Thinking about finally homebrewing an HF amp

[timbo]

I've been collecting parts for an HF amp for almost a decade...I have a couple of 3-500's, some 813's and a couple of 4-1000's to choose from...I'm leaning towards the 4-1000's (using only one of course ).

I've built lots of things over the years, even repaired some HF amps for friends but never have built one from scratch.

I have been collecting parts over the years, even picked up a B&W tank circuit a few Nearfests back that is supposed to have the correct impedance range for a 4-1000 running about 5KV on the plate.

I'm running out of excuses to start building this thing.

I will need to run 220VAC to my shack and come up with a high power tuner as well to run this if/when I eventually finish it.

If there is anyone here that has built one before, do you mind if I pick your brain from time to time?

 

[drgrant]

If you're gonna homebrew, build something you can't buy... preferably involving "Tetrodes with handles... "

If he's still around, seek out Rich Measures.... he was on AMPS reflector on yahoo at one point.

-Mike

 

[one-eyed Jack]

I've been licensed since 1966. This thread brings back memories. Home brewing/kit building was a way of life back then. Built tube amps for HF, Heathkit and Eico audio stuff, Push-pull audio amps, Heathkit color tv kits and more. Jack W1FKG.

 

[Uzi2]

If you're gonna homebrew, build something you can't buy... preferably involving "Tetrodes with handles... "

If he's still around, seek out Rich Measures.... he was on AMPS reflector on yahoo at one point.

-Mike

Rich L. Measures passed away January 4th of 2018, his obit is online.

Smart guy, I've conversed with him over the phone a few times back in the 90's.....lost a great asset to the ham community.

 

[timbo]

If you're gonna homebrew, build something you can't buy... preferably involving "Tetrodes with handles... "

If he's still around, seek out Rich Measures.... he was on AMPS reflector on yahoo at one point.

-Mike

Rich became an SK this past January...we communicated quite often via emails and I learned quite a bit from him...He was actually the one that suggested I use a 4-1000 (also a tetrode but without handles) because it was so forgiving and because I had most of the parts already, even then. He put me onto this site: 4-1000A Amplifier Menu with a few changes. I still have a lot of our email exchanges stored away on a thumb drive.

 

[radioman]

What do you have for a power transformer? The bigger the better. Ever since Peter Dahl went out these are becoming harder to find. The elusive pole pig that everyone seems to brag about I’ve never seen one? Maybe they do exist? Post a photo of you find one. I think most/all of the new units are out of China. My Ameratron has a PD clone. It was built a few months after the end of PD I just missed out. The Chinese unit looks and is supposed to be the exact same?

 

[timbo]

What do you have for a power transformer? The bigger the better. Ever since Peter Dahl went out these are becoming harder to find. The elusive pole pig that everyone seems to brag about I’ve never seen one? Maybe they do exist? Post a photo of you find one. I think most/all of the new units are out of China. My Ameratron has a PD clone. It was built a few months after the end of PD I just missed out. The Chinese unit looks and is supposed to be the exact same?

I have a massive transformer that was given to me...I can barely lift it. The guy I got it from years ago thought it was out of a pole pig. When I unbury it, I'll send along a few pictures of it.

 

[Uzi2]

This is what is going in my next HV supply. Its a center tapped secondary and its good for several amps at any of the output voltages. Weighs about 300lbs+ and is a bear to move.

Its a UTC LS 185. Dimensions are 13" high, 10 inches wide, and 20 inches long.

That is a five gallon bucket on top for reference.

 

[n1oty]

Seek out Uncle Griz on this forum.

 

[drgrant]

Rich L. Measures passed away January 4th of 2018, his obit is online.

Smart guy, I've conversed with him over the phone a few times back in the 90's.....lost a great asset to the ham community.

Rich became an SK this past January...we communicated quite often via emails and I learned quite a bit from him...He was actually the one that suggested I use a 4-1000 (also a tetrode but without handles) because it was so forgiving and because I had most of the parts already, even then. He put me onto this site: 4-1000A Amplifier Menu with a few changes. I still have a lot of our email exchanges stored away on a thumb drive.

This is sad, wasn't aware of him passing. May he rest in peace.

Rich was a wealth of knowledge for people working on any kind of large amp, his influence and knowledge went far beyond even the ham community. He also had some witty comebacks for the stereotypical "pious part 97" types on some of those AMPS threads. I think eons ago I communicated with him about one thing or another regarding different amps I was looking at. He was always helpful, and I learned a lot from the stuff that he
had posted.

-Mike

 

[AHM]

I've been licensed since 1966. ... Built ... Heathkit color tv kits ...

Any tentative date on when you're gonna finish the TV(s)?

Hubby of one of my mother's church lady pals was building one.

Spoiler: Their living room looked like this for many years

Hi, hi.

 

[timbo]

Rich could be controversial with some of his ideas but there was nothing that he suggested to me that didn't work. When I first ran into him, I was having issues with a Kenwood TL922A linear amp I used to own that was driving me bonkers...it kept zorching contacts on the band switch. He helped me troubleshoot it and got it working...then he suggested I sell it

The band switch on that amp was way under rated. I've had a slew of amps over the years but all were off the shelf, commercially made amps. I've always wanted to make one from scratch and so I probably will.

 

[Parker Duofold]

I have an Amp Supply LK-800C for sale. Google it. $2500.
Three 3CX800s.

