Working on fix ECUs... AND FIXING WITH SUCCESS!!!

[Nacho-RT74]

I used the 5 just because the other one wasn't available, and was for componment test what prooved ON MY CASE both modules failing on same component.

Now mick checked a diff component failure

MICK, which exactly resistor failed ? The pic posted by musicman is an FBO module

It's the long open wirewound resistor right in the centre of the PCB. It had gone open circuit at one end. It looks like the legs are just crimped on, maybe that's the reason it failed.

thats a ballast kind resistor as far I know

[Mick70RR]

Well I re-fitted the FBO unit this morning and took the car for a long drive. Everything seemed fine so I stopped to check the timing and noticed it was two degrees advanced from where I normally run it. I didn't check the timing with the old unit so I'm not sure if this was something to do with the FBO module or whether I had previously set it a few degrees advanced by accident. While I was out I did a few full throttle runs and did a bit of cruising round town and didn't notice anything out of the ordinary. Think I'll leave it fitted and keep the old unit in the trunk.

[nascarxx29]

Any of this ECU info current
http://www.badassmopars.com/1967coronettechElectroniccecus.htm

[ODZKing]

How about P4120505. 
The number on that Transistor are as follows:
793266
9M179 VL
9M 649
MYS
I can't seen to get that to cross to anything.   

[Mick70RR]

How about P4120505. 
The number on that Transistor are as follows:
793266
9M179 VL
9M 649
MYS
I can't seen to get that to cross to anything.   

It seems that transistor is made by ST Microelectronics and has been used on both the orange and chrome boxes. The chrome box currently for sale on the Summit website used the MJ10012 so the two transistors must be similar.

[Pete in NH]

I came across this thread from last year and the amazing work done by Nacho- RT74 on these ECU boxes. I'm a retired electrical engineer now but, back in the early 80's I did some work with the then new Motorola MC-3334 High Energy Ignition Controller. The MC-3334 was designed by Motorola for Delco's new HEI ignition system and used the MJ10012 transistor to drive the coil. There is an interesting statement in the MC-3334's application note concerning the MJ10012. It states-" A 350 volt zener clamp is required when using the standard MJ10012. This clamp is not required if using a selected 550 volt version is used". The standard MJ10012 is 400 volts.

It is quite common to have transistor manufacturers such as Motorola sort transistors for special characteristics if you are buying large quantities of them. It would not be unusual for Chrysler to have requested selected MJ10012's and have them marked with a special part number. It would save them the cost of the zener clamp diodes which would add up in the quantity of ECU's Chrysler once built. Motorola would happily do the sorting to get orders for the really large quantities involved.

Here we are 35 years later and I have to wonder if the current Orange and Chrome boxes are getting selected MJ10012's or if the people building them even know about this issue. The guy's who did the original engineering on these boxes have likely retired long ago and did the information get passed on or in the much lower quantities of these ECU's being built, perhaps by others than Chrysler, can they even get these selected transistors? All of this is an educated guess but, it wouldn't be the first time something like it caused product quality to go down hill.

This thread prompted me to do some research. I don't think Motorola is even in the transistor business anymore and may have sold out to ON Semiconductor.  I could not find any current sources for the MJ10012. I have an Orange box in my 71 Charger and it has an ST Microelectronics transistor in it.  I'm almost certain the ST transistors are a ST type BU941 which is a type specifically for electronic ignition systems. The BU941 is still available from Mouser Electronics (mouser.com) for $2.29. They have 1300 in stock but the type # is listed for end of life and will be discontinued sometime in the future. The BU941 is very close to the MJ10012 in characteristics and the data sheet also calls for clamping the voltage across the transistor to 400 volts maximum. So, the ECU's may also be using selected BU941's. One important characteristic of these ignition transistors is how fast they turn off. Both the MJ10012 and BU941 have specified turn off speeds while driving an ignition coil, types like the MJ10005 don't. Slower turn off speeds can result in weaker spark.

