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Kundo Transistor for kundo clock

corvetteboy

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May 3, 2020
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Hello everyone, I hope im posting this in the correct area, please forgive me if not im still new and this is my first post here and ive really enjoyed all the info ive read so far, but i need alittle help on an old kundo electro-magnetic clock i aquired. I know issue is in the coil and it is the type with the old tf65 transistor, which i have checked and determinded its bad. i was also able to check both coils and they check good. My question is, and ive been reading alot too,:D anyway ive read a few posts that mention ac125 as a good replacement but i actually think ive found another possible one. Its nte102a, can anyone verify that it will work? All specs check out and its a PNP and germanium junction as well. The only issue maybe is it is in a metal case but its the same size as the old tf65. Please let me know what yall think. I truly appreciate any help.
 
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Toughtool

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Aug 12, 2016
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Seen like the AC125 should work. Here is a link to where they talk about it, including your clock. Looks like the Nte102A may work as well. it has a gain of 65, similar to the AC125. There is also a listing on Amazon.com that indicates a replacment for the AC125. https://www.amazon.com/Transistors-...words=AC125+transistor&qid=1588545822&sr=8-15


Siemens TF65 Transistor - Industrial Alchemy
They say: "The TF65 is a germanium junction transistor that introduced in 1957. This transistor was made in both a silver and black cased version; the black version is shown here. This model of transistor is best known for it's use inside Kundo's line of electromagnetic pendulum clocks, which make use of the transistor in the pendulum drive circuit. The TF65 is a common point of failure in these clocks, requiring replacement with a more readily available germanium part number, the AC125 being the most common choice."



Photos
 
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whatgoesaround

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Jan 22, 2008
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It seems I remember reading that the metal does play havoc with the magnetic functioning, but someone with a lot more knowledge than me will hopefully come along with the right info on that.
 

Toughtool

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I wouldn't think the metal cap would interfere since it is not magnetized, but it may if it was in the way of the magnetic field produced by the coil or close to it. A photo of the clock would be nice to see, to determine where the transistor is physically located in relation to the pendulum. The Industrial Alchemy.org site only show the plastic version (Black) and a US quarter.
 
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corvetteboy

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May 3, 2020
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Hi toughtool, thank you for that info, yes I was thinking the nte would possibly work too. I checked out the specs and it seems to be right in line with the tf transistor. I actually just got the clock given to me just this weekend, it's pretty tarnished and needs a deep cleaning, it is the rectangular shaped glass on all sides. But one panel is cracked and the back glass is missing, but the clock itself is complete. I've already taken the coil apart and checked out both coils and they check out fine. Thankfully this one doesn't have the green chemical buildup like so many here have had issues with. I also checked the transistor and it definitely is shorted. It's the style where the transistor is built into the bobbin beside both coils. Once I get it cleaned up alil and better, I'll definitely get some pictures.
 

Toughtool

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Aug 12, 2016
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It's the style where the transistor is built into the bobbin beside both coils.
From your comments I would look for a plastic transistor. Too bad about the broken glass. Hope you can replace it. I obtained a 1955 model IBM secondary with a missing domed glass and believe it or not, I found a company who still makes domed glass in quite a few different diameters. I needed two and so I ordered three. The internet is wonderful!