Hot rodding boat anchors

Discussion in '"Boat Anchor" & Classic Equipment' started by AC9QC, Jun 7, 2017.

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  1. AC9QC

    AC9QC Ham Member QRZ Page

  2. WB5WSV

    WB5WSV Ham Member QRZ Page

    Well, do what I did. Look at the schematic of a receiver you want to improve, look up the tube base pin outs in an old copy of the ARRL Handbook , and then go see which tubes match that base. Then go look up the detailed tube data, my favorite source is:

    Next, figure out whether a replacement tube will improve things. That same website also provides some info on equivalent tubes. Note that some tubes may be listed as having the same pin out or as an equivalent but are not necessarily. For example, a remote cut off pentode versus a sharp cut off pentode; in some circuits they might work well but others, no..

    Right now I am wondering if I can replace the front end tube of an NC Sixty Special with something better, but that is a series connected tube filament string so it is more of a challenge.

    Of course, you can rewire tube sockets and/or make other circuit changes but that is lot more of a challenge. The 5670 tube is a higher frequency version of some more common tubes but the pin out is different. One possible approach is to look at higher performance receivers made by the same company and see what they did there. The NC-155, NC-270, and NC-303 all use the same basic 2nd LO circuit and I used that info to change to a crystal controlled LO (the NC-270 manual on BAMA was not clear enough but I found what I needed in the NC-303 manual).

    Good luck, and let us know what you find out!

    WA4SIX likes this.
  3. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    Much better than using the ARRL Handbooks for tube information is to acquire an RCA Receiving Tube Manual. The Handbook has only a small number of tubes and not that much information. The RCA Manuals usually have all sorts of data on various applications of the tube including at different voltages and for CCA versus ICAS.

    Glen, K9STH
    N2EY likes this.
  4. WR2E

    WR2E Ham Member QRZ Page

    WA2TAK has a hot rod DX100-GTO. pic on his qrz page
  5. N2EY

    N2EY Premium Subscriber QRZ Page

    The Handbooks are good for quick reference. Also some data on the use of receiving tubes in transmitters. But the Tube Manuals generally give much more info.

    Both the RCA Transmitting Tube Manuals and Receiving Tube Manuals of various vintages are online for free download.

    Besides the tube data, the introductory chapters about tube data are excellent.

    Here are some links:

    Scroll down and you will find links to Receiving Tube manuals RC-14 and RC-22, and Transmitting Tube manuals TT-3 and TT-5. Also other tube data.

    has an enormous selection of tube data, organized by manufacturer. RCA manuals a plenty!

    has tube data from the HB-3. However these datasheets are by tube type.

    73 de Jim, N2EY
  6. WB5WSV

    WB5WSV Ham Member QRZ Page

    The great thing about the ARRL handbook is that you can look up the original tube in the radio, note its pin out code, and then go through and write down all of the tubes listed with the same pin out code in a matter of a few minutes.

    THEN you go to the RCA Receiving Tube Manual (I have a copy) or that website I provided the link to and look up each tube that has the same pin-out. That's the data to determine whether a "hotter" tube will work at all, characteristics, voltages, curves, etc.

    I don't think it is easy to look in the RCA Receiving Tube Manual and quickly figure out which tubes have the same pin-out, but I have never tried that approach.

  7. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    The ARRL Handbook has only a VERY few, relatively, tubes listed. The RCA tube manuals, as well as the tube manuals published by other manufacturers, have many more tubes with the same base and, quite often, those tubes are more suitable for "hot rodding" equipment.

    Glen, K9STH
  8. KA9JLM

    KA9JLM Ham Member QRZ Page

    I think it sucked after they stopped printing the tube pin out.

    Is Morse code in the new one ?
  9. N8CMQ

    N8CMQ XML Subscriber QRZ Page

    While there are many tube swaps and mods out there, one thing a few people overlook is the tube sockets.

    My Halli SX-101 MK-3 had one socket that was crispy, and with the power on, you could see it burning little pinpoints of light over it.
    Some of the other sockets had continuity between pins with nothing soldered to it.

    Rather than trying to replace a few sockets, I replaced all of the sockets with ceramic sockets which ended up eliminating strange noise problems I was having at random times with the receiver. When I was done, I had swapped all of the resistors, capacitors and tube sockets for new style units. The noise in the receiver with no antenna connected is so low, I can turn the RF gain and audio gain up full and all I hear is a low hum from the power supply, and you have to be close to the speaker to hear that. I made the mistake of trying to attach the antenna with the gains up full, once... :eek:

    Also, by using better tubes, changing some circuitry, eliminating one IF amp and installing a product detector, I had improved the MK-3 to an A!

    I am still working on the receiver, and with the new mods, I will be able to hook up some digital toys so I can use a laptop to enhance the operation. At that point, I will be calling it an SX-101B! :) And it still has the top band too! 160 meters was removed in the A model, which was a mistake in my book.

    If you do decide to mod your equipment, try to document the changes, as you never know if/when YOU may need to go back and change or repair it!

    N8CMQ Jeff
    KC8YLT and N2EY like this.
  10. KM1H

    KM1H Ham Member QRZ Page

    My souped up receivers range from a 75A4 with 7360's to replace the noisy and overload prone 6BA7's in both mixers, a 6GM6 RF amp, an added 6BA6 IF amp (below chassis on a small bracket) between cascaded Collins filters, a SS hang AGC, plus a few other minor changes. This was all done 1965-67 in stages and I still use it often as a fantastic CW radio. No extra holes drilled and the radio still appears bone stock.

    The 6BZ6 and 6GM6 are my favorite RF amp swaps for the 7 pin miniatures and a 6SG7 for the octals.

    A 6BY6 replaces a 6BE6 when AGC isnt used and a 6SB7Y is a direct swap for a 6SA7 and an easy mod for a 6K8. The 6BY6 is also a good swap for a 6BE6 as a Product Detector.

    The 6J6, 12AT7, 6EA8, 6SN7, all make excellent Pullen mixers.

    Some other swaps required different sockets but I rarely like to do obvious changes. A pair of the latter were SX-140's. One had a small add on chassis with a pair of 6BA6 262 kc IF amps using auto radio transformers. The stock IF amp was changed to a 6BY6 converter for double conversion, some other tube swaps added a product detector and improved RF performance.
    Another 140 was double converted to 455 and KIWA ceramic filters were added for AM/SSB/CW. These radios were used at our summer cottage in Maine where space was tight. Various compact TX were used over the close to 20 years until the kids moved on.

    Some of the other radios Ive made changes to for myself and customers include: SX-17, SX-25, SX28; HQ-120 thru 150, WW2 Super Pros and the later SP-400, and SP-600's; Collins 75A3, R-388, 51J4, R-390A; NC-200, NC-240D, NC-183, NC-183D, HRO-50 thru 60, plus numerous "house" radios, mostly wooden cabinet 30's and 40's from table to floor models.


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