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Old 05-03-2014, 12:05   #1
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Autohelm ST6000 Repair - Service Manual

Hello everybody,I'm trying to repair an old autohelm st6000 autopilot and i'm looking for the service manual where i can find the schematics of the course computer.
The model i'm trying to repair is the one with the Z051 course computer which has a philips microcontroller MAB 8049H P A135.If you have the service manual i can send my email address via PM.

I think the microcontroller is not working properly or is broken because when i power up the system all i get is a short been and a blank screen on the display unit.
The course computer was working fine,reading values from the fluxgate and displaying on the screen standby and auto mode,but while i was fixing the power amp board i probably shorted some contacts and damaged the microcontroller.

On the course computer board there is an EEPROM chip which i think store the program the microcontroller runs so if i replace the microcontroller with a new one,a blank one,it should work again fine,what do you think?
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Old 05-03-2014, 13:05   #2
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Re: Autohelm ST6000 Repair - Service Manual

You can get the datasheet for the microcontroller here:
philips 8049H datasheet & application note - Datasheet Archive
I'm not sure if you can buy them anymore.
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Old 05-03-2014, 13:26   #3
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Re: Autohelm ST6000 Repair - Service Manual

You can buy em pretty easily - but the problem will likely be the internal ROM in the controller. There's 2K of onboard mask rom on the microcontroller - the eprom is likely additional data or more program. 'because if they didn't mask the 2k, why not use a 8039 instead? I'm not sure, but I think my aged ST4000 has an 8749 in it - but don't count me on that.

If you're lucky, they got surplus 49's cheap (masked wrong) -and slaved em external. If pin 5 (EA) is pulled high all the time, it's gonna only use external ROM and you can replace the processor with any 8039 or 8049. Look at the datasheet for pinouts.

I'd check VPP first, make sure that's 5v.
Then check the xtal inputs to see if it's clocking. PSEN will also be toggling away if the CPU is functional.

8039's should be about a buck in qty 1 lots. Surplus 49's may be pennies.
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Old 05-03-2014, 14:09   #4
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Re: Autohelm ST6000 Repair - Service Manual

Quote:
Originally Posted by jeepbluetj View Post
You can buy em pretty easily - but the problem will likely be the internal ROM in the controller. There's 2K of onboard mask rom on the microcontroller - the eprom is likely additional data or more program. 'because if they didn't mask the 2k, why not use a 8039 instead? I'm not sure, but I think my aged ST4000 has an 8749 in it - but don't count me on that.
I was hoping there was no use for the 2k onboard ROM and that the complete program was saved on the external EEPROM chip.I'm not sure i understand well(English is not my mother tongue)are you saying that the 8749 has no internal ROM?

Quote:
Originally Posted by jeepbluetj View Post
If you're lucky, they got surplus 49's cheap (masked wrong) -and slaved em external. If pin 5 (EA) is pulled high all the time, it's gonna only use external ROM and you can replace the processor with any 8039 or 8049. Look at the datasheet for pinouts.

I'd check VPP first, make sure that's 5v.
Then check the xtal inputs to see if it's clocking. PSEN will also be toggling away if the CPU is functional.
Thanks this are some useful informations,I'll check these pins but I'm not really sure how to do the measurements.I checked VPP and it's reading 5V with the multimeter;to check if the EA pin(which is pin number 7 on the 8049) i just put the positive rod on the pin and the negative rod on the negative of the power supply?How do i check the xtal pins and PSEN?
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Old 05-03-2014, 14:10   #5
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Re: Autohelm ST6000 Repair - Service Manual

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Originally Posted by azsailor12 View Post
You can get the datasheet for the microcontroller here:
philips 8049H datasheet & application note - Datasheet Archive
I'm not sure if you can buy them anymore.
Thanks i already have it
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Old 05-03-2014, 14:58   #6
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Re: Autohelm ST6000 Repair - Service Manual

