This video explains how to set the reference frequency, "30.7200 MHz" oscillator, despite the service manuals Wrong Instructions. This also addresses the HPL Lock alignment procedure instructions, and other warnings.
I have repaired hundreds of ham radios, errors in the alignment instructions are common. It's important for any technican to have a good understanding of how circuits work in order to recognize errors and determine what is really needed to get things done. Thanks for the video Mr Carlson.
I grew up next door to a WWII veteran ham operator. He helped me get my Novice license about 1977. Sometime in the 80's he replaced his Drake Line with a IC-751A Icom. He invited me over to see it and he said for me to sit down and give it a spin. After turning the knob a few turns smoke arose out of the display area bigtime. Wow i felt bad. He was cool about it as always. I miss that guy almost as much as my dad. Oh, you are obviously a very smart fellow. Enjoy your videos very much, Thanks for going to all the trouble for us to enjoy your adventures. Chuck, AF4O
Thanks for comment! That's quite the story. I can imagine the moment when the magic smoke came out. I Bought a Icom IC-746 some time back, it's the one on the bench...... Anyways, I owned it for one day, and the display went out. I couldn't believe it! So... I pulled it apart and found a small transistor in the display unit that had been so hot, it desoldered itself. The little heat sink tab was blue! So I redesigned the area, built a circuit that would be fine running in the linear region, and all has been good since. There were also a bunch for IC's that took some heatsinks too. I don't believe in running parts hot enough to cook things.
Paul, thanks for bringing these mistakes in the service manual to light. Also the battery backup for the ram hasn't failed yet. I've had this rig since 86 and it works marvelous. I have the 250 hz filter in the 9mhz and 455kc IFs. It's like a barn door is slammed shut on the noise when their engaged.
Wow what timing! I installed a CR-64 yesterday in my IC-751A and was trying to set the ref. freq. with no luck thinking I had an equipment issue.... so I searched RU-vid and found your post and yes the Service manual has it wrong!! I clipped my probe on the R11 by the IC5 (pin1) to made my tweak's. THANK YOU for posting! Jonathan-KN4G
I had my old IC 751 (not the A version) for 34 years before it lost some caps and went west. A donation to another more fortunate ham who tried to fix it. I bought a new IC 7300 which makes mincemeat of almost anything in its class. Good call, Paul! KQ2E
It's been a year now... I am SO happy with my IC-7300 that I couldn't be happier. I am STILL finding "new stuff" to change or improve my usage of the receiver. I'm hoping that my old rig hasn't hit the bottom of a large steel bin... LOL
Hai there Peter this 9m2du ..as i said i have the same problem as mention upon the memories ,till today i have not get it fix instead i like you comment as time pass by i just too old to get it fix up. don't know what to do with it ,rest in peace i guest.. it good to hear you most comment i will follow you on repairing it great and interesting upon learning on it .
I just purchased this (working) radio at yesterdays Bryan/College Station TX ARRL Field Day from a local member. I thought I would look on RU-vid to see what people said and I saw your link. WOW, am I glad I listened to what you said about the battery. I KNOW I would have been one of those people to just yank it out. Thanks. I will also look now to see what other helpful advice you have on this ICOM IC-751A radio.
Hi Paul, it is really hard to believe but there are so many mistakes in original service manuals, sometime a real nightmare... very nice worked out 73 O.-Peter
If you DO get that Piexx board, be SURE to follow the setup directions EXACTLY. Not doing so will have "very bad things" happening in short order. Make sure a warning sticker is affixed to the board to save the day in case someone plays with the EEPROM board... and requires the setup afterward.
Hi Paul this is Burt - you might remember me asking you to look at my yaesu 857d. I now have a icom 751A - was wondering if you might have some time to look at it. Let me know.
You might want to repeat the Icom 751A BFO alignment errors for others (like me) who need them. Have you checked that the model 751 manual also has those errors? Thanks... Bruce KQ2E
Everytime I go to the Ham radio store they always say Icom and and Yaesu are the same quality radio. I'm sure you know more about it than the sales folks....do you think they are built to the same standards internally? would love to hear your thoughts on both of them.
Hi there. First of all, I thank you for sharing such valuable information with us. I would like to know if you can send me the file that I should use to reprogram an ICOM RAM BOARD from an IC 751A. I have built an interface that I got based on an IC CD4040 and using the ICOM-RAM.EXE program which indicates that the recording process has been carried out correctly, when reading the ICOM RAM again I see that it actually contains information, but when installing the board in the IC 751A the equipment does not work correctly, I would like to try it with a different .BIN than the one I have if you can send it to me. Thank you again for your attention. Greetings from Argentina
Mr Carlson, be advised that the best replacement for the volatile memory board is made by the Piexx people - - for IC-745 and IC-751 radios. Reasonable price, essy installation, and peace of mind.
Mr Carlson's Lab That's good! He'll certainly dlep bette st night! I did so for my IC-745 (Old Betsy} snd she was a happy camper. By the way, may I know your call sign? ..and I loved your resto on your "Gothic" Hammarlund receiver up the way there! What an inspiration.
Mr. Carlson... I have an ICOM 750 (which I understand is the same as a 751 only sold originally in a different country). I've owned it about 15 years. I've never changed the battery. Would you suggest I let sleeping dogs lie and leave it alone or change it to a new one (and take the precautions you mention)? And thanks for a great video!
Buy the EEPROM version board for $75 US and be done with the problem. But save the old board in case you need it. I built a special double battery backup board with diodes to make changing the battery a "no brainer." THEN I bought the new board. Duh. LOL
+Mr Carlson's Lab Engl Guitar amps is famous for having incomplete & just plain wrong information in their schematics. Some of the techs in Germany, where the amps are made, suspect it is done on purpose. All I know is they are so bad, I simply refuse to even acknowledge they exist & pretend they don't. I work on them like no schematic exists. That way, I don't get thrown off by their erroneous information, & it keeps their nonsense from entering my brain, and giving me any preconceived notions, about what they actually did. Turning the amps away at the door, works even better.
Bonjour dommage que tu ne montres pas precicement ou faire les mesures je ne suis pas electronicien t'as video ne m'aide pas beaucoup dommage ! 73 Eric FK8HM
