Raytheon R21X display unit dead probably ROM needed [!!!FIXED!!!]

[TrickyNekro]

Hello guys,

I have an old unit from a small scale ship radar, more specifically I need to repair the display unit.
The unit is quite old and Raytheon (now Raymarine or whatever they have split to) no longer offers service.

The unit is unresponsive, it powers up but does nothing. I have checked thus far the CRT which is good, the power rails which are also good and ripple free.
I do suspect two things mainly, either the ROM lost the stored program which can be very problematic since I have to find a functional unit and get the program out
or it could be a failed generic IC. There are a couple 74HC221 on the board and one is definitely replaced (single Hitachi on a Toshiba and NEC board :-P).
I did the finger test, temperatures are OK, nothing overheats apart from some resistors meant for some pilot lights for the front panel, but even with the pilot lights
disconnected nothing changes.

Does someone have experience with equipment like that? Is there a way to acquire a working ROM or the .hex file, somehow?

Thanks in advance for your reply / help!
Best Regards,
Lefteris

[uncle_bob]

Hi

The internals of the ROM are the property of whoever Raytheon turned into. Passing them around frowned upon (as in they might come after you). It's a good bet they made multiple versions of the beast and multiple firmware images. You need to match up whatever the revs on the board are to the firmware image. Once you do all that, you may find that the CRT that looks ok when the unit is not fully working, is a bit dim when it is running ....

Bob

[TrickyNekro]

The internals of the ROM are the property of whoever Raytheon turned into. Passing them around frowned upon (as in they might come after you).

It´s a unit they will no longer service even if you pay them for, and that comes from their main website.
Sure it´s their property but there is no way I will be actively stealing profits, either from their sales or service department.
And in the end it´s always a matter of finding another working unit of the same series, it is just luck.
Just calling for help on the internet widens your changes.

BTW, pretty ironic comment in a forum which is beating the sh*t out of the Rigols, but I guess that in that case, it worked like advertisement. 

Now, the EPROM on the unit is an AM27C512 has the code 7DERD 0106 JRC. If someone is willing to help that would be great, or else
I am in for the long run. 

Thank you for your time and effort in advance,

Cheers,
Lefteris

[Smith]

If you have a scope, its a good idea to check the digital lines of the logic, rom, eeprom, clocks etc. Digital logic can fail without becomming hot. Sometimes the risetimes become to slow, or they can't get to a logic level, and get stuck somewhere in between.

[uncle_bob]

The internals of the ROM are the property of whoever Raytheon turned into. Passing them around frowned upon (as in they might come after you).

It´s a unit they will no longer service even if you pay them for, and that comes from their main website.
Sure it´s their property but there is no way I will be actively stealing profits, either from their sales or service department.
And in the end it´s always a matter of finding another working unit of the same series, it is just luck.
Just calling for help on the internet widens your changes.

BTW, pretty ironic comment in a forum which is beating the sh*t out of the Rigols, but I guess that in that case, it worked like advertisement. 

Now, the EPROM on the unit is an AM27C512 has the code 7DERD 0106 JRC. If someone is willing to help that would be great, or else
I am in for the long run. 

Thank you for your time and effort in advance,

Cheers,
Lefteris

Hi

Just because one company does not go in for IP protection does not mean that a company in a *very* different business also looks at it the same way.

Bob

[TrickyNekro]

Hi

Just because one company does not go in for IP protection does not mean that a company in a *very* different business also looks at it the same way.

Bob

Dear Bob,

I am trying to repair something for free for a close relative, I am well aware that the "letter" of the law gets you fined, but most of us
in our daily life follow the spirit of the law. Let´s not make this post about what is legal or what is not, I´m trying to find in the end someone,
who has experience with repairing these systems to throw around some hints and if they can some "help", when not it is like this, I´ll have to accept it. 

If you have a scope, its a good idea to check the digital lines of the logic, rom, eeprom, clocks etc. Digital logic can fail without becomming hot. Sometimes the risetimes become to slow, or they can't get to a logic level, and get stuck somewhere in between.

I do have access to a scope, although I´ll have to transport the unit. Guess a DSO can only get you thus far, that this is a toy, I can not for now check faster signals.
They do use some 74HC04 with some crystals which don´t seem to do anything although they are powered normally and the board was for sure repaired before as
there is a clear mismatch with some ICs, most are from Toshiba and then somewhere a small Hitachi with some small flux residue. 

It was a bit strange to see that they don´t use any filtering with the crystals (which I think are resonators not crystals but with no middle ground pin). Just the crystal
straight to the IC. Don´t get me wrong it works but, it´s exactly like this, you power up the thing one day and it doesn´t anymore.
Although I don´t expect to see anything with the DSO, it could have been that I would be able to see some heavily aliased signal. True enough I need access to a real
scope though, I have no illusions.

Oddly enough, most repair videos that I have seen in that sense, like from Signal Path, the problem could be with the RAM, which will be a pain the the ass to retrofit
as the original ICs are in SIP package.

I´ll get the thing under a real scope and have a go with it, it´s not that complicated after all.


BTW does someone know by experience the average data retention time for UV erasable EPROMs like the AM27C512 here? The unit should be at least 20 years old,
but the EPROM failing is really strange. In the end that´s what I was told by the previous "engineer", who had a go with repairing it. I don´t want to be biased in my
approach.


Thanks for your time and advice, for me it´s a quite interesting repair so I´ll keep you informed, if anyone has more suggestions I am in debt!

