R71a with a hum & slight vibration

[Ryangn]

I bought a R71a on ebay and when I plugged it in it didn't power up but it sounded like it was taking power when I pushed in the power button. Anyways gave it a little tap on the back and it came on and then off again. I took the bottom off and the screw that holds the power board to the bracket was very loose - tightened it and the radio stayes on. Could that really have been the culprit causing it too short out? However now that it is staying on it has a fairly audible hum coming from the inside (not the speaker) and I can feel a slight vibration, especially on the bottom of the radio. Any idea what may be causing that? I am not a technical person and the person I bought the radio from said worked perfect prior to shipping but if it's not working now that it was insured and not a problem but it's a good looking radio and if very easily fixable I would like to keep it. Gonna poke around in there again tomorrow but any suggestions would be appreciated. Thanks.

 

[RC286]

overloaded power transformer would be my thought if you mentioned power supply issues, and that the humming is not coming from the speaker.

 

[bob550]

Tightening that screw could certainly have solved your immediate problem. However, if one screw was loose, others may be as well. I'd take both top and bottom covers off, and tighten every screw you can find and access. Don't get too medieval with the screws. Just tighten until snug. While you're inside, re-seat every connector you can reach as well.

At this age, the R71 can certainly have failing parts. Being run on AC, they tend to run very hot, and the internal components don't like heat. For the long term, I'd run her off a 13.8V DC power supply (3 amps will do fine with some power to spare) . The pigtail to connect to for that is usually tucked inside the back of the unit. You can pick up a DC power cord off eBay. You also may find that the vibration goes away after doing so. This is how I've powered my R71, and she runs cool as a cucumber for hours.

 

[Ryangn]

Thanks for the replys! I'm going to poke around in it again tonight and I'll pay attention to that power transformer once I find it. I ordered the DC power cord off Ebay and that should be here tomorrow and I'll get it plugged into the rigrunner. If the power transformer is going bad is that an easy fix?

 

[Ryangn]

Well it's the transformer humming and causing the vibration - as best I can tell. Simple fix for the inexperienced? I am guessing I will be ok if I run it off of DC power and not have this problem? Also I noticed when running with no antenna the s-meter is at 20db as where my other R71 is at 9 db - would that difference be from the transformer going bad?

 

[iMONITOR]

It is common for the ICOM IC-R71a to have capacitors fail, as well as solder joints going bad. Have a qualified radio tech go though it, if you're not confident to do it yourself. It's worth the investment, as it is a fine receiver.

 

[Ryangn]

I'd run her off a 13.8V DC power supply (3 amps will do fine with some power to spare) . The pigtail to connect to for that is usually tucked inside the back of the unit. You can pick up a DC power cord off eBay. You also may find that the vibration goes away after doing so..

Got the DC power cable today and it runs quiet and no vibration. Thanks!

 

[RC286]

Glad to hear its working, running of DC with no issues points to power supply failure.
If you ever intend to run it off AC, have the power supply looked at.

Likely there is nothing wrong with the transformer, it is likely bad capacitors or a shorted diode in the rectifier causing the transformer to overload. Running it on DC bypasses the AC supply. Likely the previous owner pulled it apart in an attempt to repair it, and gave up which would explain why the screws were all loosened.

 

[Ryangn]

Thanks, I'll keep that in mind. Although I plan on running it off of DC for now on. Like bob550 said - it runs as cool as a cucumber I'm hoping to get some good use out of it for a while before it starts to give me any trouble. I do have a new rom board on the way so I can get that replaced. It's a great radio and it's getting more use than my R75 now!