Making a cart from scratch...

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the_wizard_666
Posts: 73
Joined: Thu Feb 25, 2021 6:52 am

Re: Making a cart from scratch...

Post by the_wizard_666 »

lidnariq wrote: Wed Apr 28, 2021 4:59 pm
the_wizard_666 wrote: Wed Apr 28, 2021 4:44 pm definitely looking like thirsty RAM.
What's the specific part numbers you're looking at? That should specify whether they're thirsty or know when to stop partying.
WRAM: ZMD U6264BDC07LL
CHR RAM: Alliance Megabit U6264BDC07LLG1

Numbers are close, so there may not be a difference, but it's worth a shot anyway.
lidnariq
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Re: Making a cart from scratch...

Post by lidnariq »

Those "LL"s at the end should indicate that it's a RAM that knows how to stop drinking. So I expect something else isn't correctly telling it when.

Theoretically, pins 12 and 2 or 38 and 40 depending on specific AX5202 should ultimately connect to RAM pins 20 and 26, so I guess I'd make sure that electrical path looks clean.
the_wizard_666
Posts: 73
Joined: Thu Feb 25, 2021 6:52 am

Re: Making a cart from scratch...

Post by the_wizard_666 »

lidnariq wrote: Wed Apr 28, 2021 5:20 pm Those "LL"s at the end should indicate that it's a RAM that knows how to stop drinking. So I expect something else isn't correctly telling it when.

Theoretically, pins 12 and 2 or 38 and 40 depending on specific AX5202 should ultimately connect to RAM pins 20 and 26, so I guess I'd make sure that electrical path looks clean.
Pin 2 on the AX5202 connects to the MMC1/3 solder pad, as does RAM pin 20, so there's a match. Pin 12 of the AX5202 appears to go to the bottom of the 27k resistor (R3). Pin 38 goes to the PRG, and pin 40 connects to a .1uf capacitor. Pin 26 of the RAM goes through the 10k resistor at R2, through the VRC/Battery pad on the battery side, and then through pins 1 and 28, and the 22uf cap at C4. It's actually hard to see the traces because the boards are completely black, so I may have made an error here, but I triple checked the paths and I'm pretty sure of them.

Your post made it sound redundant to swap the chips, but I'd already removed one when you posted so I decided to switch them anyway. It ended up being redundant, as the saves are still corrupting, but at least that's something ruled out.

Going back to the rest of your prior post that I didn't reply to, the path of pins 1 and 28 appears to have been answered now, as it connects to the middle pad of the VCC/Battery. The battery pad goes to R1, R2 and to D1 on the cathode end, while the VCC pad goes to the diode on the anode end. It would appear that the battery's path goes from the positive terminal, through D2 to the bottom of R1, sending the power through the battery pad, as well as the resistor at R2. So the issue could be in either of the 10k resistors, or the diode in D2, or possibly a combination of those. Or possibly a defective board, although everything works fine other than saving, so I'm pretty sure that's not it :P
lidnariq
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Joined: Sun Apr 13, 2008 11:12 am

Re: Making a cart from scratch...

Post by lidnariq »

the_wizard_666 wrote: Wed Apr 28, 2021 10:23 pm Pin 2 on the AX5202 connects to [...] RAM pin 20
Ok, great, you're dealing with variant "#1".
Pin 12 of the AX5202 appears to go to the bottom of the 27k resistor (R3). Pin 26 of the RAM goes through the 10k resistor at R2, through the VCC/Battery pad on the battery side
That ... doesn't sound right. Pin 12 of the AX5202 ought to connect to pin 26 of the RAM and also some side of some resistor.

If you have a multimeter with continuity test mode, that might make your life easier.

Is there another solder jumper on the back, or is it only the VCC/Battery, MMC1/MMC3, and ROM/RAM jumpers?
Or possibly a defective board, although everything works fine other than saving
Could be a bad design, I have no idea, and the black silkscreen makes it harder to figure out.

Do you have other resistors on hand?

