EETools ChipMax II - Page 1
Forum section: electronics / repair

author: ShootTheCore
author_rank: Newbie
timestamp: August 20, 2021, 10:15:10 pm
content: Hey folks - I have an EETools ChipMax II EPROM Programmer that I've used for three years to dump mask ROMs and program EPROMs on 80s and 90s arcade hardware.It recently stopped reading and writing chips, and when I run the internal hardware test, it tells me that there's a PullUp & Down failure on one of the lines.I contacted EETools to see if they would repair it, but they refuse - they only offered me a discount on purchasing a replacement unit.I've opened up the Programmer and frankly it looks much more complicated to diagnose than where I'm comfortable at currently (I don't have a formal electronics education or background - I'm a tinkerer). It does look like each pin has its own set of diodes, resistors, and capacitors - maybe one of those passive components has failed?Any suggestions on how I could isolate the culprit?Here's links to photos:https://drive.google.com/file/d/18ayxyRozQ97IWP-Q2qbeUVksKiLZqYs_/view?usp=sharinghttps://drive.google.com/file/d/1aIuoWNdhnsPWLYwRiZCrPNMwZ-btZ_SH/view?usp=sharinghttps://drive.google.com/file/d/1--jBkZ7LqX-gGcKXU5WKSsYfwapxEHPp/view?usp=sharing

author: bdunham7
author_rank: Super Contributor
timestamp: August 20, 2021, 10:49:00 pm
content: What do you have for test equipment? This may be repairable, but unless you get lucky, it won't likely be easy. I would start by testing diodes DAB24 and DA24 and their associated resistors. You can compare results with DAB23 and DA23. Next I would be looking at all of the part numbers on those chips and seeing if I could find a datasheet and a reference circuit for them. If you have a scope, you can (carefully!) look at the power-on signal on the #24 data line at various points, using #23 as a comparison.

author: ShootTheCore
author_rank: Newbie
timestamp: August 20, 2021, 11:06:18 pm
content: Thank you for the suggestion! I do have an oscilloscope (as well as a multimeter and a logic probe) so I'll test the DAB24 and DA24 components in comparison to DAB23 and DA23 and will report back.

author: YetAnotherTechie
author_rank: Regular Contributor
timestamp: August 20, 2021, 11:32:20 pm
content: Since you're new to repair, note that capacitors can fail shorted.

author: fzabkar
author_rank: Super Contributor
timestamp: August 21, 2021, 12:10:29 am
content: The first two lines of the error report appear to reflect the pin number of the 48-pin ZIF socket. The first line is the first digit, the second line is the second digit.Unless I'm misunderstanding the "X", all the errors appear to be associated with pin #24. I would start there and work inwards. That said, maybe X identifies the Grounds, so I could be wrong.

