archeocomp Posted August 8, 2020 Share Posted August 8, 2020 (edited) Hi, here is a replacement for hard to find full can oscillator 8.333MHz with duty cycle 50% for XF551 drive. It is based on 74HCT6323A 5 Volt IC. The board has exact footprint of a Full-Can Oscillator. Needed components are 1206 - resistor R1 can be 100k-2M (1M-2M2 tried and working), smaller capacitor C1 is 33p (tried 22p-33p and working), and as specified in datasheet for frequencies higher than 5MHz second resitor is to be replaced by capacitor half the capacity of C2 = that means R2 is capacitor 47p (tried also 68 and 75 and working). Crystal is double the frequency - 16.666MHz sourced from Aliexpress https://www.aliexpress.com/item/32867725002.html 74HCT6323A is configured with internal prescaler :2. This ensures perfect duty cycle 50%. Board is shared at OSH Park https://oshpark.com/profiles/archeocomp I have also made prototyping board with THT components, which can be populated with socket pins for rapid experimenting with components values without soldering. And for those who would need half can oscillator footprint but without prescaler - there are two similar boards (SMD and protoyping THT) shared at OSH Park based on 74LVC1GX04 IC. Full Can and protoboard Half Can and protoboard Full Can with crystal from Ali Edited August 8, 2020 by archeocomp 3 1 Quote Link to comment Share on other sites More sharing options...
Wally1 Posted August 9, 2020 Share Posted August 9, 2020 I prefer solderless upgrades, myself too. nice work. Quote Link to comment Share on other sites More sharing options...
Jeffrey Worley Posted December 3, 2023 Share Posted December 3, 2023 This specific frequency is very hard to find. Impossible. I DID find affordable crystals at 8.388608mhz. The difference is less than 6 tenths of 1 percent......... I'm trying this to resurrect my Skydata SK-551p disk drive. The existing 8.333mhz crystal isn't producing anything.. best, jeff Quote Link to comment Share on other sites More sharing options...
guus.assmann Posted December 4, 2023 Share Posted December 4, 2023 Hello, It's also possible to use a 25Mhz oscillator and devide the frequncy by 3. BR/ Guus 1 Quote Link to comment Share on other sites More sharing options...
Jeffrey Worley Posted December 5, 2023 Share Posted December 5, 2023 On 12/4/2023 at 12:49 PM, guus.assmann said: Hello, It's also possible to use a 25Mhz oscillator and devide the frequncy by 3. BR/ Guus Do you think the 8.388mhz crystal will work? Quote Link to comment Share on other sites More sharing options...
+bob1200xl Posted December 6, 2023 Share Posted December 6, 2023 I would guess that the tolerance of an off-the-shelf oscillator would be 1%? You're pretty close to that. They use 8.33mhz to sync with a 288 RPM Atari drive. Should not be that picky... A 1050 works OK off speed from 288, right? Bob Quote Link to comment Share on other sites More sharing options...
Simius Posted December 6, 2023 Share Posted December 6, 2023 XF551 use 8.333M crystal to sync with 300RPM standard PC drive. The nominal clock of the WD1772 controller is 8M. 300/288 *8 = ~8.333. This is only 4% but it make difference. 8.388M will probably work. It's only 0.6% deviation. Quote Link to comment Share on other sites More sharing options...
Jeffrey Worley Posted December 6, 2023 Share Posted December 6, 2023 Thank you for your good news and encouragement! If this crystal works, I'll have them available for the ask. best, jeff Quote Link to comment Share on other sites More sharing options...
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