I got some P1225 radios super cheap and I accidentally put reverse voltage across one when testing it without batteries… stupid mistake, I know. Do these have a pico fuse or something similar like Motorola mobiles, and if so is there anyone with photos or guidance as to where it is or what it looks like? If that’s not it, what did I blow up? My power supply was at 9V and limited to 15 mA but it may have got a current spike from capacitors. The volume knob was off at the time and I immediately realized my mistake before powering it on (slight spark and current limit indicator on power supply). Thank you.
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I blew up a Radius P1225 :(
- Thread starter knockoffham
- Start date
DeeEx
Member
There’s probably a reverse polarity diode blown. I’d imagine schematics are easy to come by for a radio so mass-produced.
tunnelmot
Member
No biggie you can replace the diode. In your case of the reversed polarity it was the sacrificial lamb so to speak. You can even clip the burnt one out and replace with solid wire, you just need to make sure you never do it again , then you'll REALLY fry the radio. I don't know why people clip the power leads almost flush with the mobiles when they remove a radio.
Thank you! Exactly the info I was looking for.
I’ll see. These radios are too rough for me to sell so I might just use them personally or for rentals. If they’re personal I might take my chances with making the radio a bomb.
Asunakiyori
Lurker
yea you use a nichrome wire and tape a firecraker to it! lol
The trick is you use batteries that are horrible enough that even when shorted they can’t provide enough current to be dangerous.
That's not the way it works. A protection diode bridges the positive and negative power rails. When the power is reversed the diode conducts and blows the fuse. Yes there is a fuse for that radio. Adding a jumper wire will kill any fuse you replace. Find the fuse and replace that, diode should be fine.
Now jumper the diode and the fuse with some 18 ga and put the battery back on. Fun times for sure!
Now jumper the diode and the fuse with some 18 ga and put the battery back on. Fun times for sure!
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I’ve successfully got the radio apart except for the little plastic riser with 3 contacts on it that connects to the battery. Unfortunately it covers one side of the board where the trace coming from B+ is. I could probably de-solder this riser just fine but I worry when putting it back I will get solder other places and short things. I have resistance and continuity tested several components that look like possible fuses, and hooked up power leads and checked voltage to no avail. I cannot find a service manual or schematic for the life of me- I found something service-like on one website but it just listed some replacement parts and accessories.
It's been a long while since I cracked open a P1225. None the less, the fuse should be a surface mount device on the board. Don't try to jimmy the battery contacts, you won't get anywhere with that. The fuse will be one of the larger SMD pieces on the board. It shouldbe labeled with the amperage rating on it. Scan around and see if you can find it.
Thank you. Unfortunately I think it is hidden under the plastic, or doesn’t look like a typical SMD fuse. I can’t find it anywhere else on either side.
I think I may have found it! There’s a small component marked that looks a little burnt and connects 2 large traces, and has no continuity across it, and one side is shorter to B+. It also shares a trace with a beefy diode.
That was it! Thank you so much, the photo really helped. I will probably just replace it with some solder and hopefully nothing spectacular happens.
Put a blob of solder over it and also replaced the very squishy PTT switch while I was in there and the radio is ready for programming tomorrow. Thanks!
Or anything else. What had died was the fuse as ramal121 stated. Diode is fine. I’ll see if I have a similar rated SMD fuse around I can put in it. For now I am not too worried, the radio is under $10 and until I physically clean up the case and decide if it is nice enough for others to use it will probably sit in a drawer. I’ll probably order a fuse, antennas, and batteries in a couple weeks. Also the only reverse polarity scenario is some dumbass with alligator clips was just guessing when the power was hooked up for testing (me, oops). Thanks
