G3 Blues slightly different resistors problem

  • Hi all,

    I received two days ago my G3 Blues kit and first thing I do before starting is checking the Bill of Material. Everything's there except 3 resistors are pencil-marked with their supposed value, but the color code and my multimeter says otherwise : R3, R19, R21 should be 68k (blue-gray-orange-gold) but are instead blue-brown-black-red-brown, so should actually be 61k and that's exactly what I read on the multimeter.

    61K is only slightly off the 5% tolerance of a 68K resistor so I guess they should be acceptable and they have been voluntarily put in my order as replacement for unavailable 68K ones, but these resistors are connected to tube pins which are measurement points. So my questions are :

    - Am I right to assume that 61K resistors instead of 68K ones shouldn't affect the functionning of the amp ?
    - If answer to 1st question is yes, how will it affect the voltage in the measurement ? If it's outside of the given range, how do I know it's still OK ?


  • Hi Francis, welcome to the forum!
    First of all I assume the second band is not brown but red because 61k isn't any E-Value-Standard but 62k is (E24). For R19/R21 (grid stoppers) the different value (62k instead of 68k) is no issue at all. For R3 I also don't expect any issue (slightly different anode voltage due to lower resistance) so you can use it. Can you measure the voltages and post the measuremt sheet for your amp please.

  • Hi Martin,

    Thanks for your answer.

    I haven't finish assembling the amp yet as I was waiting for your answer before soldering R3 (my philosophy being that the less you desolder, the cleaner is your board). I finished the board and the front panel and still have to finish the rest. I used the given resistor for R3.

    I'm a bit puzzled by these resistors. Using a different multimeter, I found 67.5k, which suggest they actually are 68k resistors (my first multimeter was a bit low on battery, so might have given erroneous values). But for sure the second ring isn't grey. They are 1% tolerance resistors so maybe are E96 series ?

    Just for curiosity, because the problem is solved anyway, there is a scan of them. If the second ring is orange and not brown, I then read blue-orange-black-red-brown : 630 x 100 = 63K. But 630 doesn't normally exist neither in the E48, nor in the E96 range ! ?(

    Edit : seeing this scan after publishing it, the second ring really looks grey. I guess I'm getting old and my eyes are betraying me, or I should work with a better light.
    Sorry for the useless thread. (going away full of shame :whistling: )

  • Hi,

    I finished to build my G3 Blues. The voltage in my house is a bit high, so are the measurements. Here is the measurement sheet, if you could please tell me if the values are still OK :

    Some pics of the finish amp in its casing are coming soon.


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