AOIP SA 32 - Page 1
Forum section: electronics / testgear

author: masterx81
author_rank: Frequent Contributor
timestamp: January 04, 2025, 09:16:20 pm
content: Hi to all...I have an AOIP SA 32 that i've bought cheap as spare parts for another AOIP device (a really nice AOIP PJ 6301) that i've recently repaired (thanks the valuable help of the forum), but this one it's in bad shape, seem also a "mix" of 2 different devices (probably someone have mixed the boards for have one device working).I've bought it mainly for the display, but the display have the backlight not working. I've already repaired the inverter, and ordered the new el sheet.The logic board else seem quite fine, and the lcd will be soon ok.So, why not try to get it working?Now i'm trying to repair the analog board, as i get an error of communication between boards.The boards communicate via a couple of photodiodes/phototransistors. For first thing i've checked the voltages, and are all "quite" fine. The 5v is a bit unstable, i think due the lack of some sort of voltage regulator (there is only a switching with a feedback on the primary winding), but this isn't causing (now) problems as i've tryied to stabilize it with an external psu and nothing changed.So i've followed the path of the output of the phototransistor, and after some hex inverter it goes to an unpopulated socket.Someone have some photos of what sort of ic can be in those sockets?And here, the photo of the board:Thanks!

author: masterx81
author_rank: Frequent Contributor
timestamp: January 05, 2025, 05:02:34 pm
content: Little update.After searching a bit more, i've found that a track from the phototransistor (after the inv. Buffers) was going via an inner layer (this board have more than 4 layers...) to the main cpu (nec uPD70320L). Maybe those sockets are fine unpopulated.So, i can confirm that the cpu is receiving the command. Then i've checked if the cpu was able to respond to the command, and all seem fine on the tx diode. Simply, the cpu desn't answer to the received message (no signal on output pin).Then, i've checked if the data and address buses from cpu to the eprom were fine, and i can confirm that all the addresses and data lines are ok (i see with the logic analyzer that all the lines are working, and that there is an active data exchange).While i was here, i've made a dump of all the eproms (also backed up the eproms of the pj6301...).I tought that maybe was a cpu failure, and in this case i've tried to swap logic board cpu with analog board cpu (they are the same), with same result (rx ok, no tx on acq board)...I hope that the cpu isn't responding due to a mismatch on what the logic board is sending, and what the acq board is expecting to receive (due to a "mixup" of boards). This will be a problem.Sooooo, what would be the next step?Thanks for the help...----After futher search, seem that the cpu works correctly for almost 1 second, i see it from the crystal oscillating. Then it stop the crystal, and doesn't do anything anymore. If i reset it manually (reset pin to gnd), it start working for 1 sec, etc.Actually, the cpu was resetting itself via a watchdog to a power management ic (max691) in loop, so i've disabled this reset, but the cpu still stops working.What can cause a cpu to hang so much that disable the oscillator?Thanks!---While searching something bad, i've tried swapping the upd431000 with the logic board (as i not have a tester that can test it), i've read the p28f256 content, erased, tried to write a custom pattern and verify, and all is ok, so i've wrote back it's original content.The only thing that i wasn't able to test is the bq3287, seem that my tl866 can't read it. I hope that it not had some bytes inside, and that the integrated battery is dead.Also the gal seem fine, as i correctly get signals on almost all the pins.In the near 1sec that works after the power on, it write on both flash and sram (write enable pin active).I really not know what can cause a total shutdown of the oscillator chip of the cpu. I have fear that i need to disassemble the eprom content for know why the cpu crash, as phisically seem almost all fine.I have the feel that the code can't do something, and crash/stop execution (seem that the halt instruction will actally stop the clock).----Some more findings, the 5v live was a little bit unstable due to the continous stall of the cpu. Every time the watchdog from the cpu was missing, the MAX691 was issuing a reset.Said so, i've found 5 point in the assembler where is issued an HLT command (used ndisasm for disasseble), but i suspect that the hlt must not be a normal occurence (ie: stop waiting an interrupt from -for example- a serial buffer receive), as there is the watchdog (a square wave signal) that must be issued to the power management IC continuously.

