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JM Precision Reproduced 6502 POD

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pikadroo View Drop Down
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    Posted: 18 Jun 2020 at 2:36am
I am curious if anyone here has tried to build the JM Precision (Jerry Walker) 6502 pod for the Fluke 9010A. I purchased the bare board and really spared no expense in the building of it and it simply does not work. I can only get the "pod time out attempting reset" error (which could mean anything). If I unplug from the test port I also get can cause a uut power error.

So I figured well, let's look for a clock signal on the pod. All I get for clock over the whole pod is either a sine wave or a sine wave with a hint of square wave in it. It makes no sense and seeing as I do not have a working 6502 test pod to test the test pod I am totally stuck.

If anyone has tried to build one I am curious how it's working. I can't imagine what's gone wrong here but it's breaking my heart that it doesn't work. Cry

Thanks!
Drew
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jun 2020 at 3:13pm
Apologies if you have already figured this bit out but I am nearing the end of building the Z80 pod from the same place.

The part that I had the biggest problem with was the connection between the Pod and the fluke.
It's a 25 pin D plug like the old parallel port and I could see the numbering on the port underneath the fluke.

The problem for me was the numbering of the connection on the replica PCB.

I didn't want to assume it started with 1 on the top left with pin two being below so I used my continuity tester and found pin one is actually the top right pin if you are looking from the component side with pin two being below it.



So if I had gone with my assumption I would have wired it to the fluke wrong.
I'm assuming the 6502 pod replica has the same pinout and if you have it the wrong way it might account for your problem.

Like I said if you had already figured it out and have it connected properly unless someone else has any ideas I should have mine finished in a week after the last components arrive and I can see if mine works.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ace` Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jun 2020 at 5:57pm
I am pretty sure the clock is only used for self test and the rest of the time it takes the clock from the uut (unit under test).

I've had some issues with a couple of original pods before, the main issues outside of bad ttl were bad 6532. You have to be careful where you buy them too as a lot are fake / DOA. I seem to remember something about needing a 6532A rather than a standard 6532 because of the speed, I could be wrong though and it might depend on the pod.

You can test / source 6532s from Atari 2600s.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pikadroo Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jun 2020 at 8:10pm
Originally posted by Ace` Ace` wrote:

I am pretty sure the clock is only used for self test and the rest of the time it takes the clock from the uut (unit under test).

I've had some issues with a couple of original pods before, the main issues outside of bad ttl were bad 6532. You have to be careful where you buy them too as a lot are fake / DOA. I seem to remember something about needing a 6532A rather than a standard 6532 because of the speed, I could be wrong though and it might depend on the pod.

You can test / source 6532s from Atari 2600s.


I am actually suspicious of the 6532 because it's getting hotter than I would expect. I ordered another one from the same source so... maybe it's time to get a 2600. LOL

Drew
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pikadroo Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jun 2020 at 8:30pm
Originally posted by Lurch666 Lurch666 wrote:

Apologies if you have already figured this bit out but I am nearing the end of building the Z80 pod from the same place.

The part that I had the biggest problem with was the connection between the Pod and the fluke.
It's a 25 pin D plug like the old parallel port and I could see the numbering on the port underneath the fluke.

The problem for me was the numbering of the connection on the replica PCB.

I didn't want to assume it started with 1 on the top left with pin two being below so I used my continuity tester and found pin one is actually the top right pin if you are looking from the component side with pin two being below it.


See, that's good! That makes me feel better someone can confirm that. It took me months to figure that out and finally I just took apart my 8086 pod and tested out where the pins went on the cable. I figured it made sense fluke would keep this connection standard across pods, so I just reproduced a cable that worked in the 8086 pod and that was how I figured out pin one. I didn't see a trace on that pin so I had no idea where to find the other end of it and this appears to be a 4 layer board because I can't see all the traces. Anyhow... yeah that was a problem.

So the 74LS140 has been an impossible find and I thought it was supposed to be a 4 in 1 out NAND because I couldn't find anyone selling a 74LS140, not even a good fake. So the two chips I have tried may not be right. I have a 74S140 on the way I have to try that... maybe that is the problem.

I do have a Z80 pod too that I am going to start next week, so yeah I am curious to see how it works out for you as well.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jun 2020 at 8:43pm
for the 74LS140 I ended up getting a 54S140 which is the military version of the same chip from silicon ark.
I'm guessing that it will work the same.

Bit worried about the 6532 now myself. Will have to see when I finish the pod but if it doesn't work I also don't have a 2600 but I do have a 7800-I will have to see if that uses the same chip.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pikadroo Quote  Post ReplyReply Direct Link To This Post Posted: 18 Jun 2020 at 9:51pm
Originally posted by Lurch666 Lurch666 wrote:

for the 74LS140 I ended up getting a 54S140 which is the military version of the same chip from silicon ark.


I tried both a SNJ54S140J and a CD74HCT20EE4 in place of the 74LS140 but I still got the other one coming. I really suspect the 6532 now.