Cheers,
Lefteris

[uncle_bob]

Hi

Retention life on most eproms is rated to be around 20 years. It is highly dependent on operating environment (temperature). There have been a number of issues both with eproms and mask roms over the years. Some batches / processes turned out to be far less reliable than they should have been. Of course, the same can be said for the MCU on the board.

We seem to be focusing in on the memory pretty quickly. Are you sure that the processor is working properly? A dead crystal on the MPU would pretty much explain all the symptoms you have reported.

Bob

[TrickyNekro]

Retention life on most eproms is rated to be around 20 years. It is highly dependent on operating environment (temperature). There have been a number of issues both with eproms and mask roms over the years. Some batches / processes turned out to be far less reliable than they should have been. Of course, the same can be said for the MCU on the board.

The unit if not completely water proof it is water resistant, the vertical driver for the CRT seems to get hot but on the safe side and some filtering ferrites on the output of the push pull driver
of the power supply, still nothing abnormal. Switching transistors are backplate heatsinked. The metal body seems to protect the logic board against direct heat, so judging by volume it
shouldn´t get more than +20°C ambient in the enclosure. Though problem is summers can be really warm in Greece, you could be looking at +38°C or more during the day.
I have to say though, for a unit to be so close to the sea, it didn´t seem to have any problems with corrosion, although that´s something I would want to triple check. Plus I have no idea to
which extend the unit was used. Before I opened it though I really expected to see many many bad things, given the age, I was quite positively surprised.

We seem to be focusing in on the memory pretty quickly. Are you sure that the processor is working properly? A dead crystal on the MPU would pretty much explain all the symptoms you have reported.

No idea, but oscillators generally, and there are many on the board, are something that I definitely want to be checking. When they gave me the unit, they told me that it just didn´t work
the last time they powered it up and it´s been like this ever since. I need access to a serious scope for that, they got some TDS1002 here in the university, but I have to bring the thing from
my home here and preferring to commute with the bicycle hasn´t help. It´s not heavy but it´s quite cumbersome. Doesn´t seem that I can avoid it though.

I guess that would be enough material for now. I´ll bring it to the university next week and I´ll give it a try here.

BTW, I have already tried the "place it in whatever the f*** orientation" to see if the problem is thermomechanical. Still it didn´t bodge... Meh...
Although one time that I placed it in a specific orientation, I recall something like a beep but that´s a bit of a witch hunt.

Thanks for your reply,

Cheers,
Lefteris

[uncle_bob]

Hi

I would *guess* that it is far more likely to be a power supply capacitor than anything else. Both tantalum and aluminum electrolytic caps are prone to die over time. When they do, something else in series with them may open up ... no heat ... no obvious smoke. Next on the list for "completely dead" is anything in the boot up process. Oscillators are an easy thing to check and fairly simple to fix. Reset lines and power management IC's are next on the list, not quite as easy to check or fix. Even with bad ROM's / data lines / address lines, most gear will still boot and give some indication of life.

Bob

[TrickyNekro]

Even with bad ROM's / data lines / address lines, most gear will still boot and give some indication of life.

This is exactly what got me thinking all the time over and over again, some distorted graphics maybe repeated boot loops, something like this
but not completely dead. From memory speaking most caps are ceramic or electrolytic, even for decoupling. But there are also some old style "rolled" film capacitors.

Thank you for the confidence vote :-)

[uncle_bob]

Hi

First step:

Take a critical look at all the caps. If one looks at all bad, just replace it. Use a DVM to make sure they all have some sort of voltage on them. If you find one with zero volts, trace back the connection and replace the series resistor or coil.

Second step: I believe it's a CRT device from what you have said. The high voltage supply is the next suspect. Unfortunately a high voltage probe is about the only easy way to check it without a schematic. They are cheap and you may be able to borrow one.

Bob

[SeanB]

The crystal can fail, so either replace it with another of the same frequency or simply unsolder it and turn it around and solder it back in. this often does get it oscillating again for a while. Otherwise with a scope check the power rails for ripple ( bad caps) and that there actually is a clock to the microprocessor, along with a reset signal ( of the appropriate logic level to enable it to run, depending on the processor used) being there.

[CJay]

Voltage rails, clock signals, reset lines, all things to check and make sure are working before you go pulling bits out or replacing stuff.

[TrickyNekro]

So ladies and gents success story!!!

So, I got the thing under the scope, checked clocks all good, checked rails all good!!! So I started checking the memories and the fun begins!

It so seems that it the SRAM(HM6264) in the thing was battery backed through a battery control IC(PST532). So the Vcc of the SRAM was supplied by this IC.
Somewhere in the vicinity there was also a "suspiciously looking" electrolytic cap which has decided that the happy puppy days of hard work were over.
Honestly it was pretty difficult to spot on the first or second pass having a ton of things in the way in between :-/

Long story short, the acids had vanished a hair thin trace which was transferring power to the SRAM. TRAP FOR YOUNG PLAYERS, the SRAM is CMOS
so when powered the VCC was looking good!!! Only some tinny glitches on the rails would perhaps suggest second thoughts but still they were not big enough
to actually consider poor decoupling.

Some bogie bogiety bogie time later, voila! It gave the beep of life and here I am with a happy puppy back to business!




Thanks for your support and inspiration!
Best regards,
Lefteris, Greece

[jonathanscottjames]

i wish i knew where the parameter is to make the range go to 170miles.
does anyone know if a modified satellite tv receiver lnb in place of the mic would lower the noise on the rx?
and would a pi3 with an 8bit  50msps adc  be better than the 21xx computer proscessing?
and is there a generic radar vector video computer?
and will a Navico work? what is a Navico?