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RobT

Alphanumeric dead display

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Hi all :)

Quick question, looking at replacing the dead display on the Chances Unlimited machine. 

I've checked the display on another machine and it isn't working sadly.  I've looked at an old thread from 2015 and discussed was white sections in the corners, looking at the one have it doesn't look that bad, not sure if it's something else that might of gone pop!?

Just seeing if anyone else has had a faulty display and managed to get it working, or  replaced it with a newer display adapting it somehow?

Thought I would ask the question :)

Thanks all

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Edited by RobT

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Possible that a board fault is causing no alpha, but could be alpha faulty 

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Cheers Crest, yep one of the two.  The display looks in good shape when compared to my Lucky Strike machine.  I'm leaning towards the board being faulty, just no clue how or what to check tbh.

If I can even modify (somehow a newer board off Ebay) I would give that a go too :)

Its just a pain not having it working

 

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well someone has been there before you as it has wire wrapped around each end keeping the display to the board behind it! most likely the display heaters and the 90v generator (oscillator) is not working, look at it in the dark and you should see the faint red glow of the heater wires from one end to the other, but I don't think that will be there 

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Pretty sure I have one, but it’ll be MPU4 the connector will need to be changed 

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7 minutes ago, Andrew96_ said:

well someone has been there before you as it has wire wrapped around each end keeping the display to the board behind it! most likely the display heaters and the 90v generator (oscillator) is not working, look at it in the dark and you should see the faint red glow of the heater wires from one end to the other, but I don't think that will be there 

You've got an eagle eye, nice spot :)

I'll check that out tomorrow see if it glows up, failing would you think its fixable or knackered?

Cheers Andrew

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10 minutes ago, -Crest- said:

Pretty sure I have one, but it’ll be MPU4 the connector will need to be changed 

Thanks Crest, I'm good with a soldering iron just pointing at what to do :) there have been a few on ebay too, but just not sure what would work/adaptable.  If you do have one that'll be fantastic, just say how much matey :)

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41 minutes ago, -Crest- said:

Pretty sure I have one, but it’ll be MPU4 the connector will need to be changed 

don't you have to add a 12v regulator on the back of MPU4 ones like the MPU3 ones have as MPU3 work off 15v not 12v as MPU4 are so are well over run if that's not done!

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Oh you might be right thought they were fully backwards compatible, MPU5 are with MPU4.

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some of those display have that wire on them to keep the display from pulling away from the the board behind it

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18 minutes ago, -Crest- said:

Oh you might be right thought they were fully backwards compatible, MPU5 are with MPU4.

yes because both MPU4 and 5 run on 12v for the display, mpu3 has 15v on the AUX connector for the displays, so  if the high voltage side is around 90v at 12v input this goes up to 112v at 15v, also the heater voltage will rise too so the vacuum fluorescent displays will be well over run and would very likely  have a much shorter life, but I do wonder if anyone would be bothered by that, it works lets leave it! lol

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actually just looking at the diagrams for 12v displays in barcrest the oscillator and transformer generates -40v for the display and 5.6vac for the heaters, so by upping the input to 15v for using that display on 15v for MPU3 that means the -40v becomes -50v and 5.6v ac becomes 7vac which is not too good for the displays I guess

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Ok so the MPU4 display will be no good for the MPU3?

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59 minutes ago, Andrew96_ said:

yes because both MPU4 and 5 run on 12v for the display, mpu3 has 15v on the AUX connector for the displays, so  if the high voltage side is around 90v at 12v input this goes up to 112v at 15v, also the heater voltage will rise too so the vacuum fluorescent displays will be well over run and would very likely  have a much shorter life, but I do wonder if anyone would be bothered by that, it works lets leave it! lol

Never knew they had that much voltage. Thought they were perfectly safe to go near when on :lol:

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Must admit i thought the the mpu4 early alpha s were identical to the mpu3 s .I'm not sure about weather the later mpu4  machines  from say 88 onwards were any different which would stand a good chance !would love to know .midibob did look into the whole alpha thing and I'm sure some of the mpu4 alpha s were the same as mpu3  .there were differences in some of the main ic s used and this I think effected small things like showing "£" signs on the display .over to you Bob! 

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I think the £ sign issue was due to the 10937 chip that was used. There was a custom one for the UK market.

I must admit I've never had an MPU3 and 4 alpha next to each other to compare but as Andrew correctly says the MPU3 supplies 15v, the MPU4, 12v. The only regulation is the 5v logic supply on the alpha itself.

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Cheers all for the messages :)

I suppose I just need to keep an eye out for an mpu3 version on ebay which I imagine is super rare to come by but will keep a look out anyway. I will have to check out if the red glow happens when powered up, will do that tomorrow, thanks all :)

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rob, send me your address and i will send you a mpu3 alpha display 

 

soon as i can get one and send it you 

 

merry christmas

 

private message me  .. 

Edited by riche100
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41 minutes ago, RobT said:

Cheers all for the messages :)

I suppose I just need to keep an eye out for an mpu3 version on ebay which I imagine is super rare to come by but will keep a look out anyway. I will have to check out if the red glow happens when powered up, will do that tomorrow, thanks all :)

Sorry I couldn’t send you one but it doesn’t seem like the MPU4 ones would work as the chat mentioned 

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Cheers anyway Crest really appreciate the thought :)

Just doing an ebay search now may of found something (I think) :)

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18 minutes ago, riche100 said:

rob, send me your address and i will send you a mpu3 alpha display 

 

soon as i can get one and send it you 

 

merry christmas

 

private message me  .. 

Sorry Richie I missed this, what a star you are 🙂 thank you 🙂

I'll message you now.

Happy Christmas 🍻

 

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