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Hi Jim. I tried a large value electrolytic across the bias string and every time I keyed up, the ZSAC would take a while to stabilise at the set level. When I stuck something like a 22uF in its place

Francois,? ?with zero bias on the L4B, using Eimac 3-500Z's ( MU=130)? the? idle current is 220-230 ma = 575w to 600 watts of idle power.... = blast furnace. If using Chinese 3-500Z's (

John and Alek, my friend just spoke to Tibi at OM Power the other day. ?He called to order some FU728 tubes. ?Tibi said to him that his supplier of tubes in China is making a design change inside

What should happen if I add the red components in the attached schematic. I have the impression that it would do the opposite of the desired effect, we would block the tube on a strong RF input. I

Yes. At 2.5kV plate volts, you probably don't need bias. At 3kV in the TL-922, you definitely want bias but as VK6JX mentioned, forward biased string of 6A10 diodes is a lot cheaper than a 50W zener

Hi Francois. In my experience, the 7.5V Zener provides a little bit of bias to limit the quiescent current of a pair of 3-500Zs running at around 3kV to 150mA. This is the requirement for Class

Hello Now that both of my 3-500Zs have been de-gassed, I have a new question. · In the L7 (Drake) the bias is at 0 volts · In the Kenwood TL-522 it is -7.5 V as shown in the

1-2 hrs max...per tube. Alright. Then I'll do the second 3-500Z valve. Then I'll do the full voltage tests with the Drake's HT transformer -- F1AMM Fran?ois De la part de Jim VE7RF via

1-2 hrs max...per tube.

Hello Cooking the tubes. It was necessary to modify the tube polarization system. As shown previously, the HT power supply is floating relative to ground. This trick allows the cathode voltage

I had a bad relay on my Al-811H and went this route. There’s a write up on DX World here: https://www.worldwidedx.com/threads/ameritron-al811-relay-headache-solved-my-way.265840/ I bought special

The AL1500 relay is a typical 3pdt 12v relay. ?There is nothing magical about it. ?There are many relays that can be subsidized for it if the original cannot be found. ?With Ameritron going out of

Try w8JI, CTR Engineering, he may have one. 73? Andy? K9ATX -- "Where the Old Soo crossed the

The output relay in my Ameritron AL-1500 needs to be changed. I checked with MFJ since they are still selling some Ameritron replacement parts, but no luck.? From the user manual, this is "RLY1" and

Here's an update on the SVHFS 2025 Conference; Deadline for papers has been extended to March 17 Registration is open; details are in the attached file. Thanks, Robin Midgett K4IDC

WRX, with 200w drive, how much grid and plate current was it running? Bob W4JFA [email protected]> wrote:

Which models had 4kv on the plate? A Triode is only going to give 10 to 12 DB of gain. Man, I have worked on and rebuilt pretty much all of these amps and even the later 3KA with its HD supply won't

The Tokyo High power HL2K? with 3-500s was also such a amp. It had proper cooling(fully pressurised) On 240 VAC it could easily hit 2KW pep even though it was rated for 1.2KW PEP. Much like the TL922

It’s a well known fact that the Ameritron AL80b can obtain 1kw output ?pep?with a single 3-500. They only run 3000 volts anode voltage. ?The old Henry amps made prior to the power rule change

Which henry amps were rated at 2kw out Jim? C ________________________________ Sent: Friday, February 14, 2025 3:29 AM To: [email protected] <[email protected]> Subject: Re: