R2014D/0900HS muddled display

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ac2pl
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Posts: 2
Joined: Mon Apr 08, 2019 8:40 am

R2014D/0900HS muddled display

Post by ac2pl »

Dear all,

New member here - I mostly use an IFR 500A and an IFR 1200S for Ham repair and repeater work, but I just acquired an R2014D which on the exterior appears to have lived a rough life but looks pretty clean on the interior. It has one major issue which I need to clear up before I can move on to its testing, repair and alignment.

The display shows nearly all question marks where blanks are expected and many of the other characters which are supposed to be present are clearly swapped for another letter/number. I have read every post on this board about the R2001D machines and found one (R2001D keypad jibberish #p496109 by W8TMT) which at first seemed like it was the solution. In Terry's case, the special function code 70 reset yielded a clear and intelligible display. In my case however, neither codes 70 nor 79 did anything to change the problem.

I then thought that perhaps the keypresses were being misinterpreted by the machine. So I set about to blindly set the frequency, generate output, and measure with a counter. This worked perfectly. The keypresses (using virtually every key in some combination) were interpreted and the frequency was set correctly.

I switched over to SA mode (not many question marks and a good trace) and was able to set the center frequency. The peak as measured by transmissions on 40m and 2m matched the center position well. FM modulation was observed as well.

Browsing through the service manual, I see that character generation is handled by A14 and A7 (as described in sections 14.2.4.1-3). I fathom that that is where I'm headed next (along with buying a small mountain of electrolytic caps and perhaps some tantalums for recapping).

Here is a link to a pdf containing a small deck of pics for the initial testing:

https://drive.google.com/open?id=1FKCoO ... Bq0fb4DQCo_

In the pictures you may note that the digits for 0 1 2 and 3 display correctly (as do 8 and 9) while 4 5 6 and 7 are displayed as 0 1 2 3 (??).

Any advice would be gratefully appreciated. Thanks for such a helpful board!

73 de ac2pl
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kcbooboo
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Re: R2014D/0900HS muddled display

Post by kcbooboo »

Most of the data in the R2001 series is sent around as binary-coded, over four or eight lines. I immediately noticed that the "4" bit is stuck in one position, since 0,1,2,3 display correctly but 4,5,6,7 show up at 0,1,2,3. In binary, 3 = 00100011, 7 = 00100111, so the 00000100 bit seems to be the problem. It could be a stuck driver IC or a defective receiver IC or even a gated buffer, since the data lines are shared by all boards. Since everything else seems to work, chances are it's a problem on the display board where the data bits select a character to be generated on the screen.

A scope should at least let you probe around to see if that data bit is moving at all or always stays in one state. You may eventually need an extender board or two to elevate the offending board to test further.

Bob M.
ac2pl
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Posts: 2
Joined: Mon Apr 08, 2019 8:40 am

Re: R2014D/0900HS muddled display

Post by ac2pl »

Dear Bob M.,

Excellent, thank you. I will further explore the block diagrams and schematics with this in mind. I appreciate your insight.

I also found that the pins of U52 on the A14 board appear to be covered with corrosion due to a (perhaps) spill of something which leaked onto the board. The leak must have been small, as the corrosion was localized to that immediate area. Some of the traces around there also appear darkened - I have yet to confirm the various continuities.

73s de ac2pl
com501
Posts: 1088
Joined: Fri Nov 02, 2001 4:00 pm
What radios do you own?: Over 50 - All Motorola

Re: R2014D/0900HS muddled display

Post by com501 »

Change your caps, fix the corrosion and re-examine the display board. A bad/leaky cap could also cause the driver in question to not work correctly.
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