Christ thats bloody irritating!!!!

[Retropin]

Fixing the CPU on zaccaria DEVIL RIDERS. I have a fault on the RESET cct preventing the CPU from booting. Basically this cct has an LM399 voltage comparitor on the power supply which is fed a 5V from the CPU RESET cct.
My CPU doesnt feed the 5V.
Its important that all components on this are within spec so replacing the 10uf cap and 1n4148 diode is imperative etc.

cct still does not work so i start to look at the 74ls14 first... still no go.

Im trying really hard to not go near the 3081 transistor array as i dont want to have to replace it if i can help it. My line of thinking here is that if i dont test it then i dont have to replace it... yeh i know.. stupid logic, but these are becoming really hard to find.

Anyway..... 3081 tests faulty so i HAVE to rreplace it. I only have 2 of these left so im trying hard to keep hold of them if possible... but needs be and all that... i have no choice but to use one.

Im going off the cct diagrams here, gates, type of chip etc.

So i TRY to remove old 3081 complete but its a no go and i end up cutting off the legs to remove and desolder.

I pull out a socket and solder in place.. then go to put the 3081 array in.

WTF?????   Ive got an 14 pin array trying to go into a 16 pin socket?

Now im stressing... i look at the old array and it says on the top ULN 2081... NOT 3081!!!!!

Check schematics and also manual that lists all components... clearly states 3081.

Check the very few online resources there are and all state 3081.

Double check with PINBALL FIXERS website ( have ALL zaccaria schematics on there) and my board  1B1165/1 is meant to be exactly the same as 1B1365/1... same schematics..... same as schematics that came with the game ORIGINALLY... 3081.

Hell... 3081 are hard enough to find.... 2081 even harder!


Now i have this quote im holding back on... i have found the last 9  2065ACPU chips in the world... they aint cheap and guy wants US$130 postage.
Ive checked his website and he has 2081 arrays in stock.

Ive emailed the guy to add to the order and PLEASE can we do something about the shipping cost.

And WTF does my machine have a board that doesnt exist????

But man... cutting that array out has really pissed me!


Oh and to cap it off, my probe on my CRO fell apart.

Maybe i should give up for today and sink beer instead?

[goodolddays]

Very Frustrating Gav, expecially when it involves these hard to source parts . I'd walk away from it for today if I were you .

Good luck with it.

[Homepin]

Mate there is nothing special at all about ULN2081 or 3081. They are just an array of seperate, general purpose transistors put in an IC package simply for assembly convenience.

You could very easily make up a replacement with seperate BC547's - I certainly wouldn't be paying anyone big bucks for them....

[Retropin]

Mate there is nothing special at all about ULN2081 or 3081. They are just an array of seperate, general purpose transistors put in an IC package simply for assembly convenience.

You could very easily make up a replacement with seperate BC547's - I certainly wouldn't be paying anyone big bucks for them....

Thanks Homepin.... yeh i know its just a packaging... ill see how much they are before i make a decision.

It does explain why my Ic tested faulty though... schematics have pin 9 as COLLECTOR..... its actually VCC..

looking closer, i have a small ceramic cap that ties to ground.. this is not on the schematics and i bet its my faulty component... LOL - dont want to test it for short... would just about kill me after the day ive had!

[FirePower]

Mate there is nothing special at all about ULN2081 or 3081. They are just an array of seperate, general purpose transistors put in an IC package simply for assembly convenience.

You could very easily make up a replacement with seperate BC547's - I certainly wouldn't be paying anyone big bucks for them....

Agree and one way to do this fairly neatly and reversibly without bodging the original board is to install a socket in the original board location. Then make up your substitute circuit on veroboard or similar and wire this with flying leads to another socket that can plug in to the original location.  So the original board is preserved and if you ever find the original component at a fair price you can just plug it in.

[Homepin]

Gav, I had a play and whipped up a test "replacement" ULN3081. Looking at the Zaccaria schematics and also the spec sheet for a CA3081 I made up the board below using BC548's. If you would like to give it a try please PM me and let's see how it goes.

[Retropin]

Gav, I had a play and whipped up a test "replacement" ULN3081. Looking at the Zaccaria schematics and also the spec sheet for a CA3081 I made up the board below using BC548's. If you would like to give it a try please PM me and let's see how it goes.

Holy cow... mate that is unreal!! I cant believe you did this.

Look , i would absolutely love to try it but the array i need is a 2081... my schematics state 3081 as does manual, but the IC's in place are a 16 pin package 2081... this is why i cocked up so bad... im reading schematics and testing pin outs only to find my board is bloody diferent.

Ive been onto www.pinballfixers.com
 Owen has all the Zac diagrams on there... cant see my boartd though with 2081 arrays and a cap tying TR4 to ground

[FirePower]

Very neat Homepin - that's exactly what I meant but a lot neater than I imagined.  Something about a picture (and schematic) being worth a few words.  Well done  

[Homepin]

I can't find any info on a "2081" - the 3081 is a 16pin package - maybe they are the same or very similar???

Do you have any info on 2081?? As you say - all of the Zac circuits show 3081.....

[Retropin]

Ach - jeez!!! Er can i just go hide under a rock and come back in 5 unread pages later?

This is awful cos i have to confess to a major cock up here.... my IC's do say 2081... my problem was that i didnt pull out a 3081 transistor array to put in its place... i pulled out a LM380N.

Not sure whats more irritating me or me?

Ok... lets move on shall we?

Now i DONT have 2 off 3081 IC's.. i do however have 2 off LM380N... no bloody good to me right now. I do have a 3081 that is a pull out of another cct.. have no idea whether it works or not... ive put this into the machine and she still dont boot.

So Mike, id love to try your version of the 3081... cant thank you enough for taking the time to do this..

in the meantime... think i need a couple of days break from this CPU

[Homepin]

No problem - FYI an LM380 is an audio amplifier. The ULN3081 (CA3081) is simply a transistor array.

I can send it in the post tommorow - please PM me your address.

[Retropin]

No problem - FYI an LM380 is an audio amplifier. The ULN3081 (CA3081) is simply a transistor array.

I can send it in the post tommorow - please PM me your address.

Yeh i know... trying to lay low here...

Pm sent

[Strangeways]

Gav - you need a holiday mate 

[Homepin]

Why I HATE Veroboard!

OK - so I bundle up the test, replacement ULN3081 and get it ready to post - "Hmmm",   I thought - "I really should test this".

So I decided to build a test jig using Veroboard and that's when I realised just how CRAP this stuff is! Look at the mess below, I'm embarassed to say I had anything to do with it.

Anyway at least it showed up a fault in my PCB layout - I had reversed the emitter and base on one transistor. At least now I can sent the part with 100% confidence that it is right

In all honesty I could have designed a PCB layout and made a dedicated PCB for this jig in the SAME TIME it took to make this Veroboard one and had I realised just how shitty it would look I would have done that.