Crystal replacement

emulators, hardware and classic software for atom + system machines
Post Reply
User avatar
sirmorris
Posts: 786
Joined: Wed Feb 11, 2009 12:18 pm
Location: oxfordshire uk
Contact:

Crystal replacement

Post by sirmorris » Sat May 23, 2020 11:18 am

Hi all,

A crystal on my issue 3 is huge. ENORMOUS. I'd like to replace it with something a little more discreet. Well both actually. In case I come to fit a RAMROM.
crystaltips.jpg
From my readings there are parallel and series cut crystals. They have different use cases. Referencing the Atom schematic it looks as if I should probably select a series cut. I tried a parts bin 4mhz low profile crystal when I was starting my resurrection I couldn't get the clock to start until I strapped a couple of 12pf caps from ground to the crystal's pins. Even then it was intermittent. Is there a difference between the big-can crystals and their low profile equivalents? Do they, for example, have the caps already integrated? Does anyone have any advice for swapping out the crystals for modern equivalents?

Thanks

C

Prime
Posts: 2858
Joined: Mon Jun 01, 2009 12:52 am
Contact:

Re: Crystal replacement

Post by Prime » Sat May 23, 2020 11:31 am

I've used low profile ones for both the 4MHz and the 3.57MHz ones on a couple of my Atoms, I pretty much supply a low profile 4MHz with a RAMROM these days as even the reasonable sized normal crystal will foul with it.

Cheers.

Phill.

User avatar
oss003
Posts: 3257
Joined: Tue Jul 14, 2009 12:57 pm
Location: Netherlands
Contact:

Re: Crystal replacement

Post by oss003 » Sat May 23, 2020 11:45 am

Or locate the crystal on the other side of the mainboard ... if it fits there.

Greetings
Kees

User avatar
1024MAK
Posts: 9906
Joined: Mon Apr 18, 2011 5:46 pm
Location: Looking forward to summer in Somerset, UK...
Contact:

Re: Crystal replacement

Post by 1024MAK » Sat May 23, 2020 12:30 pm

Different crystals may need different loading capacitors.

Try with a new crystal from a mainstream supplier (so you can look up the actual spec and data).

Mark

User avatar
anightin
Posts: 453
Joined: Thu Aug 23, 2018 2:03 pm
Location: Cambridge UK
Contact:

Re: Crystal replacement

Post by anightin » Sat May 23, 2020 12:44 pm

Prime wrote:
Sat May 23, 2020 11:31 am
I've used low profile ones for both the 4MHz and the 3.57MHz ones on a couple of my Atoms, I pretty much supply a low profile 4MHz with a RAMROM these days as even the reasonable sized normal crystal will foul with it.

Cheers.

Phill.
Have low profile crystals in my Atoms now (since mid last year) and quite necessary to save space as Phill says :)
5E94B2F7-3AA8-4C59-A121-69F8A1E50842.jpeg
I guess I got lucky when picking some from eBay, I remember the 4MHZ one was 49HCS

Kazzie
Posts: 1402
Joined: Sun Oct 15, 2017 8:10 pm
Location: North Wales
Contact:

Re: Crystal replacement

Post by Kazzie » Sat May 23, 2020 2:04 pm

anightin wrote:
Sat May 23, 2020 12:44 pm
I guess I got lucky when picking some from eBay, I remember the 4MHZ one was 49HCS
HC-49/S will be a description of the physical package size. (Non-low profile ones would be HC-49/U or HC-49. I think the huge ones as pictured in the first photo may be HC-51.)
BBC Model B 32k issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM, ZIDEFS with 512MB CF card
Acorn System 1 home-made replica

Post Reply

Return to “acorn atom and acorn system series”