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TSE45 change to TSE2A3

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modern 2a3's and had lot's of hum.

The hum you experienced was likely because the filament regulator on the board was operating on the edge of dropout. For the regulator to be hum free the voltage across C1 needs to be 3.3 to 4 volts. Sometimes a big cap in parallel with C1 helps.

The 2A3 draws 2.5 amps nominal from a 2.5 volt source for the filament. This is right at the limit for the 5 amp regulator on the TSE board. Some "modern" 2A3's draw more than 2.5 amps, while some draw less. I have not tested any 2A3's in 6 or 8 years so I can't say which is which any more with certainty.

The XPWR 131 was created by another forum member for 45's and 300B's but 2A3 operation was never intended for that transformer. The 6.3 volt winding is only rated for 4 amps. At the time Edcor stated that they could not offer a 6 amp or so 6.3 volt winding on that sized core.

My 2A3 amp used a Hammond 272JX transformer, but this was done over 10 years ago. I have been told that modern versions of this transformer put out too much high voltage, but I haven't tried it myself.

To use 2A3's in a TSE board you need a 6.3 volt CT winding that can provide 6 amps or more. This could come from a separate transformer.

The heat sinking on the regulator chip will need to be upgraded. I used an old CPU heat sink from a Pentium 1 chip (yeah it was a while ago).
 
Sounds nice. Doing FM upstairs.
 

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this experiment will stop.

If it works.....

The filament regulator will simple shut down if it gets too hot. Obvious symptoms, loss of sound. It just fades out as the filaments go dark. Usually power cycling is needed to restore operation, but sometimes the regulator will restart once it cools off. In this case check the heat sink. If it's too hot to touch (after you have pulled the power plug) add some additional heat sinking.

Check your power transformer. Again if it's too hot to touch an upgrade is needed.

Note, this is the usual rule of thumb. My original Lexan TSE has its second power transformer. The original transformer got really wet during a hurricane, and still lived for a year despite being full of rust inside (determined by autopsy). The second power transformer is a "too small" Allied 6K56VG (made by Hammond) which gets too hot to touch and starts to smell funny after several hours of continuous play with 300B's, yet lives on. Over 10 years now however most use has been with NX483's (5 volt 45's).
 
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