Honeywell quartz clock component

[stj]

Re: Honeywell quartz clock component

the battery *can* be short circuit because it must be connected to the clock via a resistor and maybe a bypass-diode to limit the charge current.

[sofTest]

Re: Honeywell quartz clock component

The battery is not shorted, nor leaking. I've read that shorting only happened in battery packs, due to reversal, not in single cells? My battery is probably bad due to cadmium crystal build up. (Yes, I've been reading up on batteries and charging, also.)

Yes, I found that the clock can run without the battery. But since the the clock normally is only monitored once a week, I find it best to have a backup battery in, in case of power outages.
Info 1 -> Google translation
Info 2 -> Google translation

Anyway, due to the unknown handling of charging (overcharging) in the clock, I find it most safe to replace with a NiCd. I found a source for a 110 mAh NiCD, but it's not stocked, so there is some delivery time.

I'm enclosing a new picture of the board, with annotations.

Thanks for now. I'll report back when I know more.

[stj]

Re: Honeywell quartz clock component

nicad's can short, i had a slotmachine that wouldnt start because the nicad was dragging the power down.

[Pyr0Beast]

Re: Honeywell quartz clock component

Yup. They can short. Zap it and it should work.

[Radio Fox]

Re: Honeywell quartz clock component

the battery *can* be short circuit because it must be connected to the clock via a resistor and maybe a bypass-diode to limit the charge current.

Yup. They can short. Zap it and it should work.

The circuit is a very basic design. The zener diode, electrolytic smoothing capacitor, and battery are all connected in parallel across the supply pins of the IC. If the battery was a dead short, the clock would stop.

It seems to me that the battery is acting like a resistor, drawing current & pulling down the supply volts. This could be causing the IC to operate erratically, perhaps causing it to "miss a beat" every now & again, slowing the clock down.

...Anyway, due to the unknown handling of charging (overcharging) in the clock, I find it most safe to replace with a NiCd. I found a source for a 110 mAh NiCD, but it's not stocked, so there is some delivery time...

I'm surprised you found one. I thought they were extinct.

[Pyr0Beast]

Re: Honeywell quartz clock component

The circuit is a very basic design. The zener diode, electrolytic smoothing capacitor, and battery are all connected in parallel across the supply pins of the IC. If the battery was a dead short, the clock would stop.

It seems to me that the battery is acting like a resistor, drawing current & pulling down the supply volts. This could be causing the IC to operate erratically, perhaps causing it to "miss a beat" every now & again, slowing the clock down.

I would agree with that.

[999999999]

Re: Honeywell quartz clock component

IMO, there is one most likely fault, the trimmer capacitor. It is unlikely the crystal itself would drift this much, at so high a rate.

You might try turning that capacitor through it's full range several times, but first marking what position it had and counting turns so you can return it to the original position, and do some comparitive testing for how much changing it's position one direction or the other changes the time rate of change.

[kc8adu]

Re: Honeywell quartz clock component

IMO, there is one most likely fault, the trimmer capacitor. It is unlikely the crystal itself would drift this much, at so high a rate.

You might try turning that capacitor through it's full range several times, but first marking what position it had and counting turns so you can return it to the original position, and do some comparitive testing for how much changing it's position one direction or the other changes the time rate of change.

i mentioned the glue being the problem earlier.
i would have replaced the trimmer earlier in the game.set it by using a counter and adjusting to 32.768 khz.

[Radio Fox]

Re: Honeywell quartz clock component

IMO, there is one most likely fault, the trimmer capacitor. It is unlikely the crystal itself would drift this much, at so high a rate.

You might try turning that capacitor through it's full range several times, but first marking what position it had and counting turns so you can return it to the original position, and do some comparitive testing for how much changing it's position one direction or the other changes the time rate of change.

I suggested turning the trimmer in post #8, but that was before sofTest said how slow the clock was running. It is running at 1/3 of normal. There is no way a trimmer will pull a Xtal to a third of it's frequency. I think a very rough rule of thumb is 1KHz per MHz of Xtal frequency.

btw...why do you need to count the turns on the trimmer?

