EPROM for homebrew 4k game cartridge

[nooly]

Hello,

I'm lost. I'd be glad if somebody helped me. I made a 4k game, I made PCBs and I bought EPROMs and hex inverters. I followed this guide: http://www.grandideastudio.com/wp-content/uploads/pp_atari2600_instructions.pdf

 

My hex inverter is this one: https://www.gme.cz/74ls04-dip14-texas-instruments My EPROM is this one: HITACHI HN482732AG-20. I programmed the EPROM, the data is there. When I turn on my computer, nothing happens. As the cartridge in not present at all. All my other carts work. The game works when using harmony cart. Should I try another EPROM? If so, which manufacturer and model?

Edited July 10, 2020 by nooly

[Kevin McGrath]

Can you upload pictures of both sides of the PCB?  There might be something someone can see visually that's the issue.

 

Also, you've read the EPROM in the burner and did a binary compare to the data you expect?  Do you have a logic probe?  Have you made sure that both ICs are getting power to the correct pins?  It's super easy to install a chip backwards/flipped, especially on a PCB where you're putting chips on both sides of the board.

[Kevin McGrath]

Also, if you have an ohm meter with conductivity testing, try testing all of the connections between the pins of the two chips, looking for a short.  It's very easy to have a bit too much solder and create a bridge between pins.  If you use too much heat, you could even bridge nearby pins your not even soldering (or destroy the chip).  Photos of the PCB might also help identify bridged pins.

 

Were you able to get the cartridge working?

[nooly]

Kevin, thanks a lot for your answer.

I must admit I'm not expert solder so yes, there could be shorts! I'll check for that. And yes, I did binary compare, it was OK. I haven't found solution yet. I made 5 carts and there's slim possibility that every one of them has a short.

 

I uploaded pic of PCB, is there something that could be wrong with the combination of PCB and EPROM I'm using?

[+splendidnut]

I see your problem... you forgot to put the chips on it

[Kevin McGrath]

5 hours ago, nooly said:

Kevin, thanks a lot for your answer.

I must admit I'm not expert solder so yes, there could be shorts! I'll check for that. And yes, I did binary compare, it was OK. I haven't found solution yet. I made 5 carts and there's slim possibility that every one of them has a short.

 

I uploaded pic of PCB, is there something that could be wrong with the combination of PCB and EPROM I'm using?

Ah yes, sorry, I did mean a picture with the boards populated with parts that you're attempting to get working.  ?

 

If you made five carts, and they are all not working, and you're 100% sure the 2600 you're using to test works with another game, then I would think one (or perhaps both) of the chips was just soldered in the wrong way around.  Meaning the notch on the white silk screen on the PCB showing which pin is pin 1 (the actual pin 1 is also a square pad on the PCB).

 

The EPROM you're using specifically states that it's compatible with the Intel 2732A in its datasheet, and the pinout looks identical to my eyes.  So I doubt that's the issue.

 

If you have more PCBs, EPROMs and hex inverter chips, I'd get a 24-pin and a 14-pin sockets and solder them in, instead of the chips, so that you can use it to test if the chips work at all.  Taking ICs out of a socket is a whole lot easier than desoldering them each time.  You can even get a 24-pin ZIF socket (zero insertion force), probably like the same one used for your EPROM burner, to make it very easy to go from burning an EPROM to testing it in a 2600.

 

But, what I would do is:

• Confirm both ICs are properly installed, with the notch/dot on the ICs matching the notch on the white PCB graphic silk screen.
• Check for shorts between pins using an ohm meter.  Some shorts may be intentional, check the PCB photos to make sure that there's a trace going between those two pins.
• When the cartridge is in the 2600, confirm that both ICs are getting +5V to Vcc (pin 24 and pin 14, the square pad on the PCB for each chip is pin 1, the pin on the opposite side of the chip is pin 24/14).  You will need to attach the ground of the ohm meter to ground on the PCB, I'd pick the wire coming off of the capacitor where the silk screen says "C1" (one side of GND, the side nearest the edge connector, the other side is +5V) to clip the ground of the ohm meter onto.
• You can look for a broken trace visually too, but if all five carts are not working in the same way then I would guess it's not a random broken trace.

All of this is most likely overkill though, AtariAge will sell you a custom Atari 2600 cart with your game and a label for like $25.  Certainly a lot cheaper than individual EPROMs, an EPROM burner, PCBs, LS04s, an ohm meter and cases.  Hard to beat that price, IMO:  https://atariage.com/store/index.php?l=product_detail&p=949

[Robson Zandoná]

Good afternoon.
I would like to know if anyone has a GERDER of the PCB 28 pins, because this one of the topic of 24 I am not finding eprom in Brazil?
Is there any other way or tip?