U2000 Color Transistor Heat Sink Mod

zenomorp

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Trying to bulletproof some U2000 color transistors. We all know that these things get H-O-T and will either cause the pads to lift, burn up the transistor itself, burn the board, etc. This is due to the heat sinks being junk and not doing their jobs properly. The late model neck boards had new heat sink designs from the factory that alleviated the issue (for the most part), so with the help of a co-worker, I have fashioned 6 new heat sinks modeled after the late model factory ones and installed them (plus another new transistor) on the two U2000s I repaired last night. The new heat sinks are working great on both chassis'. I don't have a digital temperature gauge, but just based on touch and radiant heat, they are a vast improvement on the originals. Thinking about doing this to all the U2000/K7400/K7500/U5000 chassis' I come across. Here are some pics. Just wanted to share. Thanks.















 
You want to sell a set of those? I'm messing with a U5000 now and those transistors are toasted and some of the pads are lifting also.
 
We used a piece of scrap sheet metal out of the scrap bin at work. It's supposed to all go to the recycling bin but we snagged the piece to make them. Can't sell them or make kits because we'd most likely get fired.
 
We used a piece of scrap sheet metal out of the scrap bin at work. It's supposed to all go to the recycling bin but we snagged the piece to make them. Can't sell them or make kits because we'd most likely get fired.

No worries, but thanks for the post. i will try and copy it on my own. Great Job
 
No worries, but thanks for the post. i will try and copy it on my own. Great Job

Thanks! I'm in the process of sending one of the original lade model ones that I used as a template to a fellow collector who is going to use a water jet machine to potentially mass produce them. I'll keep you updated if he's able to do it.
 
Just got work from Robb Traxx (ex-Wells employee) we should be using an ECG/NTE 198 Transistor. It has better max voltage, slightly better gain for the tubes, runs half the temperature, and a direct solder in replacement. That's great info!
 
OK -- I can see how the NTE198 can be better with a higher voltage range and may replace the 2507 but I don't agree with the rest.

The NTE2507 can operate at far, far higher frequencies... not that it really matters here.
The NTE2507 has slightly higher gain than the NTE198 (40min-320max vs 30min-150max).
They both have the same R-theta-JC so thermal dissipation is the same.
Since these operate in the analog realm, VCEsat has no meaning here (although they are nearly identical).
The actual power they are dissipating is established by the circuit they are operating within and not by the part themselves. This being the case - they are both dissipating the same amount of power and have same thermal dissipation hence the operating temperature will be the same.

The heat sinking as shown in this thread is what makes a world of difference.
 
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