First Homebrew HF power amp

Discussion in 'Amateur Radio Amplifiers' started by N7GTB, Jan 9, 2012.

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  1. W9GB

    W9GB Ham Member QRZ Page

    Jim, W6PQL has released his "latest" amplifier control board (version 6) for Solid-State Amplifiers

    based on his work for his latest LDMOS based 1 kW 2-meter (VHF) amplifier
    Last edited: Jan 25, 2012
  2. N7GTB

    N7GTB Ham Member QRZ Page

    Got another question... My ceramic sockets are flat four pin sockets, but I noticed that the tubes all have small pins on the side of the tube bases. I've also noticed there are sockets available with bayonet rings that appear to be made so as to index or retain the tube... I'm assuming the 'bayonet' sockets are for equipment where the tubes might be mounted sideways...(?)

    Any reason to need them if the tubes will be used in an upright position?
  3. KO6WB

    KO6WB Premium Subscriber QRZ Page

    There are different types of sockets for the 811. The sockets you have are very good. The ones made with the spring type clips and unsupported can be bad. If the guide collar is not used and they usually aren't, then it's possible to insert the tube incorrectly. This makes the amplifier very unhappy. That little pin on the side of the base of an 811 is for use with the guide collar. BTW the 572B is a more rugged tube but it has more difficulties with quality control from the manufacturers in China then the Chinese 811's do. The 811's are not immune to these problems though and there are a lot of failures. You just have to take your chances. Some of the retail outlets test the tubes before they send them out, most have a warranty.
    Hope this helps
    Last edited: Jan 27, 2012
  4. N7GTB

    N7GTB Ham Member QRZ Page

    It does. I tested a four pin tube with one of my sockets and easily plugged it in backwards. So I'll be using the type with the bayonet ring and not the flat types with spring clips... :)
  5. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    It really depends on the quality of the socket. The "olde tyme" sockets, which were almost always ceramic, had different sized holes which made it a practical impossibility to install the tube incorrectly. "Modern" sockets, unfortunately, are generally cheaper made and do not have absolute protection like the older one.

    Glen, K9STH
  6. KM1H

    KM1H Ham Member QRZ Page


    Thats only true with the Chinese crap such as in the AL-811/572 amps. Thos sockets are also not always making pin contact even when in correctly.


    Thats not what they were made for. That base serves 2 purposes....securely holds the tube and also acts as a ground which improves neutralization and stability. It dates to the 1920's.

    You got it backwards. There is only one current 572B factory and quality ranges from good to almost very good. Ive had very little problems with Shuguan, Taylor, RFP, Penta and other names on them. One thing to remember is that they are rated at only 125W PD, not 165W as the US Cetron's. Beat them too hard and they lose emission fast.
    OTOH 811's are in a zoo of their own and are basically audiophool level crap. Continuous failures of AL-811 amps is driving customers and Ameritron crazy. Until its resolved I strongly urge buying something else or switching to 572B's in them.

  7. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    The truth be known, the guide pin on the side of certain tubes allows the tubes to be used with the socket designs that were very popular in the early 1920s. Those sockets did not have any clamps in which the pins are inserted but are flat plates with tension placed on the plates when the tube is inserted into the socket and then twisted to lock the tube in place. Some sockets did have spring-loaded clips that made connection to the tube pins.

    Since the tube bases are insulated, there is no grounding through the pin. Now, if the portion of the socket (sleeve) in which the pin rests is metal, then it can add a little to the shielding. However, tube sockets made during that time frame are not necessarily metal. Some are and some are not. The vast majority of tube sockets with the sleeve were used in receivers with tubes like the 01A.

    Attached are photos of the types of sockets using the guide pin. The "flat plate" version also has a bakelite sleeve and is from a Crosley 51 receiver. The "spring clip" version has a metal sleeve and is from an Acme Y-1 detector unit. Both use the 01A series tubes.

    Glen, K9STH

    pin socket-1.jpg pin socket-2.jpg
  8. N7GTB

    N7GTB Ham Member QRZ Page

    Thanks everyone for the clarification on the four pin sockets. :)

    Here's a transformer that I started 'prepping' for rewind:

    IMG_0137_small.jpg IMG_0138_small.jpg
  9. N7GTB

    N7GTB Ham Member QRZ Page

    Sorry about the rotation... :p Didn't think to correct that until after posting.

    The aspect ratio is different in these views, but at least you don't have to break your neck...
    IMG_0137_small.jpg IMG_0138_small.jpg

    Attached Files:

  10. K9FV

    K9FV Ham Member QRZ Page

    Good photos and an interesting project. Keep us informed on project. Will this be a HV transformer? Voltage/current goals?

    This could be worthy of it's own thread.

    73 de Ken H>
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