[AMPS] Siemens triodes

[John Lyles]

To VK6APK, Alek.

The RS1016 is a power triode used for industrial RF heaters, dielectric
type. The Amperex 5868 is identical. The base on these tubes is SLIGHTLY
different than a 3-500Z, enough that they are incompatible plug ins.

The filament is 10 VAC, 9.9 Amperes, thoriated tungsten, fast heating

Plate voltage rating is 4 KV DC, up to 5 Amp peak cathode current, 0.7
Amperes DC current

Plate dissipation is 450 Watts

The tube us good to about 100 MHz with slight derating.

Capacitances:
Cath - Grid 8 pf
Cath - Plate 0.17pf
Grid - Plate 7 pf

Amplification factor Mu = 28
Transconductance s = 4.5mA/V (or 4500 micromhos)

Forced air needed, similar to 3-500Z or 4-400Z, but direct at the plate cap
and the base (no chimney).

Hence it makes a nice self-oscillator for RF heat. As a matter of fact, I
have one in my shed in a W.T. LaRose and Assoc. Thermall plastic preheater.
I picked it up at a junk yard for about $20. It puts a lot of heat between
two plates, and the plate current tripout is set for about 600 Ma. Thing
runs around 90 Mhz i believe.

The Siemens data show following operation, only as oscillator:
100 Mhz
1630 watts output
4 KV DC from 3 phase bridge, no filter cap
-360 V grid voltage
590 V peak RF voltage on grid
16% feedback factor (RF heating oscillator spec)
535 mA plate current
120 mA grid current (quite high, hence it's ruggedness for RF heating work
where the load swings all over creation, and grid current must stay within
burnout limits)
67 watts drive (from feedback)
440 watts plate dissipation
25 watts grid dissipation
76% efficiency
4 K Ohm plate load resistance

I have an Amperex sheet for the 5868, and it shows HF class C telegraphy RF
power amplifier application:
The numbers are virtually identical to the above application.

Nowhere in the data is a class AB operation, although they do list class B
audio performance.

-----------------------

Now, compare this to the Eimac 3-500Z data.
The RS1016 has muchos higher feedback capacitance, as the 500Z is only 0.07
pf Cath-plate capacitance in grounded grid. Also, the output C is only 4.7
pF in the 500Z, versus 7 in the RS1016.

Mu is 130 in the 3-500Z, versus 28 in this tube. (HIGH Mu versus MEDIUM to
LOW Mu)

Plate dissipation is nearly the same, and grid dissipation is 20 W for the
500Z, 50W for the RS1016.

In a pair, you will need >100 watts of drive to run these in AB2 'linear'
operation.

Now the bad news. The 'zero bias' triodes from Eimac, Svetlana, or whoever,
are truly that. At 3 KV on the plate, they draw just over 100 mA of idling
current. This RS1016 beast would draw almost an Ampere! You would want to
put a bias supply on it, or zener/723 regulator circuit in the cathode DC
connection. Otherwise expect melt down quickly.

I wouldn't recommend these tubes for linear amateur operation, as they
really are optimized for industrial heating. The low Mu is typically what
is needed there, where the grid current varies greatly, and they want
enough drive to swamp this, to keep it oscillating. They have strong
feedback to remain in oscillation with a tuned-plate tuned-grid circuit
(TPTG). All of this goes against what we hams want in tubes, unless you
want a power oscillator to scare everyone away with, or light up your Tesla
Coil, or melt plastic.

John
K5PRO








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