test equipment .
It will nominally be 15 ohms and perfect to use.
400 mA sound fairly right for that type and design of radio.
JJ

Hello Matthew.

I used to fix a lot of these radios when I was an apprentice.

400mA sounds way too much. There is a current measuring socket on the radio, but just measure the total current.
Have the volume set not too loud nor too soft. Watch the current drawn by the radio and turn the bias setting control,item 100 on the circuit so that the current goes downwards. Turn the control down until the audio begins to distort (cross over distortion) and then turn the control back the other way slowly until the distortion just disappears, and then a fraction more.

The speaker should ideally be 15 ohms but will measure lower. We are talking a D.C. resistance and not the A.C. impedance at 400 Hertzs or whatever frequency it is measured.

I have a Plessy 9"x6" oval speaker that was common in early cars. I had it re-coned and I never used it. Newer speakers have a magnet on the back far too large to use as a replacement in cars such as my old 1960 Holden..

I mostly found that an output transistor would fail and the owner would replace the fuse with a three inch nail and incinerate the radio. But, back then I could order new input chokes and output transformers.

Good luck.

Wayne.

The dial lights alone would pull a fair bit of current.
But biasing the outputs, if miss adjusted conceded.
It is after all designed as a car radio not a battery operated portable.
But yes, may be a little high.

Hi folks
I think, for almost every response I have now received about this old radio, there is then a person offering an opposite and contradictory view.
When I measure the speaker using a decent digital meter I get 10.5 ohms across the terminals. Is that not a reliable method for DC applications? That’s interesting. I was lead to believe lower resistance speakers than 15 or 16 ohm can damage the radio, so that’s the concern I want to address. The new speaker I have is supposed to be designed for this radio application, but as a cynic I like to check and make sure because stuff nowadays is often made to low QC standards.
Wayne thanks for the advice there, I will attempt a ‘novice’ bias adjustment to reduce the current. I will report back soon.
Incidentally, what fuse is correct for this radio?
Thanks
Matthew

Impedance and pure resistance are two different things, although both measured in ohms.
Impedance relates to resistance to AC, and pure resistance relates to DC.
So, the speaker you have is 15 ohms impedance not resistance.
Measuring the speaker with an ordinary meter measuring resistance will give a rough inaccurate reading of the specified impedance.
The correct speaker for directly coupled solid state equipment is more critical of the correct loading, ie speaker impedance.
What you have is correct, but it would probably run quite happily with say an eight ohm speaker.
As would happen if you were to connect an extra speaker parallel, eg rear speaker in car.
It would be a good idea to check/replace all coupling electros in this radio before attempting bias adjustment.
By the way sometimes some comments might seem contradictory because it’s very hard to answer one question without opening an other angle to that same question. Some are engineers but not hands on servicemen, Others are servicemen with little correct theory,
And then there are the ones that spend too much time on Google and believe it all.
As with several others on this forum, this was my full time job sixteen to sixty five plus .
JJ

It sounds to me that you need to test the continuity of the output transformer. Just put a nine volt battery across the primary when you have a speaker connected. If you get no crackle then its open circuit.