308 Speedo, Odo, Sender System Fix

another thought . . I was just checking out other OEM sending units on Summit and it looks like something might adapt pretty easily to the stock 308 mounting position on the gearbox (easy being if you have a mill and lathe ) . .. there's a new kid working at Kragen that's been real helpful when I walk in with something in hand . . . might give that a try.

 

Hi Sean
Measure the threads on the sender mount, it is standard M14 or something. This should translate to after market 'cable to electronic' senders from most aftermarket speedo manufacturers. An example might be http://www.magsensors.com/vss.html Another source is http://www.jagsthatrun.com/Pages/SpeedSensors_Speedometer.html
BTW I really really wnat to see your 'ring removal' gadget, that is the most scary operation you can perfomr on an instrument. I can't imagine replacing a ring, where would you get one? I had to remove one on a broken 365GT4 clock that was heading to a concours event. Took a year off my life.

Gerrit

 

thanks Gerrit .. I'll make it a point to take some pics.

 

M18X1.5 is the thread on the stock piece . .. well it measured .670 which is 17mm but the major dia of the thread is stripped so pretty sure it's the next size (seen this a few times) . . so I can just get away with a thread adapter and one of the parts from the Jag place for $75 (square drive looks correct) . . or call the other place since no prices online but can do custom apps which means pricey.

 

here's what I did to bend the lip back . . . and a pic of the tach adjustment pot that did not have enough range to re-scale the stock Ferrari tach . .. which got me on the whole gauge swap thing.

don't know what happened to the removal tool pic . . I'll take another one
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if I was doing something I was worrying about destroying I'd make a ring to support the o.d. of the bezel (maybe just c'bore the install ring I made) and a second ring for the tool to lever against instead of pushing on the plastic . . there's a way to mount this on a rotary table too if you do it for a living . .. let me know and I'll tell you how I'd do it . . then you'd be able to peel the lip back and close it just like a canning machine .. but it'd be a semi-complicated arrangement but might be worth it for what you're working on.

as you can see I just made it from a miniature pair of cutters


cheers
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Hi
I can't say I do it for a living but I am doing 1 or 2 a month. I will get modify the aluminum plate I am already using to add a 'peeler'. Rolling the rim back down would be ok with just a roller. The rim doesn't need to be rolled back very far to create enough wiggle room over the plastic lip, at least not on the tach and speedo. The clock is a different matter, due to its much smaller diameter and the fact that the case is metal.
Thank you for the insiration to create a better tool to make this less scary

Gerrit

 

I have a small stable of Italian vehicles from the '70's and they _all_ (Ducati, Moto Guzzi, Ferrari, Vespa, Alfa Romeo) have the same speedo threads and square drive for the cable. In fact, I have an Alfa spider tach on my Guzzi. Screwed right on, no issues at all.

Moto Guzzi uses these same angle attachments. Your local (ha!) Moto Guzzi dealer can get both 90* and 60* versions. MG Cycle (mgcycle.com) has them mail order:

17768360 90 degree cable drive gear $44.00
Used on many models, particularly with fairings where cable clearance is tight, also for custom consoles

23768310 60 degree cable drive gear $54.95

 

dude . .. glad I could help . . .you're welcome

I've worked on some industrial canning machines for Coke and Del Monte just incase your biz grows

cheers

 

thanks . . I wondered if there was an easier way and another poster on here said he got the speedo apart without bending the bezel.

Hey doesn't one of you guys owe me a chip or something?

 

Hey Bob, how are things?
I use the pry, twist approach as well but it scares me. Some of the units worked on have been opened before and the case starts to crack right on the lip line. I will modify the aluminum support plate I use to incorporate something like Luckydynes approach.

Lucky,
I thought you got a chip already? If not, send me an email. We will come to an arrangement

Gerrit

 

Sono Verace dall'italia sono in cerca di un say115y dove posso trovarlo?

 

Non disponibile

 

Hi all,

For rallying with my ’77 308 (in "old ladies" category obviously), I need a Tripmaster.

To install thnis device, I intercepted the red wire (pulse wire - I have strictly the same odometer as the one described by RJay) to connect it to the Tripmaster via a Brantz interface and …the system does not work!

First of all, I must precise that I’m totally dumb in electricity/electronic but
- my odo works fine;
- I tested my derivation registering the pulse at the end of the wire I installed; so, for this part, all is OK.

Re-reading the Brantz interface instruction, I read that “analogue sources are not suitable”.
Anybody knows if the pulse coming from the sender is a digital or an analogue signal?
Personally, I have no idea on the difference between the two things and how to distinguish them...

Thanks in advance.

Paul

 

Gerrit,

Did you ever get a working version of the chip?

Thanks,

Joe

 

First off, I don't own a Ferrari but the information in this thread was useful for a friend who has one with a faulty speedo so I thought I'd return the favour.

My friend who is currently in our house in Australia, (we're in his place in the UK), has found a source for the SAY115Y IC - there were three (3) available, now there's only two (2) left.

The shop is not on the internet which is probably why he still has them and the owner is currently selling off all his stock, (the shop has been there at least 35 years that I remember - I used to live near it).

