Repair of Icom IC-24AT - Page 1
Forum section: electronics / repair

author: DaneH3
author_rank: Contributor
timestamp: December 14, 2017, 06:53:49 am
content: EDIT 9/28/2018:Replacement of the DC jack was successful and was the culprit for not powering up. Here is my explanation of the complete fix for this radio. You can simply disregard the rest of my replies.I contacted Icom about a replacement DC jack and they got back to me in a reasonable time, sending me a replacement in about a week. After soldering the new DC jack into place and powering the radio via the AC adapter, the radio made audible static and responded to squelch and volume control, but showed no readout on the screen or any other sign of life.At this point, I tried resetting the CPU via the method of holding the FUNC button and A button while turning the radio on, but the CPU did not reset. (Nothing on the display)After that, I concluded through some poking around with a continuity tester that the connections between the PTT board and the LOGIC board were faulty; looks simply like they broke from stress over time from pressing the button repeatedly. A reflow of the solder on the joints did the trick and restored the connection between the two boards.I re-assembled the radio and performed a CPU reset, and the radio is now in operation.The rotary encoder that works as the tuning knob only registers movement in one direction, but that is a seperate repair for another day.I learned a lot about this radio, so if anyone has one and would like more information on my insight don't hesitate to contact me, I'd love to help!Cheers! o7OLD INFO:So I recently came across an old Icom IC-24AT Dual Band radio in a box of miscellaneous radio items won at an auction for super-duper cheap. Of course, the radio was the only thing of worth in the box. That, however, is not the point.The version I have came with a standard 6xAA battery case so of course, I put in some batteries and tried booting it up. No avail! The status light failed to come on, and no life could be seen from the poor guy.I had heard this particular model of Icom had a backup Panasonic VL2020 battery that was required for the radio to run, and the one already installed was far past it's prime. I ordered a replacement, soldered it in place - yet again no dice.- the battery culpritNow realizing there's likely a more complex (or simple, I've been known to look over obvious things before) solution, I set out to discover a solution to the fact that absolutely nothing was happening when the radio was plugged in via the battery or the supplied 13.8V wall wart.A visual inspection led me to be more confused, I checked all caps, connections, etc. Things that would commonly be issues yet none of them seemed out of order in any way.- (both sides of the power/main board which is likely the culprit, not the logic board)Poking around voltages when plugged into the wall power shows that the wall wart is actually giving me roughly 15 volts, but using a bench supply with 13.8v doesn't bring it to life either. I don't have much experience with these miniaturized circuits, many things are too compacted to get a good view of, but even then nothing really seems to be out of the order. I'm at a loss!When measuring voltages that should be the standard Vcc of the radio (15-ish Volts) when measuring them from the ground on the wall wart, they show as 15v. But even when the radio's "on", while measuring from the ground of the radio chassis/motherboard ground it shows a relatively low voltage (0.5-ish Volts).(voltage when measured from the chassis, which is strangely not connected to the ground on the DC plug??)It's likely that I'm tired, or stuck in a wild goose chase, but it does seem a bit odd to be behaving the way it is. I'm unsure where to start troubleshooting in a circuit like this, so any and all pointers or ideas are greatly appreciated. I'd skip fixing this guy and just buy a modern Dual Bander, but I'm short on money and I like the way this vintage Icom looks and feels.A great service manual for my radio can be had here:http://www.radiomanual.info/schemi/IC24_AT_ET_serv.pdf( I presume the solution is hidden here somewhere)If I've left out any vital information please ask and I'll fill in the gaps.Thanks,Dane.

author: TheSteve
author_rank: Unknown
timestamp: December 14, 2017, 08:41:12 am
content: I'd be very suspicious of the DC power in jack - it is a common failure point.

author: tru3533
author_rank: Regular Contributor
timestamp: December 14, 2017, 12:15:25 pm
content: Don't forget to reset the CPUPage 2 of the manualhttp://www.repeater-builder.com/icom/pdfs/ic-24at-et-inst-man.pdf

author: DaneH3
author_rank: Contributor
timestamp: December 14, 2017, 05:34:40 pm
content: Quote from: TheSteve on December 14, 2017, 08:41:12 amI was also suspicious of the DC jack, but I have also tried powering it via the included battery pack with no luck. I might try hooking up 13.8V from my variable supply straight to the power rails.Quote from: tru3533 on December 14, 2017, 12:15:25 pmThat was one of the things I tried before anything else, but I can't reset the CPU without any power. Once it gets powered up, that'll be the first thing I do.

author: TheSteve
author_rank: Unknown
timestamp: December 14, 2017, 05:36:38 pm
content: Connect power direct (carefully) - that DC jack generally switches battery power so it can kill functionality from both the DC in and the battery in at the same time.

author: DaneH3
author_rank: Contributor
timestamp: December 14, 2017, 05:55:42 pm
content: Quote from: TheSteve on December 14, 2017, 05:36:38 pmI am somewhat unsure of where the power should be connected on the main rails. On the page I'm referencing (page 34 of Service Manual), I can see that there are four connections related to the DC jack.EXT - Is this referring to external power?(-) - It's pretty obvious that's likely the negative railHV - I'm not entirely sure what HV refers toGND - GroundShould I be connecting from EXT to (-) or GND? Or possibly HV?It just seems a bit confusing because the colors don't seem to correspond with what I'm used to, as HV is black - which I would normally assume to be a ground.Thanks

author: DaneH3
author_rank: Contributor
timestamp: December 15, 2017, 12:45:43 am
content: Okay, after connecting power straight to the railsstillnothing happens. I've checked the leads on the power switch in the off chance it was faulty, but it works just fine.Does this mean that there might be a problem with the power regulator circuit? Sadly I can't buy one considering that it's a by far outdated radio.I'm out of ideas! (not giving up!)I would appreciate any guidance on where to go next.

