ADC Super Six software

[retrogear]

Took me awhile to read up how to transfer files across user directories.
Here is all the ,MAC sources from USER 4. Oops MONITOR.MAC has some corruption

 

[Endersending]

Ive been trying these images and I am still being stuck with no CCP prompt. At one point I reset the machine and I think I got a prompt but it was a random character. Upon reset again I would get the prompt with a bunch the same character being repeated (as if a key on the keyboard was being held down).
I think this is another memory problem. Since CPM 3 needs 128K memory maybe I have a bad chip in the second bank. I guess I am not sure in which bank the CCP is being stored.
I'm going to move ram chips around and see if the problem changes.
Edit: I wanted to add a screen shot of an error I received trying to boot.

 

[retrogear]

Looking at the BOOT.MAC ccp.com is loaded off disk to bank 1 then copied to bank 2 to be reloaded when necessary.

 

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While testing on this board, I noticed the little LED on the top of the board would come on just as CCP.COM would not load. At first I thought this was a bank selection LED. But I think it shows parity errors. Although all of the DRAM chips passed in my chip tester, I was getting parity errors. I swapped all DRAM from bank 0 to bank 1 and now the machine won't even show the monitor sign on. This is good. This means I have more bad ram. Unfortunately I ran out of good 4164 chips so I have to wait for more to arrive to swap and find the bad ones.
So close! Thanks for all the help. Hopefully it will be operational soon.

 

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I installed some new ram modules. The machine boots and I get a prompt! I can run DIR and things like that. The machine works for a few minutes and then freezes up. I still get the parity error light when it loads CPM. My computer skills are not amazing but I did a little investigating and found an curious problem:
I found I can manipulate the memory banks using the super six monitor and the In and Out commands. The memory of each bank is split into 16K chunks that can be turned on and off. If I turn on bank 1 chunks 0,1,2 and leave the top chunk on bank 0 (where the ERPOM is), I can fill memory and it seems to be fine and everything is stable, filling and viewing. I think the parity errors are happening in the top chunk of bank 1.
I would assume that either there is still bad ram in that area, or the circuitry to switch in that chunk of bank 1, or to turn off that chunk is bank 0 is not working.
Should I order more ram and keep trying to replace bad dram chips, or do I pursue a bad chip in the bank selection circuitry?
I always appreciate that advice and thanks for all of the help.

 

[retrogear]

I wouldn't be too concerned about the parity light. Mine goes on or stays off at will. When I boot TurboDOS on the hard drive it even flickers
but I get no lockups.

 

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New ram for the machine arrived but did not change anything. The card still hangs within a minute of booting. I started hunting around for different ICs to check and I am having a very interesting problem with U76 which is a 74LS245. I found if I swap the chip (with 3 others) the machine will not boot. If I pull U76 there is no difference - the machine will boot and lock up within a minute. U76 is a bi-direction buffer for the data bus. I am bewildered by the fact that if this certain chip isn't in there it won't work but if I leave the socket empty it will. From my testing I don't think it is U76 but something else on the data bus that is having problems. My first guess is that U76 (original chip) is not fully working so it's okay to be on the bus where a good chip locks it up (because something else is trying to talk). Maybe U76 was burned out by another chip pulling against it?
I think I have to go through and figure out which data bus chip is causing problems. I am also thinking it is on the data bus because of they way I get garbage on the screen during lockups and resets. The address bus points to the DART chip and then sends it garbage, because something is talking when it is not supposed to.
Odd this only happens when bank selecting is being used. I have checked U37, U67 and U74 and they don't seem to make a difference. I can pull them out of the sockets and the machine still acts the same - boots and locks.
I am hoping that writing this will maybe help me figure out the problem. If anyone has a guess on what I should be checking or any other advice on how to trouble shoot this I always appreciate the feedback.
I am going to keep swapping/pulling chips and see if I can find the culprit.

