First thought: Your tech did not find and correct ALL the battery gunk problems. So often the best solution (albeit, a time consuming one), is to build and install a'clone' board. Your time and money might be better spent going with the KIWI-6 upgrade board.
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noddyspuncture@hotmail.com [PolySix]" <
PolySix@yahoogroups.com> wrote:
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Hi folks, been a while since I was here, but I have another question for the P6 experts amongst us.
I looked at this issue a while back and then shelved it, but now am revisiting it to hopefully solve the issue.
My P6 had the battery problem and was professionally repaired before I bought it and it worked great for a long time. Then is started acting up - finally settling down to having all LEDs lit and with the usual mangled sound.
I have confirmed that there are no broken tracks and scoped all IC pins and there is activity. I just bought myself a logic probe but my problem is that basically I don't understand multiplexing and although I can see whether or not there are high's and low's, I cant decide if that is what they should be... especially on the main 8048 processor.
On the main processor there is activity, both on my scope and using my new logic probe, I have a waveform on ALE and also the crystal is running with a nice waveform on pins 2 and 3.
WR & RD read high on my probe constantly and on TP4 (Pin 32) there is 2.76 volts and a very strange looking washed out waveform on my scope.
Pin 1 of connector-11 has nothing on it - as do all the other connector-11 pins - so the CPU seemingly isn't scanning the panel controls.
My main concern is around IC27 though. Pins 5,6 & 7 are all sitting at 1.995 volts (I know 6 & 7 are connected together) and both my logic probe and scope are dead when probing them. I am getting a healthy pulsing 'high' on pin 1 though... which feeds the inputs of the 4051's.
I get a feeling that because of a fault here I can't complete the setting procedure outlined for VR's 1,6 & 7 in the manual - as all LED's stay lit...!
Reset (pin 4 of the 8048) is working fine - probed with my logic probe. I can add the 56Kohm resistor, set VR1 for a 'low' on pin 4 and it goes to 'high' when the resistor is removed, so that looks fine.
I have swapped out IC27... albeit for a normal dual op-amp (I have a 4560 on order) but it's just the same.
So I am beginning to suspect the HA17408P D/A converter. Would anyone agree, going off my findings please? Has anyone ever had a D/A converter go on a P6...?
Cheers,
Tom