Yaesu FL-2100Z - 572B issue - Draws current in stand-by position
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- Опубликовано: 15 окт 2024
- I do not use this amplifier frequently and maybe it is a mistake. I mainly work in CW with 50 W and that's enough for me.
So last week, I turned it back on and after a few minutes I saw, that in the "stand-by" position, there was an anode flow of about 100mA.
Absolutely abnormal !!!
A 572B exibits a short-circuit between grid and filament.
I have the same problem with my 2100Z. One tube Grid is short to filament. Also found that both 33ohm 3w grid resistors ( R7 and R8 ) roasted. One open circuit. Other showing 40ohm When run only with the good tube on the side with the 40ohm side, output is about 200W on 80m band. Loading is at minimum. I will update when new tubes and resistors are replaced.
Hello and thank you for your comment.
Like you, resistors R7 and R8 got hot, not to the point of roasting them, when I saw the current flow, i immediately cut-off the power.
It must also be said that the horizontal position of the tubes is not ideal.
If you know of a good source for the tubes, I'd be happy to know.
Good traffic.
73 Denis
@@radiorider8249 I replaced the resistors and ran only with the good tube and got about 250W out. For the shorted tube, I took a 3.2V LifePO4 battery and first heated up the filament to get the tube warm and then connected both filament pins together and applied 3.2V across the filament pins and the grid. The shorted grid line started glowing and fused within about 5 seconds :) . No more short between the grid and the filament !. Ran both tubes and got about 450W out but my joy didn't last long.... after about 10-15 minutes of work IP went to 100mA on standby , again the same tube got shorted. Now ordered 2 x PSVANE tubes from China and awaiting delivery.
Could you please confirm the value of C30 door knob at the end of plate choke ? Mine is a 1000p but the schematic shows 5000p and again part list shows 1000p. Not sure which is correct !. and I'm using a dummy load and when tuning Loading always peaks at minimum at 0 position for any band. Is this usual with a dummy load ?
@@nalaka_adelaide Let me a couple of days, I'll check.
do you know if the two bias 33 ohm resisters have to be carbon or can they be metal oxide type..i have more Q’s after this…ie taking out the bias control and grounding the grids directly..what effect does this have..still work the same ? if so why do they put this -58 volt system … thanks..
I replaced with 2 new psvane tubes from China. Replaced the 33ohm resistors as well. Now I get 600w in to dummy load on 40m with 60w CW signal. It doesn't seems to increase plate current/ output even if I increased the input. I think that's the max I can get with the Chinese tubes or May be my new plate cap is not up to the mark.
Thanks a lot for info, 600 W is a good result. I checked on my PA, C30 is 1000 pF. I hope your tubes will have a long life. 🙂 73 Denis
Hi just came across this video.
The Chinese tube that I got were rubbish.
Tried different 572B's from different supplier none of them worked for long.
I now use G-811 tubes made in Russia which are old stock.
These work very well for 400W (legal power in Australia).
I reduced the HT to 1.7Kv by changing the tap on the power transformer.
Set bias voltage to -2V gives 60mA.
The G-811 will give About 700W but get too hot.
Cheers
Kevin
This is very bad news. 😊
Thank you Kevin for your comment and information. I suspected that these Asian tubes were not very reliable.
Thanks for the tip about the 811s, I'll see what I can do.
73 from F to VK.
Denis F6CRP
Can you please exactly explain how you reduced HT?
Wire your amplifier to work 234v if not, the filament 6.3v is exceeded, these 572b are tungsten-thoriated filaments witch are 5% tolerance. This is valid to 811, 813, 3-500z tubes. If you your filaments out of tolerance you will extinguish the thorium and you will kill the tubes in 2 or 3 mounts. Don't use your amplifier with more than 70 watts drive cw, 600 watts out or you will deform the grids, because high grid current. This is a RMS 1kW input amplifier, 1kW x 60% efficiency is 600W out. After this there is the plate limitation in 572B or T-160L 160 watt x 2 = 320 Watt plate dissipation. The transformer can handle just 1kW, if not the the voltage drop under 2000v, so splatter, flat top, distortion .... no miracles.
You can use Chinese tubes they work well if matched and DO NOT over run the filament more than 6.6 v
Hello Antonio,
thanks for the information about the 572B. The amp is already wired for 230V, on the other hand I didn't think about measuring the filament voltage, it's a very good idea. I never use a HF amplifier, but I don't like having something broken in my station. 😉
Thank you for your comment.
73 Denis F6CRP
Short in a capacitor or tube
In the tube...
A known issue on this amplifier.
So how is it resolved?
@@cl5ltd Hi Christopher. The problem mainly comes from the tubes. You should not ask for too much power, 500W max p to have a good longevity of the 572B.
Il va falloir essayer les tubes chinois...