Kundo Kundo Coil/transistor Testing

[simos]

Hi Kundo experts!

I'm attempting to return my Kundo electronic to working order - incidentally it's one of the more recent models with a triangular shaped base and case.

The symptoms are that it won't run. I've had a number of this and the ATO type clocks so am familiar with all the usual mechanical checks (battery, suspension, movement, pawl, etc). I've successfully extracted the yellow plastic 'bobbin' (without damaging the case!) and am faced with what looks like pristine inners, with the transistor and resistor neatly packaged on one side and the wrapped coils on the other - I'd say it has not been opened previously.

I'm assuming my problem is either one or both of the 2 coils, or the transistor. So I have done some limited checks with a basic digital multimeter. I should declare at this point that I am not knowledgeable about electric or electronic components or circuits. So, looking at pic Kundo 3, a close up of the transistor, which from what I've read may be a TF65, I have called the wires from left to right, E, B, C. These wires may be the Emitter, Base, and Collector, but might also be the other way round as I did not want to dismantle the thing just yet.

I set the multimeter to the 20k ohm scale, and then took readings between the 3 wires E,B,C, firstly with the probes from 'plus' to 'minus', then readings with the probes reversed. So for example Test 1. was across E and B (minus to plus), then reversed between E and B (plus to minus). In this case the Table shows open cct E(-) to B(+) , but with probes reversed the reading was 0.221 Then the same for E-C and B-C.

My question therefore is; can anyone interpret these results to determine where the problem lies? Or suggest other tests I could do? I'm obviously hoping it is just the transistor, not the coils.

Many thanks

Simon

 

[Raymond101]

Hi. If you're multimeter has diode test setting use that . 20k won't tell you anything useful.
There is a YouTube video that shows an example. Search transistor testing.
Try putting your meter on the coil leads
And set to low volts dc . Meter should show a pulse . The lead going to the coil from the transistor is C .

 

[Schatznut]

Here's a copy of the patent which contains a circuit diagram. Figure 1 most likely describes what you've got. I've never seen one with a bad transistor (it's germanium, with around .2V junction drop). What usually happens is a failure of one or more of the solder joints between the lead wires and the coils. It appears Schatz used a strong flux to get through the insulation on the magnet wire and over time it corrodes the joint until continuity is lost. The only solution that I know of is to strip off and replace both windings. Good luck and let us know how it goes.

 

[Raymond101]

I did notice on the photo what looked like a bad connections. Check .solder short .

 

[TQ60]

Place your ohm meter across the battery wires.

Does it read open or short.

If you put it back together and connect the ohm meter to the battery wires and swing the pendulum, you should see the meter move as the pendulum swings through the magnet.

It will show both ways depending on direction.

 

[simos]

Place your ohm meter across the battery wires.

Does it read open or short.

If you put it back together and connect the ohm meter to the battery wires and swing the pendulum, you should see the meter move as the pendulum swings through the magnet.

It will show both ways depending on direction.

Hi, I'll try to reply to this and the other 3 above, and thank you. Incidentally, I've found what I believe to be the Kundo circuit I've got, attached. And just to clarify, my test readings were done without the battery connected.

If I connect the meter (set to 20k ohms) across the battery wires there is no reading either way. If I use the 200k ohm scale the reading is 20 one way and zero the other. Could this indicate that the transistor is passing current in one direction and not the other?
I don't want to put it back together yet until I've established what the problem is.

I've examined the connections from the transistor very closely and am sure they are good.

Ref Shatsnut comments, I was hoping that the multimeter readings I've shown in the table would guide someone who understands circuits to pinpoint where my problem lies, i.e. a coil problem or a transistor problem, before I go to the final solution of stripping out the coils!

 

[Raymond101]

Your circuit diagram is the same as what Schatznut showed. Just drawn different.
Don't open the coils. 99.9% they are good .
First you have to learn how to use your meter. Ohms on a transistor won't work.
You can measure the coil winding with ohms . Direct on coil leads but as there is a resistor in parallel it will give you a false reading .
Measure from the battery terminals the meter will only show a positive swing.
Ie it's set to DC.
Show a picture of your multimeter.
I have put a sketch of how to test a transistor. Set to the diodes symbol. --<|-- if you are using a cheapo China meter the result may be wrong.
Reading should show 0.6 to 0.8 VOLTS apx .
The changes are there is a bad connection or a dry joint . If the old solder has turned gray the tin has wiskered. 60/40 sn/pb

 

[simos]