Back in the early 80's I had a prototype MC-3334 based Chrysler type ECU running on a test stand but not a real engine. It operated for several hundred hours before I ended the testing. It was quite a nice little box and didn't use a ballast resistor as the MC-3334 electronically limits the current through the coil.

[ODZKing]

While I am limited in my electronic knowledge, meaning I know just enough to get me in trouble most times ... this stuff amazes me.   
Good work.  I have an orange box that died on me last year if anyone wants to mess with it.

Bob

[Nacho-RT74]

as far the transistor is available, SHOULD BE... the problem is find a good and correct transistor.


also need to know that NOT ALLWAYS the transistor could be the culprit, BUT, maybe 70% of the times ? based on my experience.


Pete! if you find some "TRUSTABLE" source for the Chromed MP transistor ( Motorola, ON or any other correct replacement ), please let me know! I'll be happy to get some of them. I have being affraid to get this from a China or any other "seller", being how they can be easily false

I'm not really an engineer or electrician tech, just that being a sound tech, I'm familiar with some therms and have some skills. That's all. So any advice, or help from a real tech will be GREAT, and will save lot of Modules around, on the cheap

[Pete in NH]

I think right now the ST Micro is the best transistor for the repair I can find. ST Micro is a first class European company that produces high quality parts. I agree that I would not trust any parts from China marked MJ10012. Especially since I could not find any current production MJ10012's.

I think I would try the following as a repair when replacing the transistor. Replace the transistor with a BU941 and add the clamp diodes to protect the transistor. For the clamp diodes I would try three 1N5380B diodes in series (end to end) , with the banded ends all in the same direction. I think they might fit better if arranged in a "U" shape in the area of the big transistor. Connect the banded end to one of the transistor mounting bolts and the other end should be soldered to the side if the steel box, which is ground. This will give you a 360 Volt protection circuit for the transistor and should allow an off the shelf transistor to work in the original circuit without problems.

The BU941's are available from Mouser Electronics (mouser.com)  as part number 511-BU941 and the 1N5380B's are part number 863-1N5380BG. Mouser is an authorized ST Micro distributor and I buy parts from them frequently. I'll be buying a few spare BU941's and 1N5380B's for my self on my next Mouser order.

By the way how are you getting that black potting compound out? Usually once that stuff is poured in it's almost impossible to get it out without damaging something.

Bob, thanks for the offer. I wish I still had my little test rig for these boxes, I'd take a crack at fixing yours. Maybe it's time to build up another test rig.

[Nacho-RT74]

I never thought on replace all the black compound on the fully dissasemblied Module UNLESS find to replace the compund correctly, just really fix the one I cut at Transistors end... was to USE simply RTV silicone to fill the compound cuts up I made.


somebody gave me a website about epoxy material for electrical stuff long time ago...


I don't get what you meant about the diodes

[Nacho-RT74]

I didn't found the website I got once, but maybe something like this:

http://www.cslsilicones.com/sealants/category/electronic-and-electrical

[Pete in NH]

What question did you have about the diodes?

[ODZKing]

I'll drop it off if The Crunch play the Monarchs in the playoffs  

[Nacho-RT74]

What question did you have about the diodes?

didn't got how to fit them on circuit... but will read further your post later. I'm really distracted latelly for several personal reasons

what do you think about these MJ10012 transistors ?... do they look to be original Motorola pieces ?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=151035623066&ssPageName=ADME:B:WNA:US:1123

[Pete in NH]

Hi Nacho,

Yes, they look like original Motorola MJ10012's. Some are also ST Micro MJ10012's. The four digit numbers under the part numbers are date codes of when the devices were made. For example 7814 = the 14th week of 1978. So, they are old enough to be real Motorola.

On the diodes, they have a white band on one end. You connect three diodes in series (end to end) with the white bands all facing in the same direction. So, you end up with one big diode. Connect the white band end to the transistor mounting screw connection which is the collector of the transistor. The other end of the diode connects to the metal case of the ECU.

