Ham Radio - Repair of the PLL in an ICOM 751A.
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- Опубликовано: 29 авг 2024
- A little long, but I thought I'd leave much of the troubleshooting process in there for interest.
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Very good video Kevin. Those plastic trimmers are always a problem in these radios. Icom went cheap on these. The 745 also. I did two videos on this a while back, #25 and #38. There is also a plastic trimmer in the 2nd LO. I change this to a different value and add a 20 pf NPO on the back side of the board. This makes the LO more stable. Great job on the rig, enjoyed this repair.
Thanks Kevin for a great video on the trimmer caps. I hope I can get new caps from Icom for my 751A
You continue to "Wow!" me. Your explanations while troubleshooting and possible causes are amazing to me. You follow with a repair and retest and the problem is repaired. Question: Why hasn't some repair shop snatched you up? You might consider a mail order repair business for ham equipment. Repair tech's in my area (NE Ohio) are either poorly advertised or non-existing. I would prefer to have a repair rather than discard and buy new. I do fine with manipulating the external controls of equipment and leave the internal controls to the experts. I am an operator type ham not a fixer type ham.
Nice video. Great explanations!
Just love my ICom 751. Still working fine. It puts out great audio on transmit. It still has the original internal battery. Bought it the year they came out.
@Johnny Rebellion mine is 81
Terry Morris got it all right. You "WOW!" me too with your explanations.
Except for a couple of local hams in our club locally who will do some troubleshooting, most people round here have to send their equipment off to the manufacturer for any repairs. Its nice to see someone who can figure it out, and get her done.
Oh, I am getting ready to receive a couple of old Heathkit radios and accessories. From the photos its hard to see exactly what models they are (cell phone pictures), but they were in the guy's ham shack untouched since he passed away. They are going to wrap them in newspaper and box them up for me. From the pictures, I think I found the matching (?) radios. They are a HA-10 1KW linear amp, speaker amp, DX-100-B phone/cw transmitter, HR-10 receiver, HX-10 SSB transmitter, TX-1 transmitter, 2 different power supplies, and a few odd pieces. I just get to drive 1100 miles to go get them, then drive back. But what a find. All I have to do is cook up a meal for the entire 165 member church. They must love Cajun Cooking a lot.
73
Moe K2JDM
These trimming capacitors often cause problems, and of course not only in ICOM devices ;-)
Well done Kevin, thumbs up.
Mny tnx fr video ..... 73 Bernd
I really liked the video, Kevin. Nice job of explaining everything.
Trying to change the trimmer caps on my 751a getting the lid off the shielding can is a real pain! There has got to be an easier way.
Hello Kevin, this old school radio, is what i have. The IC-751A is not open for 11m CB. Can you help me?
Nice work I enjoy your videos thanks
Yet another problem Radio Shack contact cleaning and lubricating spray probably would have solved; or at least diagnosed. You can still mail order it. I did. That stuff has worked wonders around my audio recording studio. It even fixed a computer whose CPU wasn't making good contact.
Question: my Icom 751has an intermittent problem. Happens during receive. I can be on any band. The receive will go silent, the display shows 0.100.0 and no transmit. The main frequency was present, 30.72 MHz. All others were also there except the CW frequency of 9.01060 MHz. I'm thinking it is the RAM board. Got me...
It could be the RAM board, the firmware is maintained in random access memory by a battery. There is an upgrade out there that replaces it with a read-only memory. Shouldn't be hard to find within a couple of Google searches. But it sounds more like the PLL to me. They was known issues with the trimmer capacitors they used on their boards aging badly. There are capacitor kits available as well that you can replace all of those with. Those are the only ideas I can come up with, good luck.
Pourquoi vous ne montrai pas exactement les points de mesure ?
Have replace MANY of those plastic trimmers in both Icom & Yaesu. I keep a supply of the ceramics on hand.
Hi.... Thanks for your video.
I,d like to know how I can transmit on the eleven(11) meters band. Due to ham/ gen function .. 27555 is in Gen mode bu default . Is there any way to put 11 m in ham mode ??
Thanks
It may not work on that can, because the corners are so far apart, and it is basically a big heat sink, but I have had pretty good luck getting things like that can apart by using chip quick solder, or some equivalent low temperature solder. It stays liquid to pretty low temperatures, and if you are fast enough, you can possibly get all four of those corners heated above the melting temperature of the chip quick long enough to pull it off in one go. I've never tried it with points so far apart, so I can't be sure it would work, but it could be worth a shot. It would probably work with a heat gun though. The only drawback is that you want to make sure to get as much of it off as possible once it has done its job so that it doesn't reduce the efficacy of your normal solder when you solder things back together.
great vid! i just got myself an icom r70 rx and its needing some things. the plastic trimmers of course and im gonna replace them but im not sure where i can buy some good ceramics at the correct values. any ideas on where i can get the right ones? tnx!
Mouser or digikey.
Is a trimmer something a hobbyist can replace? Is it difficult?
If you're good with a soldering iron and cleanly desoldering through hole components to replace them.
@@loughkb thank you
So if it is nothing to do with the Synthesizer chip could it a dried up electrolytic capacitor or something else.
Thank you for a very interesting video. May i ask a question? I also have an ICOMIC751A, but the LCD screen has developed a fault and is burnt. Do you know of anywhere that i can get a replacement display od even get it repaired? Thank you for your time. Kind regards
You'd have to find the part from a dead radio, I think. It's a vacuum phosphorescent display. Specialized for those radios and probably rare.
I've seen the display used but working on ebay .
Hello from Russia. Please help with advice. I have an icom ic750 transceiver. At ambient temperatures below 20 degrees Celsius, there is no reception / transmission on bands below 10MHz. After warming up the transceiver for 10 minutes, reception and transmission starts intermittently. Thank you!
Some of the trimmer caps need to be replaced. The originals used plastic for the trimmer bodies and failed with age, well known issue. They need to be replaced with ceramic trimmers. I think there's even cap kits for the 750 series.
@@loughkb Thanks a lot for the hint!
@@user-cc5hx1ys2y Внутри трансивера есть микротумблер 50/100Вт, на передней панели ручка плавной установки выходной мощности RF PWR.
@@user-cc5hx1ys2y Я с волгограду. Сервисманаула под рукой нет, но там описана полностью схема, и все необходимое для настройки :)
А еще там энергозависимая память с прошивкой, которая питается от встроенной литивой батарейки :)
Hello, I wanted to ask if your radio is for sale
I sold it years ago.
Ain't technology great? :)
I've seen things that made me say "No way!" and then be unable to reproduce it. But I know it happened.
Where can I get these trimmers as Icom don't keep them any more and my 751A sounds very gargled..
groups.io/g/IC-735/topic/79739453?p=Created%2C%2C%2C20%2C2%2C0%2C0