VK Logger Ham Radio Forum Archive

I am looking for a HV transformer for a 6/2m valve linear amp project 220v = 850-1000v 1amp about secondary pref located in ZL. Alternativly where can I get a transformer wound for me. Could I use a MOT or is this not realy an option due to voltage or current restrictions . Any help or advise wil be appriciated. Thanks Lawrence ZL1LDS Item now aquired, many thanks Bob ZL1RS

A microwave oven transformer is a pretty cheap option, but pretty far off the mark of your specs. They typically deliver 2200VAC, 1/2 amp at best. By the time you full wave rectify that, you are closer to 3 kV. If you could find two IDENTICAL ones, you could series the primaries and parallel the secondaries. That would give you around 1100 VAC, somewhat closer to 1 amp. If they aren't identical, of course, they will fight each other. These days, you are unlikely to be able to remove any turns from the secondary without damaging the rest. Sometimes you can sneak a few more turns on the primary, but not enough to 1/2 the high side voltage.

Maybe you should look at another valve? Gi-6b's can be had for $7 USD each, and will do close to 500 watts each on 6, slightly less on 2 mtrs. Nobody recommends that you slam 3 kV on their anodes (though some have, and lived to tell the tale), but 2.5 kV is well within reach....

73
John VK4TJ

ZL1LDS wrote:I am looking for a HV transformer for a 6/2m valve linear amp project 220v = 850-1000v 1amp about secondary pref located in ZL. Alternativly where can I get a transformer wound for me. Could I use a MOT or is this not realy an option due to voltage or current restrictions . Any help or advise wil be appriciated. Thanks Lawrence ZL1LDS

I bought 2 from this supplier 2 years ago - excellent value, service & first class product.

http://stores.ebay.com.au/Antek-inc/Tra ... 34.c0.m322

What valve(s) are you going to use Lawrence? 850-1000V ac seems a bit low, unless you are going to use a voltage doubler? In that case you would get better performance with a more secondary voltage and full wave bridge or full wave center tap secondary configuration ... and for which I have transformers that would suit.

73, Bob ZL1RS

I bought 2 from this supplier 2 years ago - excellent value, service & first class product.

http://stores.ebay.com.au/Antek-inc/Tra ... 34.c0.m322

I've used these too. Excellent if you want to buy new. At his web site http://www.antekinc.com/ he offers an 800VA toroid with 800+800V secondary windings http://www.antekinc.com/details.php?p=135 that I used in my 2M amp http://www.qsl.net/zl1rs/8877port.html

In my amp the two secondary winding are in series giving 1600v AC and a bridge rectifier + capacitive filter provides around 2000V DC to the anode under load. The PA runs 700W of JT65b on 2M for hours on end without any drama despite exceeding the 800VA rating during the transmit sequence (however the toroid is cooled with air passing by from the tube's blower).

73, Bob ZL1RS

Hi All, thanks for the response and tips. I am new to valve amps, so I am trying the GI-7BT x 2. This looks like an easy one to start off on and to learn construction techniques. Yes I was following some ideas on the net and was going to use a voltage doubler, so in actual I will require 2kv of the likes you have Bob. The 800x 800 sounds good then I do not have to use a doubler. cheers My email is lawrence.sorina at clear.net.nz

I'll send you an e-mail Lawrence.
I can drop off a transformer when I am back in the country in about 4 or 5 weeks.
In the meantime get the other bits and a chassis/cabinet together ......

73, Bob ZL1RS