Author Topic: IFR repair? SPECTRUM ANALYZER ! king has died (Read 46862 times)

vaualbus · « **Reply #100 on:** August 09, 2013, 08:56:21 pm »

Do you have make some more progress on the repair?

Rerouter · « **Reply #101 on:** August 09, 2013, 10:08:13 pm »

golden rule of old test equipment, always backup roms before repair, still more and more a dead CPU is sounding like a problem in my own 68K based unit so i thank you for going through everything you tried,

SArepairman · « **Reply #102 on:** August 09, 2013, 11:07:07 pm »

im in the process of replacing every component on a board that experienced 12V on the 5V rail (thankfully no memory or anything) due to my negligence

i took a break for a while, I am just replacing all the jellybean parts on all the modules that are shady.

Still waiting on a DAC from china though.

If I get it to the point where it was before I will hook up a nice logic analyzer to things to try to get a feel for what is going on.

maybe replacing 50$ of this 7400 series crap will fix it.

senso · « **Reply #103 on:** August 09, 2013, 11:14:32 pm »

You should have a little bit more care, you keep over volting and reversing the voltage everywhere

SArepairman · « **Reply #104 on:** August 10, 2013, 01:59:55 am »

Quote from: senso on August 09, 2013, 11:14:32 pm

You should have a little bit more care, you keep over volting and reversing the voltage everywhere

yea I spend too much time on it in one sitting and get frustrated, I have trouble taking breaks

eventually my self imposed economic warfare will translate to carefullness though

SArepairman · « **Reply #105 on:** August 13, 2013, 12:14:30 am »

I can't figure why the thing won't display anything, power rails are ok...

how do these old machines typically boot up? I can see the clocks are working

i am getting very sick of this thing it was wayyy beyond my ability

Rerouter · « **Reply #106 on:** August 13, 2013, 08:30:22 am »

in my ones case, it is held idle by a reset signal while it waits for the 5V rail to become stable, then after a time constant releases it, the CPU then scans through its address lines until it finds an instruction and goes from there

SArepairman · « **Reply #107 on:** August 13, 2013, 06:55:22 pm »

Well it looks like this unit has two inverters connected to the reset line of the z80, I am guessing thats acting as a delay.

I will probe a bunch of stuff with the logic analyzer to see if there is any activity on startup, hopefully its not hanging when it tries to read the roms

SArepairman · « **Reply #108 on:** August 13, 2013, 07:45:57 pm »

Hmmm I wonder why the reset line has a square wave on it, I don't think hex inverters without feedback should be generating square waves....

The reset line goes to multiple boards but as far as I know it should be be sunk by anything its connected to (they all appear to be inputs)...

hMMMMMMMM

Rerouter · « **Reply #109 on:** August 13, 2013, 08:24:46 pm »

if its a square wave then it could be the watchdog timer, something making it unhappy or a general timeout for a status update,

SArepairman · « **Reply #110 on:** August 13, 2013, 08:28:04 pm »

Quote from: Rerouter on August 13, 2013, 08:24:46 pm

if its a square wave then it could be the watchdog timer, something making it unhappy or a general timeout for a status update,

But as far as I know none of those chips has the ability to pull to ground, they are all inputs.

Rerouter · « **Reply #111 on:** August 13, 2013, 08:37:11 pm »

what about on the CPU board, something feeding in to the inverters,

for reference here is the schematic for my Motorola 68000 based ones reset and watchdog,

unless it pulls low "TIMCLR" in the upper right LOW in under 64ms it will trigger a reset, (also worth noting the INIT line on mine is an open collector output so until i probed it it was possible for other boards to pull it down,

mine ended up with a reset roughly 4 times a second thanks to the big time constant, and I'm now tracking down what may be causing the timeout,

hope it helps,

SArepairman · « **Reply #112 on:** August 13, 2013, 09:20:38 pm »

Quote from: Rerouter on August 13, 2013, 08:37:11 pm

what about on the CPU board, something feeding in to the inverters,

for reference here is the schematic for my Motorola 68000 based ones reset and watchdog,

unless it pulls low "TIMCLR" in the upper right LOW in under 64ms it will trigger a reset, (also worth noting the INIT line on mine is an open collector output so until i probed it it was possible for other boards to pull it down,

mine ended up with a reset roughly 4 times a second thanks to the big time constant, and I'm now tracking down what may be causing the timeout,

hope it helps,

I need to study that more but the inverter is just hooked up to the 5V line.. I figure the delay caused by two inverters is enough to let the thing stabilize?

5v -> inverter -> inverter -> z80 reset pin

Rerouter · « **Reply #113 on:** August 14, 2013, 07:01:11 am »

unless they are also open collector outputs, e.g. 74LS05 with a RC time constant on one or both, i would very much say not, the time delay of 2 unloaded inverters is approaching nanoseconds, equally that would mean it would be releasing the reset line at ~3V which makes near no sense,

unless you have a schematic to share it really sounds like you haven't traced it out right...

