I fired up the scope and had nice patterns on MSM5524 pins 26 thru 31 about
20 volt PP but pin 25 had about 3volts PP . Later I pulled the chip and
bent pin 25 out and plugged it back and voila, no center segment, anytime.
While the chip was out I checked the pull down resistors and they're all
about 100K ohms. Pin 25 which controls the center segment appears to be the
problem. Now what I need to know is the the IC or could it be something
else?
tnx
--
73
Hank WD5JFR
"Mark S. Holden" wrote in message
...
Henry Kolesnik wrote:
Peter
Thanks for the tip but I had previously checked the voltages on the
transistors you mention and all are B +4.44, E +4.58 and C -22.4 volts.
I
discounted them as being the problem because there's only five and there
are
seven segments. My guess is that these transistors are the individual
digit
drivers as there are five digits and the segments are muxed from the
msm5524. If I look closely at the copy of a copy many times over of the
schematic I can see where a prevoius owner made notes indicating that the
center segment is driven by pin 25. Any more tips appreciated. As you
can
tell I'm out of my league with this kind of stuff.
This web page:
http://www.crocuta.com/FRG7700/html/page20.html
indicates the segments are controlled by Q1052 - Q1058 (2SA733A-Q)
So there should be seven transistors there.
If the transistor isn't identified in the schematic, you can narrow down
the segment to one of two by tuning to all 1's and then all 2's. 2
segments will have the -25 voltage on them for both tests. You may be
able to get a better handle on which of the
two is bad by tuning to 15,555 - the segment that consistently reads the
full -25 (or -22.5) is probably the bad one.
I'm not familiar with your radio - just basic trouble shooting.
--
73
Hank WD5JFR
"eddumweer" wrote in message
...
Check the segment transistors position Q1052-Q1056 (2sa733a-q)
One of them will probably be shorted. The signals for the transistors
are
coming from ic msm5524 controlling the frequency and time display.
Greetings Peter
"Henry Kolesnik" schreef in bericht
m...
It's a five digit display made of seven segment digits. The center or
"G" segment doesn't blank when zero is displayed so zero looks like an
eight. It has leading zero suppression and instead of the zero being
totally suppressed the center segment appears as a minus sign.
--
73
Hank WD5JFR
"dxAce" wrote in message
...
Henry Kolesnik wrote:
All the center segments stay bright, no blinking.
OK, what is it you wish to blank then? I owned a FRG-7700 for several
years.
What exactly do you mean by 'center segments'?
tnx
--
73
Hank WD5JFR
"dxAce" wrote in message
...
Henry Kolesnik wrote:
The freqency /time display doesn't blank any of the center
segments
on
either time or frequency function. Any suggestions on a fix
appreciated.
The serial number is 59,800 and I wonder if anyone can tell me if
this is
an
early or late model?
tnx
Blank or blink?
--
73
Hank WD5JFR
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