Your circuit diagram is the same as what Schatznut showed. Just drawn different.
Don't open the coils. 99.9% they are good .
First you have to learn how to use your meter. Ohms on a transistor won't work.
You can measure the coil winding with ohms . Direct on coil leads but as there is a resistor in parallel it will give you a false reading .
Measure from the battery terminals the meter will only show a positive swing.
Ie it's set to DC.
Show a picture of your multimeter.
I have put a sketch of how to test a transistor. Set to the diodes symbol. --<|-- if you are using a cheapo China meter the result may be wrong.
Reading should show 0.6 to 0.8 VOLTS apx .
The changes are there is a bad connection or a dry joint . If the old solder has turned gray the tin has wiskered. 60/40 sn/pb

View attachment 756638

Hi Raymond,

Thanks for your sketch, very helpful. I've done what you said on the transistor, which is still connected into the circuit (not removed). BTW because it is inside a housing it's very difficult to see it there's a larger gap, I'd say the 2 gaps are the same (using a jewellers glass!).
With the multimeter set to 'diode' and touching on the LH wire (believe to be the Emitter) with the positive probe, and the centre wire (hopefully the Base) with the negative probe I get a reading of 0.217. I get the same reading going between the RH (Collector?) wire and the centre Base. Reversing the probes, no reading. And yes, sorry, I am using a cheapo Chinese meter.

And on your other point about old solder, you can see from the pic that the 3 junction points are pretty grey.

So does this help? The reading is less than you said . . .

 

[Raymond101]

I didn't think I had tell you . But atleast 2 wires must be disconnected to do that test as there is a coil between B & E and also B & C . The transistor B is energize from the mag pass though the coil .
The base voltage rises to anything above gating voltage normal apx 0.6v to 1v .
If you think of it as a 2 way switch. It's a flip flop . Using the voltage generated in the reverse coil .
Sorry I'm trying to keep it kind of non technical.
I would suggest getting some solder wick remove that old solder open atleast 2 connections . Recheck the transistor.
Which I guess is probably ok . If your Chinese meter didn't wack 9v though it on the 20k ohms scale . This transistor is a GE planner . And are pretty robust.
What ever you do never use ohms scale on the BASE . as the meter uses a voltage above 1v and the break down voltage on the base may only be about twice the max gating voltage ie 0.6 x 2 ..

 

[simos]

I didn't think I had tell you . But atleast 2 wires must be disconnected to do that test as there is a coil between B & E and also B & C . The transistor B is energize from the mag pass though the coil .
The base voltage rises to anything above gating voltage normal apx 0.6v to 1v .
If you think of it as a 2 way switch. It's a flip flop . Using the voltage generated in the reverse coil .
Sorry I'm trying to keep it kind of non technical.
I would suggest getting some solder wick remove that old solder open atleast 2 connections . Recheck the transistor.
Which I guess is probably ok . If your Chinese meter didn't wack 9v though it on the 20k ohms scale . This transistor is a GE planner . And are pretty robust.
What ever you do never use ohms scale on the BASE . as the meter uses a voltage above 1v and the break down voltage on the base may only be about twice the max gating voltage ie 0.6 x 2 ..

As I said at the beginning, I'm no electrician.

I think I'll remove the transistor and maybe buy a replacement - I've read an AC125 would do. I'm encouraged by your earlier remarks about the coils being unlikely to have failed. Thanks for your advice.

 

[Raymond101]

The AC126 is a general purpose pnp .
I would re do all solder joints all those connections use 60/40 or better still 63/37 cored solder which has a lower melting temp 280 - 320 C.
If you are going to repair electronic clocks as a hobby as a friend I suggest buying a better digital meter with a built-in transistor tester .
There is more to a semi conductor than just if it's passes a diode test . They fail also due to Gate break down. And can only be seen by using a curve trace .
But there are some cheap multi components checker for around $30.
They can tell you good or bad plus what the connection are etc .
BSide ESR02 Pro is a good tool for you easy to use 1 button
Plus it can check coils .resistors . Capacitors, Npn,pnp,mosfet etc .
It will cover everything you will ever need .
Raymond.

 

[Raymond101]

I made a typo I wrote AC126.
Instead of AC125 PNP which is the correct equivalent for your a TF65

 

[TQ60]

In looking at the schematics, the circuit seems simple.

We have a couple and never looked.

There are 2 coils, one across emitter and base, the other between collector and battery, battery also to emitter.

Basic electricity, move a magnetic field pass a loop after wire and result is generation of electricity.

The coil across emitter and base generates electricity, it turns on the transistor .

That connects emitter to collector, connecting the other coil to the battery.

The coil should read very low resistance.

If you place your meter in voltage mode you can slide the magnet through the coil and measure voltage on the wires.

If you had a meter with the diode check function it would power the clock, ours does.

