Radio Preppers

General Category => Technical Corner => Topic started by: White Tiger on November 03, 2012, 01:00:59 AM

Title: Tech Special: ICOM IC-271A with frequency drift
Post by: White Tiger on November 03, 2012, 01:00:59 AM
Anyone have one of these with a similar problem? I bought this rig and the one problem the seller mentioned was frequency drift...

I checked the Interwebs and found that one reason for this was due to ICOM using plastic trimmer capacitors in the PLL/VCO & RF/YGR circuits - the fix is to swap out the plastic trimmer caps with ceramic ones (6pf, 10pf and 20pf's). I just can't seem to find out if this is something a novice like me can do...or if I need to take it to a real radio repairman (which means I no longer got such a "deal" on the unit).

Anyone have any information/experience with this fix?

Any help would be appreciated!
Title: Re: Tech Special: ICOM IC-271A with frequency drift
Post by: gil on November 03, 2012, 01:24:41 AM
As soon as you mentioned that last time I suspected a capacitor issue... I can swap them for you Tim, but it's gonna cost you another hot chocolate...

Gil.
Title: Tech Special: ICOM IC-271A with frequency drift
Post by: White Tiger on November 03, 2012, 03:36:38 AM
Heheh, thats right, you did! and I'll take you up on it - what a BARGAIN!
Title: Re: Tech Special: ICOM IC-271A with frequency drift
Post by: gil on November 03, 2012, 12:55:45 PM
When you buy the capacitors, make sure they are NPO types, which means more temperature-stable...

Gil.
Title: Tech Special: ICOM IC-271A with frequency drift
Post by: White Tiger on November 03, 2012, 01:45:45 PM
I bought the ceramic ones rated with a minimum range indicated (6pf, 10pf and 20pf) - but there was no mention of NPO?

The radio arrived today, haven't tried it - except the VFO, which appears to be a bit sticky...how does your VFO turn?

Title: Re: Tech Special: ICOM IC-271A with frequency drift
Post by: gil on November 03, 2012, 01:56:27 PM
If they are the variable type, then forget what I said..

Gil.
Title: Tech Special: ICOM IC-271A with frequency drift
Post by: White Tiger on November 04, 2012, 01:12:40 AM
Quote from: gil on November 03, 2012, 01:56:27 PM
If they are the variable type, then forget what I said..

Gil.

Hah!

Wait...which should I forget...that they should be NPO or forget the offer to swap them out!?
Title: Re: Tech Special: ICOM IC-271A with frequency drift
Post by: gil on November 04, 2012, 12:18:24 PM
That they should be NPO  ;D

Gil.
Title: Tech Special: ICOM IC-271A with frequency drift
Post by: White Tiger on November 04, 2012, 12:58:20 PM
Oh, whew...

....regarding the sticky VFO - does yours have "sticky" areas along the dial? Some owners have mentioned that the rubber gasket warps and causes the sticking - but I don't see any warping?
Title: Re: Tech Special: ICOM IC-271A with frequency drift
Post by: WA4STO on November 04, 2012, 02:02:51 PM
Tim -- the IC271A is specified to use 6amps @ 13.8v DC while in transmit mode.

Here's the manual for it -- see Page one for specs.

http://www.hurderconsulting.net/radiostuff/ic271a.pdf (http://www.hurderconsulting.net/radiostuff/ic271a.pdf)

I've had a number of the multimode VHF and UHF icoms.  They are just fabulous for satellite work.  Only major thing now is getting some decent 144 - 148 mHz antennas up.

Wonder how far away the local two meter repeaters are for you?

Best 73 de Luck, WA4STO
Title: Tech Special: ICOM IC-271A with frequency drift
Post by: White Tiger on November 04, 2012, 02:41:18 PM
Quote from: WA4STO on November 04, 2012, 02:02:51 PM
Tim -- the IC271A is specified to use 6amps @ 13.8v DC while in transmit mode.

Here's the manual for it -- see Page one for specs.

http://www.hurderconsulting.net/radiostuff/ic271a.pdf (http://www.hurderconsulting.net/radiostuff/ic271a.pdf)

I've had a number of the multimode VHF and UHF icoms.  They are just fabulous for satellite work.  Only major thing now is getting some decent 144 - 148 mHz antennas up.

Wonder how far away the local two meter repeaters are for you?

Best 73 de Luck, WA4STO


Thanks Luck!

There are four 2m repeaters near me - between 3.9 & 4.6 miles from my location.
Title: Tech Special: ICOM IC-271A with frequency drift
Post by: White Tiger on November 04, 2012, 05:27:21 PM
I read the "power supply" section which says to use at least 6 amps, and it's maximum consumption is 6amps...but it also defines the external VDC power supply as the Icom IC-PS15.

When I looked on eBay I found that exact unit - BUT - it is listed as a 20 amp power supply....?

I have an external 13.8vdc, 10 amp supply - would it simply blow the fuse if I were to try to hook it up? I'd like to see if my "Tech Special" ...actually powers up!?
Title: Re: Tech Special: ICOM IC-271A with frequency drift
Post by: cockpitbob on November 04, 2012, 08:43:07 PM
Tim,
The 10A power supply will be fine powering a 6A rig.  Even if the rig draws more than the 10A your supply is rated for, it shouldn't cook anything. 
Title: Re: Tech Special: ICOM IC-271A with frequency drift
Post by: gil on November 04, 2012, 09:10:37 PM
Yours doesn't have the built-in power supply? Mine plugs in directly in 110.. The only problem with it are the power switch that sometimes stops working (I leave it on and plug/unplug) and the RF gain button that seems to do nothing.. Otherwise, no sticky areas. That's probably the encoder being dirty. Easy to fix I'd expect. I really like the 271A because I didn't have to spend extra money for a tone board.. The 25W output is also a plus, compared with it's predecessors 10W.

Gil.
Title: Tech Special: ICOM IC-271A with frequency drift
Post by: White Tiger on November 04, 2012, 09:35:23 PM
Gil - No, it did not come with the internal AC power supply. that was an upgrade attachement. If you got one, then you got a good deal, they are difficult to source on eBay.

Yes, I agree, overall I'm really impressed with the 271A - and that it fell within my [strike]cheapskate[/strike], budget conscious ways - while being able to give me an all-mode local communication option.

cockpitbob & WA4STO thank you both for the excellent source information regarding the power supply!
Title: Tech Special: ICOM IC-271A with frequency drift
Post by: White Tiger on November 04, 2012, 09:56:07 PM
Hey - just powered it up - all the lights came on and the signal meter pegged to the right...until I get an antenna (and once I see Gil's Slim Jim - I'm going to actually BUILD it), that will have to do for now...

Hoping that the sticky VFO is just a matter of needing some cleaning!

With the help of the folks on this board - my shack is beginning to come together!
Title: Tech Special: ICOM IC-271A with frequency drift
Post by: White Tiger on November 20, 2012, 03:24:32 AM
Well, after taking Gil up on his gracious offer to help me swap out the trimmer caps, we discovered that there isn't anything wrong with the ol' IC-271A!!

Gil connected it to his power supply, and his nifty homebrew slim-jim, we waited, and waited, and waited (while having some interesting conversations about HT's college, travel, etc., even listened to some repeaters)...

...that darn thing NEVER drifted...probably had it on for 40 to 45 minutes and remained rock solid! The VFO is still sticky, but like the song says: ...things were better off than I had feared!

Thanks again Gil, it was kind of you to offer, and even kinder to actually invite me in TO help!

Again, I appreciate your time!