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Author Topic: 24hr digital clock  (Read 954 times)

KE2KB

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24hr digital clock
« on: June 06, 2020, 04:37:00 PM »

Hey guys;
I am looking for a new LED digital clock for my shack/bedroom. I need LED so I can see it at night, and I need 24hr.
I found the MFJ LED desk clock at DX Engineering. Model MFJ-113. The cost is $24.95.
Is this a decent clock, or should I look elsewhere?
My thinking is to buy a clock specifically designed for hams, as it might have some additional RFI mitigation that a standard consumer model will not.
That said, I operate a Yaesu FT-450D barefoot (100W max), and I haven't noticed any issues even with my old RS (line powered) LED clock.

thanks for your advice
Frank <KE2KB>
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KC6RCM

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Re: 24hr digital clock
« Reply #1 on: June 06, 2020, 05:06:12 PM »

I have the CK-2 dual time version from Electronics USA and it's very accurate. Unfortunately, it's a little pricy... http://www.electronicsusa.com/ck1.html 

For the price, MFJ is hard to beat.
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KE2KB

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Re: 24hr digital clock
« Reply #2 on: June 06, 2020, 05:20:18 PM »

I have the CK-2 dual time version from Electronics USA and it's very accurate. Unfortunately, it's a little pricy... http://www.electronicsusa.com/ck1.html 

For the price, MFJ is hard to beat.
Yes, I would have to agree with you that it is a bit pricy. I'm even considering adding a LED display to my Raspberry Pi to display time. I could probably do that for a few bucks and a bit of coding. But I will never get around to doing that, so I will probably go for the MFJ.
I am trying to compare prices between DX Engineering (charges $9.95 s/h), Amazon (probably free s/h but higher price) and HRO, but at the moment, HRO's website is down. I cannot even ping it.
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K5LXP

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Re: 24hr digital clock
« Reply #3 on: June 07, 2020, 07:37:38 PM »

I bought one of these for my camper so I could see it at night without having to push a button for a backlight, which is how most "travel" clocks work.  It does do 24 hours.

https://www.amazon.com/gp/product/B01IAXYPE0

Mark K5LXP
Albuquerque, NM
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VE7DQ

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Re: 24hr digital clock
« Reply #4 on: June 07, 2020, 07:44:04 PM »

I am most pleased with my CK-2, "Designed and Assembled in the USA".  I doubt that that could be said for the MFJ device.
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KE2KB

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Re: 24hr digital clock
« Reply #5 on: June 16, 2020, 05:48:25 AM »

Unfortunately, I made my decision to go with the MFJ-113 before seeing K5LXP's post on the travel clock. In hindsight, I think that would have been a better choice.

When I first opened the plastic packaging the MFJ came in, I heard something rattling around inside the clock. I didn't want to plug it in, thinking the loose part could be a screw, which would short out.
I shook the clock several times until a small piece of red plastic - probably broken off from the inside of the bezel - dropped out. There was no obvious damage to the bezel, except a slight scuff which does not interfere with the display.

Plugging the clock in, I was impressed with the size and brightness of the display. I would certainly not have any trouble reading it from anywhere.
However, the look and feel of this clock is cheap. I guess this is what we have come to expect from MFJ these days. But it's only a clock; not a radio or anything critical like an antenna switch. That's why I chose the Alpha Delta antenna switch, and not one from MFJ.

The clock appeared to function properly. I set it to the 24 hour format.
But later in the evening, I found that the leftmost digit of the display had only one segment lit. The time was 20:23.
Here is what it looked like:
https://drive.google.com/file/d/1TkqJOLkXD4V3izSKY0f6N7LbDdp41b19/view?usp=sharing

If I tapped the case, I could get the digit to light properly or not.
At this point, I had two choices:
1. Contact either Gigaparts where I had purchased the clock, or MFJ - depending on the return policy - and ship it back for a replacement or a refund.
2. Open the case and check it out for myself.

Considering that I would have had to pay return shipping, then wait who knows how long to receive another (probably defective) unit, I decided to do what we hams do, and attempt repair myself.
I figured the problem was just a poor solder joint, which I could fix easily. If it turned out to be something else and non-repairable, I could just pack it up and send it back.

Opening the case, I found yet another example of MFJ poor quality and workmanship. The PCB's are all phenolic (well, what did I expect, G10/FR4 fiberglass? NOT).
Then there is the main PCB just hanging from the display PCB on its stiff flat cable. This isn't really an issue though, as the cable is substantial, and this clock isn't being used in a vehicle or other high-vibration environment.

I could not detect any poor solder joints, so I plugged the clock in and carefully inspected it. I quickly found the source of the problem: The 12/24 hour switch. It is one of those $0.01 switches with a set of contacts on the bottom, just sitting on the PCB, held in place only by the plastic housing of the case.
There was grease on the switch contacts and PCB, I assume to allow the switch to move freely. I am familiar with this type of grease being used in larger switches handling some current, but I would think that it would only impede the flow of current in this extremely low current circuit. The grease was on the 12/24 hr and the alarm switches.
I removed the grease with rubbing alcohol and replaced the switch body. Still the contact was not good. So I began playing with the contacts, bending them outward to apply more pressure against the PCB.
This appeared to work, and I re-assembled the clock.
It is now working properly.

I have decided that when (not if) the switch loses contact again, I will jumper it out in the 24 hour position. I will also jumper the alarm switch to off, since I will never be using that feature.

