[R-390] Two new tutorials posted on the R390A FAQ site

[w1nzr at cs.com]

Thank you Perrier


-----Original Message-----
From: Perry Sandeen via R-390 <r-390 at mailman.qth.net>
To: r-390 <r-390 at mailman.qth.net>
Sent: Tue, Jul 23, 2019 10:16 pm
Subject: [R-390] Two new tutorials posted on the R390A FAQ site

Yo Bubba Dudes!,
Al has posted two new tutorials I've written.
The first is how to replace the OEM large and dangerous AC input filter, FL101 with a modern computer input style filter.  They are smaller and work better than the OEM and best of all won't shock the dickens out of you if there is no 3 wire ground ans you are grounded when touching it.

The second is an electronic regulated PS circuit.
Now why would you really want to use it.
I'm so glad you asked.
Besides good B+ regulation there is IMNSHO a much more important feature.
Almost all have given up 26Z5's because of cost and use SS diodes.  And here lies the problem.  When first turned on before the filaments have a chance to warm, up full B+ is applied to the tubes and filter capacitors. Both aren't happy with this. This causes tubes to be stressed and causes premature failure.
Now they're not making the tubes we use anymore and the prices are slowly rising so prolonging their life has direct economic benefits for us.

This wasn't a problem with filament rectifiers as B+ would slowly rise as the tube warmed up.

So the circuit I came up with has a RC delay for a slow B+ rise.
An additional benefit that is new to this is the LR8 three terminal programmable HV IC. With just two resistors it can be set from 12 to 450V.  This can be used on any B/A receiver.  Used alone it can replace a 0A2 or any other gas regulator. What is so very helpful is that one doesn't need an input dropping resistor.
All the details are on the tutorial.
Regards,
Perrier






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