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Nite a Nudge Lamps problem middle reel

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Hi i have a 1986 Lite a Nudge on MSP2 and all 3 bulbs on the middle reel will not light i have checked the loom and its fine so am guessing its a Motherboard problem

 

is anyone on here familiar with this board that can help me?

 

thanks 

 

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Swap the reel connectors around on the back of the reel cage, see if the problem moves with the connector.

Don't discount the bulbs being blown !!!!

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MPS2 has no triacs on the MPU - they are on the hex pack.

 

Possible that one of the transistors has gone short circuit (Q1-Q16) top left. they are each protected by resistor (R1-R16) respectivley... the 2.2 ohm resistor is also fusible so goes open circuit for protection.

 

Sometimes it's just the resistor that has gone open circuit and thr transistor is OK.

 

Transistor is a TIPP116 - also found on maygay M1b, JPM system5 and possibley Impact (Maybe more) but is no longer made.

 

Fusible resistor can be a pain to get but aparantely can't be replaced by a normal carbon film 2.2 ohm resistor as the transistor can burn through the board.

 

I did get a load of suposed fusible resistors but found them to not fuse so I only use ones from scrap boards these days.

 

I'd start by checking the resistance of R1 to R16. one or more will probabley be open circuit...

Edited by Louie Bee
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Hi thank you this is great info am gonna leave it i can live with the bulb not being on 

if i ever get brave il take the main board out and replace battery too 

 

thanks again

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TIPP116 OK (but expensive), Carbon resistors no good. not fusible. Not sure on the last one can't remember the larger transistor on MPS2 as onlu seen 1 fail.

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you'd better be brave on the battery before it eats the MPU ;)

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Battery looks ok to be honest i know the the wires that come from the centre reel bulbs to the main connector are pins 1 49 and 50 or the 3 pins to the right of teh connector they tested ok to the loom but not sure how to trace these to (Q1-Q16)  (R1-R16) i can test all the resistors one by one but not the Transistors no might have to just leave it 

 

​thanks for your help ;)

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There will probs be only 1 open cct resistor... say it's r8 then transistor 8 is suspect... if you check the resistance between each of its 3 pins, 2 of them will be really low. Can compare with same pins on any of the other 15 transistors and you'll see it's way different.

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Just looking on Diagrams it says HD2 reel lamps are using pins 47 48 49 and 50 if 4 reels 

now on the lamp diagram it says R1 R2 R3 R4 combined with Q1 Q2 Q3 and Q4 are also used for HD2 pins 47 48 49 50 

 

so R1 and Q1 is for HD2 pin 49 or S00 R2 and Q2 is for HD2 pin 50 or S01 R3 and Q3 is for HD2 pin 47 S02 R3 and Q3 is for HD2 pin 47 S03   Pins 1 2 and 4 from HD2 are Sink lines what ever that is ?

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Have you checked the connections between the bulbs and the MPS board are good? As the reel bulbs are multiplexed it could only take one poor connection to stop all three bulbs working.

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the manual says r1 to r16 is 2r2 5 percent half a watt mate 

louie would no more  :)

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Have you checked the connections between the bulbs and the MPS board are good? As the reel bulbs are multiplexed it could only take one poor connection to stop all three bulbs working.

The wire to the reels has no voltage i replaced all new holders and bulbs first ;)

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R1 to R16 are fusible or why do they go open circuit after the transistor fails? The one in my link is half what fusible 2.2 ohm so matches.

 

Think the originals were metal film where the one in my link are ceramic.

 

Check resistance of all 16 without removing them from circuit. Open circuit ones are obvious as are way more than 2.2 ohm

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