5AR4 @ 250mA

[scott17]

So thats where they all went. I only have a few hundred left....That's what I have been using and I haven't noticed anything nasty yet. I also find that it helps to float the 6.3 volt heater winding 30 to 50 volts above ground with a 0.1 to 0.5 uF cap to ground.

Well maybe not a million but I've got plenty. I am using a mu follower gain stage/cathodyne inverter, and have raised my heaters to 55V. Seems to work fine so far. Thanks for the info.

Scott

 

[Burnedfingers]

I first introduced the diode mod back in 2002.

My Power Supply Schematic with mods drawn in.

Original Burnedfingers
diyAudio Member


Join Date: Nov 2002 My Power Supply Schematic with mods drawn in.

Note: The first large cap is 850/475V
second is 330/500V
Attached Images pc180069.jpg (66.5 KB, 897 views)
post number 32

"Quicksilver KT88 mono 60 watt amp schematic."

Put the diodes in the amps back in 2002 and their still working with the same rectifiers. It used to eat a pair of 5AR4's in 6 months or less. The diode mod works.

 

[Tom Bavis]

There will be no "recovery" effect (and thus no noise from the diode) in this circuit, so 1N4007 will be fine without worrying about snubber.

 

[alexg]

On a related topic, if I parallel 2 5ar4 to get higher current, how do I compute for the voltage drop?

Sorry for hijacking the thread.

 

[scott17]

OK, so I installed a 1N4007 on each plate of the 5AR4 rectifier, after the series limiting resistors. Cathodes on the plates. Now the PT hums. I'm guessing that has something to do with half-wave now going to the plates.

It did not hum before adding the diodes.

 

[trobbins]

Just to correct the record - the 2002 reference by Burnedfingers was for a ss bridge before 2x GZ34 that were rewired in parallel and in series with the rectified output - the mod was made by someone else beforehand (Burnedfingers just updated a schematic) - and the thread viewed the mod as providing soft-start rather than protection.

 

[mooreamps]

The 5AR4 is rated for 825 mA RMS - and over 3 A peak... I doubt it'll fail at 250 mA.

~Tom

ah, no..... 825 mA is not "RMS"..... is dc.

 

[jhstewart9]

The 5AR4 is rated for 825 mA RMS - and over 3 A peak... I doubt it'll fail at 250 mA.

~Tom

5AR4 spec sheet sez 825 mA peak, not RMS. With choke input filter 250 mA, with cap in filter 225 mA continuous. 5AR4 forward drop is very good. Translated that means more volts at the load.

 

[egellings]

If you are going to put diodes in series with the anodes of the 5AR4, why not just use the diodes for the rectification, and light up the 5AR4 for the aesthetics?

 

[trobbins]

This thread is from 2012, so probably best not to extend discussion unless correcting earlier errors.

 

[TonyTecson]

the Japanese 5g-k22 is rated for 275ma......