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Tuesday, October 16, 2018

Tube of the Month : The 19DE3

Hi!

For this month I pulled a rather odd TV Damper tube from my collection, the 19DE3.




I just came across a box labelled 19DE3 in my tube storage and opened it since I was totally unaware that he had these.

I first thought it is just another odd heater voltage variant of a 6.3V type. As there are the 19AU4, 17AX4, 25AX4 and many others. But when I looked it up I realised that there never seems to have been a 6DE3 and this type was only made with a 19V / 0.6A heater for use in series heater arrangement and obviously for Damper service in color TVs. It has the late 12 Pin Compactron base and the cathode connection is brought out to a top cap. Color TVs required some hefty Damper diodes with high current and voltage capability. The 19DE3 can deliver 350mA steady DC current and can handle peaks of just over 1A. With that it is similar to the 6CG3. Like other TV Dampers this diode is perfectly usable for rectification although the tube manufacturers never advertised their Damper tubes for that. They have a slow heater warm up which brings up the voltage nicely and can deliver large currents. This is usually combined with a rather low voltage drop which in case of the 19DE3 is extremely low and comparable to mercury vapour rectifiers like the 866A. See the plate characteristic below.



Many tube amplifier builders have realised the usability of TV Dampers. So the usual Octal types with 6.3V heater have become a bit scarcer compared to years ago. But they are still easy to find at reasonable prices.




If you are on an extremely limited budget or if you need them in larger quantities, such compactron dampers or those with odd heater voltage are still sold for next to nothing and tube dealers are happy to sell them in volume at discounts.




So if you plan to do a small series production of tube amplifiers or if you need current and voltage capabilities beyond those of the classic rectifiers, TV Dampers are the way to go.




They had been produced in millions which enabled the tube manufacturers to sort out all potential weaknesses and they were designed to withstand the stressful operation in TV sets without frequent failures.




Let's have a look at some 19DE3 in detail.




This one was made by Sylvania.







The top cap:




The 12 pin base:




Some close ups:






Despite being a mass market product a solid construction.




Another Sylvania in later box, after Sylvania was acquired by Philips:




General Electric 19DE3:








Slightly different construction compared to the Sylvania above.






RCA:






Again different in construction, so no cross branding with these.






That's all the different 19DE3 tubes I have.




Now let's open one and inspect the internal construction.




Glas removed:




The top showing the heater inside it's insulation spiral within the pate:




Bottom side:





Getter ring:




The heater:






Heater wire removed from the insulation spiral:





The cathode:




Plate:





And lastly a 19DE3 with the heater lit up:





Close Up:




I hope you enjoyed the presentation of yet another TV Damper in the Tube of the Month series.

Best regards

Thomas



Wednesday, October 10, 2018

More Amplifiers With The 46

Hi!

The 46 amplifiers, especially the 46 drive 46 are gaining popularity. Several more projects are in the pipe.




Readers of my blog who followed the progression of other amplifiers probably predicted these.




A fully differential push pull version of the 46 drive 46 concept is in the testing phase.




Yes that is 4 46 tubes per mono block. Doubling the output power.

Here a view of the underside of the top plate:




The other modules of the amp:






And of course a version of the single ended 46 drive 46 with all silver transformers is also in the making.




New silver transformers custom made by Lundahl for me. The next module which will mount under the top plate:




Below that the power supply section will reside at the bottom of the chassis.

Stay tuned for updates as thee projects get finished

Best regards

Thomas