Honeywell quartz clock component

[sofTest]

This quartz clock is increasingly slowing. The capacitors (one removed in picture), resistors and diodes tests OK. I'm suspecting the 4194.304 kHz quartz crystal, but don't have any tools to test it. The clock is about 20 years old, and the oscillation might be failing.

I'm wondering if anyone can identify the component I've ringed on the picture. There are no markings on the board.

I'll probably order a new crystal at DigiKey next time I've got something more to order. Does anyone know how much importance the Load Capacitance has on a crystal? I can't find a datasheet on the original ITT 1385 part.



Thanks for any help.

[stj]

Re: Honeywell quartz clock component

that looks a lot like a fuse.

[stj]

Re: Honeywell quartz clock component

btw, the green ajuster on the right is a variable capacitor to fine-tune the crystal - maybe it's contaminated (fucked)

[sofTest]

Re: Honeywell quartz clock component

Thanks for the input.

I've enclosed a picture of the trace side of the board. If the brown component were on the power input, I would have thought it was a fuse also. Also there is no continuity across the legs of the component. The clock does work (slowly), so I knew there was no broken fuse. So I just did something I didn't think of before, measured the capacitance. Bingo, 122.2 uF. So, the brown component is some kind of 100 uF 10v capacitor (ESR 0.75).

I thought the green component was a variable resistor, but wouldn't bet on it. I can measure resistance, but no capacitance, in circuit.

[stj]

Re: Honeywell quartz clock component

is the thing in the yellow paper sleeve a backup battery?
the brown thing looks like a fuse 2a if the foto was better i'd bet it had a voltage printed too.

the green variable capacitor wont show on most meters - it's in the pf range.

[kc8adu]

Re: Honeywell quartz clock component

looks like that dammed brown glue on the trimmer.
likely the problem.
cusses and resumes digging the stuff from a ts-440 vco......

[stj]

Re: Honeywell quartz clock component

you do RF work?
rather you than me!

[Radio Fox]

Re: Honeywell quartz clock component

This quartz clock is increasingly slowing...

What kind of error are you getting?

As stj says, the green component is a low value (2 - 22pF ?) trimmer capacitor. It's purpose is to trim the crystal so that it oscillates on it's correct frequency.

Adjust it slightly to see if it makes any difference to the accuracy of the clock. I have found that those trimmers tend to stick, so give it one complete revolution first, to free it up.

[ratdude747]

Re: Honeywell quartz clock component

that board looks awful burnt...

[Radio Fox]

Re: Honeywell quartz clock component

...the brown thing looks like a fuse 2a if the foto was better i'd bet it had a voltage printed too...

Looking at the tracks on the back of the board, that component is in series with the clock mechanism, so if it was a blown fuse, the clock wouldn't be working at all.

[sofTest]

Re: Honeywell quartz clock component

is the thing in the yellow paper sleeve a backup battery?
the brown thing looks like a fuse 2a if the foto was better i'd bet it had a voltage printed too.

the green variable capacitor wont show on most meters - it's in the pf range.

The yellow thing might be a battery, but dead now. No markings on it. Just a metal can under the yellow paper. There are +/- markings on the trace side of the board for it. Could a failed battery cause this? The circuit doesn't seem to depend on it.

As I said in my last post, the brown thing is a capacitor of some type.

Among the ranges my meter do, is 0-500 nF, lowest 0.01 nF, so it should measure from 10pF and up.

looks like that dammed brown glue on the trimmer.
likely the problem.
cusses and resumes digging the stuff from a ts-440 vco......

No glue on this board.

What kind of error are you getting?

As stj says, the green component is a low value (2 - 22pF ?) trimmer capacitor. It's purpose is to trim the crystal so that it oscillates on it's correct frequency.

Adjust it slightly to see if it makes any difference to the accuracy of the clock. I have found that those trimmers tend to stick, so give it one complete revolution first, to free it up.

The time on the clock slowed increasingly. Around Christmas at a rate of 16 hours a week, until I replaced it last Tuesday it slowed 48 hours of the past 72 hours. So the problem was accelerating. That leads me to think of a failing component, not an adjustment being off.

The trimmer doesn't stick. I've tried to find information on failure of trimmers, but have not found anything. What are their failure modes?

that board looks awful burnt...

No, not burnt at all. Old type circuit board.

Thanks all.

[Krankshaft]

Re: Honeywell quartz clock component

I thought in a clock of this vintage they would use a synchronous motor.

I have a GE radio / clock from the 80s and it uses a synchronous motor with 50 or 60 Hz capability. Nothings a cheaper timing pulse than line frequency.