author: masterx81
author_rank: Frequent Contributor
timestamp: January 13, 2025, 12:03:58 pm
content: This thing have almost every type of storage available at that time...27010 EPROM program memoryExternal uPD431000 128k*8 SRAM (the mcu have already 256by on the mcu itself)External P28F256 32k*8 FlashExternal X24C01P 512*8 EEPROMBackup battery for the analog boardMain battery for the whole unit.In the meantime, i'm trying to understand why the cpu hang... In past i've worked asm on RISC architecture, but a disassembled 8086 is way more difficult to understand.I've also mapped every I/O of the cpu where is connected, for try to understand why it stop working after almost 1 second (for example is there is an input that notdo what is supposed to).

author: squadchannel
author_rank: Frequent Contributor
timestamp: January 13, 2025, 01:48:02 pm
content: corrupted data in NVRAM(bq3287)?

author: masterx81
author_rank: Frequent Contributor
timestamp: January 13, 2025, 05:30:48 pm
content: Good question... My programmer doesn't support that type of chip, but all other devices that have a custom programming inside have a label. The RTC/NVRAM doesn't have it,as the 24c and the flash. I hope that those devices are wrote during the use...If that is the case, the disassembly of the code in eprom is the only thing to bring it back to life...

author: coromonadalix
author_rank: Super Contributor
timestamp: January 13, 2025, 06:01:28 pm
content: i would politely remove the main cpu, and re-seat it, those's sockets are sometimes expanding and or creating bad contactsfor sure the bq3287 is year 95 ?? if not mistakenis the MAX662 okayhttps://www.analog.com/media/en/technical-documentation/data-sheets/MAX662A.pdfand you have voltages test points do theses are okay as you said, some opto's can get bad over time

author: masterx81
author_rank: Frequent Contributor
timestamp: January 13, 2025, 07:44:41 pm
content: I've already switched the cpu with the digital board, and nothing changed. The socket is fine.The bq3287 is OLD, as the other things inside. I'll replace it with a necroware unit (bq3285+normal button battery).The variuos voltages are fine (+/-15, and two different 5v.The max 662 generates correctly the 12v Vpp needed for flash programming...In the next days i follow the traces of every cpu pin, and check what is connected to, and of all ok...

author: masterx81
author_rank: Frequent Contributor
timestamp: January 17, 2025, 08:28:29 pm
content: While searching for what isn't working on the analog board, it's arrived the el sheet for the backlight from aliexpress.On the left the original, on the right the new one.Quite good result.

author: masterx81
author_rank: Frequent Contributor
timestamp: January 18, 2025, 02:24:36 pm
content: I'm quite happy as it started working... but i've not done anythingI've desoldered some components, replacend minor things that anyways tested ok, done a lot of measurements for trace connections, etc. And now seem to work as nothing happenedNevermind, stopped working after few minutesOne thing that i've done, was erasing the flash and eeprom content.---Got it! There must be something wrong in the flash content, if i erase the flash content, it works ok, when i write something back to the flash, it cause the cpu to stop working. Or the flash is damaged, or it can't read/write correctly to it.----Quite strange, the flash itself seem fine, if i fill it with random data, write a verify on the tl866, it never fail. But if the device write on it, when i power off an then back on the unit, hangs the cpu, as if it had written wrong data on it. I've already checked the max662 that generate the vpp, and it generate the 12v, but maybe worth trying to check the pump capacitors, as if the vpp isn!t stable, i think that it can cause some problems----I've ordered some spare flash memories... The signals from the cpu are all fine (address and data), the capacitors of the chargepump for vpp are fine... i!ll try to replace it, as i not know what can be wrong.In the meantime i've used it a bit, it's not easy without an instruction manual, but i've managed to understand how it works. It's a nice unit! For sure can be useful in some occasion a 32 channel with 1 common wire every group of 4 input, or 16 individual channels or 8 in 4 wire... plus one "bonus" front input.Measure v, ma (with external 50ohm shunt), thermocouples, etc.I miss the back connector, i can't find the manifacteur.I've found online an image of the connector:Anyone know what type is?Another problem, is that i need to identify the serial protocol, or get my hands on the original software... it's a shame to have this unit and use it offline.Maybe worth asking directly at AOIP...

