Anyone interested in seeing an AM/FM radio restoration?

Not sure how appropriate this is for the forum, so thought I'd better ask before I waste some effort:

Recently I got my grubby little hands on a Delco AM/FM radio from a '66 Skylark Special. Despite having no real use for it, I intend to technically restore it to as close to its former glory as possible. By 'restoring' I mean using the original electronics, not gutting the radio and putting new electronics in it. ETA for completion: This year.

From experience I know there are a fair amount of misunderstandings and urban legends floating around when it comes to the proper care and feeding of old radios. Thus I was was wondering if people were curious about seeing what it takes to do a proper restoration of a radio from one of the classic Buicks? I could document my work as I progressed and then post a little write-up with photos once I am done. Note that I cannot really write a how-to for the interested DIYer, as most car enthusiasts cannot be expected to have the tools and test equipment needed.

Wouldn't mind a gentle nod or a shake from one of the administrators.

 

I sure would like to see it.

Rick

 

x2

 

It is a very interesting topic yet to be demonstrated on this Board. It would be well received.

 

I'm all for it. I think it could be interesting.
Might encourage or scare some people.

 

I'm interested in reading and seeing. Maybe buying when finished.

 

Count me in, I've got one and would like to find a way to fix it for less than the $500+ I've been quoted.

 

I wouldn't mind a lesson on how to use current speakers w/o damaging my OEM radio....and how to get the most out of it. While I'm at it, how about the best way to integrate an ipod into an OEM system.

Rick

 

Do It!

 

Yes please!

 

I wouldn't even have asked the question... it is clear that this is very useful information.

 

All of the above posts reflect my answer. Please show us how it's done. Any knowledge on this topic that is shared with others, is good knowledge, even if most are not able to duplicate what is involved!!

 

Yes definately show us . I don't think that has been covered and should be very interesting.

 

Do it

And be prepared for alot of questions

 

Thanks guys, looks like that was a popular idea. :beers2:

ragtops,

Not sure whether I wish to sell or trade the radio once done. I don't even know yet if it has a terminal problem, which cannot be fixed. From a first inspection this seems unlikely though, as almost any problem can be fixed in these radios.

Rick,

That is an interesting suggestion, about the speakers and the iPod connection. I actually have an idea about how one might 'gently' attach an external audio source to one of these radios. Would require a bit of soldering in many cases though. Will think up some speaker info as well.

Scott,

My radio is a Delco type 7293914. and it has both AM and FM, flip dial scale and all. There are two IFs in such a radio, 10.7MHz for the FM receiver and either 262 or 455 KHz for AM. Delco used a 262 KHz IF in some of their car radios, though I have yet to determine what is used in this one. I have a generic schematic for this particular model year, 1966, but that document doesn't include alignment instructions.

Those instructions aren't needed though, as they are themselves the subject of one of the amusing myths surrounding old radios. Basically many radio manufacturers only published a simplified set of alignment instructions for their receivers, if they published any at all. This was apparently because most electronics repair shops back in the day simply couldn't be expected to have the required electronics test equipment needed for, say, properly aligning an FM receiver.

As a result many old radios, FM receivers in particular, have anything but the original audio quality. Many are quite poor in fact, as their owners or a clueless repair guy might have tried to 'align' the radio by ear. ProTip: It is utterly *impossible* to tune an FM receiver by ear, and one would be extremely likely to only make matters worse if one tried to do so. Additionally there is a good chance you would mehanically break stuff just by trying, because most people wouldn't use the proper tool for the job (which would be a plastic knitting needle!)

In any case I intend to align the radio using the proper equipment, which in this case means using a sweep generator in addition to the more common RF signal generator. A proper alignment using a sweep generator is essential if you wish to regain the original audio quality a FM receiver had from the factory.

Stay tuned everyone to radio V8Buick for more info and photos. Lots of photos. :Brow:

----

PS: Please don't use contact cleaner spray or anything similar on your scratching volume pots while you wait. :spank: :laugh:

 

With the original radios using a different ohm speaker than todays radios , where can we get the speakers with the correct ohms ? I have a nice working factory AM/FM and do not want to cause any damage to it by using wrong speakers.

 

Thanks Scott .

 

[...]

 

I'm sure that you could find a speaker with the correct resistance ( ohms ) made new- check out All Electronics or MCM Electronics- they carry a lot of speakers for mono radios. Just a quickie- I think the old speakers were rated at 16 ohms, if you use an 8 ohm speaker, it will "see" 2x the power output of your radio ( probably somewhere around 3~5 watts ) and the reverse is true if you go to 32 ohms, the speaker will see 1/2 the rated power. If you have (2) 4 ohm speakers and put them in series +-+- it will add up to 8 ohms, if you take 2 16 ohm speakers and put them in parallel ++-- it will add up to 8 ohms. Find yourself a good modern speaker with the same resistance and physical size, a nice 2 way speaker with a woofer and built in tweeter, and you will get MUCH better sound than with the OE paper full range speaker. You are correct about the resistance rating of the speakers with regards to your radio- you dont want to get too far away from the OE rating or you can overload the output stage of the radios amplifier. Do yourself a favor and do whatever you can to get a schematic of your radio- I remember from my childhood tinkering that some of the old Delcos and such had a schematic printed and glued inside the housing- you might get lucky!
I've done a fair share of this type of work over the years- if I can be of help, let me know !:beer

Robert

 

The rated speaker load for all of these radios that I have seen is 10 (ten) ohms, of all things. So a single modern 8 ohm speaker or speaker system should be OK, and so should 2x 4 ohm wired in series.

The trouble people may run into come from that you mostly get a 4 ohm speaker, if you just walk into any odd auto store and buy something to replace the single original. Single 8 ohm speakers are very much available if you look around and know what to ask for.

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Edit: 'All these radios' = Delco car radios dating to between the late fifties and at least up into the mid seventies. Haven't really been looking outside this time frame. Note that some other brands of car radios do indeed differ here, this is just for Delco/GM. For instance I have in my collection a '59 Philips AM/FM car radio, which needs either a 3 or a 5 ohm speaker.