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Thorn 2000 Tripler Rebuild

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With having four Thorn/BRC 2000 sets its imperative I have a spare or two in stock. The idea here is to test the ability to rebuild a 2000 tripler and document how it was done.

These triplers are getting on now and will start to fail, I already have a couple of failed ones. One has a broken VDR the other has a failed selenium rectifier stick. First I needed to find a suitable potting compound, you cannot just use any old silicon, it has to be voltage and temperature rated. I settled on a compound called Silcoset.


Next was to decide on the diodes, BY8410, BY182 or NOS selenium sticks?

The BY8410 were tempting but due to their tiny size it might present issues with flash-over. Also they are so efficient, another person found that they produced way too much EHT. One possibilty is to use one or two less but the tiny package still means the flash-over risk needs careful attention and management, not impossible but a risk.




Next BY182’s were considered, the package on these are more robust, less flash-over risk but perhaps again too efficient.



So it was decided to fit NOS selenium rectifier sticks. These were the ones used in the 3000/3500 triplers. A little smaller than the originals and some lead-outs would need to be attached but likely as efficient as the originals.

BRC 3000/3500 sticks


I rebuilt the tripler over a couple of evenings carefully removing all the old silcone insulation and de-soldering the old sticks. I then installed the new rectifiers and fitted the lead-outs ensuring they were securely strapped to negate movement. Finally I potted it with the silicone. Then waited 48+ hours for it to cure before testing in a set.

2701-y 2701-z 2701-zz1 2701-zz2 2701-zz3 2701-zz4

After waiting 60hrs I felt the curing of the compound should be pretty much done. I tested the rebuilt tripler in the Ferguson 3700, happy to report its a complete success as can be seen below.

Hope this helps others to give it a go.

2701-zz5 2701-zz6


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5 years ago

Hi crusty,
That’s a fine job, where did you get the diode’s?, my own 2k is going to need a triplet when it’s restored.

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