author: ShootTheCore
author_rank: Newbie
timestamp: August 23, 2021, 07:27:18 am
content: Alright, I broke out the multimeter and tested the components around DA24 and DB24. Here are closeup photos of each area:https://drive.google.com/file/d/1-oE2yIr8bD5s_TAYNtKUfiARwBXFRDKY/view?usp=sharinghttps://drive.google.com/file/d/1-oFUKbdxmCZiVx788v7J6nGEGJ5vrAdX/view?usp=sharingDA24 has a diode and a transistor.The diode passes 0.548V in forward bias and 1.2V in reverse bias. The diodes on the DA adjacent pin line circuits read 0.459V in forward bias and 1.498V in reverse bias. When measuring reverse bias, the meter slowly ticks down on Pin 24, but slowly ticks up on the adjacent pin line circuits.I didn't test the transistor.DBA24 has a diode, two resistors and a capacitor.The diode passes 0.543V in forward bias and 1.103 in reverse bias. The diodes on the adjacent DBA pin line circuits read 0.546V in forward bias and 1.520 in reverse bias.The first resistor reads 0.992 k-ohms. The equivalent resistors on the neighboring pin line circuits read identically.The second resistor reads 467.3 ohms. The equivalent resistors on the neighboring pin line circuits read 480.5 ohms and 472.1 ohmsI get no reading (0.L) on the capacitor but I get the same reading from the capacitors on the adjacent circuits. I've confirmed that I have my meter set for capacitor measurement.Next, I fired up my scope and connected the probe to the Pin 24 slot in the socket, and the probe ground to the ground rail on one of the voltage regulators.https://drive.google.com/file/d/1-qDY7CFEWXEguWFJWJUJte4KmGCZWluW/view?usp=sharingI set the scope to run a Single capture on a Pulse trigger. Then I ran the Pull Up & Down test, which recorded a failure on Pin 24 as usual.https://drive.google.com/file/d/1-b-3rKoqAFJofaKdOW0EEt-VtZFd4F6M/view?usp=sharingThe scope recorded two pulses. The first pulse is 1.9V for 91 ms. The second pulse is 4.86V for 4.4ms. Pics of the measurements along with using the Cursor to read the two pulses are here:https://drive.google.com/file/d/1-e5qdwZdNxc6TOgRSGUJXUdLwfVFcacg/view?usp=sharinghttps://drive.google.com/file/d/1-hR0ODK3aayRSn1o3TM2NtekO0Mychml/view?usp=sharingNext, I moved the probe up a few slots in the connector to Pin 18 so I could read how a healthy pin measures.Again, the scope recorded two pulses. The first pulse is 1.9V for 88ms. The second pulse is 4.8V for 26ms. Pics of the measurements along with using the Cursor to read the two pulses are here:https://drive.google.com/file/d/1-Z4rGP8WFBcDFCPCSKJN6KTzfW7duw0s/view?usp=sharinghttps://drive.google.com/file/d/1-X8etj2KHX1pYuOnXtCLWJQAAhVKJoDv/view?usp=sharingIt looks to me that there is some variance in how the two DA24 and DBA24 diodes measure compared to the equivalents in the circuits around them, but I'd have to pull them and measure them out of circuit to be 100% certain, correct? As far as the scope goes, it looks like the first pulse is pretty much the same but the second pulse is cut off abruputly for Pin 24 compared to Pin 18.Where should I go from here?

author: bdunham7
author_rank: Super Contributor
timestamp: August 25, 2021, 12:47:27 am
content: Quote from: ShootTheCore on August 23, 2021, 07:27:18 amOK, no obvious component issues there, but you obviously have a problem. Two things offhand I might try next:Check QA24 vs similar units the same way, presumably these are transistors. Try and read the part number on them and look them up.Trace the Q24 circuits to see which ICs they go to, then get the part numbers off of those, then try and find a datasheet and a reference design circuit so you have some idea what you have.

author: ShootTheCore
author_rank: Newbie
timestamp: August 30, 2021, 06:54:02 am
content: Alright, I spent some time following traces and checking continuity out from Pin 24 and sketching a rough diagram.Each pin splits off into traces in two directions. It turns out that the board labeling is misleading - I had assumed before that the "DA24" and "DAB24" circuits were referencing Pin 24 but that appears to not be the case at all.Here's a link to my diagram sketch:https://docs.google.com/presentation/d/1Mw8BIjKI3x3mwLty0FOUM8e58pu3AMW86zSsphKGFwE/edit?usp=sharingOne Pin 24 path goes through a few vias and ends up at transistor QA37. One trace of QA37 leads to some resistor packs and then to Pin 16 (DRAIN 6) on a TPIC6B259 8-bit addressable latch. The other trace of QA37 passes through diode DA37. The other side of diode DA37 shares a thick common trace with all the other DA diodes 1-48, then passes through some resistors. I didn't follow it any further.I performed diode and transistor tests as best I could with my multimeter on QA37 and DA37. They exhibited the same readings as the equivalent circuits neighboring them.The other Pin 24 path leads through a few vias and ends up at Pin 12 (DRAIN 7) on a TPIC6A259 8-bit addressable latch.I'm not quite sure where to go from here. I suppose I could connect my logic analyzer to each latch chip one at a time, run the programmer's Hardware Test, and see if there's a problem with the signals for the DRAIN pins on each latch that Pin 24 uses. Does that seem like a good strategy?Here's some pictures of the circuits.Pin 24 starthttps://photos.app.goo.gl/fuT8VYDAgQwNp2dw5Q37, DA37, HMB9https://photos.app.goo.gl/Rcte2PHPzQmXh4Bd9HBM3https://photos.app.goo.gl/Zzq3xYCh4nWDpJwq5Thank you for any assistance folks can provide!