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74HC4060 chip in 32.768 khz oscillator

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kd4pbj

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74HC4060 chip in 32.768 khz oscillator

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A few months ago you guys helped me in an interfacing HC-TTL to CMOS question. I was looking for a good oscillator circuit for 32.768 khz and was going to use a 4069 and a 74HC4060 to divide it down to 1Hz.
I took you up on your advice to just use the 74HC4060 as the oscillator, and then divide the 2 hz output with a flip flop (tried a 74HC74 but that didn't work so I ended up using a 74LS74 with great results). I got a nice 1 Hz pulse.
I built up several versions of the circuit (used the circuit at
**broken link removed** but had to change the 10 pF to a 22 pF and the 22 pF to a 25 pF trimmer to get dead on frequency with the crystal that I had).

My question is this. I have built three versions now:
one with a DIP 74HC4060 and DIP 74LS74
one with a DIP 74HC4060 and a SOIC 74LS74
and now one with a SOIC 74HC4060 and a SOIC 74LS74

I can't get the one with a SOIC 74HC4060 to work correctly. I removed the 74LS74 and am now experimenting with just the oscillator in an attempt to get it to work. I have tried several times with different chips, board layouts, crystals, etc. thinking that I had a bad part and I just can't get it to oscillate correctly. It either oscillates in the several hundreds of kilohertz range, or in the 20-30 Mhz range as measured both with a scope and a frequency counter.
Any thoughts? I hate to give up on this one but I can't figure out why there was never any problem with the DIP version but the SOIC version of the chip won't work in this circuit.
Thanks!

Chris
 
The Reset pin (12) needs to be connected to GND. Otherwise, it may be charged to either logic 0 or logic 1. Sometimes it will work, sometimes it won't. However, if this is the problem, I wouldn't expect to see any oscillation.
Looking at the Philips datasheet, they recommend 2.2k for R2. 560k does seem really large.
 
Last edited:
Looky! Ron got his hairs cut. Is it a little smoke rising at the back? A feather?
 
The 74HC74 should have worked. Did you connect the unused inputs to +5 Volt? As Ron wrote, unused CMOS inputs must be terminated to +5V or gnd - depending on whether they are active high or active low.

In the 74HC74 case, the S & R inputs are active low so, if not used, they must be held high.
 
audioguru said:
Looky! Ron got his hairs cut. Is it a little smoke rising at the back? A feather?
Just call me Tonto (look that up in your Spanish-English dictionary).
 
Hi guys,

I did connect pin 12 (reset) to ground through a 10K pull down resistor.
The weird thing is that I got the oscillator up and running great on my first two tries (prototype 1 and 2) using a DIP counter but the SMT part doesn't give similar results for prototype 3. I didn't know if there may some other issue like less capacitance (or something else) causing this not to work.
On the 74HC74 part, I tied unused inputs to ground through a 1K resistor. Not pulling them high might indeed be why it didn't work.
Do I need to do anything with the unused inputs on the 74LS74 on prototypes 1 and 2? All works well with the circuit but if I need to go back and do the mods I will.
Also what about inputs on a 4069? From now on I will remember to do something about unused inputs but I don't have much digital experience so I didn't do it to start with.
 
Hi Ron,
I also watched The Lone Ranger with Tonto and the horse Silver when I was young.
My Wifey (from Spain) says that tonto means "stupid".

I always thought that Tonto was a Native Indian, not a Mexican.
 
