Hello all,
I’m new to old radios and the forum. I’m trying to identify and service an Astor push button car radio removed from a 66 Mercedes. I’m here to ask for help and information on repairing this unit. Currently I have no info at all.
Alas some of the blue sticker with serial number is gone so that makes it tricky to identify it for sure (it looks like A, then a P,R or D, then I can only read the last five digits 61461). I suspect it’s the original radio from the car when new.
The radio was dead, I’ve traced a loss of power to a bad solder joint and repaired that this evening. So now I have power and the light is on.
I do have to source a replacement speaker of the right impedance (15 ohm as I understand?) because the original has rotted away, but I’m not getting the slightest crackle so I expect the radio is not operating.
If anyone can help me to identify the radio, or provide any technical info or testing advice I’d be grateful.
I should note that I’m an a/c technician so I can test circuits and follow wiring diagrams, use a meter, solder, etc., but I have absolutely no experience of radios, so in that respect, please treat me like a dummy.
Thank you,
Matthew

Hello Matthew & welcome to the Forums.

All Astor radios have a model/serial number stamped somewhere on the case/chassis. Being a push-button model the prefix should start with the letter P. Have a look and see what you can find. Also email some pictures to Brad, the administrator. He will upload them here to your post. Technical information for Astor car radios is well documented and once identified we can direct you to some excellent online resources.

Thank you for the reply.
I have sent some pictures to Brad for including in this post.
There is a stamped code on one side of the radio, G 34770. I can’t see any other numbers on the chassis. The main circuit board is labelled CD59B.

Does this radio have 11 transistors including 2 TO3 type AT1138 power transistors on the outside of the case?

I doubt Coralpolyp would have any reason to know what a TO3 transistor case looked like...

This might help:

http://www.interfacebus.com/semiconductor-transistor-packages-TO-3.html

Thanks for the link...
Yes there are two of those power transistors on the top, and both of them are labelled 2N301 F. As for the nine other transistors, what do they look like?

Using the power of the interweb, I think I have identified eight transistors, but I can’t find a ninth one.

Photos uploaded.

The other nine transistors will be on the main board. They will most likely be in small metal packages about the size of a corn kernel.

I'm now guessing it could be a Astor Diamond Dot PDC12J if it has a dual-polarity switch. There is a similar version, Air Chief PNC12N, negative earth, which is designed to suit HD & HR Holdens. Then there are what appears to be later negative earth versions using some different transistor types, models PNC12P & PNC12Q. All models mentioned appear to be basically your standard Astor 11 transistor push-button car radio.

One last question: is there a code on the track side of the main board with something like OP59A?

Anyway, In the meantime check these out:

https://www.kevinchant.com/uploads/7/1/0/8/7108231/pn-c12p_mn-c12p.pdf
https://www.kevinchant.com/uploads/7/1/0/8/7108231/pd-c12j_md-c12j.pdf
https://www.kevinchant.com/uploads/7/1/0/8/7108231/pn-c12n_mn-c12n.pdf
https://www.kevinchant.com/uploads/7/1/0/8/7108231/pn-c12q.pdf

Have a look for the missing transistor inbetween the two output transistors on the swing up cover.

Wayne.

It does have a dual polarity switch.
Yes, it does, the board is marked OP 59B.
I will check out the links, thank you, and see if I can find that last transistor.

It does look like you’re right, it appears to be a PD-C12J. Thank you!
Now, can someone provide a dummy’s guide to what is likely to need testing or replacing, and where I might source parts and a 15 ohm speaker?
Thanks to everyone so far.

We need the dimensions of the speaker; A lot were 5 x 7 inches.

The caramel caps are either new, or closer to the 70's, a lot of them had little ones of around 3/8" dia & 1/2" long and wonderfully unreliable.

I would suggest that all of the Electrolytic caps will be a problem, these I am finding are drying out, replacement is the only cure.

Any 15 Ohm speaker will do to test it.

Marc

Hello Marc
The speaker is 8 by 4. I have found them on eBay at $55, for restoring old Holdens, that might be the best option unless someone can advise on a cheaper source.
Is it just the tube shaped capacitors that usually fail, I think I can manage replacing them - or do the little disc ones dry out too? There are a lot of those! Are these types of capacitors generally available, or do I need a specialist?
Thanks
Matthew

I would definitely replace the disc capacitors. They are called Ducon Red Caps, distinguished by the red mark on top. These red caps often turn into resistors. You can measure the leakage of these Red Caps with the high ohms range on a multi-meter. In the past I've replaced them with Greencaps, ceramic or monolithic caps with the same value, though I am not an expert on which would be the best type to use. The blue Philips electrolytics I've found to be reliable as with the mustard Philips poly caps. Get rid of any cap, except perhaps the Styroseals, with Ducon written on it.