[Nacho-RT74]

Connect the white band end to the transistor mounting screw connection which is the collector of the transistor. The other end of the diode connects to the metal case of the ECU.

that was my question... thanks!

[Nacho-RT74]

I won the auction and already in hands ( I'm in Spain right now )... althought I was interested just on the ones for the chromed ECU... what could be the applications for the other two ?

MJ2501 and MJ3001

searchinga round for datasheets, it seems they are somekind related

[Pete in NH]

Hi Nacho,

Yes, the MJ2501 and MJ3001 are related. They are what is called a complimentary pair and are used together in audio amplifiers. The MJ2501 is a PNP type, the MJ3001 is a NPN. Both are 80 volt 10 amp devices with very high gain. Gain= 4000 at 5 Amps. Both are not suitable for ignition systems, voltage is too low and the 2501 is the wrong polarity. I have the data book on these if you need more information.

[Nacho-RT74]

yeap, read later the PNP and NPN configuration making them complimentary. Would be nice what kind of audio amps could use it, since I work with Audio stuff.

I found the PDFs for them... will search further what kind of audio amps could use those

[Pete in NH]

An update on the replacement transistor situation for the Chrysler ECU's. I tried ordering some MJ10012's from a distributor that claimed to have them in stock several months ago. Recently they canceled my order and send a refund.  I take it they are no longer available. I have been unable to find any other source for MJ10012's other than Ebay.

On the ST Microelectronics BU941P in a metal case, called a TO-3 package, I was able to order 5 pieces from Mouser Electronics. Shortly after receiving them I was informed by Mouser they were being discontinued by ST. I checked the Mouser website and the metal case BU941P's are no longer available.  ST Microelectronics has replaced them with a newer type the BU941ZP. This new transistor now contains a protective zener diode mentioned in my previous posts. That's the good news, the bad news is they are only available in a metal and plastic package that is completely different from the old all metal type.

This makes me wonder what the future of the orange and chrome Chrysler ECU's might be. Will they get redesigned to use the new transistors? Did Chrysler buy a whole lot of metal cased transistors, known as a last time buy, to keep building ECU's for a while longer? Or, will these boxes simply disappear because there is little interest in supporting 30 some year old technology with little demand? I guess time will tell.

[Ghoste]

I'm going to go with your last guess.

[Nacho-RT74]

well, at least I have 2 originals... Hope they are really fine.

wondering now about the FBO piece. I don't think Don will share the info of those... or Yes?

[beat]

hi nacho,
by surching for the keyworth MJ10012 I cam to your interesting post.
not as I own ore repair such big cars as you, no, I do just made my own transistoriced Ignitions for my 1973 english Motorcycle.
and I do use the Mj10012 from this Ebay seller from Canada, the stuff is sent from Hongkong / China.

and I have to say, - they are good quality.

the last one was working 6 years, a very simply circuit with a zenerdiode of 8 Volt and a 27 Ohm Resistore on the BASE and a 376 V zenerdiode across the Colector / Emiter.
and the most important:  I know why it is brocken down now!

a Voltage drop in the all wiring was the reason, caused by a brocken MAINSWITCH Contact.
so this cheap MJ10012 doing a good job, just a very low Voltage is killing them for shure.

if you are interested I can send you a copy of the circuit of this first generation Trans. Switch and as well a circuit of the new generation, using a NTE98 Transistore and a 7805 Voltage Regulator on the BASE for more stable voltage to the BASE.
greetings
beat

[Nacho-RT74]

all I can say is I don't really understand everything about electronic components LOL...

[Nacho-RT74]

It seems we got a newer suplier for Chromed boxes?

http://www.ebay.com/itm/Mopar-Ignition-Control-Unit-P4120534-/271373671855?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f2f219daf&vxp=mtr

Note diff decal and transistor!