 

[Endersending]

I may have found the problem. U37 is a 74S287 PROM. From the data sheet it looks to be a programmable gate logic? I was thinking about how it seems that the second bank upper memory was having a problem but I think the 2732 PROM or data bus buffers were getting enabled while the second bank was selected. The machine was in running condition. I pulled U37 and powered the machine one which gave me a screen full of junk characters. Plugging the chip back in made no difference. Same junk characters which now the chip is really having problems after being pulled from its socket.
If this is a bad chip I would need to get a dump of a good chip and program a new one.
Has anyone dealt with a chip like this?

 

[retrogear]

I think your PROM would hold the system monitor which seems to be running ok. I see there are two 74LS245 data buffers U74 and U76. Those have been a failure on two different Apple //e's.
Here;s a waveform of what a failed buffer chip on the address or data bus would look like. This waveform I managed to get on an Apple II+ with a failed 8T97 buffer. This is 1V per division. Notice the
data shadow on the right side ? That is good 5V TTL. I noticed a shadow at 2V level then I managed to lock onto the problem by moving the trigger level until the 2V signal was highlighted and that was the fault line where I followed it to all chips on that line until I came to an 8T97 buffer where more than one leg of the chip had 2V data. Replacing that brought the machine back to life. This is an example of how to find a bad buffer chip. Scope the data and look for a lower level that shouldn't be there.

 

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Tonight I will be doing some more poking. Using your advice I started looking at my data pins. Instantly I found D6 running at 2 volts. most of the other data lines show a full 5 volts. I started pulling chips and have not found the culprit. I have pulled every chip the schematic shows tied to D6 but I didn't find the problem. Currently I have U67(74ls373), U74, U76(74ls245) buffers and the EPROM chip pulled and it is still there. U74 is the input buffer from the backplane so with that pulled the backplane's data bus is disconnected from the supersix. The only time I can make it go away is pulling the CPU. I swapped the CPU with another and the signal still shows 2 volts. I pulled both ram chips connected to D6 and that did not change anything. I am currently going through pulling chips one by one to see if I can find something else.
Thanks for the advice. I had been using a logic analyzer before which doesn't show the details of the signal like an oscilloscope can. I will keep looking and report back if I have more news.

 

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Here is some more information. The photos are of D6 from the EPROM socket. the nice looking waveform is without U36 installed. The ugly waveform is with it installed. I think this PAL controls the what memory is selected. This chip is not directly connected to the bus and I assume it is controlling the chip that is making the bad signal.
Notice the almost 2 volt peaks in the middle. The other data lines don't have that. With all the buffers and eprom chips pulled I don't see the 5 volt square waves I see 2.2 volt sawtooth waves.
Also I think these signals are refresh signals. It was captured while in a non booting state.

 

[retrogear]

Well if it was me I would trigger on that waveform for channel A and use another scope channel B to check those regions circled
for problems elsewhere. You mentioned pulling a chip and seeing 2.2 V sawtooth. That would be normal
if the removed chip had the pullup resistor internally.

 

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Some more info.
These are probes of the Z80 CPU while the machine is in a working state. The rest of the pins looked normal (to me). This is a good visual for me to see a snapshot of the pins.

 

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Could this be a power problem? I see 5.13 volts everywhere so everything has power. When I test resistance on capacitors I am getting 65 ohms (not powered on of course). This seems low and I posted about this before but since the board would work I just left it alone. I am back to wondering about this and trying to solve it. I replaced a bunch of capacitors awhile ago. Either there is still a bad capacitor or an almost short somewhere.
I wonder if those small 2-volt teeth looking signals are a chip trying to pull the signal low but falls on its face because it doesn't have good power? The sawtooth parts of the signals look like a capacitor charging with a resistor inline.
I have been trying to locate where the 2volt signal is coming from but the only way I can make it go away is if I pull the CPU. I have 3 different CPU's and they all do they same thing.
I also went through and resoldered the buffer and ram pins on the board. now the sign on screen instead of saying advanced digital .. it outputs garbage characters. Like the prompt is correct, but bits are wrong and does not proceed to boot. So I either fixed something and narrowed the problem down or I made something worse. I was really surprised as I resoldered things how much solder most joints took, how much air came out, and how bad the quality of the copper rings and formal coating are.

