I am using two burners right now. I had a GQ-4X for like 8 years now. Great device, does the 25Vpp chips like 2532, 2732, 2716 that some of the lower end burners will not do.

I bought a TOP3000 to be able to program the DIP42 EEPROM MX29F1615 which the GQ4X does not support. The TOP3000 software is a little more quirky, but it is faster to program and overall has larger range of compatibility GQ4X. Downfall for TOP3000 is it does not program 21Vpp and 25Vpp chips. They are listed in the device list but they won't program. I am using TOP3000 for everything but 2732, 2532, and 2716 which I burn on GQ-4X.

I think the GQ-4X would work well for you needs if you want to focus on the old bally/stern games. Yes it likely needs an external power supply depending on the USB port. I reused an old wall wart DC power supply.

How long does a chip take to erase?.... depends.... 5min to 60min. The M2732A bootlegs commonly available with a tiny die erase very fast. Some of the late 70s and early 80s chips with very large die inside the window can take much longer to erase. Best I can tell is generally erase time mostly based on how big the die is inside the chip.

How many are bad? ... depends again. The M2732A bootleg batches range from 100% all work to 50% are dead on arrival. Pretty much if it burns OK and verifies OK the chip is fine and will run forever. If you get an immediate write error or the chip refuses to erase it is bad. W27C512, M27C040, M27C160 and MX29F1615 are chips I commonly use and those ones have a much high success rate than the DIP24 chips like 2732

Can you erase non windowed chips?.... depends on the device. If the device is OTP (one time programmable) than you get one shot at burning it, no erasing. If it is a UV EPROM you bake it in UV light to erase. If it is an EEPROM the burner will erase it pretty much instantly. AT28C16 is an EEPROM version of 2716. M27C512 is an EEPROM version of 27515.

Where do you get chips? ... All the chips used on old bally games are long obsolete so you are reusing chips pulled off of board or at the mercy of the grey market sellers mostly from China. They are typically less than a dollar each and expect some to be dead on arrival. Most of the time, most of the chips will all work. Occasionally i've had bad lots. Usually they come from China erased, cleaned up, and legs refinished.... so ready to use.

Typically you pick what EPROM to use based on the file size of the ROM AND how the board is jumpered. A smaller memory size can be replaced by a larger memory size when the pin count and pin out matches. So a 2732 can replace a 2716. A 27512 and replace a 2764, 27128, or 27256 because they are all DIP28 ROMs following a standard pin out. You just fill up the larger EPROM with repeated copies of the data so no matter where the CPU is set to look for the program it will find it.

This chart from wikipedia helps with EPROM sizes.
Untitled (resized).png

Seems like the over exposure is pretty extreme and not something to worry about for the most part. Sometimes I just set it to the max time length and let it go. I've had one or two stubborn chips end up baking for multiple hours before it finally erased all the way. Then it burned and worked fine.

The little Blue/grey Chinese eraser Quench posted is the one I use. I've had it nearly 10 years now I figure and it is still going on fine. Lamp has never burned out or anything. It erases a M2732A with a small die in about 10 min.

https://www.datasheetarchive.com/pdf/download.php?id=e8467a019888cd98787e9bfd7582e8a236d07d&type=O&term=AM2732DC

looks like AM2732DC is a +25v Vpp chip.

resistor or cap in the clock circuit can adjust the speed. The original caps probably have big tolerance ranges.

Changing these caps to 220pF gives you pretty close to the MPU200 clock rate.

I have an older model which you have to install the driver manually. it does not plug and play properly.

Download and extract
http://www.mcumall.com/downloads/download.asp?DownloadID=56

From memory... plug in usb plug the burner

open up device manager (search for device manager in the win10 search by the start button)

find the unknown device in other devices expanded part. If there is more than one unplug / plug in the burner noticing what disapears/comes back.

Update driver. Choose browse for driver manually. Point at the folder from the download link.

Sounds like there is some bit / btye confusion going on and some of that may be Stern's fault. Documentation may be wrong or the EPROM size got larger in later versions but they did not update documentation.

EPROMs follow a standard pin out so a larger EPROM can usually replace a smaller size in the same pin count package. IE 27512 can replace a 2764, 27128, and 27256

Use the file size of the image to decide what ROM to use. In windows it shows bytes so mutiply by eight. If your file is 128KB in windows explorer would go fit on a 1Mbit 27C010 but you could also use any of the other 32pin JEDEC standard pin out EPROMs as a replacement IE 27C040. Just fill up the EPROM with repeated copies of data until full.

Here is a chart on wikipedia that will help pick an EPROM based on the file size.
https://en.wikipedia.org/wiki/EPROM#EPROM_generations,_sizes_and_types

After you change chip profile in GQ-4X reopen the image file.

If you open a 4k image while a 2k chip is selected and then select a 4k chip the software will truncate the last half of the image. So you must reopen the file again. I hope that makes sense.

Get the largest size EEPROM in the pin count package. It feels like a waste of money to stock 2764, 27128, 27256 and 27512 when a W27C512 can replace all of those and is probably the cheapest. There might be some rare cases where you need to pad the data in a certain way to use a 27C512 as a 27256 (supposedly some R-Dog sys 11, but not sure as the stock boards work fine with larger mem), but normally you can fill up the chip with repeated copies.

SST27SF256

has good endurance, 1000 cycles 100 years. But ive seen some flash memory I end up not buying because they are only guaranteed to hold memory for ten years after a burn, which is probably a conservative estimate, but worth looking at the datasheet and considering.

When i fixed original boards the PROMs on William's speech boards very often had bit rot. There would just a few a words garbled. Read back the chip and it was mostly good. Those are masked ROMs though if it matters. I can't really remember any other bit rot like issues on old EPROMs that where not a total failure of the EPROM and usually caused by over voltage or plugging the chip in "upside down".

I got back a GTB System 3 MPU where the six pin power connectors for the power board got swapped. Every EPROM in the game but the GPROM was damaged to a point it was totally dead. The MPU GPROM did not verify right but was close, I was able to erase and reburn it and it seemed fine.

My BSD occasionally gets a credit dot for ROM checksum error at power on. It always plays fine, I've ignored it for a couple years now.

I've had shit luck with any 24 pin EPROM lately. Years ago I the 2732 pulls from China where generally OK enough. Get bad batch every now and again. I bought from a few batches from different sellers and most of the 24pin erpoms like 2732 wouldn't take a burn.

Bigger the die, bigger the fail rate. At least it seems so... Even applies with the 27C160s I use. Whenever I peal a label off a 27C160 and see it is the giant sized window version, I go dammit. I don't think I've successfully re-used one of those yet. Rarely have an issue with the 28-32p EPROMs

Been meaning to try some AT28C16 salvages. Strange and unfortunate they didn't make AT28C32... skipped over to 64K

As far as the bootleg 2732s... start at the lowest voltage and work your way up. If it takes an abnormally long time to program, probably need to go to the next voltage up.

i'd consider that a remark.