The 8749 was the on-board EPROM version. That would leave me to believe the on-board ROM is used on my st4000. However, these were very small-run devices. The 6000 is different. Autohelm may have thought it better to not mask the rom, and just use external ROM. Since that's an EPROM on your board, it may be the case. (EPROMs weren't cheap to buy or program but much cheaper than the 8749 versions of the CPU)

Looking at EA is the definite way to test to see if the internal ROM is used.. Yup, it's pin 7, pin 5 was wrong. As far as I know, all of the manufacturers of the 8049 derivatives used the same pinout. You can follow the traces from pin7 to see if it's pulled low or high. Or look at the voltage when it's powered up.

The xtal pins are best checked with an oscilloscope.

PSEN and ALE can be checked with a cheapie logic probe (like http://www.amazon.com/Elenco-Electronics-LP-560-Logic-Probe/dp/B000Z9HAP4)

In general, if it's clocking and generating buss traffic (PSEN, ALE, RD) - the CPU is running.
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Old 05-03-2014, 15:32   #7
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Re: Autohelm ST6000 Repair - Service Manual

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Originally Posted by jeepbluetj View Post
The 8749 was the on-board EPROM version. That would leave me to believe the on-board ROM is used on my st4000. However, these were very small-run devices. The 6000 is different. Autohelm may have thought it better to not mask the rom, and just use external ROM. Since that's an EPROM on your board, it may be the case. (EPROMs weren't cheap to buy or program but much cheaper than the 8749 versions of the CPU)

Looking at EA is the definite way to test to see if the internal ROM is used.. Yup, it's pin 7, pin 5 was wrong. As far as I know, all of the manufacturers of the 8049 derivatives used the same pinout. You can follow the traces from pin7 to see if it's pulled low or high. Or look at the voltage when it's powered up.

The xtal pins are best checked with an oscilloscope.

PSEN and ALE can be checked with a cheapie logic probe (like http://www.amazon.com/Elenco-Electronics-LP-560-Logic-Probe/dp/B000Z9HAP4)

In general, if it's clocking and generating buss traffic (PSEN, ALE, RD) - the CPU is running.
Many thanks!
A quick check with the multimeter on the EA pin reads 5 Volts;The pcb has two layers so it's not so simple and i don't have the schematic,but I'll try anyway to follow the traces and see where it goes.

I'll try also to check if the CPU is running measuring the clock and the traffic on PSEN and ALE as you suggest...just need to find an oscilloscope and a logic probe.

So in conclusion:


If pin EA is pulled high the microcontroller can be swapped with another new one without any firmware needed because everything is on the EPROM external chip.

If there is no clock or bus traffic the microcontroller is not working and need to be replaced.

Is it right?
Thanks for your help i will try to find a new microcontroller and see if everything else is allright.
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Old 05-03-2014, 15:45   #8
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Re: Autohelm ST6000 Repair - Service Manual

Yes - If EA is a solid 5v, the internal ROM is never used. (Unless something very odd was done, like booting internal then changing to external.. Most folks wouldn't do that but who knows... You couldn't tell without a schematic or lots of poking around)

No clock or buss traffic does indeed mean that the microcontroller is not running. If so, check Vdd - if that's held low (IIRC, check the datasheet) the processor is forced into a low-power standby mode.

Other circuitry on the board may be to blame - i.e. the microcontroller may be fine, but other inputs cause the software to crash quickly.

But it it was mine, I put in a socket and try another processor. An 8039 should work just as well as a 8049.

Barring that - I assume you're looking for a used head unit.
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Old 05-03-2014, 16:51   #9
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Re: Autohelm ST6000 Repair - Service Manual

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Originally Posted by jeepbluetj View Post
Yes - If EA is a solid 5v, the internal ROM is never used.
Ok following the traces on the pcb pin EA is definitely pulled high on 5V.