On the Fluke DB25 to Pod cable I used mouser part 571-2-87456-2 and 571-1873094 which I think are an exact match for the original parts. Made a pretty sweet cable from an old external SCSI drive cable.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pikadroo Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2020 at 7:14pm
I've tried different chips and at this point I have to cut my losses. It's cost me too much money to try to figure this out and I could have had an original working pod at this point. I'll try to assemble the Z80 board but I don't expect much from that. There is literately ZERO support with these units.

Drew
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ace` Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2020 at 7:43pm
It might be worth uploading some high res pictures front and back to see if anyone can spot any mistakes / issues. There's a pretty active fluke thread on klov too.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ColinD Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2020 at 9:08pm
Can you not use a 74LS20 instead of the 74LS140 ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ColinD Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2020 at 9:17pm
I have been following his Fluke 9010A Tape Drive replacement, really good, he will supply a kit of parts including a programmed microcontroller (no doubt security locked), but says the 3d print for the holder that slots into the case flap 'won't be cheap' as it takes a long time to print so you can design your own and print it off.. but he's not sharing the file.... so that's put me right off buying his kit now as seems a bit of a strange attitude.... No one is going to copy his electronics and will buy directly from him, so he's got nothing to lose releasing the 3d print files as he's reluctant to print you one, so that you can mount his module that he's sold you into your case !!

Edited by ColinD - 25 Jun 2020 at 9:21pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ace` Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2020 at 9:44pm
The tape drive replacement lost me at custom memory cards, one proprietary format to another. Some of what he claims you have to take with a pinch of salt, as he often says he sells at cost or with just a small amount of profit and just wants to get this stuff 'out there'. Then charges £200+ for two blank pcbs. LOL

Charge what you like but don't mislead people, as most people are going to know that a £1 pic chip and a 40p idc ribbon connector isn't the reason your kit is £100.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ColinD Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2020 at 10:10pm
Originally posted by Ace` Ace` wrote:

The tape drive replacement lost me at custom memory cards, one proprietary format to another. Some of what he claims you have to take with a pinch of salt, as he often says he sells at cost or with just a small amount of profit and just wants to get this stuff 'out there'. Then charges £200+ for two blank pcbs. LOL

Charge what you like but don't mislead people, as most people are going to know that a £1 pic chip and a 40p idc ribbon connector isn't the reason your kit is £100.


I can see where he is coming from, the £1 chip took a month to write and debug the code for. He might sell 20 kits straight away and then it's down to a trickle..... he has bills to pay.  I really don't have any issues with that.  Using off the shelf memory cards might need more work to support and he want's to keep it simple. 8 ? Tape Slots should be enough anyway. (I would be looking at socketing the memory chip). 

However, If I were selling Take away meals.... I would not be saying.... bring your own food container or if you really have to, you can buy my expensive ones.....

Having sold parts myself, yes, some customers can be a right pain in the arse.... It's like going to the optician complaining that your new contact lenses have made your feet start to hurt.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2020 at 10:16pm
Should have the final chips I need to finish my Z80 build in a day or two so I'm curious to see if this thing works.

You should do as suggested and post good pictures of your 6502 build just in case you might have missed something.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ace` Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2020 at 10:21pm
I understand a lot of work and time goes into these projects, the prices don't bother me, it's that he is saying the prices are near cost, which clearly isn't the case.

Keeping the 3d printer files private is an odd one, maybe it's part of the no after sales support, if people find it doesn't fit or something. LOL

I'm not sure this product was needed anyway with the USB / wifi replacement serial cards that have been about for a while, but I guess it's another option.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pikadroo Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jun 2020 at 4:22am
Originally posted by Lurch666 Lurch666 wrote:

Should have the final chips I need to finish my Z80 build in a day or two so I'm curious to see if this thing works.

You should do as suggested and post good pictures of your 6502 build just in case you might have missed something.


I'll take some tomorrow and post up here. I completely concede it could be my error. I did have problems with the solder reaching the other side of the board at times but it appeared a solid connection was made every time.

I still plan to build the Z80 board because at this point I have everything to do it and I'll only be out a few sockets if it don't work. LOL

Drew
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pikadroo Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jun 2020 at 4:47am
Originally posted by ColinD ColinD wrote:

Can you not use a 74LS20 instead of the 74LS140 ?


I didn't try it because I assumed the unit needs the 50 ohm line drive feature and frankly I am not really sure why it needs that. I don't recall seeing any 4 to 1 nand in my 8086 pod I took apart. CD74HCT20EE4 doesn't have that feature either but I kind of tried that by mistake having not realized the difference. 74S140 has the line drive feature but isn't designated low power.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jun 2020 at 3:12pm
Z80 all built now just waiting for the 74LS574 chips to arrive.

Did notice that I only have 74LS245 instead of 74HC245 for this pod.
Going to try with the LS but have ordered HC just in case.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pikadroo Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jun 2020 at 6:59pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jun 2020 at 7:55pm
I notice you have 74LS245 instead of 74HC245.
Will have to see if it makes a difference on my Z80 build.
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