[Radio Fox]

Re: Honeywell quartz clock component

i mentioned the glue being the problem earlier.
i would have replaced the trimmer earlier in the game.set it by using a counter and adjusting to 32.768 khz.

You've even less chance of pulling a 4194.304kHz Xtal down to 32.768kHz.

[999999999]

Re: Honeywell quartz clock component

^ but, if the battery is acting as a resistor and it's now out of circuit, we need to know what that result is.

I don't fault sofTest for it, because we all have only a finite amount of time to spend, but ultimately proposed tests, data gathering, parts swaps if all else fails, might help.

Then again, what is the point when you can buy a new clock mechanism for dirt cheap that is more accurate than something decades old? If it were a valuable vintage antique that the owner sought to sell as-was, then I see the advantage of keeping it all original.

[stj]

Re: Honeywell quartz clock component

isnt this fixed yet?

if i had it i would draw a schematic.

[Radio Fox]

Re: Honeywell quartz clock component

^ but, if the battery is acting as a resistor and it's now out of circuit, we need to know what that result is.

I don't fault sofTest for it, because we all have only a finite amount of time to spend, but ultimately proposed tests, data gathering, parts swaps if all else fails, might help.

Then again, what is the point when you can buy a new clock mechanism for dirt cheap that is more accurate than something decades old? If it were a valuable vintage antique that the owner sought to sell as-was, then I see the advantage of keeping it all original.

I get the impression that it's a bit of a long job putting it all back together. Perhaps that's why sofTest wants to wait until it's all back to how he wants it, before refitting the clock.

I assume it's some kind of central heating timer (although he hasn't actually said what it's used in). In an earlier post sofTest said a replacement timer would cost over 200 US dollars!!!

[Radio Fox]

Re: Honeywell quartz clock component

isnt this fixed yet?

if i had it i would draw a schematic.

He must still be waiting for the replacement NiCd.

I drew a schematic from the photos sofTest posted.

[kc8adu]

Re: Honeywell quartz clock component

You've even less chance of pulling a 4194.304kHz Xtal down to 32.768kHz.

guess i didnt see that.
so used to seeing 32.768.
btw the trimmer is a single turn.the rock COULD be bad and be that far off....
had a 20m rock in a yaesu 101 that was off by a mile.surprised it even ran.

[sofTest]

Re: Honeywell quartz clock component

Hi.

I'm still waiting for the battery. The shop in Norway I first ordered it from, changed delivery time from 2-14 days to 2-30 days two days after I ordered. So I cancelled, and re-ordered from Tower Hobbies in the US. It was confirmed shipped last Friday, so it shouldn't be long before I receive it.

As for the repair, according to the Germans who has experience with this clock, the usual fault is the battery, and sometimes the electrolytes. As the electrolytes are out already, I will replace them also. I would have liked to replace the trimmer also, but as I don't have any equipment to calibrate a new one (beside a time consuming observe and adjust), I will leave the old one in, unless the battery and electrolytes replacements fail. I have tried turning the trimmer, and the action is smooth, and no sticking, if that is any indication.

Yes, the clock is part of a old building heating system, regulating daytime/night time/weekend temperature. The clock is sold used for €60-80 on eBay, and I've found new ones from around USD 200 and up. There are of course more modern and accurate systems, but that would involve replacing more than the clock. For its time, the Honeywell Aquatrol W964F system was quite advanced, and still does the job, when it keep the time. A small drift in time isn't a problem either.

Thanks for still looking in.

[Pyr0Beast]

Re: Honeywell quartz clock component

Trimming resistors do fail. But I'm not sure if trimming capacitors do the same as well since there isn't any direct electrical contact.

[stj]

Re: Honeywell quartz clock component

variable capacitors get contaminated or tarnished and it creates a resistive path and effects overall capacitance.

[Radio Fox]

Re: Honeywell quartz clock component

...the rock COULD be bad and be that far off....
had a 20m rock in a yaesu 101 that was off by a mile.surprised it even ran.

Out of interest, did that Xtal run high or low? Just wondering whether the Xtal may have cracked causing it to run high.

[kc8adu]

Re: Honeywell quartz clock component

way high.