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Post by mastertech on Jun 30, 2014 12:11:48 GMT -5
Something else just came to mind. Back to CP406 where you tested +5v on pin 1.
Do a voltage test on pins 1 thru 13 and give those individual readings.
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Post by jeremy on Jun 30, 2014 13:10:07 GMT -5
Okay got the readings:
1) +5.192vdc
2) +5.192vdc
3) +5.192vdc
4) +4.690vdc
5) +4.732vdc
6) +4.671vdc
7) +2.2 mvdc
8) +4.740vdc
9) +4.755vdc
10) +5.008vdc
11) +3.7 mvdc
12) +0.7 mvdc
13) +5.132vdc
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Post by mastertech on Jun 30, 2014 14:33:24 GMT -5
You may have a problem with the function control. I believe pin 6 and 7 should be the same. Go to the function control board (standby/on switch on same board) and test ZD310 and ZD311 for short. If both diodes test ok, then remove R377 and R378 and see if the receiver turns on.
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Post by jeremy on Jun 30, 2014 16:38:33 GMT -5
Checked both those diodes, they both read.727 one way, and open the other, pulled those resistors out, tried turning it on, and still stuck in standby.
For what its worth I checked the good receiver pin 6 and 7 on CP406, 7 reads 1.8mvdc and 6 reads 1.6mvdc on the good unit.
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Post by mastertech on Jun 30, 2014 17:02:01 GMT -5
I just remembered that we already verified the problem is strictly on the CPU board so the voltage problem cannot be from the function board. Sorry, brain lapse.
And as you have verified, the 2 pins should have the same voltage.
Since pin 6 and pin 7 go directly to pins 71 and 72 of ic401 there are only 3 possibilities.
1) Bad solder joint of pins 6 and 7 at CP406.
2) Bad solder joint of pin 71 and 72 at ic401.
3) Problem with ic401.
You can try doing a continuity test from pin 6 to pin 71 and then pin 7 to pin 72 and see if you have good continuity on both.
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Post by mastertech on Jun 30, 2014 17:03:33 GMT -5
You are sure there is not a problem with the receiver you now have this board in, correct. It may be worth while to swap boards again and see if the problem readings remain constant.
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Post by mastertech on Jun 30, 2014 17:06:07 GMT -5
Checked both those diodes, they both read.727 one way, and open the other, pulled those resistors out, tried turning it on, and still stuck in standby. Did you recheck these two pin voltages (6 and 7) at CP406 with the resistors removed? |
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Post by jeremy on Jun 30, 2014 17:25:57 GMT -5
Checked both those diodes, they both read.727 one way, and open the other, pulled those resistors out, tried turning it on, and still stuck in standby. Did you recheck these two pin voltages (6 and 7) at CP406 with the resistors removed? Pin 6 is +128mvdc with the resistors removed, pin 7 is the same as before. |
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Post by jeremy on Jun 30, 2014 17:26:47 GMT -5
You are sure there is not a problem with the receiver you now have this board in, correct. It may be worth while to swap boards again and see if the problem readings remain constant. Positive the receiver was working. I was using it in the garage.  |
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Post by jeremy on Jun 30, 2014 17:27:52 GMT -5
I just remembered that we already verified the problem is strictly on the CPU board so the voltage problem cannot be from the function board. Sorry, brain lapse. And as you have verified, the 2 pins should have the same voltage. Since pin 6 and pin 7 go directly to pins 71 and 72 of ic401 there are only 3 possibilities. 1) Bad solder joint of pins 6 and 7 at CP406. 2) Bad solder joint of pin 71 and 72 at ic401. 3) Problem with ic401. You can try doing a continuity test from pin 6 to pin 71 and then pin 7 to pin 72 and see if you have good continuity on both. Will do that and get back to you with what I find. I hope its just bad solder joints on either the connection or the CPU.. and not the CPU itself, then the thing is truly a parts only receiver. Ill post back when I got the info. |
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Post by jeremy on Jun 30, 2014 17:43:13 GMT -5
MT, I think IC401 is hosed, there is continuity between pin 6 on CP406 to pin 71 on IC401, and continuity from pin 7 on CP406 to pin 72 on IC401. I tested continuity on the CPU pin top, not the pad it solders to, to make sure I got an accurate test.
What's next?
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Post by jeremy on Jun 30, 2014 17:46:47 GMT -5
I did find some jumpers on the top that connect directly to pins 71, 72, 73, and 74. I could check for voltage if needed?
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Post by mastertech on Jun 30, 2014 21:06:54 GMT -5
Well I am still not convinced that ic401 is bad. It is not pulling main power down, the standby led is lit, the on signal is being triggered. These are not usually signs of a bad ic.
There are only a few things left to try.
There are not many transistors and diodes left on this board so maybe just an overall DMM diode test looking for any shorts. I am kinda leaning on a possible bad Eeprom. I think it just takes a blank one and writes to it but I can't seem to confirm this. But they are cheap to just try. I don't think the crystal is bad, again because the standby led is on.
All the voltages seem correct but clearly we were not testing right at the processor so a bad solder joint on the cpu is possible. Maybe just go over all the pins with an iron as a last resort.
It was odd that removing those resistors on the function board fixed the different voltages though.
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Post by jeremy on Jun 30, 2014 21:23:32 GMT -5
I'll go over IC401's pins just to make sure they are getting good contact, I have time tonight to mess with it so why not, it'll be a chance to enhance my soldering skillz.
If there's anything you want me to do im up for it.
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Post by mastertech on Jun 30, 2014 21:26:50 GMT -5
If there's anything you want me to do im up for it. Sure. Swap the Eeproms between boards and see what happens, LOL.  |
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