4046 Oscillators progressively getting worse over time

[elmegil]

Have you checked all the outputs to see if they behave the same?

What happens if you put a signal into the PWM input?

[LektroiD]

Odd, when I plugged them into the modular supply (rather than the bench PSU) the problems are still present, except there is nothing wrong with the PW now.

I think Oscillator 1 & 2 is going to be a case of further cleaning the tempcos, but Oscillator 3 is going to pose a bigger problem.

[diablojoy]

Wow Do the recleaning and see if you can get 1 and 2 up and going correctly first on the modular supply, then you can go over number 3 and run some comparisons
The bench supply changes the behaviour ? perhaps a dodgy rail or ground connection. little else should have changed. hmmm but 4 is working ok on the bench supply ? this is very strange
I wonder if in cleaning this thermal paste has spread causing these other issue's
maybe try googling the best way of cleaning it off completely

[LektroiD]

I think isopropyl alcohol and a toothbrush should fetch off the remainder of the gunk. Although this is going to have to go on hold for a couple of weeks, as I'll be away...

[LektroiD]

I'm back now after a much needed break in the Canary Islands...

While I was away, I had a delivery of some SSM 2210 chips as well as a very kind donation of tempcos. I replaced the tempcos first to see if that sorts the issues, and now I have two operational oscillators.

However, the other two are still proving difficult, so I swapped the hand matched transistors for a SSM2210 and seated the tempco into the groove of the DIP socket, and firmly installed the SSM2210. It is still fluctuating in frequency. I have not fed this into a frequency counter, but it sounds to my ear like it is jumping around within a semitone, intermittently.

I have not installed the SSM 2210 into the last oscillator yet. I will do that tomorrow, I just wanted to post an update on my current progress and see if anyone could maybe shed some light on the fluctuations I'm having.

[LektroiD]

I left it on overnight and it seems to have got worse... Now, rather than intermittent fluctuations, it now sounds like a dying fly... I'm totally baffled as to what it could be. I'll try going through all the chips again, I just don't know what else it could be?

[emmaker]

If you are using the ERA Panasonic tempco resistors they are pretty sensitive to physical abuse. The data sheet can be found at:

http://www.panasonic.com/industrial/electronic-components/parametric-search.aspx?src=/www-cgi/jvcr21pz.cgi?E%2BPZ%2B3%2BAOF0001%2B4%2B%2BAM

In the Safety Precautions section you'll find this. Items 3-9 might apply here.

1. Keep the rated power and ambient temperature within the specifi ed derating curve.
* When positioning and mounting Metal Film Thermosensitive Chip Resistors (hereafter called the resistors), make
allowance for the effect of heat generated through close contact between the resistors and neigh bor ing components
and for the temperature rise of adjacent heat-generating components.
2. If a transient load (heavy load in a short time) like a pulse is expected to be applied, check and evaluate the operations
of the resistors when installed in your products before use.
When applying pulses to the resistors, keep the pulse peak within the rated voltage.
3. Do not use halogen-based or other high-activity flux. Otherwise, the residue may impair the resistors' performance and/or reliability.
4. When soldering with a soldering iron, never touch the resistors' bodies with the tip of the soldering iron. When using a
soldering iron with a high temperature tip, finish soldering as quickly as possible (within three seconds at 350 °C max.).
5. As the amount of applied solder becomes larger, the mechanical stress applied to the resistors increases, causing
problems such as cracks and faulty characteristics. Avoid applying an excessive amount of solder.
6. When the resistors' protective coatings are chipped, flawed, or removed, the characteristics of the resistors may be
impaired. Take special care not to apply mechanical shock during automatic mounting or cause damage during
handling of the boards with the resistors mounted.
7. Do not apply shock to the resistors or pinch them with a hard tool (e.g. pliers and tweezers). Otherwise, the resistors'
protective coatings and bodies may be chipped, affecting their performance.
8. Avoid excessive bending of printed circuit boards in order to protect the resistors from abnormal stress.
9. Do not immerse the resistors in solvent for a long time. Before using solvent, carefully check the effects of immersion.
· Reflow soldering shall be performed a maximum of
two times.
· Please contact us for additional information when
used in conditions other than those specified.
· Please measure the temperature of the terminals
and study every kind of solder and printed circuit
board for solderability be fore actual use.

[LektroiD]

I originally used surface mounted tempcos, then replaced them with these:
http://www.akaneohm.com/catalogue/LT.pdf

Same problem with both types...