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Dr A. 33 1.5IE

Hello everyone,

although this is my first post I 've been following this forum for some time now.
As many people before me I 've seen to face problems regarding the rev-meter of their AR33. There is something else they could try after they clean up the electrical contacts behind the instrument cluster; if you take out the rev0meter from the instrument casing, underneath the circuits of the instrument you can see a screw-regulator kind of thing. It actually calibrates the needle position at idle speed. Spray that screw with some electrical contact cleaner and turn it several times from side to side. In order to calibrate the position of the screw at idle you need to connect the rev-meter somehow to the instrument casing again. That worked perfectly from me!!!

Now here is my question. I also tried to clean up the tachometer instrument. Unfortunatelly I removed the tachometer clock showing the total Kms (around 172000 kms) and whatever I did although it works I never managed to align the numbers next to each other!

Can anyone help with that??? Confused

Alfa 33 1.5 IE (An Athenian now in Nicosia)

chrisc not loggedin · Guest

I wouldnt bother. Ive owned/currently own 2 lancia betas, a fiat x1/9 and an alfa sprint. All with history and nothing to suggest clocking, in fact I am 100% sure their mileage was genuine on all of them. Not one of them had numbers that lined up properly.

Dr. A. 1.5 IE · Guest

That means there is no fix or I should change the tachometer with another???

done_fishin · Posted: Mon Aug 15, 2005 5:08 pm Post subject: Speedo's & stuff

Hi all
I am familiar with the problem that Alfa speedo / tacho units are temperamental and remember a supervisor of mine from years back asking my help to fix his. I find myself now in the same position of needing help, since I am now the owner of an '85 Alfa 33 where the tacho works but I have neither speedo nor mileage counter functions. My supervisor of old had brought his unit into work having stripped it down himself. I am wondering where to start .. what is required to dismantle the speedo/tacho unit from the car and what should I be especially careful of! Also , If I need brushes etc , Who can recommend a source for spares either in Greece or the UK.
I also note that I have lost the mainbeam from one headlamp. I assume that the problem is due to a faulty relay although I have had a similar fault on another car where a wire had broken on the direction indicator lever by the steering wheel. Can anyone advise about an electrical circuit or send me a scan.
Many Thanks

kaBOOM · Posted: Fri Aug 19, 2005 10:00 am Post subject:

I'll have a look, I had a cct for one somewhere, gimme a few days to dig it out....

It has something do do with one of the timeing caps on the PCB, where I don't know.... :-/

paulhide · Posted: Fri Aug 19, 2005 4:22 pm Post subject:

Easiest way is to just get another speedo/console. As for headlamp, as long as bulb is not duff, first check main beam fuse is seated happily.Check wiring under back of headlight on EITHER side and also check main wiring loom junction beneath brake fluid reservoir. However if your car has a dim/dip relay (not sure if the early 33s had one?) this is a common fault - on a series 2 it sits near the fuse box next to, I think, the windscreen wiper relay. Both quite big, about 4cm square. And then there are also the normal relays on the fuse box? Swap them about to see if there is any change. Wink

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http://www.alfa-pages.co.uk/viewtopic.php?t=5188

ZeNiTh-PbArM · Posted: Sun Aug 21, 2005 10:46 am Post subject:

Hi,

On most 33s, speedo woes are due to the infamous connectors at the back of the instrument clusters. The amplitude of the signal coming from the gearbox is so small that even a small connection resistance is enough to kill it. After one or two dismantling/cleaning/bending contacts attempts, i soldered the wiring directly on the board (have to be careful since the "pcb" melts quickly...) . did it two years ago, no problems so far!

best regards,
zp

done_fishin · Posted: Mon Aug 22, 2005 1:17 pm Post subject:

I am checking out my speedo & the sensor. Has anyone figured out what sits inside the gearbox and feeds the pulses to the sensor? I have tried to find something inside the Alfa 33 workshop manual but it seems that little is mentioned or discussed. I have made some calcualations according to the Jaeger on my car ( 4632 impulses per Kilometer) and discovered that for every 10 kph it requires 13 pulses per second. If, as I suspect, something on the main shaft triggers a pulse into the sensor (according to speed) the pulse width will vary according to speed. The speedo kicks in at 20kph, which means 26 pulses per second or a pulse repetition rate of 38mS. At 200 kph (we are discussing the speedo not the cars ability!) this would drop to 3,8mS.
What I would like to know is
1. the diameter of the axis where the sensor is mounted &
2. what %age of the circumference of the axis where the sensor is mounted is allocated to create the pulse by the rotor?
Does anyone happen to have a gearbox open where they could peek inside and let me know?
I have made a simple Test circuit to check out the speedo but it is limited to a fixed width of 10 microseconds (for those who don't know 1000 microSecs =1mS). If I assumed that the sensor was sensing on a 50% basis (ie half the axis is covered by the rotor to create a pulse) then the physical speed at 10 microS would be approaching 4000 kph .. who said highly unlikely? So I would like to know a bit more about the physical properties of the sensor , the rotor and the relationships between.
Can anyone help?? This will also help me to try & make a tester for the sensor ..
_________________
A Brit in Athens since '87
resurrecting an '85 Alfa 33 1200

Bellamachinna · Posted: Mon Aug 22, 2005 11:17 pm Post subject:

Sorry, for the reply, and dont take it personally, but it seems that you are needing a trip to the nearest pub, and relax a bit more.