Quote:
Originally Posted by jeepbluetj View Post
(Unless something very odd was done, like booting internal then changing to external.. Most folks wouldn't do that but who knows... You couldn't tell without a schematic or lots of poking around)
Hope nothing like that was implemented on this board

Quote:
Originally Posted by jeepbluetj View Post
No clock or buss traffic does indeed mean that the microcontroller is not running. If so, check Vdd - if that's held low (IIRC, check the datasheet) the processor is forced into a low-power standby mode.
Checking the traces on the pcb VDD seems permanently connected to 5V...

Quote:
Originally Posted by jeepbluetj View Post
Other circuitry on the board may be to blame - i.e. the microcontroller may be fine, but other inputs cause the software to crash quickly.

But it it was mine, I put in a socket and try another processor. An 8039 should work just as well as a 8049.
Assuming the microcontroller is fine will I be able to see normal clocking and bus operation even if there is something else on the board that cause the software to fail and crash quickly?

Quote:
Originally Posted by jeepbluetj View Post
Barring that - I assume you're looking for a used head unit.
Well actually the autopilot I'm trying to fix it's not mine,but the owner maybe will buy a replacement part or a used unit if he can find one.
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Old 05-03-2014, 16:59   #10
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Re: Autohelm ST6000 Repair - Service Manual

Iirc. An 8049 will just keep running when it crashes. May need to look to see if there is a sleep instruction but it's a pretty good bet you'll get some sort of clocking on ALE if it's running.
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Old 05-03-2014, 17:36   #11
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Re: Autohelm ST6000 Repair - Service Manual

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Originally Posted by jeepbluetj View Post
Iirc. An 8049 will just keep running when it crashes. May need to look to see if there is a sleep instruction but it's a pretty good bet you'll get some sort of clocking on ALE if it's running.
Ok so i can check if the microcontroller is working or if it's something else on the board causing the problem;need a logic probe.

Thanks again for your help
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Old 06-03-2014, 08:57   #12
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Re: Autohelm ST6000 Repair - Service Manual

Checked PSEN, ALE and RD with a logic probe:

PSEN - flashing

ALE - flashing

RD - high

Does this mean the microcontroller is in working condition?
I can't check the xtal pins because I don't have an oscilloscope but maybe the fault is on another component of the board...need to find the schematics.
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Old 06-03-2014, 09:50   #13
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Re: Autohelm ST6000 Repair - Service Manual

Yup. That means that the microcontroller is likely in working condition. It may just be looping around aimlessly because the instruction decoder is bad but the clock and bus fetch stuff is good, but that's not very likely. If you had the source and an ICE, it'd be easy now... But nobody has that stuff.

Next step, I agree that you do need to find the schematics, or one that works to compare it to.

Blast from the past, I haven't looked at a pinout for a 8049 for 20+ years. wow.
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Old 06-03-2014, 10:55   #14
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Re: Autohelm ST6000 Repair - Service Manual

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Originally Posted by jeepbluetj View Post
Yup. That means that the microcontroller is likely in working condition. It may just be looping around aimlessly because the instruction decoder is bad but the clock and bus fetch stuff is good, but that's not very likely. If you had the source and an ICE, it'd be easy now... But nobody has that stuff.
What is an ICE?
Anyway now I don't know if it's worth to buy a new micro and try the swap,hoping that it will work again

Quote:
Originally Posted by jeepbluetj View Post
Next step, I agree that you do need to find the schematics, or one that works to compare it to.
This schematics seems to be impossible to find...I'll look if I can find a used working board...

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Originally Posted by jeepbluetj View Post
Blast from the past, I haven't looked at a pinout for a 8049 for 20+ years. wow.
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Old 06-03-2014, 13:40   #15
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Re: Autohelm ST6000 Repair - Service Manual

An ICE == In Circuit Emulator.

I personally don't think it's the CPU. But hey, it may be. It may be the ROM - i.e. you could write a really simple toggle a output port program and burn a rom and test it. All of this is likely way more work than an aged autopilot deserves.
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