Dragon's Lair Fans - Arcade Lifestyle

General Chat => Technical Area => Topic started by: anunaki on March 28, 2014, 10:47:41 PM

Title: replacing a crystal on a PCB
Post by: anunaki on March 28, 2014, 10:47:41 PM

Hi,

I have a MK sound PCB that doesn´t work. I also have a working one and I see the 3,58MHz crystal is missing on the non working one

Does the replacement part have to be the exact same MHz? Or can it be a little higher? I tried googling it, but didn't fin the answer.

Cheers,

Patrick

Title: Re: replacing a crystal on a PCB
Post by: Robinholland on March 28, 2014, 11:04:51 PM

exact same MHz

Title: Re: replacing a crystal on a PCB
Post by: anunaki on March 28, 2014, 11:05:16 PM

ok tx Robin

Title: Re: replacing a crystal on a PCB
Post by: level42 on March 28, 2014, 11:24:58 PM

You can go a little higher.................If you want a faster game ;););)

Stick with Robins advice :)

Title: Re: replacing a crystal on a PCB
Post by: level42 on April 05, 2014, 10:23:59 AM

Did you find one Patrick ?

Crystals often break during transport because they stand up so high on the PCB. The old crystals were really tall:

(http://www.gabotronics.com/components/com_virtuemart/shop_image/product/Standard_Crystal_4b6e12872dcdc.jpg)

today you can get them at a MUCH lower profile:

(http://thumbs.dreamstime.com/z/electronic-component-6517262.jpg)

I always try to use these when replacing but sometimes it is hard to find them in this shape with exactly the right frequency.

Title: Re: replacing a crystal on a PCB
Post by: anunaki on April 05, 2014, 11:02:46 AM

well, I found there were crystals and crystal oscillators and they're not the same?

didn't find the right spec chrystal yet

your post actually helps me, because I was looking for the exact matching component

Title: Re: replacing a crystal on a PCB
Post by: level42 on April 05, 2014, 11:39:06 AM

Crystal oscillators are different beasts. They contain not only the crystal but also the "surrounding parts" that normally required when using a bare crystal.
Crystal oscillators are bigger and flat rectangular shape and only started to be on boards from around the mid 80s.
Here's a picture of one opened:
(http://upload.wikimedia.org/wikipedia/commons/8/8f/Crystal_oscillator_internals.JPG)

Title: Re: replacing a crystal on a PCB
Post by: level42 on April 05, 2014, 11:40:37 AM

So what do you need a bare crystal or a crystal oscillator ?

I'm going to my local electronics dealer today anyway so I can pick one or two up for you if you like.

They are 3,579545 MHz though, to be precise :)

Title: Re: replacing a crystal on a PCB
Post by: anunaki on April 05, 2014, 12:30:06 PM

I need a 3.8mhz bare crystal. It for the sound cpu of my spare mk1 sound board

Title: Re: replacing a crystal on a PCB
Post by: level42 on April 05, 2014, 01:22:42 PM

Yeah, just checked the schematics....there really are 3,58 MHz crystals so the one they are selling is a fraction slower. Unlikely anyone could hear the difference, but if would want the perfect one in there too....

The site doesn't list the 3,58 MHz but I'll ask. Do you want me to get one or two ? They are around 2 euro.

Title: Re: replacing a crystal on a PCB
Post by: anunaki on April 05, 2014, 01:28:36 PM

Yeagh if they have them, please take 2 of them for me