CB Radio Repair - Vintage Midland 77-912A Help! - Page 1
Forum section: electronics / repair

author: zker666
author_rank: Contributor
timestamp: February 17, 2020, 09:58:35 pm
content: So I've had an old handheld CB radio for over ten years that I got from my late grandfather, and the thing still works, but the solder job on the inside is pretty messy and the radio produces a ton of static, with faint voices coming through every once in a while. The 4/8W Transmitter still functions flawlessly and can easily be picked up by my friends around the city. I've already replaced a bulged electrolytic, but the problem of fuzzy static on the receiver output remains. I would like to know if anybody has any info on this unit, as a schematic or repair manual would be greatly appreciated because, I cannot find any info on this unit anywhere besides the FCC OET database, let alone pictures or schematics. I know the thing's a piece of junk, but it was my late grandfather's piece of junk so I'd like to see it working well. If anybody by any chance has ANY info on this CB radio, please let me know! Again, any info is helpful, thanks!Below are some pictures of the unit.FCC OET Search:https://apps.fcc.gov/eas/GetEas731Report.do?applicationId=ymmP7Vem8KSt978luCjDuQ%3D%3D&fcc_id=AK577912A

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: February 17, 2020, 11:33:57 pm
content: Never tried to fix this radio, I cannot find manuals and the traditional CB source, CB Tricks is down.However, here is what I would do;Clean the board with isopropyl alcohol and a cheap solder flux brush or old toothbrush. Clean and check the push to talk button and all switches.Mark all of the adjustable cans in line with the screwdriver slot in case you miss-align one. Do not attempt to align yet, you do not know which ones are transmit and which are receive.Look at all the solder joints and re-solder anything that looks slightly bad. A lot of problems are just bad component connections.If you can, while listening to an active channel, push on the components and see if you can narrow down any problem, sometimes pushing on part of the board will tell you where the problem is.Replace ALL of the electrolytic caps if you can. ("The Usual Suspects")Check the antenna connection even though Transmit works, maybe try a long wire attached to the antenna....These are things you can do without any electronic tools, I do not know if you have any, so start with these suggestions.Maybe another similar Midland radio has schematics and maybe you can find something, several radios were slightly altered and a new number was assigned...

author: zker666
author_rank: Contributor
timestamp: February 18, 2020, 12:39:28 am
content: Thanks for the reply. I was thinking about all of these things, and it has obviously been repaired in the past, given the variety of different manufacturer's components strewn about. I will probably just disassemble the entire unit and resolder every joint and clean it up nice with isopropyl and new components. Given the amount of bodge wires, resistors, and caps, I think my granddad had a heavy hand in getting this thing to work himself. Thanks again

author: Gregg
author_rank: Super Contributor
timestamp: February 18, 2020, 01:44:13 am
content: a long time ago I had a Radio Shack version of that type of CB; maybe even a re-badge of the same model. It didn't work correctly from the start and I took it back but they wouldn't refund my money and sent it off for "repair". When I got it back, it wasn't any better and since I knew I wasn't going to get my money back; I resoldered every joint. And then it worked!

author: mcovington
author_rank: Regular Contributor
timestamp: February 18, 2020, 03:54:45 am
content: Cleaning the volume control may work miracles. Try that first.

author: spongella
author_rank: Contributor
timestamp: April 04, 2020, 11:35:38 am
content: I'd also pull off any plug-type connectors and squirt contact cleaner (I use Deoxit) on them.Some Midland manuals can be found on mods.dk; while they may not have that specific model's manual they might have the precursor or predecessor of that radio which might be similar in design.Previous posters have excellent suggestions. Good luck and I hope you get Grandpa's radio up and running.