That yellow thing does look like some type of battery probably a nicad rechargeable. A battery backup perhaps? If that's what it is there is no need to replace it.

I would check the trimmer cap it's possible that it's intermittent. There is no reason for a static setting to suddenly change without a drift or fault in some component.

[stj]

Re: Honeywell quartz clock component

that board looks awful burnt...

it's not burned, it's made from Paxoline.
something before your time.

[stj]

Re: Honeywell quartz clock component

how wide & deep is that brown thing?
it's either a 100uf 10v electrolytic - ancient type.
or a fuse like this:

http://www.littelfuse.com/products/F...831200000.html

[sofTest]

Re: Honeywell quartz clock component

I thought in a clock of this vintage they would use a synchronous motor.

I have a GE radio / clock from the 80s and it uses a synchronous motor with 50 or 60 Hz capability. Nothings a cheaper timing pulse than line frequency.

That yellow thing does look like some type of battery probably a nicad rechargeable. A battery backup perhaps? If that's what it is there is no need to replace it.

I would check the trimmer cap it's possible that it's intermittent. There is no reason for a static setting to suddenly change without a drift or fault in some component.

I'm not sure if I understand you correctly, but surely the crystal is the timer in a quartz clock like this? Or do you mean in general? There are several variants of this clock; at least 18V, 24V and 230V. So I'm guessing one design, with minor alterations.

If the trimmer is meant to fine tune the crystal, would a fault in that cause a drift of 48 hours out of 72 hours? Doesn't sound like a fine tune. Also, wouldn't the crystal be as likely a candidate?

If the trimmer is in the range below 10 pF (as it seem to, if it's working), I've got no way of testing it. I could remove it, to see if that gives a stable drift.

[sofTest]

Re: Honeywell quartz clock component

how wide & deep is that brown thing?
it's either a 100uf 10v electrolytic - ancient type.
or a fuse like this:

http://www.littelfuse.com/products/F...831200000.html

It's definitely a capacitor, as it got a capacitance of 122.2 uF. 11 mm wide x 13 mm high.

The weird thing, is that there is a modern type electrolytic of 16v 10uF there (removed on the picture).

[Krankshaft]

Re: Honeywell quartz clock component

No I was talking in general. Synchronous motors don't need crystals their rotation is synced to line frequency no crystal is required. Since line frequency is stable it's a good time reference.

Quartz crystals are very fragile it doesn't take much to damage them. One drop to the floor and you've got a 50-50 chance of a damaged one. The synthetic quartz is a tissue thin wafer. They also can become damaged or intermittent with age.

The only way to check it is with a crystal checker hooked up to a frequency counter. Or a scope to eyeball it to see if it's outputting a stable frequency.

Of course since this clock is line run (I don't see a transformer) if you had a scope you'd need to hook the clock up to an isolation transformer.

I'd replace the crystal first and go from there. I thought the clock was just a little bit off if it's lagging as much as you say. Then the crystal which is the reference for the clock circuit would be the first suspect.

[Wizard]

Re: Honeywell quartz clock component

variable capacitor is open circuit and yes that can change the tuning so much. Replace it with similar from a old clock. Not rare.

The type of components design tells me this is far older than 20. Looks like 30 years or older. Very early quartz clock.

Cheers, Wizard

[Radio Fox]

Re: Honeywell quartz clock component

...If the trimmer is meant to fine tune the crystal, would a fault in that cause a drift of 48 hours out of 72 hours? Doesn't sound like a fine tune...

You're right. With the kind of inaccuracy you're getting, it's way beyond the fine tuning of that trimmer.

I am wondering about the supply to the chip on that board. I assume there is a zener diode somewhere on the board, probably between the unknown component, and (what looks like) the battery. If it is a rechargable NiCad and is no longer holding a charge, then there's a good chance that one or more cells have shorted. This may be pulling the supply volts down, causing the chip to operate erratically. Just a thought.

EDIT...btw, as Krankshaft has pointed out, this clock uses a transformerless mains supply. Be very careful if you take any readings while it is powered up!

[sofTest]

Re: Honeywell quartz clock component

I just noticed a faint stamp of E80 on the board, so maybe the clock is older than I thought.

I don't have a scope or a crystal checker, so I can't do any tests on the crystal. Since a new crystal is only USD 0.58-0.75 at DigiKey, I'll probably just chance it, and order a new one next time I order in something. Do anyone know how to choose Load Capacitance in a crystal, when the original is unknown. Is it important?