Sound buzz (noise) on D.E

[MartyJ]

Yep, agreed on that MM.

Just to be complete, I put a new connector on the power plug for the audio board (just in case old earth was not making good contact).  Still no better.

Also replaced BR on PSU as well.

I am now completely stumped and out of ideas.   

[Marty Machine]

At least you've given new life to most of the board by changing parts 

I think you're at the point where you'll need a Cro to analyse the audio signal and follow it around the machine to see where it starts/stops, and look at all supplies carefully...even though you're replacing caps, maybe their too low in value by design?
for example, a large 470uf or 1,000uf might actually need an extra 1,000 to 4,700uf wired across it, to assist filtering....You might find the hum go instantly !

There might be a LAH service bulletin that states "filter cap too low in supply xxx, change to 10,000uf"
who knows ???
Maybe mark's (quiet) machine has this different cap fitted ????????

Other than that, the easy solution as a tempo measure will be the amplifier-gain mod, altering some resistors to quieten it.

Pity you dont have another LAH you could swap cards across with and see if the hum moves to the other machine.......not that i think mark will let you do that hehehehehe.

MM.

[Strangeways]

There was a service bulletin for a similar problem on the Stern Site.. It involved changing a few components from memory.

Could be a "last resort" ?

[MartyJ]

There was a service bulletin for a similar problem on the Stern Site.. It involved changing a few components from memory.

Could be a "last resort" ?

I did have quick look, but only found one for mis-wired speakers....It wasn't a thorough search as yet!

I might try to get some better speakers for it (the new ones did make some difference) (with shielding).  If I can find some, I might try installing shielded cabling for speakers as well....Just as a last ditch effort

[MartyJ]

Just for a test, before I do anything else as previously suggested I ran a new molex from the speaker out on sound board with new wires straight out of backbox a couple of metres to speaker sitting well away from machine.  No different.

So I guess this eliminates noise introduced  from loom and speakers being next to DMD.....

I just found the bulletin you were refering to Nino too.

http://www.sternpinball.com/downloads/sb133.pdf

I have no idea whether this would work on a D.E Soundboard for LAH.  I would defer to the experts on that one.

[MartyJ]

I went back to Jaycar this morning and bought some slightly less crappy 4" 4ohm speakers for the display panel.  Although the hole patterns are the same, the new ones have a tweeter which sits proud of the mounting.  I've made some wooden spacers to slip in, but I will try to get some circular spacers (mdf) to make it look a bit more professional.

I also installed some ferrite EMI things on speaker wiring.  They didn't make much difference but the speakers did.  The loud humm is now a slight humm and is now equal to that of my Simpsons, which is only slight.  I still get the G.I noise but I'm satisfied that is a factory feature...

So I think the issue is resolved now!

Thanks again for everyones input...   

[Pinball Fixers]

Interesting... so it was the crappy speakers that were used causing the problem...

That's a handy tip to know for future!

Mind you, having good speakers in pinballs does make a big difference to the sound.

[MartyJ]

Interesting... so it was the crappy speakers that were used causing the problem...

That's a handy tip to know for future!

Mind you, having good speakers in pinballs does make a big difference to the sound.

Well, yes.  But the strange thing was they were brand new crappy'olla speakers.  The new (old) ones were just single cone cardboard $3.00 specials.  The only reason I bought them because they were almost identical to the old ones..But still the humm, just slightly different tone.

With the new ones (dual cone) $30.00 ones from Jaycar - really did make a big difference.  It now sounds the same as what Marks did at the factory. 

So I guess the moral of the story is that if you have a hum, and its not transformer vibration on the cab, and its not a grounding issue, and its not a cap issue, and its not a BR issue then upgrade the speakers in question and you should be better!

[Strangeways]

Great perseverance, Marty..

A 5 minute job next time you buy a DE !

 

[MartyJ]

Great perseverance, Marty..

A 5 minute job next time you buy a DE !

 

After taking your advise to go to Marks (& got away without buying a machine    ) I knew mine wasn't right.

I'm not happy with the mounting at the moment (if someone was to look, it does look a bit backyardish) but I've bought a set of MDF ring spacers for 4" speakers on Ebay. $8.95.  They will be sprayed black then put in.

Not sure if I would buy another D.E...Not that I dislike them, but other than a GNR I think that would be it.  (although the LAH was a sleeper and not expected)...

I really love the Sys 11 Williams.  Such a nice game to play.  But I should spread the love to a Gottlieb, a Stern (to keep wifey happy) and I wouldn't mind an Alvin G as I know nothing about them...

To be honest, any machine that comes along at the right price I wont discriminate!

[Marty Machine]

Wow, nice solve....eventually.

I think you mentioned earlier that the hum was dominate more in one speaker only?
I wonder if maybe the speaker was suffering a partially burnt coil form being overdriven too much (previous owner) and possible making it a little more resonant at low frequencies, especially 50Hz hum????

Also, i wonder if the original speakers are maybe generic audio speakers 20hz-20khz, and your replacements might be generic mid-range speakers for the 100's Hz upwards scale, therefore not being too resonant at low frequencies like 50Hz hum????

Also, the new speakers are now mounted on a spacer/washer/, i wonder if that's helping to isolate hum from the speaker into the spaeker-panel too??

Quite possibly the supply of cheapy generic speakers has been the problem right from manufacture.

I would have thought to use mid-high Freq speakers up top, and keep all the bass stuff in the cabinet bottom driver.

Nice find, glad you got thru it ;-)
MM.

[MartyJ]

Just a couple of photos of finished product.  Spacers are just generic MDF ones from eBay...Cost about $8.00....Slight modification to get them to fit and all good.

[Strangeways]

Great work, Marty..

 

[Nug]

hey not to rain on the parade, but i dont think that would have fixed it...my guess is you had the speaker cableing wrapped around something and inducted the noise, which since playing around in this general vicinity could also have 'moved' something else in the loom.

the other thing was it a 50hz hum or lamp matrix hum ( first is constant, second changes with lamp show)

glad you sorted it nonetheless

 

[MartyJ]

Hi Nug,

The G.I noise is still there...Thats not going anywhere.  The humm has gone from being very loud to quiet...The only thing which did this was a better quality speaker...??