kd4pbj said:
I did connect pin 12 (reset) to ground through a 10K pull down resistor.
Good but you don't really need a resistor to pull inputs low; a direct gnd is adequate.
kd4pbj said:
The weird thing is that I got the oscillator up and running great on my first two tries (prototype 1 and 2) using a DIP counter but the SMT part doesn't give similar results for prototype 3. I didn't know if there may some other issue like less capacitance (or something else) causing this not to work.
Did you connect 100 nF bypass capacitors across the Vdd ~ Vss pins of the ICs? If not, this can cause strange results.
kd4pbj said:
On the 74HC74 part, I tied unused inputs to ground through a 1K resistor. Not pulling them high might indeed be why it didn't work.
Yes, they are Active Low, so a low on one or both pins will prevent the FF from toggling.
kd4pbj said:
Do I need to do anything with the unused inputs on the 74LS74 on prototypes 1 and 2? All works well with the circuit but if I need to go back and do the mods I will.
No, the 74LS series is TTL which treats an open as a high. That's why it works. However, CMOS is not really designed to drive TTL, but there is obviously enough current sink capabilty in the CMOS for your purpose. I would replace it with the 74HC74.
kd4pbj said:
Also what about inputs on a 4069? From now on I will remember to do something about unused inputs but I don't have much digital experience so I didn't do it to start with.
The 4069 inputs can be held high or low. It does not matter in this case since it is a Hex inverter.
 
audioguru said:
Hi Ron,
I also watched The Lone Ranger with Tonto and the horse Silver when I was young.
My Wifey (from Spain) says that tonto means "stupid".

I always thought that Tonto was a Native Indian, not a Mexican.
Tonto was an Indian, but in the American Southwest, Spanish words and phrases were and are pretty commonly mixed with English. Having said that, Wikipedia says that it means "wild one" in his native tongue. The Spanish meaning is apparently just a coincidence.
All kids admired Tonto. I didn't know what the word meant until I studied Spanish in high school. Tonto was certainly no idiot, as played by Jay Silverheels on TV - a Canadian, by the way!

My avatar is actually my son Dave. I took the picture on the same day he took the one that I took the one that I made my old "headphones and baseball cap" avatar from. I later added the feather and headband using Microsoft Paint, just fooling around.
Here is one of my favorite Far Side cartoons, with thanks to Gary Larson.

I apologize for cluttering up the forum with this off-topic stuff.
 

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My parents got their first color TV (with a round screen) after I left home.
I got my first color TV (half ICs and half vacuum tubes) a few years later and it still works! It was made in 1970.
 
audioguru said:
I got my first color TV (half ICs and half vacuum tubes) a few years later and it still works! It was made in 1970.

'Half' IC's?, how many IC's does it have, and what types?.

IC's in TV's were exceedingly rare back in those days!, more likely to be half transistor and half valve, particularly in North America were they still produced valve sets for years after Europe had gone all solid state.
 
Philips made extremely complicated all-valve sets in Canada for a few years then in 1969 used their jungle IC and a few more small signal ICs in the new design. The high voltage and high power parts were still valves.
 
audioguru said:
Philips made extremely complicated all-valve sets in Canada for a few years then in 1969 used their jungle IC and a few more small signal ICs in the new design. The high voltage and high power parts were still valves.

I think you are too early at 1969?. The 1970 Mullard (now renamed Philips Components) databook lists just ONE IC, the TAD100 (an AM radio chip). The 1973/74 book lists a small number of IC's for colour TV's - bear in mind this is the book sent to set designers (along with the datasheets, we used to get those as well), so generally the books pre-date the sets. Unfortunately I can't find 71/72 - or any later ones.

The Philips G6 (all valve set) was a truely horrific monster!!!. Most other sets were hybrids, with transistorised small signal sections (too early for IC's) and valve output stages. We even had KB (ITT) sets here which were hand built - NO PCB'S - built by hand on tag strips, now that's another horrific thought!, although they were quite good sets!.

In the UK we were lucky, in that Ferguson (part of the Thorn group) NEVER made a colour TV with any valves in it, they went direct to all transistor, years before anyone else.
 
Nigel Goodwin said:
I think you are too early at 1969?
I am 1 year too early. My old Philips TV is called Model C70 because it was designed in Canada and first sold in 1970. The Philips jungle IC is the TAA700. The picture tube was made by RCA in the US. I have many Technical Service Bulletins for it up to 1974.
 
audioguru said:
I am 1 year too early. My old Philips TV is called Model C70 because it was designed in Canada and first sold in 1970. The Philips jungle IC is the TAA700. The picture tube was made by RCA in the US. I have many Technical Service Bulletins for it up to 1974.

It's in the 73/74 databook, but not the 1970 book.
 
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