 

[one-eyed Jack]

Any tentative date on when you're gonna finish the TV(s)?

Hubby of one of my mother's church lady pals was building one.

Spoiler: Their living room looked like this for many years

Hi, hi.

The TVs were finished and gone LONG time ago. To build the kits was 30 hrs each. Jack.

 

[timbo]

I have an Amp Supply LK-800C for sale. Google it. $2500.
Three 3CX800s.

I had an LK-500 some years ago...it was a nice amp. As a matter of fact, I bought it after I sold the TL922.

 

[drgrant]

I have an Amp Supply LK-800C for sale. Google it. $2500.
Three 3CX800s.

That's funny you mention this, I had an LK-800C just like that years ago and that's about how much I sold it for, I sold it to a dude for about $2200 because the tubes were a little soft , although it was still trivially easy to bang the needle off the end of the scale on my Yaesu 2KW power meter when I rigged that thing into a dummy load... those were nice, smooth beasts... external power supply, too.

-Mike

 

[timbo]

That's funny you mention this, I had an LK-800C just like that years ago and that's about how much I sold it for, I sold it to a dude for about $2200 because the tubes were a little soft , although it was still trivially easy to bang the needle off the end of the scale on my Yaesu 2KW power meter when I rigged that thing into a dummy load... those were nice, smooth beasts... external power supply, too.

-Mike

My favorite amp that I owned was a TenTec Titan...it would loaf along at 1500 watts out...to this day, I still regret selling it. It used two 3CX800A7's. I loved that amp. I sold it to buy an 8877 amp which never materialized for one reason or another...the Titan was the last amp I owned.

 

[Parker Duofold]

I would drive the LK800C with about 25 watts to get 1000 watts out. Hitting it hard was only necessary when you absolutely, positively had to get through right then. The tubes in this one are excellent.

The 4-1000s are going to require a bit of drive I think.

 

[timbo]

I would drive the LK800C with about 25 watts to get 1000 watts out. Hitting it hard was only necessary when you absolutely, positively had to get through right then. The tubes in this one are excellent.

The 4-1000s are going to require a bit of drive I think.

Yes, with 5KV on the plate, it will take about 100 watts to drive it to legal limit (running it in grounded grid). That's assuming you have a tuned input which I plan on. There is a way to build a 4-1000 amp as a tetrode which requires way less drive but it also complicates the design quite a bit (extra screen supply, etc).

 

[AHM]

To build the kits was 30 hrs each.

(To hear Sal tell it, it took more than 30 hours just to pre-read the directions, and a few months to count the components. Or maybe that was his wife's story...).

 

[radioman]

I haven’t pulled out my amp in quite some time as my
shack has been down because of family commitments.
I have a Ameritron AL-82. This thread inspired me to look up
and see if they still even made that unit.
Over 3K for that amp now. Holy over driven tubes Batman!
They don’t give them away. I paid about 1/2 that.
I could run 1500 all day long. Had it on a 240v circuit.
Gave it plenty of juice to eat. It never gave me any trouble.

 

[UJay]

Let me know if you want a Ten-Tec Titan / 425 @timbo . I have 3 of them with good tubes available. 2 need power supply work.

I'm moving to Solid State amplifiers here.... building them. Spent the last number of years keeping the LK-500 (2-holers), TL-922, Titan's, Commander 2500 working.

The VHF Station had 8877 on 2m, 2x 3cpx800 on 6m, 220 and 432. The 6, 2, 220 and 432 "tower of power" shared the same power supply in a single rack. We broke out the 6m with a fresh new Peter Dahl transformer that we built the power supply around and similarly broke out the 2m. The 6m used to vaporize TR relays feeding 7el at 180'.


uj

 

[timbo]

Let me know if you want a Ten-Tec Titan / 425 @timbo . I have 3 of them with good tubes available. 2 need power supply work.

I'm moving to Solid State amplifiers here.... building them. Spent the last number of years keeping the LK-500 (2-holers), TL-922, Titan's, Commander 2500 working.

The VHF Station had 8877 on 2m, 2x 3cpx800 on 6m, 220 and 432. The 6, 2, 220 and 432 "tower of power" shared the same power supply in a single rack. We broke out the 6m with a fresh new Peter Dahl transformer that we built the power supply around and similarly broke out the 2m. The 6m used to vaporize TR relays feeding 7el at 180'.


uj

I'm very tempted but no way could I get the bank account deletion past my wife. I really miss mine...especially with these terrible conditions lately.

 

[timbo]

So I dragged out that HV transformer I mentioned in a previous post...I don't think it's a polepig xfrmr...it is pretty rugged though. I put a suicide cord on the primary and ran it up on a variac until the secondary was reading 500VAC. I measured the primary voltage and found it was 28VAC.

Doing the math...500/28 is a 1:17.8 turns ratio. 17.8 x 240=4272 VAC. That should be fine for a 4-1000. I just ordered four 20KV 3A diodes. I have a bunch of high voltage oil filled caps...ahhh, the smell of hot PCB's

There are several smaller wires poking out the windings...I'm wondering if they may be screen grid taps...my experience has been that screen grid voltage is developed using a separate transformer to keep the regulated voltage stiff. I should measure that voltage with 28 volts in.

EDIT: well, I measured those taps. It seems to be a 1:1 winding. 28VAC in 28VAC on the taps