Systemic Development > Bipolar System Disorders
I think my System is virtually finished
steve:
I found out (probably should have known) that the JJ output tubes use solder without lead
in the tube pins. Unleaded solders tend to thin the sound vs quad solders with lead.
So I added some quad solder to the cathode, grid, screen, and plates pins of the KT88s. The sound
did fill out a little. I like both the JJ KT88s and the new Tung Sols (given to me years before the war).
I am also testing lower filament voltage and its effects on life on new, small signal tubes. In general
there are several causes of reduced tube life.
1. Residual gas/ ion bombardment
2. Too high of filament voltage "boiling" off of oxides
3. Too low of filament voltage causing excessive space charge depletion
4. Cathode sleeve impurities causing poisoning of the oxides
It may or may not take some time of use to hopefully arrive at a conclusion or two.
Cheers
steve
steve:
I posted this in another string but I feel it is very important as tubes are getting
quite expensive, especially NOS.
This is not a truly representative test as only 1 used JJ E88cc tube with two sections,
A, B are being tested. I will have to perform more tests with more JJ E88cc tubes for
better overall accuracy but should give us a good indication. Tube has been turned
off just a couple of times so far.
Test started on 8-11-24, measurements below are from 8-15-24.
Very early on, approximately 90 hours, the tube appears stable.
I did make a change from 2 watt to dual 12 watt plate resistors on 8-11
for increased heat related stability. Different RL resistance values A and B
are due to availability from the old parts box.
RL A are two Mills 12 watt resistors in parallel for 7.11K ohms
RL B are two Mills 12 watt resistors in parallel for 7.71K ohms
Voltages and currents are approximates.
Filament 5.85 volts dc
B+ voltage 142
Plate A voltage 71.8 volts
Plate B voltage 63.8 volts
Plate A current 9.86ma
Plate B current 10.13 ma
We'll see how the tube acts over time.
cheers
steve
steve:
Hear are some results after ~ 450 hours using a used JJ E88cc tube, at ~5.85 filament volts.
The AC line voltage varies slightly, which I can adjust, so there is only a slight DC voltage variations,
but not enough to cause a problem. I can adjust the line voltage for exactly 5.58 filament volts at
measurement times. Military Grade Mills RL's A and B values remain stable since the dissipation
is only ~0,7 watt dissipation vs 24 watt rating.
Filament 5.85 volts 5.85 volts
B+ voltage 142 volts 141.7 volts
Plate A voltage 71.8 volts 72.2 volts
Plate B voltage 63.8 volts 63.7 volts
Will continue to add hours, and will check in later.
cheers
steve
steve:
--- Quote from: steve on September 03, 2024, 04:52:15 PM ---Hear are some results after ~ 450 hours using a used JJ E88cc tube, at ~5.85 filament volts.
The AC line voltage varies slightly, which I can adjust, so there is only a slight DC voltage variations,
but not enough to cause a problem. I can adjust the line voltage for exactly 5.58 filament volts at
measurement times. Military Grade Mills RL's A and B values remain stable since the dissipation
is only ~0,7 watt dissipation vs 24 watt rating.
Filament 5.85 volts 5.85 volts
B+ voltage 142 volts 141.7 volts
Plate A voltage 71.8 volts 72.2 volts
Plate B voltage 63.8 volts 63.7 volts
Will continue to add hours, and will check in later.
cheers
steve
--- End quote ---
9-28-2024 ~600 hours
Fil voltage 5.85 volts
B+ 141.2 volts
Plate A Voltage 72.9 volts
Plate B Voltage 64.3 volts
Voltage changed slightly but within 2%. Will continue.
steve
steve:
Here are the results after approximately 984 more hours, for a total of ~1434 hours.
Filament Voltage: 5.85 volts
B+ voltage 140.8 volts Initial Voltage 142.0 volts is within 1% change, meter tolerance
Plate A voltage 72.8 volts Initial Voltage 71.8 volts is within 1.5% change
Plate B voltage 64.5 volts Initial Voltage 63.8 volts is within 1.1% change
Although this experiment consists of one tube, two sections, I am quite impressed with the performance
so far. In fact, I have adjusted the filament voltage in both my 11A Line Preamplifier and my Monoblock
Amplifiers.
The cathode deterioration is quite modest after some 1400 hours at the lower filament voltage. This
kind of performance is certainly not consistent with 6.3 volts. As such I would venture that cathode
material vaporization is a main component of cathode degradation.
I would say ion bombardment is causing little deterioration of the cathode. The
plate voltage rises rather slowly, taking many many miliseconds to reach high voltage.
Ions are quite light mass and there is not much acceleration at lower plate voltages, as the
voltage ramps up in value. Although this conclusion is not scientific, I feel quite comfortable in this
conclusion.
As mentioned above, I have lowered the filament voltage in both my 11A Line Preamplifier and My
Monoblock amps. I have not kept track of the hours of service, but my last check showed virtually no
deterioration of either my small signal tubes nor my new Tung Sol 6550 output tubes, even
though the side getters are turning Milky.
Caveat: Although I feel lowering the filament voltage would be advantageous with other brand tubes,
I cannot guarantee this would be the case.
As such, I am finishing my experiment.
Cheers
steve
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