# 32.768 Khz Oscillator Problem.

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#### chemelec

##### Well-Known Member
I have some older watch crystals that I removed from old digital watches.
I made some oscillator circuits for them.
One circuit using a 4069, and some with transistors and also fets circuits.
All circuits Work Perfectly.

However, I also have some NEWER, Physically Smaller crystals but the SAME Frequency.
These are made by "Seiko", They are New parts on taped reels.

But NONE of these will work in any of these same circuits.
And I have tried all modifications/part value changes I can think of.

Anyone have any ideas as to why?
Or a Circuit that I might try?

#### kchriste

##### New Member
Forum Supporter
The only reason I can think of, other than that they are faulty, is that they have a different loading/drive spec than the older ones. I suspect you've already tried searching for a datasheet.

#### Boncuk

##### New Member
They might have the burden capacitors built in with the ground connected to the case. Try to use them without external caps and see if they work.

Boncuk

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#### chemelec

##### Well-Known Member
This is a Seiko Crystal, Part Number SSP-T6-7PF-20PPM.
From what I can determine, Loading Capacitance is 7PF, as stated in the Part Number.

But I can't find anything else about it, Such as the Resistor value.
I Think it should be abut 40K ohms.

The "T6", I Don't know what that is, Unless it the Case Style.

#### kchriste

##### New Member
Forum Supporter
The 4060 has an input capacitance of 5-7pF. The 4069 has 6-15pF. Maybe try it with no capacitor.
This is all I could find on those crystals:

#### Attachments

• ssp-t6.pdf
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#### Diver300

##### Well-Known Member
The smaller crystals will have a larger ESR (Equivalent Series Resistance) so they need more gain in the circuit that drives it.

The load capacitors don't have a lot to do with it, but if there is a series resistor you could try reducing it. Similarly, the parallel resistor needed with a 4069 or 4060 should be 10 MΩ or more.

https://ndap3-net.ebz.epson.co.jp/w/www/PDFS/epdoc_qd.nsf/2668203aa9368a6349256a9c001d58b3/737394e88f20bfba4925736b002b4c07/$FILE/FC-12M_E093.pdf https://ndap3-net.ebz.epson.co.jp/w/www/PDFS/epdoc_qd.nsf/2668203aa9368a6349256a9c001d58b3/f6f1fd30adfd76b64925707c003af46e/$FILE/C-TYPE_E08X.pdf

The smallest crystal has an ESR of up to 90 kΩ while the standard watch crystal (3.1mm diameter can) has and ESR of up to 35 kΩ. Therefore it will be loosing 3 times as much power, so making it oscillate is more difficult.

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