author: masterx81
author_rank: Frequent Contributor
timestamp: February 06, 2025, 09:48:50 pm
content: So, little update...I've bought 2 flash P28F256A (Old intel) from aliexpress. I've tested them on the programmer, checked with the original one removed from the unit and... with little more than 1$ seem that i've got 2 genuine flash chips. I've mounted one on the unit, and... it works! When i save the program values on the flash, the analog board start correctly without hanging on startup. I not understad what had wrong the old flash memory, tested good on the programmer. Filled with random data, and reread, and all was fine. Maybe have slowed down a bit, so that with the programmer all was going good, but when wrote by the unit, eventually was wrote a bit faster than the programmer and failed.In any case, i'm happy!Every startup i get a strange warning:wrong checksum of the DVM coeff.I really not know what to check. In any case the unit works well also with this warning.Seem a bit out of cal, but not too much.As a maintenance routine i've also replaced the 3v battery on the logic board. The old wasn't discharged, but in this way i not need to worry about it.AOIP never ansered me back, so i not know where source the back connector, and also i not know where get the license of the software.Anyone have an idea on where i can source the back connector?Thanks!

author: masterx81
author_rank: Frequent Contributor
timestamp: February 10, 2025, 07:44:02 pm
content: Found a compatible connector.Ept 108-40074Perfect match! Now i can do a little board to adopt some 5.08mm spaced screw terminals, or i solder the terminals directly over the connector. I think that it can do the job.---Bought 16 of this:https://it.farnell.com/phoenix-contact/smkds-2-5-2-5-08/blocco-term-pcb-5-08mm-bifase/dp/1793040Hope that they arrive soon...

author: masterx81
author_rank: Frequent Contributor
timestamp: February 13, 2025, 09:10:23 pm
content: And this is the result.It not has any secure locking it, but the friction of the contacts have quite a good grip.

author: masterx81
author_rank: Frequent Contributor
timestamp: February 15, 2025, 04:39:53 pm
content: Some new safety binding posts that had laying around, replaced some backup batteries that it had (3.6 80mah original nicd, replaced with compatible ni mh), used tonpower the analog board for short period of time without supply, and it's almost ready.Checked the accuracy vs the other meter that i have, and not seem too much out of cal.Checked only the fron connector, as it's quitentime consuming check 33 channels 😅-Pj6301 range 600mv out set to 50mv: pj 49.9982 hp 49.9972 sa32 50.000 fluke 87v 50.007.-Pj6301 range 600mv out set to -50mv: pj -50.0006 hp -50.0013 sa32 -49.994 fluke 87v -49.998.-Pj6301 range 600mv out set to 500mv: pj 500.006 hp 499.996 sa32 499.990 fluke 87v 500.00.-Pj6301 range 600mv out set to -100mv: pj -100.003 hp -99.9998 sa32 -99.990 fluke 87v -99.99.-Pj6301 range 6v out set to 5v: pj 5.00001 hp 4.99999 sa32 5.00074 fluke 5.0004In any case i've tested all the inputs, and the voltage read was the same for all the inputs, so i think that is good enough.I still have this warning:But not seem to affect how it works. Anyone know what is a "DVM Coefficient?"Still need to manifacture a new back panel (as when i've bought it wasn't present). And it's ready to be added to the bench.