When I do need to open the clock again, I would like also to investigate adding a brightness control - using a photo detector of some sort. I don't know if the clock chip they used has this feature, but I suppose I could design a simple circuit regardless.
The display is very bright. Not really a problem for me, but it would have been desirable to have the display dim when the room is dark.

I thought that MFJ could build something simple like a clock, but I guess not. The design and QC of this product is the poorest I have ever seen in such a product. Even the old Radio Shack clock which this one replaced was better made. It was still working after 20+ years. I only wanted to replace it with a 24 hour model with brighter display. Well, at least the MFJ does fit that bill. But I am absolutely certain that 20 years from now, this clock will be at the bottom of some junk heap (or its parts will have been recycled).

I can say without doubt that this clock is the last MFJ product I will ever buy.
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N0XAS

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Re: 24hr digital clock
« Reply #6 on: June 16, 2020, 09:14:34 AM »

It has been said that MFJ products are "semi-kits" that you finish building yourself.  Personally I haven't had a lot of trouble with the few that I've owned, but all have required some work at some point.

For "cool factor" you can't beat a Nixie tube clock.  I bought a couple of kits years ago from a guy in the UK.  They're not cheap, but they do carry bragging rights!  :)
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KE2KB

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Re: 24hr digital clock
« Reply #7 on: June 16, 2020, 09:39:47 AM »

It has been said that MFJ products are "semi-kits" that you finish building yourself.  Personally I haven't had a lot of trouble with the few that I've owned, but all have required some work at some point.

For "cool factor" you can't beat a Nixie tube clock.  I bought a couple of kits years ago from a guy in the UK.  They're not cheap, but they do carry bragging rights!  :)
I used to love building Heathkits! I would prefer if MFJ were to sell complete kits instead of 'semi-kits' as you referred.

Several years ago when I was looking for an antenna analyzer, I considered MFJ, but decided instead to spend a bit more on the RigExpert. I'm happy that I did, but have read some fairly good reviews on the MFJ analyzer.

Funny you should mention a Nixie Tube clock. I thought about that before I bought the MFJ. I never researched it though. Next time I'm looking for a clock, that may be an option.

I don't think the MFJ-113 clock is going to last very long. For one thing, the lousy switches - but those can be jumpered as I mentioned. It's the line transformer I have doubts about. Looks really cheap, and will most likely burn itself out within a year or two.
Perhaps I will preempt a failure by replacing its power supply with a wall wart.
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W1VT

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Re: 24hr digital clock
« Reply #8 on: June 16, 2020, 01:14:52 PM »

I use a computer running WSJT.  :)   It has a box that displays the date and time.
2020 Jun 16
 20:13:14

And, if it is decoding FT8 transmissions, I know that Windows hasn't messed with its time sync.

Zak W1VT
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OK4FX

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Re: 24hr digital clock
« Reply #9 on: June 16, 2020, 01:34:10 PM »

... For "cool factor" you can't beat a Nixie tube clock ...

If you want to spend a lot of money you can buy a Nixies with 10 years warranty for almost 1500 EUR. If you are interested, you can obtain link from included picture. :-)

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Mira OK4FX

K2DFC

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Re: 24hr digital clock
« Reply #10 on: July 17, 2020, 08:10:17 AM »

Back in the 60's and 70's digital clock kits were advertised in ham magazines all the time. I built a few of them. In fact I still have one operating in my shack today. 50 years old and keeps on ticking.
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N6YFM

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Re: 24hr digital clock
« Reply #11 on: July 23, 2020, 10:57:21 PM »

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N9LCD

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Re: 24hr digital clock
« Reply #12 on: August 29, 2020, 08:44:25 AM »

Whatever brand of 24-hour clock you buy, make sure it takes a backup battery.  A slight "dip" in voltage can cause some clocks to lose "time" and require resetting.

Or  buy  Marathon "Navigator" watch; it's 24-hours.  And, best of all,  I don't have to remove it when going through TSA security at ORD!
 
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KG4RUL

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Re: 24hr digital clock
« Reply #13 on: August 29, 2020, 09:11:23 AM »

I have a Nixie tube clock but, alas, it has an RFI issue so I have stopped using it.
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KE2KB

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Re: 24hr digital clock
« Reply #14 on: September 22, 2020, 05:21:38 PM »

I have discovered that the MFJ-113 12/24hr digital clock is actually a TIME MACHINE!
Well, of course it is. Any clock is a 'time machine'. But I'm talking about HG Wells Time Machine!
Today, I lost power for about an hour or so. My APC Back-UPS kicked in, and this MFJ-113 clock was being powered by it.
The clock began ticking away about 2 minutes for each actual minute that passed. A time machine! So I am now about 1 hour and 10 minutes in the future - according to the MFJ clock.

Of course I know what is happening here. The AC waveform from the APC Back-UPS is an 'approximated sine wave', and I have observed this waveform on my oscilloscope. It has several peaks, which the clock is interpreting as cycles, so it's reading 120HZ, not 60HZ.
Simple way to create a time machine...

I am going to change the clock to one of the non-battery back-ups outlets on the APC. Then it will only run on its internal 9V battery for backup. I think that's a tad more accurate than the 'approximated sine wave'.

Of course, I shut down my computer equipment shortly after the power failed. It's a great thing to have - avoids data loss - but I wouldn't want my expensive computer equipment running continuously on this 'approximated sine wave'.
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