 

[simos]

The AC126 is a general purpose pnp .
I would re do all solder joints all those connections use 60/40 or better still 63/37 cored solder which has a lower melting temp 280 - 320 C.
If you are going to repair electronic clocks as a hobby as a friend I suggest buying a better digital meter with a built-in transistor tester .
There is more to a semi conductor than just if it's passes a diode test . They fail also due to Gate break down. And can only be seen by using a curve trace .
But there are some cheap multi components checker for around $30.
They can tell you good or bad plus what the connection are etc .
BSide ESR02 Pro is a good tool for you easy to use 1 button
Plus it can check coils .resistors . Capacitors, Npn,pnp,mosfet etc .
It will cover everything you will ever need .
Raymond.

View attachment 756685

Hi, that sounds like good advice! I was thinking of getting something better; I'm just looking at your BSide ESR02 Pro . . . hmm, does it also measure the usual A/V/O units? Maybe at the moment I just need a better multi tester with the usual V/A/O and with a proper semi conductor test facility as you suggest. I'll check some reviews.

As you suggest I'll replace all the soldered junctions with fresh, and try the AC125, have already ordered it, along with some solder wick and the 63/37 solder itself. Sounds good for a start. I will report back, hopefully with good news!

Simon

 

[Raymond101]

Simon . The BSide is only a component checker . No O V Amp. These clocks only draw 1ma apx . So take this into consideration when buying a meter that it can measure micro amps as well.
Also play with your meter on other components not on the clock.
Watch some YouTube vids on how to use a multi meter . It's a little bit like checking a car tyre pressure the guage may read 24. But it maybe not correct for that tyre .
Or in other words 24psi or 24mpa or 24bar ( hope not ).
Do some research & have fun while learning .

Good luck

 

[Schatznut]

The solder joints that fail in these clocks are not accessible, with the exception of the one on the outside of the winding, which is still under the insulating tape. So you will gain nothing by trying to solder stuff that doesn't need to be soldered. Between the base and emitter of the transistor you should see between 1600 and 1700 ohms of resistance. Between the collector and the emitter, you should see approximately 1000 ohms of resistance (this is the coil resistance of about 1200 ohms in parallel with the 5.6kohm shunt resistor. Agree with others here that you need a DVM that has a diode check function to learn all you need to know

 

[simos]

The solder joints that fail in these clocks are not accessible, with the exception of the one on the outside of the winding, which is still under the insulating tape. So you will gain nothing by trying to solder stuff that doesn't need to be soldered. Between the base and emitter of the transistor you should see between 1600 and 1700 ohms of resistance. Between the collector and the emitter, you should see approximately 1000 ohms of resistance (this is the coil resistance of about 1200 ohms in parallel with the 5.6kohm shunt resistor. Agree with others here that you need a DVM that has a diode check function to learn all you need to know

Yes, I appreciate the difficult soldered joints are inside. Today I've de-soldered the transistor and taken some measurements (using my cheapo Chinese DMM). I'm assuming the the transistor wires are E, B, C from left to right, looking at the closeup photo in my original post, above.

So, using the diode test setting on my multimeter (also says 2k) 1got a reading of 0.221v E to B (+ive probe on E), and 0.219v C to B ( +ive probe on C. Does this indicate the transistor is working?

Then I tested the resistance across the 3 wires the transistor was connected to. To cut straight to the answer, they were all zero reading, using the 20K ohm scale - which doesn't sound good, based on your suggested values above! I rechecked using the diode 2k setting and still no reading, whichever way round the probes were.

I've closely examined the soldered visible joints, unfortunately they are all buried in the narrow yellow plastic slots, but they don't look shiny, just rather dull. They can be seen quite clearly in the photo above, Kundo 4. I think I'm going to have to start pulling it all apart to get a better look. I'm still hoping one or more of these soldered connections are not conducting, hmmm.

 

[Schatznut]

The transistor forward voltages are correct so it should not be the problem. You're facing the classic failure in these coils. See post #3 above. You won't be able to get to the joints between the lead wires and the windings without destroying the windings. Your readings indicate you have one or more open connections. And even if you were able to fix one, the others would be in the same condition and would soon fail anyway. So you're facing pulling off and replacing both windings. It can be done.

 

[simos]

The transistor forward voltages are correct so it should not be the problem. You're facing the classic failure in these coils. See post #3 above. You won't be able to get to the joints between the lead wires and the windings without destroying the windings. Your readings indicate you have one or more open connections. And even if you were able to fix one, the others would be in the same condition and would soon fail anyway. So you're facing pulling off and replacing both windings. It can be done.

Yes, I agree. I'll give it a go, nothing to lose now. Thank you and the other contributors for your advice.