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Along the same lines as I mentioned the other day, QRO Technology made a blunder on the HF 2500 amplifier. ?I found this problem when a local ham called me and told me that his HF 2500 would restart

I have drawn a simplified diagram of the L-7 power supply. I have drawn in red an additional bridge to establish to prevent the cathode from being isolated. In emission, the ammeter is shunted by the

Hi fellas Sounds like you guys learned in your hobby what I used to teach my junior electrical engineers. Of course, they all worried about the hot wire. I told them in order of importance, it’s

Hello Your participation is very interesting because I am in the process of putting a Drake L-7 back into service. I understand very well the electrical problem that you mention and the original

Lou can chime in on this one.? On? the..... "big 3"? ? ameritron amps....... they don't use a resistor at all.? On RX it's wide open !? ?I got into an argument with W8JI about this years ago.?

Low mu triodes are useless for GG.? ?Reason is...... they require a stupid high amount of bias V? to obtain normal idle current.? ?You can see that effect asap, by looking at the constant current

Hi Everyone, I thought I might find a bad tube by swapping both tubes in and out one at a time.?? Only thing I confirmed is that what ever the problem is, it hasn't healed itself.?? FWIW I checked

An 'A1' triode is a Low Mu Tube and will NOT work as an amplifier at Radio Frequencies. Like Medium Mu Triodes, designation ending in A3 and A5 also will not work in RF Amplifier service They are used

Well, I picked up the amp and it looks pretty much complete minus the tubes and vacuum variable which I have already found one. I was looking at some of the Russian tubes and found that they have a

Just letting you know, Effective? Nov 2024 ECONCO no longer tests tubes at no charge. The fee is now $150 per tube. thanks to the new corporate owner TransDigm. Reid Re: Need Help with Amp Supply

That helps, I was thinking maybe he meant the plate choke. Thanks [email protected]> wrote:

Plate Blocker is the big capacitor that is connected to the plate tune capacitor coming off the tube anode. Should be 5kv or more rated. Shorts won't always show with a multi meter till they get warm.

Hey Alek, How's 20 meters been down in your neck of the woods lately? Maybe we can get on and say hi again one of these days soon along with your "Jack Daniels" friend! 73 and happy new year, Bob

Hal and all, I've started testing each tube in each socket individually and will post my results hopefully later today.? The first tube doesn't show any shorts with a DMM.? I don't know what a

Yes, that's good Alan. Whenever I get an amplifier in that is wired the "wrong" way, I always make the simple change. 73, Alek.

New Harbach l4b / l7 board kits with new 330uf rubicon 5000 hr caps also 125 bucks

I have four Henry amplifiers (2-KD-Classic, 2KD-5, 3K-A, and 3K-Classic-8877), and all of them have the resistor always-in-circuit, with the relay acting as a bypass. Likewise, my Drake L-4B , with

John, It could be a cold solder joint in a tube pin. If it was an interelectrode short, you could use a DMM to explore. If it was a defective plate blocker it would show up with a meter, out of the

Happy New Year, I have a fully assembled, tested, but never used Heathkit Shop power supply upgrade board for Drake amps for sale. Price is $125.00 plus shipping from 23418. Details and pictures are

I believe Econco will function test transmitting tubes. You might check with W8JI, too. Hal Mandel W4HBM