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cyberbob

MPU4 Motherboard Repair WELL ATTEMPT

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21 minutes ago, fruit58 said:

ive been doing boards since the 80s and still fail on some we carnt win all the time bob alls we can do is keep plodding on lol

i get that,  it must be a nightmare, with unknowns too, have no idea what they have been through ect, id imagine most had hard lives anyway 

 

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yes bob thats true  and some times ive had boards where wrong ics have been fitted  and bits missing off them its all part of the game

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1 hour ago, fruit58 said:

yes bob thats true  and some times ive had boards where wrong ics have been fitted  and bits missing off them its all part of the game

i think ill stop with straight swap out of odd bits lol,  its getting too technical for me now and my limited skills.

but i will have another go, one day. how do people clean the acid up these days, or is it better to just remove everything inspect clean then refit new parts, vinegar bath was they way, but does more harm than good ive read.  i did Vinegar these and cleaned them dried them before i started, i tested before and after clean and repair attempts too.  left in airing cupboard for a few days, to make sure completely dry before i re tried them,  

now my potluck board has started to play up, wont fire 50p sometimes. so that needs tlc too now 

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some say wash with vinegar  and some say dont  the other board with the 50p  fault has that got any green fuzz on it

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here is one im doing at the moment if you look where the ics where the rot had gone under them this is what you at to look for 

20190512_162418_001.jpg

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It did, but i cleaned it up with vinegar,  fly leaded, done nothing more too it. mpu4 mod 4 with ay chip.

been perfect,  just started to play up, sometimes pays out less the 50p, keep playing then it works then it dont, hit an miss to when it works.  

the board defo needs attention, ive not repaired the tracks or anything. even thought works, id assume it needs the tannys, the diodes the caps & track repairs.  ill await the rtn of the mod 2s and then look at it. its working for the minute, 

 

 

 

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ok bob keep us posted on it another project to come

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CRAP, fired up Stop The Clock after re-attaching the base and she has developed a stuck lamp column does the solenoid clatter on power up.

Opened her up and I am ashamed to say it has the battery rot....even though I had removed the battery many years ago. It looked okish at the time and still held the memory.

Looks like I'm going to be replacing T12 & 13 left to  C12 area

IMG_20190513_141330.jpg

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Yes I have found this, removing the battery does not stop the rot, it’s like a vinegar wash, once you do it the vinegar acid gets in and under everything just slowly corroding especially copper away!  Battery alkaline is much slower once battery is off but it does happen! Well I have seen it for sure!

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So checking the lamp drive issue, I determined it was T35 that had shorted, but I compared to others in the group and was getting all kinds of odd readings that drifted around.

Went back to the ULN2803 and found odd readings on the outputs, and saw a SIL on the output pins that I did not remember from the schematic.

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Ive got the bulb schematics for it m8, i can try to photo if for you if it will help 

21 hours ago, quattrohead said:

So checking the lamp drive issue, I determined it was T35 that had shorted, but I compared to others in the group and was getting all kinds of odd readings that drifted around.

Went back to the ULN2803 and found odd readings on the outputs, and saw a SIL on the output pins that I did not remember from the schematic.

 

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Ahhhhhhhhhhhh

potluck just threw a wobbler, no display then popped fuses, i guess the battery rot even though cleaned up and worked for a few months took its toll, down to one machine now :( where's that hammer. oh well another attempt here i come, as fingers nearly healed from last attempt :) chicken shit soldering here i come :) 

 

 

 

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Second that .worth a go if.you have the time rich !

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So I am midway through repairing my MPU4 and my Weller EC1000 has decided to die on me lol. Seems like the element and temp sensor are OK so into the unit I go...WTF.

I am changing all the 4v7 zenor and 1000pF capacitors along with T12 and T13.

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1 hour ago, quattrohead said:

So I am midway through repairing my MPU4 and my Weller EC1000 has decided to die on me lol. Seems like the element and temp sensor are OK so into the unit I go...WTF.

I am changing all the 4v7 zenor and 1000pF capacitors along with T12 and T13.

Oh no repairing with the old iron the trusty one still hanging around, alias im stuck at the moment.

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Weller is unrepairable, the controller board from 1983 is dead, I have ordered a $20 temp controlled Chinese miracle from Amazon, will be with me on Sunday. What could possibly go wrong lol

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OK new cheap arse temp controlled iron from Amazon and some time on my hands today.

I replaced all the rot components and used 2N3704 to replace the BC338 making sure to adjust for the different pin out. Payouts seem fine again.

However, the lamp problem has progressed to all lamp driver transistors randomly failing !!!!

I suspected T35 was shorted but noticed odd readings on a couple other drivers, indeed T37 looked like it was melting off the tab, so T32/35/37 were replaced. Another resistance check now showed another driver that did not seem right, but I wanted to test what I had done so far.

Well, it did not blow up lol and booted up fine. However, now have another stuck lamp drive. So I am going to replace them all. What has everyone else been using ? Schematic suggests BDW46 were used but I have BDX34B in my board.

Also the volume pot has decided to crap out, fucker.

Edited by quattrohead
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Any board clean with undiluted ipa.Then dry it thoroughly.Any traces of rot will carry on like rust on a car.You can get ipa in spray bottle on ebay cheap.It kills the alkalie.

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Great news guys,  i managed to temp bodge the potluck board,

No new news on the boards sent to Andrew yet, 10 days ago i know he was waiting on parts, and i think 2 are done, just the 3rd to repair, hoping it will be soon :) 

glad you sorted yours @quattrohead how you got on with the new issue ? 

 

 

 

 

 

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There back................Thanks @Andrew96_  Thanks for undoing my mess & can imagine and i knowi left a few problems 

Ill get them open & refit 1, in potluck, ill test very slowly this time :)  update soon :) 

At least i can try to learn from your repairs, learn not to attempt them :) 

so happy, PL is going to be running again right, it failed btw the other day again. 

 

 

 

 

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I'm still working slowly on mine Bob.

Quick question, if the stuck lamps turn off at reset then turn on again, does it mean the outputs from the 6821 (IC3)  are knackered but are forced off during reset ?

Edited by quattrohead
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12 hours ago, quattrohead said:

I'm still working slowly on mine Bob.

Quick question, if the stuck lamps turn off at reset then turn on again, does it mean the outputs from the 6821 (IC3)  are knackered but are forced off during reset ?

Hopefully some one with the knowledge will come along @quattrohead I'm clueless im afraid,  I know andrew fitted an IC to mine as was stuck or dead.  Certainly looks neat, much neater than my attempt, he even added fly leads for me, so i dont touch them at all :) no chicken shit soldiering :) 

Hoping to fit one today, if back lets me crouch into the back of PL :) 

Thanks again @Andrew96_

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