They're not cheap, the price was ~AU$120-140 each and contact details are:

Ringwood Speedometer Service
693 Whitehorse Road
Mitcham, Victoria
Australia
3132
Ph: +61 (0)3 9874 2260

NOTE: This information was current as of 2010-03-27, friend's been in Australia for previous 5 weeks - so I don't know exactly when he bought his IC. So if someone finds out they're all gone or buys them all I hope they'll update this thread with a post.

Anyway, hope it helps someone - now let the squabbling begin

 

Hi,

I'm having the problem of a broken speedometer at the moment, and wonder if someone might be able to advise?

I had initially thought the problem was the sender - having disconnnected it and reconnected whilst painting the chassis. Whilst on holiday; the speedo stopped. Fiddling with the send connection got it going (?) again for about 10 miles then it stopped.

I have taken the sender off and tested as described above - no pulse.
I have also replaced the transistors and now the sender gives a square wave of 0-2.5V when rotated, when connected to a 12V supply.

But the speedo still does not work.

I am wondering if the sender is still broken? Should it be giving 12V pulses? or should the 2.5V pulses work.

Can I test the speedometer by switching on the ignition and connecting a 12V pulse to the red wire?

Also, Gerrit, if you are still on here, did you come up with a fix for broken speedometers along the lines of a new circuit board?

Has anyone found any more SAY chips?

Best regards

Steven, UK

 

I've gotten heavy into the speedo circuit as I'm working on the DRD correction module from 12o'clock and a "how to" DIY for the 308.

No, the ground side is the body which is grounded by it's mounting. The other wire is the output from the internal transistors sending a low impedance signal to the speedometer.

No. The impulse generator (speedometer sender unit) outputs square wave pulses between 0.6v and 5-6v from red/blk wire when the green wire is at battery +12v and body is at ground. A 2.5v output is marginal if it works at all. Although the speedo circuit contains protection, do not put battery voltage on it. The best way to test the speedometer is using a signal generator for a square 100Hz wave and gradually increasing the amplitude.

In replacing the transistors it sounds like the biasing is off a bit. If you've gotten into the generator, I'd go the next step of drawing out the schematic and altering a resistor value or two to get the full necessary voltage.

 

Thanks Paul, for your advice. What do you mean by DRD correction module from 12o'clock.

Thanks for your thoughts on the sender and testing speedo etc. I will try over Christmas to sort a 6V square wave generator and test.

Regarding the sender (and considering I really don't know much about electronics), can you think of a reason it is giving out a nice 2V square wave after replacing the transistors, rather than the correct 5-6V? It gave nothing before.

In my mind I'm not sure why it wouldn't be working right and why the situation would occur when it would need adjusted a bit?

Perhaps if I draw down the schematic you might be able to advise on which component to tweak?

BW

Steven (UK)

 

Sorry for trying to save some ink...DRD = SpeedoDRD which is 12o'clock's product number for the motorcycle speedometer corrector module. http://www.12oclocklabs.com/p_sdrd.htm

The reason you went from a non-working Impulse Generator to one producing 2.5V pulse but need one producing 6V pulses is likely because another component is wrong or you didn't use the exact same transistors. If I knew the Impulse Generator circuit I could figure out the voltage problem (the speedometer circuit is available but not the Impulse Generator). The +6V number I use comes from the original poster, RJay, in 2006.

Input specifications for the SAY115Y chip require 2.5-3.5volts to trigger. The reason your 2.5V is inadequate is the speedometer has input protection circuit in front of the SAY115Y - integrated circuit which reduces the pulse amplitude below the required level. You just don't have quite enough voltage to trigger the SAY115Y - integrated circuit. Close by not enough to work reliably.

Can you provide pictures (digital but even detailed word pictures) or any circuit information about the Impulse Generator from your experience changing the transistors? Certainly if you already changed the transistors there is hope to get it working again...you are so close.

Incidentally, when measuring the voltage output from the Impulse Generator by meter or o'scope, assuming +12V is applied to the green wire, negative to the housing, the output wire must be connected either to the speedometer or to a pulldown resistor of about 500 ohms (RJay info).

 

Hi Paul, that's very helpful, thanks.

An instrument tech at work tested the sender with the resistor as per RJay's comments above and came up with the ~2V square wave.

I will try and draw out the schematic for the sender from the circuit board, in the mean time here are some photographs of what lies inside (before cleaning and replacing the transistors)

Is this a hall effect sender? I don't think there is a magnet attached to the rotor...

Incidently, to get it apart we machined off the top crimping - plan to make a threaded collar to reassemble, should we get it working! As you say... so close!!!
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Thanks so much for posting the Kodak moments (dual lens?). Yes, a hall effect device should have 3 leads like a transistor, is often flat, and will be placed very near to the rotating shaft which will have 2 tabs or reliefs of equal size (for a square wave) machined into it. Most parts on the pcboard are identifiable but yuk...what invaded the sensor, oil from the gearcase seeping through the seal?

 

If the rotor itself is just a piece of metal (steel), it could be a variable reluctance device. It looks like one of the components on the PCB is a vertical coil of wire on a bobbin with a steel (or magnet) center post whose end the rotor leaves pass fairly closely by -- is that so?