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Eimac 100TL Output Transformers and Bias Point ?


2005-10-13 9:38 am
I have no hands-on experience of 100TL or TH , but a friend of mine built one a year or two ago, so I'll pass on what I know .
Bear in mind the Ra drops if you are going into A2 . He used a 10K output transformer I believe , and reported very nice results, better overall than VT4C he reckoned. You will need an A2 driver for either 100TL or 100TH .
On that basis 100TH is actually no more difficult than 100TL , in fact the voltage swing for the driver is less , which helps. The 100TH are apparently cheaper than 100TL , I'm told .

I think the start point is deciding on available B+ . My friend used at least 1000, perhaps 1200 V . From that he got about 30wpc with the A2 driver. If you can decide B+ then you should be able to narrow down an operating point with some help .

The driver my friend used was the J.Ross McDonald ACM ( augmented cathode follower ) No.2 variant, using some hefty triode-wired pentodes for the driver (CF) part .