First power up problems w/ recto tube. Opinions

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Mostro
Posts: 68
Joined: Wed Jul 09, 2008 4:20 pm

Re: First power up problems w/ recto tube. Opinions

Post by Mostro »

Let me detail a bit how I got to this B+ voltage (my previous post was mostly a "it-works-I´m-jumping-in-joy" post):
I added a 100 ohm 10W resistor between each power transformer HT outs and each recto tube´s plate. I measured the tranny´s HV secondaries, and it gives me around 200 ohms from each side to grounded center tap. This was measured in circuit.
I haven´t done the numbers, I just guessed the R´s value, knowing I may have to change them, but they were fine at first try. I got the idea mainly from AX84´s october amp schem. My only concern was that they could create too much sag, but in the little testing I did so far it´s not noticeable.
The recto tube is a Sovtek 5AR4. As I´ve been reading, new rectos are really not the same as old ones, they are mostly different tubes (russian in this case) with the pinouts adapted and characteristics similar to the old ones, so that may be a factor... I think using the old datasheets as reference for this tubes can be misleading.

Structo, I don´t really know what kind of heated rectifiere this is, I -think- directly heated. My standby switch is installed already, so it´s staying there.

M fowler, the tranny was made for a 5E3 Deluxe, so it´s meant for a 5Y3 recto, so 2A filament. It´s a handmade tranny (not by me), not a commercial one, I don´t have a spec sheet... I could ask the guy who made it.
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Structo
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Joined: Wed Oct 17, 2007 1:01 am
Location: Oregon

Re: First power up problems w/ recto tube. Opinions

Post by Structo »

How hot do those 100R resistors get?

Seems like they would have a lot of currrent flowing through them?

I know the 50 watt zener I put in my Hammond amp gets too hot to touch.
Tom

Don't let that smoke out!
Mostro
Posts: 68
Joined: Wed Jul 09, 2008 4:20 pm

Re: First power up problems w/ recto tube. Opinions

Post by Mostro »

Structo, they get hot, almost too hot to touch, but they are up in the air, between the socket and a terminal strip, so I think they will survive.
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