I've been considering the plate (actuallly, cathode) current readings on the TR-4 vs with a T-4X(any).? Interestingly, the later transmitters shed their 0 - 400 mA meters, in favour of 0 - 500 mA meters.? Tuning up and loading a T-4(any) usually gives about 130W out on 40m, which frequently will be toward the upper end of the area between 300 - 400 mA.? It's therefore a little bit strange that the TR3/4 has a maximum reading of 600 mA, which would indicate a max out per tube of 200 mA.? With the same per tube current., it would be 400 mA -- which is what the older transmitters had for meters.
The TR-4C manuals advise to load to between 380 and 500 mA.? The T-4XB manual advises loading to 250 - 320 mA.? Obviously, the tubes are easily capable of going higher but that's what "The Book" says.? To get around 120W out, I load to around 360 mA and the tubes don't have a problem? On a TR-4, add one tube and you're over 500 mA.
I also run small fans over my PA's and do not go for "maximum smoke" unless the tubes are somewhat tired, as they are in my TR-4Cw RIT.? I treat this rig as a 100W rig and leave it as that but with new tubes, 200W is definitely possible...
Sorry for the ramble...
73,
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
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On Monday, January 27th, 2025 at 2:50 PM, Barry KJ5GQM via groups.io <chasbg@...> wrote:
Interested in replies to this as I have a TR-4C on my bench right now.??
One issue I chased was over-current on full power - full power tune up has the meter way over towards .6.? I've been stressing about it for a while and finally realized that the current meter is way off.? So, I'm not supplying adequate bias and my current draw at full power is probably OK.? I verified by measuring voltage drops across the 15ohm resistors. I also remember that when I put the TR-4C on the power supply which had previously been set up for my TR-3 the initial bias reading was right about .2 instead of .1.? I didn't think about it at the time and just reset the bias at .1 for the TR-4C.? Waiting on the proper resistor now so I can get bias set correctly.? This is now on my list of things to check first when I start the restoration on one of these.? Probably not related to your problem but (another) something to add to the health checkup.
I also have some freshly baked 10M xtals to try in mine as well.
On Monday, January 27, 2025 at 01:28:02 PM CST, Dave KD5FX via groups.io <land.dave@...> wrote:
So, finally had some time to get back on this project, winter field day kept me busy over the weekend. And thanks to all in advance for everyone's help and suggestions on this project. I did all the Xmit tune up procedures on page 5-6 including the neutralization. I'm getting about 100 watts PEP output on 80/40/20 and around 15 on 15 meters while 28.0 and 28.5 bands have zero output and on 28.1 I only have 5 watts PEP output. I wonder if these tubes are bad. Does that sound like the symptoms of a nearly dead set if tubes? I haven't pulled them out for testing but I could if needed. OR? Is there something else I've missed? BTW it's still receiving OK on ALL BANDS!?
73, Dave KD5FX
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