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Defender transformer re-wiring check

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Judder View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Judder Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2012 at 8:57pm
Originally posted by andyman andyman wrote:

Somehing's not right, leds should flash on successful boot, check cabling to rom board, measure +5v, +12v & -5v on the cpu board, use one of the (24) 4116 ram chips, needs very close to 5v

Just because the LED's on the PSU are on, doesn't mean you are getting the marked voltage and if under 4v, nothing will happen

Andy. 

Thanks Andy

Damn :-/ 

Sounds like it's Multimeter at the PSU first to check what that's churning out and then the rest...

Will report back what voltages I get and then see where to go from there.

BTW thought it might be nice on the forums to have an introduction section, as I keep asking for advice but have never really said 'Hi!' :-)

Alex
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andyman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote andyman Quote  Post ReplyReply Direct Link To This Post Posted: 10 May 2012 at 9:05pm
That's what this bit is for LOL
"The person you were referring to is a short, shotgun wielding nutter with a vindictive streak 3 miles long. And a Star Wars cockpit "
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Judder Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2012 at 6:09pm
Originally posted by andyman andyman wrote:

Somehing's not right, leds should flash on successful boot, check cabling to rom board, measure +5v, +12v & -5v on the cpu board, use one of the (24) 4116 ram chips, needs very close to 5v

Just because the LED's on the PSU are on, doesn't mean you are getting the marked voltage and if under 4v, nothing will happen

Andy. 

I braved my fear of being near live electronics and measured the voltages as per the Coinop.org guide and here's what we have

4J2-8 = Reference ground

and tested

4J2-12 = +5.07 (should be +5VDC)
4J2 - 3 = +11.47 (should be +12VDC regulated)
4J2 - 5 = +14.50 (should be +12VDC unregulated)
4J2 - 1 = -5.04 (should be -5VDC)
4J2 - 4 = -14.85 (should be -12VDC unregulated)

So the + and -5V seems to be pretty spot on, the +12V a little low (but OK I would have thought in limits and fits) and the + and - 12VDC unregulated seem to be high.

Any thoughts from my more learned fellows??

Thanks! Alex
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb lilley Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2012 at 6:14pm
Voltages are fine. Don't worry about the unregulated voltages being high, the boards will just pull what they need. +12VDC is a tad on the low side, but I reckon should still fire up the boards ok. So .... Your problem is elsewhere.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote andyman Quote  Post ReplyReply Direct Link To This Post Posted: 11 May 2012 at 7:04pm


Is there eproms in these sockets ?

Depending on revision/label the centre No.5 might be empty but the other two shouldn't

Otherwise

Does the screen do anything, flash, static charge, neck glow ?? forget your voltage detection stick, they give false readings anyway LOL

As a first replace the ram, this sorts most issues. Most will say here, use 4164 but I have always used 4116 in all the boards I have repaired and last did mine in 2007, still going strong on rebuilt psu Big smile

Check rom board cable and connection to cpu, usually the other ptoblem

Andy
"The person you were referring to is a short, shotgun wielding nutter with a vindictive streak 3 miles long. And a Star Wars cockpit "
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Judder Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2012 at 3:24pm
Originally posted by andyman andyman wrote:


Is there eproms in these sockets ?

Depending on revision/label the centre No.5 might be empty but the other two shouldn't


Yes, although the Eproms don't look in a wonderful state with at least 3 or 4 being replacement ones as far as I can tell. 

These ROMs are White/Red ones so not sure about socket 5 being empty but seem to remember reading somewhere that that should be correct.

I also have a green set of eprom ROM board which looks in a much better state - I might try that if all else fails (but seem to remember there's a jumper on the CPU somewhere I need to change it I do...)

Here's the current ROMs





Originally posted by andyman andyman wrote:


Otherwise

Does the screen do anything, flash, static charge, neck glow ?? forget your voltage detection stick, they give false readings anyway LOL

I trust my voltage detection stick implicitly as it warns we where that dangerous 240V electricity lies :-) 

The screen definitely makes the sound a TV makes when it turns on and powers up but there is no flickering and I haven't studied the neck long enough to see if it glows. Will do so on Monday...


Originally posted by andyman andyman wrote:


As a first replace the ram, this sorts most issues. Most will say here, use 4164 but I have always used 4116 in all the boards I have repaired and last did mine in 2007, still going strong on rebuilt psu Big smile

Check rom board cable and connection to cpu, usually the other ptoblem

Andy

Will check the ROM connection first, try replacing the ROM board, try replacing the CPU board (I have a non-tested spare of this as well) and then check on the RAM

I seem to remember I bought a whole tube of RAM in anticipation from some eBay seller in Bulgaria - seems to be the only country where they are still using it LOL

I'll put up a picture for reference...

Thanks again for the tips!

Alex
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Judder Quote  Post ReplyReply Direct Link To This Post Posted: 12 May 2012 at 7:24pm
Originally posted by Judder Judder wrote:


And the ROM board is showing 4 solid LEDs


Which according to the link below implies that either the lead to the ROM board is bad/loose/not connecting or the clock circuitry on the CPU board has failed.

http://www.arcadesolution.com/4leds.html

Time to find an IDE cable to try instead and give my replacement ROM board a go....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Judder Quote  Post ReplyReply Direct Link To This Post Posted: 14 May 2012 at 4:20pm
Originally posted by Judder Judder wrote:

Originally posted by Judder Judder wrote:


And the ROM board is showing 4 solid LEDs

and give my replacement ROM board a go....

Replacement ROM board powered-up, and the same solid 4 LED error Ermm

So I think that points more towards the CPU board, so I'm going to try swapping that out and test with the two different ROM boards.

BTW I've broken the retaining clip on two of the ROM connectors, just by removing the cables as the plastic had grown hard with age - is there any way to remove them without this happening?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote andyman Quote  Post ReplyReply Direct Link To This Post Posted: 14 May 2012 at 4:29pm
Try wiggling the rom board cable when you power up
"The person you were referring to is a short, shotgun wielding nutter with a vindictive streak 3 miles long. And a Star Wars cockpit "
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