6AU6 to 6HS6 in an SB-100/-310

Discussion in '"Boat Anchor" & Classic Equipment' started by N1WVQ, Apr 26, 2020.

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  1. N1WVQ

    N1WVQ Ham Member QRZ Page

    Can a 6AU6 tube be changed to a 6HS6? I’ve read many hams have gone the other way due to the expensive nature of the 6HS6 but with the 6AU6 about only 1/3 as sensitive, I wanted to go the other way, if possible. Thanks & 73,
    Jay (N1WVQ/V31VQ)
  2. WA1GXC

    WA1GXC Ham Member QRZ Page

    Use a 6AH6 in place of 6HS6. Normal production variations put both types squarely in the

    same performance range for almost all applications hams would find. 6AH6 is dirt cheap.

    Substituting a 6HS6 for 6AU6 gives tube operating at much higher gain, probably not a good

    thing for RF front-end or IF stages. The design engineers chose that gain range for a reason. More

    is often not better.
    AC0OB likes this.
  3. WA1GXC

    WA1GXC Ham Member QRZ Page

    Never been around Heath gear, but just looked at schematics for your radios.

    SB-100 V2, V3, V4 are isolation amp, and IF stages respectively. Absolutely do not go to the

    higher-gain tube; garbage will ensue.

    SB-310 V2 and V3 are 6AU6 mixers. Same comment as above.

    Type 6136 is a military, ruggedized version of 6AU6. $2.75 at Surplus Sales of Nebraska vs. $5-6

    for 6AU6 at multiple sellers. Also, check Fair Radio, Antique Electronic Supply, Viva Tubes,

    Vacuum Tubes Inc. All are honest and reliable businesses.
  4. N1WVQ

    N1WVQ Ham Member QRZ Page

    Will check those out! Thanks!
  5. KE4OH

    KE4OH Ham Member QRZ Page

    In the SB-100 (or SB-101), the only 6AU6 tubes that you might consider changing to 6HS6 are V10 and V11. In the nearly-identical HW-101, V-10 and V-11 are spec'ed to be 6HS6. This gives the HW-101 a theoretically more sensitive receiver than the SB-100/SB-101 has. I have both SB-101 and HW-101. I can tell you that the difference in performance isn't really perceptible by me. Both are excellent receivers.

    If you want to do a swap, there are no circuit changes required, but you will need to re-align the rig. About a 20 minute job if you've done it before. A little longer if it's your first time.

    If I remember correctly, the SB-102 came with V10 as a 6HS6 and V11 as a 6AU6. You could easily try that combo, too.
    N1WVQ likes this.
  6. N1WVQ

    N1WVQ Ham Member QRZ Page

    It would be my first time trying it, if I did it. That the receiver wouldn’t be that much more receptive it food for thought, thanks!

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