SArepairman · « **Reply #114 on:** August 14, 2013, 10:44:01 pm »

Oh no, its from the schematic.

There is a RC delay in the first inverter (which I forgot to mention)., 47uF-33kohm.

SArepairman · « **Reply #115 on:** April 19, 2014, 06:44:30 pm »

ok, I found A problem.

when i desocketed all the chips I mentioned the unit stopped working, it has been siting on a shelf for a long time. I went back to it and had a look, the custom character ROM chip cracked.. i guess it took a while for the strain to actually break the chip visually.

nightmare scenario

bloody hell de solder those chips or cut them out of circuit with a dremel never ever touch those fucking 30 year old sockets!!!

vaualbus · « **Reply #116 on:** April 19, 2014, 10:32:37 pm »

really you can't use a normal rom and program on it the program?

SArepairman · « **Reply #117 on:** April 20, 2014, 02:26:43 am »

Quote from: vaualbus on April 19, 2014, 10:32:37 pm

really you can't use a normal rom and program on it the program?

I don't have the program. All I have a half opened chip that says A8000 CHAR on it, on a little piece of paper. I just wanted to resocket the chips, as this is a common trouble shooting method.

IFR was utterly useless when I contacted them about the A8000, my only hope is that some other hobbyist will one day risk taking it out of their machine and giving me a image of it... then I just need to hope there are no revision changes....

unobtanium.

i think I am going to take it out into a field some where and shoot it while its not looking at me...

vaualbus · « **Reply #118 on:** April 20, 2014, 09:05:53 am »

Put them on ebay at least you will earn something.
In the forum there will be someone that can help you.
I wish it because this posts are very interesting.

SArepairman · « **Reply #119 on:** April 24, 2014, 06:03:47 am »

Quote from: vaualbus on April 20, 2014, 09:05:53 am

Put them on ebay at least you will earn something.
In the forum there will be someone that can help you.
I wish it because this posts are very interesting.

I am going to look at the chip under a microscope, maybe only bond wires broke

re-reading this makes me feel rather silly (at my witch hunt tactics and short temper) but I am still proud of even attempting such a task... david vs goliath

nothing a bit of white fuming nitric acid cannot decapsulate. its quite easy to make a few ml of 90%+ using drain cleaner and food preservatives with ghetto distillation techniques, or so it seems. I think you only need a drop or three. so long your starting reactants are devoid of water then the nitric acid produced is of much higher purity then the commonly available 70% NA.

I am defiantly NOT Paying for commercially made WFNA though. those prices are scandalous. not for this "corpse"

all those people buying expensive nitric acid for decapsulating chips are probably being ripped off. you can re-distill it over dry sulfuric acid several times to increase the purity to anhydrous, especially for the drop or two required for chip die extraction,

all yoou need is a test tube and a candle. you mix the ingredients and heat to start the reaction, then you insert a clean but cold nitric acid resistant object into the test tube (such as a narrower test tube or glass rod that was stored in a freezer), but not as to touch the liquid. the pure nitric acid vapors will condense on the cooled object, which you then pull out of the test tube and swab onto your chip.

also this should be done outside with a fan blowing over your work bench so you do not get any nitric acid fumes in your lungs. from what I understand it will choke yoou, burn your lungs and give you cancer. treat it like plutonium.

vaualbus · « **Reply #120 on:** April 24, 2014, 10:43:06 pm »

Don't know that "procedure".
Let's update on the situation as soon as you have make progress.

hpbo · « **Reply #121 on:** May 30, 2015, 07:46:21 pm »

Better late than never!
Here are the ROM images from my IFR A-8000.
I hope they will help to bring your king back to live.

SArepairman · « **Reply #122 on:** May 31, 2015, 02:55:14 am »

Quote from: hpbo on May 30, 2015, 07:46:21 pm

Better late than never!
Here are the ROM images from my IFR A-8000.
I hope they will help to bring your king back to live.

my god

jimmc · « **Reply #123 on:** March 25, 2020, 05:23:04 pm »

Quote from: hpbo on May 30, 2015, 07:46:21 pm

Better late than never!
Here are the ROM images from my IFR A-8000...

Just to correct the record (5 years late):

There is a slight error in the CP_U11_3271-5409-340_v3.4_F32E.BIN file, U11 is a 27128 (not a 27256 as U9)
The file should be half the size at 16384 bytes and the checksum 7997.
Inspecting the contents of the file shows that the first 16384 bytes are repeated in the second half (ie 0000-1FFF is repeated from 2000-3FFF)

I have imaged the EPROMS in my own analyser and can confirm that, with the exception of the above, all of the checksums agree.

Jim


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Author Topic: IFR repair? SPECTRUM ANALYZER ! king has died (Read 46862 times)

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