author: tru3533
author_rank: Regular Contributor
timestamp: December 15, 2017, 04:02:47 am
content: OK, check this first

author: DaneH3
author_rank: Contributor
timestamp: December 16, 2017, 09:06:17 pm
content: Quote from: tru3533 on December 15, 2017, 04:02:47 amOkay, so the DC in is now from my power supply at 14 volts. Measuring voltage while having the multimeter common on the negative lead of the power supply.When measuring the voltage of the Vcc out on the VR board with the power switch, the voltage measures 14 volts - but with the switch either off or on. Knob position doesn't matter.Oh and not only that, I can measure the voltageliterally anywhere, even parts that should be grounded, the measure is still 14 volts.This has now left me thoroughly confused. Does that mean this is a grounding problem? Possibly involving the DC jack?

author: tru3533
author_rank: Regular Contributor
timestamp: January 11, 2018, 11:41:08 pm
content: Damaged multimeter

author: DaneH3
author_rank: Contributor
timestamp: January 12, 2018, 12:18:17 am
content: Quote from: tru3533 on January 11, 2018, 11:41:08 pmAlready more than positive my multimeter is working perfectly. Double checked with other multimeters just to be safe, even.

author: Bashstreet
author_rank: Frequent Contributor
timestamp: January 12, 2018, 04:54:03 pm
content: Quote from: tru3533 on January 11, 2018, 11:41:08 pmOr the common 14 volt pixie they can make things act like that.

author: najrao
author_rank: Regular Contributor
timestamp: January 15, 2018, 09:19:11 am
content: Dane H3, there is no option but check out where the Vcc is dropping out, going logically from the supply input point to wherever else it needs to go according to the schematic. This applies to the (-) or ground as well, separately. To a novice, this might seem mind boggling, but cannot be all that difficult. Step by step is the only way. It may be easier to check through by continuity alone, without even powering up; it is also much safer.ICOM receivers however old are very reliable and well worth keeping for ever. It is a crying shame if yours has to stay bricked. Or have you found and solved the problem by now?Edit: Don't just drop out, please. I want to hear that you won!😅

author: DaneH3
author_rank: Contributor
timestamp: September 29, 2018, 01:35:42 am
content: Quote from: najrao on January 15, 2018, 09:19:11 amWell, school got in the way and I did indeed stop working on the radio for most of the year. I found it in my closet again this month and felt motivated to work on it once more! I contacted Icom about a replacement DC jack, ordered it, and replaced the jack.The radio turns on!However, there are still hurdles left to overcome...The screen doesn't turn on and the radio presents no signs of being "on" other than sound from the speakers. Squelch control works. What I am assuming is an LED light in the top left corner doesn't light up either.So close yet so far! Looks like I'll be disassembling the radio again, I just hope that it's something simple and not the CPU or something?Sorry for such a delayed update guys. Let's see if we can figure this out once and for all!EDIT:The LCD backlight button doesn't light up the LCD either. Possibly the LCD itself is to blame?

author: DaneH3
author_rank: Contributor
timestamp: September 30, 2018, 06:06:04 am
content: Bump

author: PEU
author_rank: Newbie
timestamp: October 01, 2019, 10:42:24 pm
content: Quote from: DaneH3 on December 14, 2017, 06:53:49 amHi, before anything else, sorry for resurrecting an old post, but this thread is the only hit I got regarding my problem on google, just registered in the forum to place this question.My IC24AT has this very problem, the encoder only registers movement one way, incremental, after rebuilding all the keyboard connections that were bad I'm frustrated discovering this new issue... can you give some hints regarding this? checked the connections and they seem solid, no problems at first inspection.Thanks in advance!!Pablo

author: DaneH3
author_rank: Contributor
timestamp: October 01, 2019, 10:54:01 pm
content: Quote from: PEU on October 01, 2019, 10:42:24 pmNo need to be sorry, I created this thread for the very reason of assisting anyone who had problems similar to mine.Since I repaired this radio, I actually ended up buying a second one outright, that worked out of the box.The issue with the rotary encoder seems to have come from age, I made another thread about this issue in hopes that someone with more experience could shed some light on that subject.It seems like rotary encoders can get worn and or oxidized just like many switches, but due to the nature of a rotary encoder, this failure is even more detrimental. I could recommend using some deoxidizers such as Deoxit to clean the encoder thoroughly. (I sadly can't test any theories about fixing it on mine, the IC-24AT I fixed in this thread originally is now dead again due to unknown reasons)Another option is the possibility of buying a replacement encoder, as the part number for that encoder is available and does exist, while it's a tad pricey sometimes.Hope this helps! Feel free to follow up with me if you want, I'd love to hear that another IC-24AT is in action somewhere.

author: PEU
author_rank: Newbie
timestamp: October 01, 2019, 11:47:19 pm
content: Thanks for the prompt reply, today I spent most of the time fixing the keyboard, tomorrow will look into the encoder connections, I just saw one loose wire.Pablo