Blue Shadow Analog problems (Sega Hangon Bootleg)

[RenegadeR]

So I got this Blue Shadow upright cabinet which seems to be a hangon bootleg.

The analog controls dont seem to work, in the test menu I can get the gas and brake pedal going from 78 to FF or lower but 7F seems to be the minimum and according to the Sega Hangon manual it should go to 0.

Anyone any ideas what this problem could be, I even added a pot in series with the 5v input and even when it goes down to 3v it still is showing 78 upto FF depending on the pot position.

 

[Retromanic2]

I would look for a broken tooth on the pot gear.
Then check if the gear is slipping on the pot shaft.
You might even have a wrong gear that has been fitted.
I had most of the above on my hang on controls.

 

[RenegadeR]

Thanks for your reply.
I don't think it has anything to do with the pots themself.

I already tried other pots and even when I disconnect all controls it still is at that 78 value.

Maybe it is the HEF4051 8-channel analogue multiplexer/demultiplexer?

Maybe it has like a bit stuck?

 

[Mc-Q]

you wired the pot wrong,
you need 5v on one end and ground on the other end, the wiper pin will then go from 5v to 0v smoothly

 

[RenegadeR]

Wiring is original and if I swap ground and 5v then it would be FF on default and when press brake or turn gas it will go to 78 as lowest.

 

[RenegadeR]

Are there shematics available for hangon that shows like what certain ics do?

Ok found them.

https://segaretro.org/images/d/d7/HangOn_Schematics.pdf

 

[Mc-Q]

it has a regular ADC chip but it may not be bad - probe or scope all 8 databits from it.

 

[RenegadeR]

So after probing the 8 databits all seemed just fine!

Now I noticed something when i short the steering pot output pin to ground the brake and gas handle go lower than 75 even to a point where they work just fine!?

Also the steering works on a tiny fraction of the pot the really close to 0v part then it steers if you go over a certain threshold the brake and gas mess p again.

 

[Mc-Q]

maybe there is a break in the ground/5v wires to one of the pots or a break inside one of the pots causing voltage to get messed up
i'v seen pots fail many times on pole position, but as it only uses one i dont know if it would effect anything downstream

 

[Mc-Q]

looking at outrun - which may be similar, the signals go into a selector chip before the ADC and that has a capacitor and a couple of diodes on each input
it may be worth checking the diodes
(if your board is similar)

 

[RenegadeR]

Yes there is a selector chip, which I ordered some new as I was not sure if that works as it should, i replaced the caps and checked the diodes which were fine.

Also the monitor has problems and it is a fault that matches the game name haha, it shows like a blue shadow coming from the left when there is much blue on the screen so like the blue sky and when it changes to another color like when in the test menu then the blue shadow goes away, all caps where checked and replaced if needed but I think it is on the neckboard the bf871s which I should get one of these days.

Also no sound haha this is a problem child for sure

 

[Mc-Q]

any time i used to get a machine i would go right over it so it behaved afterwards.
i dont have space anymore so just collect pcb's
what monitor is it? it must be pretty old to use bf871's instead of a chip

 

[RenegadeR]

It is an Hantarex MTC-900-e there are 2 bf871s per color on the neckboard I hope its one of those 2 in the blue circuit.

 

[Mc-Q]

i used to diagnose that type of problem by just swapping the suspect parts with those of another colour - if the problem changes colour your suspicions are confirmed.
as for the gameboard - looking at the schematic you could pull the selector chip and jump one of the pot inputs directly to the adc to test it

 

[RenegadeR]

So I got the bf871s in and replaced both of them on the blue channel and at first it looked fine but again after like 5 minutes the blue shadow came back!? And yes even when disconnecting the blue signal from the monitor that shadow came over the monitor but this times it was just black...

 

[Mc-Q]

i'm confused - can you post a picture?

 

[RenegadeR]

So it starts out ok but you can see a little on the left already


Then it gets worse and worse... colors stay fine except under that blue shine and when you go to the menu screen its slowly dissapates again?!

 

[Mc-Q]

thats just wierd,
do you have any other hantarex chassis available?
i'd almost suspect a gun/tube issue if it wasnt so fatal!

does it ever effect the upper half of the image btw, or just the lower?

 

[RenegadeR]

Upper also but you cant see it because of the blue sky.

Sadly I dont have any other chassis at the moment.

 

[Mc-Q]

i notice on the schematic the gun-drive circuits have a 3k3 resistor just before they enter the tube,
lets try something.
R141 is RED
R142 is GREEN
R143 is BLUE
if you desolder red and blue and bend them so the red signal goes to the blue pin on the tube and blue signal goes to the red pin on the tube.
see if the effect changes