Twemco BQ-50 running slow

[Johan de Jong]

Hi, just got hold of a very nice (BIG!) Twemco BQ-50.
It is working fine except it is running a bit slow: about two minutes per day.
It is quartz controlled so I would not expect that the speed would be adjustable (I do see a potentiometer on the board, but no idea what that does), and I can't yet think of any mechanical issues that could cause this.

Any ideas?

[Guest]

Any old lubrication that you can see in the gearset? The motor is directly coupled to it, but you'd have to partially disassemble, I would guess.

[flipoclock]

There will be some screws in the 'rectangular' black part, if you take these out, you will be able to pull off the black piece, revealing some gears. This looks very much like the Copal QG870. It is not exactly the same, but it does resemble it a lot.

If you needs any motor spare parts, I have a box full of complete motor/gear sets for this Copal clock, new old stock, I could send you one for little money. As I said, they are not the same, but I do see some similar parts (just playing it by eye though, not 100% sure).

[Johan de Jong]

I took it further apart but mechanically everything looks perfectly fine (like new actually).

Did a bit more research and learned that some quartz clockworks do have a trimmer capacitor that allows to tune the frequency. What I mistakenly called a potentiometer is I think such a trimmer capacitor. So I started experimenting with it. I turned it 45 degrees clockwise and now let's see what that does. Tomorrow I will know whether it made any difference and if it was in the right direction. Fingers crossed...

[Johan de Jong]

Big success! My first guess was in the right direction and also very close to the right amount
So:
clockwise = faster
45 degrees is about two minutes per day

I'll see how accurate I can tune it, but if it is within a few seconds a day I'm already very happy.

[Johan de Jong]

I cheered too early. My BQ-50 still now and then ran too slow. It is a bit irregular, some days it runs fine and on other it looses about 2 minutes.

[eathan21th]

Big success! My first guess was in the right direction and also very close to the right amount
So:
clockwise = faster
45 degrees is about two minutes per day

I'll see how accurate I can tune it, but if it is within a few seconds a day I'm already very happy.

Recently I got a twemco BQ-17, which is about 20 yrs old. It is also running a bit slow, about 2~4 mins per day.
I tried to tune the capacitor as using your method. But no matter I turned it clockwise or counter clockwise, the results are similar.

I suspect the problem of my clock is from the motor itself not the control board. I met some motor issue before on twemco BQ-58 before.

So I changed the motor this morning, I will let it run about 1~2 days to see the result.

[Johan de Jong]

Sorry, I should have updated my post. I have to admit that I cheered too early. My BQ-50 still now and then ran too slow. It is a bit irregular, some days it runs fine and on other it looses about 2 minutes. Still not a clue what could cause this.

[eathan21th]

Exactly the same case I met in these 2 days. So I tried another way to fix it, such as to change a new motor. Maybe I can update the status couple days later.

[eathan21th]

Good news! After changing a new motor couple days ago, my twemco BQ-17 seems to keep the time quite accurate in these days. So the original problem might come from the aging motor.
Here are the detail images of the motor I used to replace the original one.

[Johan de Jong]

That is good news!

I'm quite surprised and trying to analyse this (thinking out loud):
My train of thought was that it is the quartz that determines the length of a minute and engages the motor each minute. The motor than either runs or does not run, but only if it runs it will be switched off by the microswitch. And only then the next minute cycle will start.

But maybe I'm wrong. Maybe the quartz controlled counter engages the motor each minute anyway, whether it actually runs or not. And if the motor is faulty it may sometimes just not start and skip a run, so not increment the minutes. Strange though that it happens only now and then. I would expect once the motor fails to start (probably due to burnt in brushes/collector) it will not start the next time and no time after that. So the clock would just stop. But apparently that is not what happens.

I'll open up mine again and investigate the motor. Mine is different but both these motors are very common and still used in all kind of small toys, etc. They are plenty available on AliExpress and dead cheap so I think I'll just order a replacement. Let's hope that works.

Thanks for investigating and posting!

[eathan21th]

If you want to find a new motor, please make sure the motor axle is long enough or it will meet some problem as installing the gear onto the new motor.

[eathan21th]

Actually the motor of my BQ-17 is the same as yours. The motor on my BQ-58 is "RF-130CH-12250 ", but I can not get the same motor with suitable motor axle length, so I bought some FF-030PA for my BQ-58 . And I found the gearbox of these BQ-17 and BQ-58 are the same, then I just used it on my BQ-17. That's why I used this type of motor.

[eathan21th]

OK. I got another different model of motor today, which is XRF-130CH. The motor size is exactly the same as the one used on the BQ-17. I not yet test it. But I think it should work.

[Johan de Jong]

Finally got to replace the motor and it solved the issue!
It has been running exact on time for a week now.
I replaced it with a Mabuchi RF-130CH motor from AliExpress.

As I was curious what the issue with the motor was I opened up the old motor but could not see much wrong with it. Just a little wear and dirt on the brushes and collector, but nothing serious.


Thanks for your help eathan21th!

[eathan21th]

You're welcome. It's nice to hear that.