View Full Version : AM Radio restoration

12-15-2014, 10:01 AM
I really like my original Falcon radio made by Motorola with the mechanical push buttons.
Has anyone ever attempted to restore their AM radio?
Mine sort of "works" but I can tell it's not all like it was. I did a little research over the weekend. I can send it out for $200 bucks (how often do I hear that...) For example: http://www.joesclassiccarradio.com/Resto.html
They basically clean it, replace all the capacitors, check the tubes, lube the tuner, and fix anything else that needs to be fixed. It seems capacitors are typically what goes bad over time. Replacing them doesn't seem too difficult.
There are also videos on youtube- one guys just plays the radio as is, then re-solders about half the connections- plays it again- it gets better, then re-solders the rest of them- and it then like magic it plays like a new radio. Cost of replacement capacitors seems cheap.
Has anyone done any of this?

12-15-2014, 11:10 AM
Capacitors dry out. They cause a lot of hum. They can explode. I've recapped just about everything other than car radios. Old tube radios and amplifiers. I've got a room full awaiting my attention. I have "in stock" probably 1000 different capacitors. And vacuum tubes.

Electrolytic capacitors, which are most likely to fail of all, are very dangerous especially in high voltage applications (117 volts). They've been known to kill people when they discharge. Car radio electrolytics are probably less potent, but the technician knows to ground each leg to discharge them first. Also, as a side note, most old capacitors have polarity as well, which sometimes you can't determine without a schematic.

There are other potential issues with tubes (you can get those, and caps as needed, from someplace like tubesandmore.com) and some replacement transformers. But may not have much in the car radio variety.

All that said... it's a potential DIY project, but I can assure you the guy isn't getting rich at $200. He's probably going to make way less than $20 an hour. Probably closer to $10. And if there is some other part broken he's probably got a hoard of cores to pull parts from.

04-22-2017, 06:49 AM
So...work is taking me home for a meeting this coming Thursday (but fly back Sunday). Hoping to drive the falcon to work Friday...and I'm thinking about this radio project again...possibly bringing the radio back with me. I have a nice quiet basement and I can put a card table there where nobody will touch anything. It might be cheaper to send it out...but this seems like a great project.

I did buy the Motorola service manual on eBay which at least has a nice parts list and schematic. (More pics later...on iPad now...one pic limit...)

So, a few questions for master Roger or anyone else that wants to chime in?![BOW][BOW]

The pic shows the list of capacitors...but my googling this morning hasn't found any of them with these specs. Any thoughts on where to find them?

I don't see anything on the parts list or in the manual at all about the tuning rope. I do see a lot of "clutch" parts. (When I turn the tuner now it slips...) Roger, is it for sure a rope in there? Or could it be a clutch slipping? If it's the clutch...I'm wondering if parts could be a challenge.

The manual says that for testing, I should use a battery, not anything plugged in. So...no extra car batteries close to my basement...any thoughts on cheapest 12v that would get the job done?

List of tools I should bring back? I have a list in my head, but I'm sure I will forget something...

04-22-2017, 10:12 AM
Most of all the capacitors you should leave alone. They rarely fail and if changed could create a tuning need using tools you won't have. I see one electrolytic in your list which could be an issue, since electrolytic caps dry out and are the usual ones to change. These are usually in the power suppy circuit as opposed to the tuning circuit and can be a strait swap. If you cant find an exact replacement you can always go higher voltage, never lower, and capacitance increase of 20% will not usually be an issue.

I've restored tube radios, and electrolytic capacitors and tubes are common items to replace to get things working again.

I buy frim a place tubesandmore.com but there are other places I've used by searching and searching online.

I have a couple 12v power supplies, but you can also find 12v dry cell batteries, or even a motorcycle battery is small, but would probably need to purchased up there.

Have fun!

04-22-2017, 10:21 AM
C6 might also be questionable being a paper wound cap.

Is this a tube radio? Usually voltages that high would make it so. If so, what tubes are in it?

04-22-2017, 12:26 PM
Going to post a few pics of the manual so you can see the tubes.

04-22-2017, 12:27 PM
Schematic 1

04-22-2017, 12:30 PM
Schematic 2

04-22-2017, 12:38 PM
Ok, I think you can see four tubes in it according to the diagram.
Is itnworth it to take it someplace I can test them? Or better to just replace them?

Thanks for the advice on the caps...so only replace two? Doesn't sound too bad.
We were talking about going home two weeks in July...maybe it's better if I just order parts and do it at home where I already have a battery, etc.

I need a special to remove the tubes?

Any thoughts on the clutch vs tuning rope?

04-22-2017, 09:58 PM
I have a tube tester. Not many places to get them tested, so I invested in one since I restore tube radios when I get free time (HA!). One a year, at best.

I'm not sure what it takes to pull the tubes it they don't just pull out like regular vacuum tubes. I don't see anything in the pictures to suggest anything holding them in other than friction.

I'm not following the rope/clutch question. :confused:

04-23-2017, 05:07 PM
Tubes...ok, sounds easy.

On the tuner...the push buttons work fine, but when I turn the tuning knob it seems to "slip" instead of move the tuner needle. Do you think it is because a tuning control "rope" is worn out? Or a "clutch" that is worn out?

04-24-2017, 12:03 AM
Generally if the cord is intact the friction it provides is going to be OK. What happens more often than not is that the tuning capacitor driven by the cord has dried up of lube on the shaft and is making more drag than the friction of the cord can overcome. A few drops of very light oil will usually suffice on the ends of the tuning capacitor to free it up. Don't get oil on the cord. You can then work it by hand, or with the buttons, instead of using the knob until if frees up enough for the knob then to work. The push buttons are a mechanical means of moving the tuning capacitor, so that's why you can get those to work. Both move the same thing, but by different means.

Hope this makes sense.