 

[antiquekid3]

When I test resistance on capacitors I am getting 65 ohms

Ohm's Law is a wonderful tool for these kinds of things.

You say 65 ohms sounds low. But assuming you're measuring across the 5V rail, that would result in a current of 77 mA—which isn't very much.

 

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I pulled all of the chips off the board, powered on the board and used a thermal camera. There is a Resistor network RM2 was getting hot, the last leg of it was at 64 ohms. The rest were at 120 Ohms. I clipped the last leg (not sure what it goes to, It might be for the floppy drive connectors). stuck all the chip back in and it still doesn't boot, but I think it was a step in the right direction. I haven't done a full comparison but the signals do look cleaner/ more defined but the saw tooth waves are still there.

 

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I have been trying different approaches to finding the problem with those 2 volt saw tooth waves and I am not getting anywhere. I am hoping for some more advice about this. Looking at the sawtooth pattern, it looks like a capacitor charging. It also shows up on every data pin of the CPU. Also other pins seem to have to same sawtooth: look lat WAIT pin 24 (from pictures above previously posted). The signal as a curved 'top' to it and looks like a capacitor charging. pin 20 MREQ has a tapered top also.
I can pull every chip on the data bus but the problem doesn't go away until I pull the CPU (which makes the bus dead). I have 3 Z80 CPUs and they all exhibit the same problems so I don't think it is the chip itself.
Could the be a power rail problem? Could it be a leaky capacitor that is putting strain on the power rails?
Could it be a bad ground since 5 volts is 'off', zero volts is 'on', when it tries to pull to ground it's like something is never letting it stay there (capacitor recharging itself?)
More I am thinking it is not a chip problem but aboard or capacitor problem.
My next idea: pulling all the chips on the board (again) and injecting a square wave into different bus paths and see how it reacts. if the sawtooth shows up again, it would confirm my suspicion about it not being a chip problems but maybe a bad capcitor. I don't think it is a bad trace or shorted connection since it is showing on multiple bus lines.
Is this a fruitless idea or does anyone think it might be worth it?
Any advice would be great.
Thanks for all of the support.

 

[retrogear]

I read thru this entire thread to get some context once again. Back in post #13 you said the system came to life after you replaced some chips on the daughter board. I had a bad daughter board that ended up being the small regulator
transistor on it had shorted and actually split it's little case. I mentioned in post #9 that all the power rails go to the daughter board. I'm assuming what blew the fuse on yours was probably the daughter board. Maybe double check the small transistor(s) on the daughter board. There might be two of them for the +16 and -16 volt rails. Or check the bad scope waveforms with the daughter board unplugged.

 

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I checked the daughter board and everything looks fine. Running the ADC with or without the daughterboard connected makes no difference in the signals.
After looking into this I was probing around different chips looking at signals when I realized I had a sign-on screen on the terminal screen.
I was able to used the monitor prompt for a few minutes. fill memory, display memory. It would not boot from floppy, just returning to the prompt when I type 'B'. After a few minutes the machine stopped working.
The ADC works, but it doesn't... Now its looking more like a bad solder joint the way it will work when the board is cold, but after a few minutes it stops working.
The saw-tooth waves on the data bus are still there while the machine is running.
I will fiddle with it more later today and see if I can narrow down this problem.
Thanks for the help!

 

[retrogear]

I also wondered if the sawtooth waves were caused by frequency compensation of your scope probes. I never used a modern scope, just my trusty old CRO's (Cathode Ray Oscilloscope)
which of course has the probe compensation adjustment. I'm guessing modern scopes have plenty of bandwidth and don't have that problem unless it got fried somehow.
I was thinking that so decided to just say it. Sometimes random thoughts spark ideas.