• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Rectifier tube glows, sparks, then behaves. What gives? (Video inside)

yes on that sparking/dead JJ 5AR4. One of the reasons I'm curious about this tube, Visual inspection of the cathode shows those hot spots, but as you say, once the cathode is warm, it operates normally. Sparking seems to be increasing at each successive power-up, let's see how long it lasts.

anecdotally, I've been using a RCA 5U4GB in this amp for 2 years, no issues. $20 on ebay. But I love the hanging filaments on this tube, and the big shouldered bottle.
 
Hi George,
Well, you are running them hard by your own admission. Most equipment designed "back then" was conservatively designed. Normally I don't have a problem. You are quite right too, they carry all the DC current needed by everything. But they generally operate fine as they are designed for that service. They often outlast the output tubes.

Filament rectifiers can "sparkle" sometimes. But a 5AR4 doesn't heat up quickly so it conducts more gradually. Only cheap tubes and poorly designed circuits seem to kill them. That's in my experience anyway.

Hi wg_ski,
Agree completely, including your design direction.
 
Greetings, friends. I put a new-to-me rectifier tube in my amp, and it does this:


Tube is a Soviet 5Ц3C, which I believe to be their version of the venerable 5U4G. Amp is fairly low voltage, tube sees maybe 350v on each anode and makes around 130mA. It does this crazy dance at startup (5 times so far) and then behaves normally.

So what gives?
Do you have a lot of filter capacitance on the tube? That would cause tube antics on startup but settle out after the caps have reached operating voltage. Peak charging currents would shorten tube life.
 
I've been specifically advised, by Matt of CascadeAudio, that the Hammond 193J is not a "Swinging Choke" and is not appropriate for a choke-loaded supply.

But I guess that's technically hearsay. And I've seen amps that use lower-rated chokes in their supplies, so I dunno.
 
If there is an input cap it is the resistance in series with the tube up to the cap , that is like a short circuit at startup
For a transformer Rtotal = Rsecondary + n^2 x Rprimary
n is the turn ratio of the transformer to half secondary , and Rsecondary is from central tap to each plate of the rectifier
Looking at the specs I doubt that Hammond has enough resistance by itself ... soviet 5Ц3C is much worse , the max input cap stated is just 20uF
 
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The equivalent series resistance is a factor for continuous operation and steady state peak plate current (800mA for 5U4G). Your problem is the startup transient peak plate current (4A for 5U4G). The power supply design shouldn't be having a problem with a spec 5U4. My guess is that the Russian tube you have in there is below spec. The Hammond transformer should have sufficient series resistance. You said it sees about 350v per plate. The necessary effective series resistance needed is only about 50Ω. The Hammond should naturally exceed this.

You should try calculating the effective series resistance of the transformer primary. Read here: http://diyaudioprojects.com/Technical/Tube-Power-Supplies/Basic-Tube-Power-Supplies.pdf or go directly to the Reich reference.
 
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The equivalent series resistance is a factor for continuous operation and steady state peak plate current (800mA for 5U4G). Your problem is the startup transient peak plate current (4A for 5U4G).
The effective winding series resistance does certainly play a part in determining the initial transient peak plate current.

The schematic of the power supply in post #24 doesn't show series ss diodes with the valve anodes.