Bringing an EDOT to life....

jonathan1138

Active member
Joined
Jul 20, 2010
Messages
1,648
Reaction score
7
Location
Whitestone, New York
Hi all. A month or so back, i posted about an EDOT that a fellow Klov'r hooked me up with. I tore the thing down, cleaned it up, recapped the monitor, and just getting to the fun part of getting it to run.

CDJump sent me back the boards - most of them anyway (I left out the relay boards) - many thanks, he does great work.

So here is where i'm at:

PS spits out 5.10 and 11.5 (highest it will go) with J4 / J5 not hooked up (no connection to PCBs). Thats good.

But once i plug in all the PCBs (again, this thing is a monster - Flasher boards, Main PCB, Squawk and talk, etc), voltage drops considerably (below 2). I started to single boards out - for example, whats the voltage with just the S&T board (4.2). With the main PCB only, it drops to 1.29434. Flashers bring me below 4 as well. Doesnt seem to be a single PCB impacting voltage drop.

is there a wiring issue maybe? The harness looks original / unhacked....Any direction is appreciated.

Thanks.
 
Ok. Thinking about this some more.

Although i am not ruling out a connection / wiring issue - another theory: If voltage is dropping hard on the Power supply when i plug a load in, the PS seems to have regulation problems. After i posted last night i looked at this small board below the PS that i didnt send to CDJump - its got a Cap, Transistor and a couple of resistors - its titled "5V auxiliary Board".

Maybe that board also helps in regulating power? A bad cap or transistor? I will have a closer look at at.

Any other ideas would be appreciated. Thanks!
 
Your power supply has a voltage regulation failure. IIRC, the small aux board is for -5VDC?

Anyways, your power supply repair options are:
1) find someone who repairs them
2) buy a repair kit from Bob Roberts and hope that fixes it
3) buy an MCR power supply replacement kit
 
Thanks - thats what it sounds like...

But i just got it back from CD Jump, he ran it in a SH for a few days. It was rebuilt by him, he has been walking me through (kindly i might add) some quick tests.

Is there something i can check to rule that in or out?
 
Oh yeah - i wish that a Arcade Shop PS would work here - i would of had that in place a long time ago.

But i learned that with an EDOT, there is too much going on (sound board and light boards depends on the PS, no provision for it on the arcade shape adapter), so went this route....
 
Oh yeah - one other note. When hooking that PS up for the first time, it blew the 3/8 slow blo fuse at F1. CDJump suggested a 1 amp fuse, which i am using now....

I am going to pick up a 3/8 today i hope, and try it without a load, to see if it gets blown again.
 
Worse comes to worse, you could run the PCBs off the switcher and lights, etc. off the original PS? I was lazy with my Pac 60:1 restore and didn't want to hack any harnesses, so I use the original PS for the monitor and marquee and the PCBs off a switcher.
 
Agree - this can be done.

Another suggestion that came my way was to check the Transformer block - the Diode assembly at the bottom of the transformer.

Anyone know what values they are? Hoping i can score on on the way home from work just in case i find thats the problem, and the manual doesnt tell me much....
 
Double check all fuses on the transformer block. I had one go bad but looked good. Power supply would seem to regulate but system would reset, then eventually not boot at all.
If you have another MCR game, try a known working transformer block.
 
Ok - a little progress.

I tested every fuse (as i did before) - although they tested good, i still replaced them all with shiny new ones. Now, with no load, still getting 5 volts - plug it in all - drop to 3 volts (almost the same as before) BUT - i get a very loud buzzing from the speakers, and the screen is white and wavy - progress!

Sounds like something on the transformer block? Going to take that out now. Could it be the caps or the diodes (hoping its not the caps - then i have to wait for the parts!)
 
Opened up the Transformer.... I dont see any Diodes - i do see, coming off the caps, two 5 watt / 50 ohm + 10 ceramic resistors - see the pics...

Is that "normal" / supposed to be there? If not, what is the original and how do i hook it up?

DSC03274.jpg


DSC03275.jpg



I really appreciate any help.
 
Looking at an old post from KrakerJac, he suggests checking three things at the bottom of the transformer:

The big caps should be a value of 55000 and 100000 (not sure how to check that)
The rectifier. Meter test - But i dont see a rectifier!
The diodes (there are 4 of them). I dont have them either....

Anyone that has been in the underbelly of a Bally Power brick - does mine look way off? Anyone have pics or suggest how mine should be? Thanks.
 
CDJump pointed out to me the MR1120 diodes (above the big caps) are whats needed to be looked into....

Maybe i should just replace those and the big caps.
 
Sounds like something on the transformer block?

I'm still thinking it's voltage regulation failure on the PS board. While the transformer can cause voltage problems, the odds are 90 times out of 100 its the power supply board. The transformer blocks are pretty reliable, where as the PS board is a well documented failure point.
 
A glimmer of hope perhaps.

I installed new Transformer caps tonight. I actually saw Discs of Tron running!!! BUT, within a minute, the .5 amp fuse on the MCR PS turned orange and quickly ended its life.

Try to pinpoint whats causing the fuse to blow - I unplugged all PCBs, put a new .5 amp fuse in, i get 5 volts....

Plugged in all boards except the sound board and main PCB... get 5 volts....

Plug in the sound board, i drop to 3.9 volts. Turn game off, unplug sound board, plug in game board.... turn it on and get 1.3 volts.

So, something is shorting on the main PCB and / or the sound boards (CDJump just had these running....).

Question in the meantime - i am out of .5 fuses - can i use 1 amp fuse on F1 on MCR powersupply to keep going / isolate the issue?

Tomorrow i am expecting Transformer diodes - i am going to replace them just for the fun of it.

Thanks.
 
To verify that the board doesn't have a short, measure the resistance across the boards +5VDC input and its ground. If its not shorted, construct a resistor network that matches the boards resistance (the resistors probably need to be able to handle a few watts, like 10 or so) and connect to the power supply. Then you can see if the voltage still drops under load. If it does, you probably have a voltage regulation issue.

Also, you can check the voltages of the transformer itself to verify if its good; should be outputting +8VDC and +15VDC.

Link to the manual schematics and manual text...

http://users.rcn.com/jenison/mars/trouble/part/powersupply/MCR/
 
Have you checked the LM305 or the small transistor next to it in the 5V section on the regulator board? Are you sure the bottlecap transistor on the heat sink that is part of the 5V section is good?
 
Well the latest - i replaced the big caps and the 4 diodes on the transformer brick. I also rebuilt the J4 / J5 connectors to the PS. The game plays now!!! Voltage is steady.

Still having an issue though - F4 on the transformer brick is burning out within ten minutes of the game being on.

Looking at the schematics but not sure what that fuse is tied to, so that i can narrow it down to something in the wiring / PCB. If anyone knows, please let me know....
 
Back
Top Bottom