Ultimately, there's two problems, and even if they're related I think you need to solve #1 before you can address #2:

1- Something is drawing power from the battery too fast, and I suspect it's because the WRAM isn't being turned sufficiently "off"
2- Save loss might be related, or might not; Muramasa wrote:
Please note that is only for some games that have a hard time with newer SRAMs (Faster then 120ns). If you are using older SRAM or your game doesn’t have an issue then it is not needed.
and you're using 70ns RAMs (that '07')
the_wizard_666
Posts: 73
Joined: Thu Feb 25, 2021 6:52 am

Re: Making a cart from scratch...

Post by the_wizard_666 »

My poor eyesight may be a contributing factor, so I used the multimeter's continuity test. RAM pin 26 does indeed connect to pin 12 of the MMC3 in some fashion. I just have a hard time seeing the path.

There are a bunch of other solder pads, but none relevant to the RAM as far as I can tell. There's a PRG32/28 pad, a selection of CHR32/28, and three pairs for MMC1 that are not used for an MMC3 board. On the front of the board are some pads relating to the capacity of the PRG chip (256k or under, 512k flash, or 512k eprom).

So the chip itself could possibly be the issue then? I do have one other type of 6264 chip, HM6264LP-70. I'm guessing those are no better though. I also have two chips I harvested off some donor boards from other repros I've made, but they're both 4464, and with my prior experience with chips not mentioned on the boards, I'm guessing they will not work for Muramasa's boards. That blurb was in reference to the 1000pf cap, which is now in place, so I don't THINK that should be an issue anymore, but who really knows.
lidnariq
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Re: Making a cart from scratch...

Post by lidnariq »

If you have spare resistors, try replacing the 27k with something much smaller ... like 5k. If you don't have any spares, just try swapping the 27k with one of the 10ks.
the_wizard_666
Posts: 73
Joined: Thu Feb 25, 2021 6:52 am

Re: Making a cart from scratch...

Post by the_wizard_666 »

lidnariq wrote: Wed Apr 28, 2021 11:23 pm If you have spare resistors, try replacing the 27k with something much smaller ... like 5k. If you don't have any spares, just try swapping the 27k with one of the 10ks.
I have a bunch of 10k resistors and a single 1k. I'll try the 10k first, and see if that helps. Just gotta wait for the soldering iron to heat up :P
the_wizard_666
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Re: Making a cart from scratch...

Post by the_wizard_666 »

Nope, didn't work. Still corrupt.
lidnariq
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Re: Making a cart from scratch...

Post by lidnariq »

Ugh.

What loose parts do you have? Any small capacitors or diodes?
the_wizard_666
Posts: 73
Joined: Thu Feb 25, 2021 6:52 am

Re: Making a cart from scratch...

Post by the_wizard_666 »

Caps: 100pf, 1000pf, .1uf, 22uf
Resistors: 1k, 10k, 27k
Diodes: 1N4148 signal, 1N5818 Schottky

I also should be able to swing by the electronic shop on the weekend, and there's always the online route if they don't carry what I need.
lidnariq
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Re: Making a cart from scratch...

Post by lidnariq »

Try putting a 100pF capacitor in parallel with R3.
the_wizard_666
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Re: Making a cart from scratch...

Post by the_wizard_666 »

By parallel, I took that to mean both connected through the same holes. Assuming that's correct, then it still corrupts.
lidnariq
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Joined: Sun Apr 13, 2008 11:12 am

Re: Making a cart from scratch...

Post by lidnariq »

Ideally I'd try adding an asymmetric delay circuit to WRAM +CE, but that'd require cutting a trace so I'm wary of suggesting it.
the_wizard_666
Posts: 73
Joined: Thu Feb 25, 2021 6:52 am

Re: Making a cart from scratch...

Post by the_wizard_666 »

I'd noticed elsewhere that Muramasa is a member here, so I took a chance and shot him a PM and linked the thread. Hopefully he'll have some insight.
Joe
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Re: Making a cart from scratch...

Post by Joe »

Is the AX5202P draining the battery? The wiki claims it's possible. If this is what's causing the problem, you'll see it as unusually high voltage drop across one of the resistors even with the RAM completely removed from the board. (I don't know how to check it without removing the RAM. I also don't know which resistor, but there's only three of them.)
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