Take care..
(enjoy the summer)
P.Camilo
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All'interno della mia macchina, vi sedete, tenete sopra e CHIUDETE IN SU...

ZeNiTh-PbArM · Posted: Tue Aug 23, 2005 6:37 am Post subject:

hi,

from what i recall the speedo drive inside the box is done by means of square teeth milled in the right side output shaft. the cyclic ratio is 50%, which you can check with a scope hooked on the signal pulse line.
besides, it is perfectly possible to make a stand-alone speedo connected to the sensor, i made one myself using a microcontroller and a 2x16 LCD screen on a rainy sunday afternoon. but i recognize a simple bike computer and a few wires will do the trick as well (except for rearlighting perhaps).

best regards,
zp

tvatavuk · Posted: Tue Aug 23, 2005 1:29 pm Post subject:

Hi, could you give more details on that microcontroler, way u hooked it all up...
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Tino Vatavuk
Little black dress which replaced Alfa Romeo 33 S 16v Permanent 4 GMo

ZeNiTh-PbArM · Posted: Tue Aug 23, 2005 3:10 pm Post subject:

hi,

i had been using a multipurpose development card i made long ago ; microcontroller is microchip pic16f84 4MHz, LCD in 8 bits mode, and i had added a breadbord with an opamp (ltc27l2c as far as i recall since it's asymetrical supply and rail-to-rail, i have a few in stock, they're useful) but i think any comparator should have sufficient input impedance to acquire the signal correctly; and a schmitt trigger to get proper square-waves ; so the hardware is pretty straightforward.
programming the controller is easy also, you can have the sqare signal posedge triggering interrupts and counting cycles between, or poll the input while counting cycles (preferred solution). there is plenty of spare time for calculating speed (using reverse table lookup, or calculating a division, time-costly but quick enough to fit between edges ; precision 1 km/h) and driving the LCD ; note that you will have to filter a little bit to avoid too quick a variation which would cause the display to be unreadable ; a slower cpu can be used by splitting the algorithms in parts and calculating every few edges, or reducing the input signal frequency using a bunch of jk flipflops.
worked at first attempt, calibration was done during a road test using a stopwatch. i used it as my everyday speedo a few months, while i was sorting out the problems of the original one.

best regards,
zp

done_fishin · Posted: Thu Aug 25, 2005 8:35 am Post subject:

Seems like I am not the only one out here trying to find a way to go crazy ... I would have gone to the pub but I am unemployed and have better things to do with my cash .. so I settled for a few of the cheap cans from LIDL ... Must have helped since I missed a whole day yesterday with the updates to this thread.
I modified my test circuit to make the pulse width adjustable but it seems that it makes no difference to the fact that a -2V pulse is required to make the speedo work (on the bench) via a transformer coupling.

What sort of buffer was being used on that micro application to sense the pulses and did you find a way to measure it before you dived in or was it just that it worked from the start so you didn't bother checking anything else out?
It's getting hot again , so I am just back off to Lidl to get a few more brain refreshers.
_________________
A Brit in Athens since '87
resurrecting an '85 Alfa 33 1200

ZeNiTh-PbArM · Posted: Thu Aug 25, 2005 2:27 pm Post subject:

hi,

i didn't trigger the speedo with my hardware, which used its own LCD display (HD44780-based autonomous display). i just had to acquire the pulses from the gearbox sensor, which just required a pull-up, clamping diode, and an opamp ; i didn't encounter any problems with the sensor interface. if you happen to get in trouble with this let me know as i must still have the analogic daughterboard from this project gathering dust on a shelf somewhere...

best regards,
zp

done_fishin · Posted: Thu Aug 25, 2005 3:17 pm Post subject:

If it was that easy to interface I can't understand other posts that I have read stating that the impulse from the sensor is so small. Sounds like a pull-up with a j-fet will suffice .. and then maybe drive a resettable/latchable counter to give a speed indication.
Thanks for the input .. I thought this was going to be difficult.
_________________
A Brit in Athens since '87
resurrecting an '85 Alfa 33 1200

ZeNiTh-PbArM · Posted: Thu Aug 25, 2005 10:24 pm Post subject:

hi,

interfacing with the sensor is indeed that easy (it's a simple magnetic pickup anyway!) ; but triggering the speedo is not, and i confirm that even a slight series resistance due to a poor connection will kill the signal enough to prevent the speedo from working.
using a high impedance input stage soldered on the sensor wiring you don't get this problem. if you're just going to want a speed indication, i think a simple frequancy-voltage converter will be sufficient, and you can use one or two good old lm3914 for led display (or use multiple opamps and adjustable resistors to calibrate individually the speed at which every led switches)

best regards,
zp