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Millett "Starving Student" hybrid amp

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  1. Lil' Knight
    On the other side, does the solder touch the metal part of the pot?
     
  2. Juaquin
    The joints look ok, maybe a bit on the "cold" side (especially the ground ones). What kind of solder and iron are you using?
     
  3. Narwhalius
    Quote:

    Originally Posted by Lil' Knight /img/forum/go_quote.gif
    On the other side, does the solder touch the metal part of the pot?



    Its hard to see some of the points but from what I can tell yes there is solder touching all pins on the other side.

    Quote:

    Originally Posted by Juaquin /img/forum/go_quote.gif
    The joints look ok, maybe a bit on the "cold" side (especially the ground ones). What kind of solder and iron are you using?



    I'm using 62/36/2 Rosing-Core Solder from Radio Shack and a basic Radio Shack iron. Tried to keep the budget as tight as I could since its this project is for my Senior Project.
     
  4. Juaquin
    The solder is good - eutectic, which helps in preventing cold joints. The iron may not have enough power to heat the ground plane (wicks it away and dissipates it before the iron can catch up) - what wattage was the iron?
     
  5. Narwhalius
    Quote:

    Originally Posted by Juaquin /img/forum/go_quote.gif
    The solder is good - eutectic, which helps in preventing cold joints. The iron may not have enough power to heat the ground plane (wicks it away and dissipates it before the iron can catch up) - what wattage was the iron?



    I believe it's 30 watts. Though we do have a 100 watt soldering gun in the garage.
     
  6. timmyGCSE
    equalizer I'm having trouble with the tube pinout mappings from this picture:
    [​IMG]

    and your description:
    Quote:

    19J6 => 12AU7
    pin 1 => pin 6
    pin 2 => pin 1
    pin 3 => pin 4
    pin 4 => pin 5
    pin 5 => pin 2
    pin 6 => pin 7
    pin 7 => pin 3, pin 8



    right, talking about the 12AU7 pinouts here -
    pin 1 => pin 2 - thats fine, pin 1 connects to pin 6 and they both go off to the 4-terminal, so in effect pins 1&2 on the 19J6 (this is how it looks..or is it going into 5 in which case I'm totally lost)

    pin 2 => pin 5 - also cool, this is in effect joining pin 5&6 from the 19J6 and taking it to the RCA's

    pin 3/8 => pin 7 - got it, in effect pin 7 from 19J6 with a 2K resistor to ground, clearly visible in pic. But then where's the cap come from that also looks like its soldered to pin 3??

    pin 4 => pin 3 - now we get confused.. as per your pinout mappings, pin four should be pin 3 from the 19J6, which has the 150uF cap then to the 4-terminal ready for the output. but in your picture it shows as pin 4 going to ground!....which brings us to..

    pin 5 => pin 4 - I expected this to go to ground since pin 4 on the 19J6 goes directly to ground.. but from the picture, well I'm not sure where that wire goes to! and then you have the 150uF cap into that pin as well..it looks to me as if that should be pin 3 of the 19J6 but ooh god I'm so confused...


    please help [​IMG] [​IMG]
     
  7. Juaquin
    30W should be ok, just gotta let it work for a while (while being careful not to overheat the pot)
     
  8. Narwhalius
    Quote:

    Originally Posted by Juaquin /img/forum/go_quote.gif
    30W should be ok, just gotta let it work for a while (while being careful not to overheat the pot)



    I'll try again. Say I did successfully get all the joints soldered correctly, would there be any other major point that could cause this? Also, how do you know which component relates to left channel and right channel? So I could go through and make sure each left channel component is correctly soldered.
     
  9. tomb
    Quote:

    Originally Posted by Narwhalius /img/forum/go_quote.gif
    I'll try again. Say I did successfully get all the joints soldered correctly, would there be any other major point that could cause this? Also, how do you know which component relates to left channel and right channel? So I could go through and make sure each left channel component is correctly soldered.



    You took some great pics awhile ago. Can you take a couple that show the entire PCB, top and bottom? Also, it would help to get a view of the wiring to the backplate and the terminal block at the pot.
     
  10. getllamasfast
    Quote:

    Originally Posted by timmyGCSE /img/forum/go_quote.gif
    equalizer I'm having trouble with the tube pinout mappings from this picture:
    <snip>

    and your description:


    right, talking about the 12AU7 pinouts here -
    pin 1 => pin 2 - thats fine, pin 1 connects to pin 6 and they both go off to the 4-terminal, so in effect pins 1&2 on the 19J6 (this is how it looks..or is it going into 5 in which case I'm totally lost)

    pin 2 => pin 5 - also cool, this is in effect joining pin 5&6 from the 19J6 and taking it to the RCA's

    pin 3/8 => pin 7 - got it, in effect pin 7 from 19J6 with a 2K resistor to ground, clearly visible in pic. But then where's the cap come from that also looks like its soldered to pin 3??

    pin 4 => pin 3 - now we get confused.. as per your pinout mappings, pin four should be pin 3 from the 19J6, which has the 150uF cap then to the 4-terminal ready for the output. but in your picture it shows as pin 4 going to ground!....which brings us to..

    pin 5 => pin 4 - I expected this to go to ground since pin 4 on the 19J6 goes directly to ground.. but from the picture, well I'm not sure where that wire goes to! and then you have the 150uF cap into that pin as well..it looks to me as if that should be pin 3 of the 19J6 but ooh god I'm so confused...


    please help [​IMG] [​IMG]




    Are you following the vanilla ssmh schematic or are you following the one with Dsavitsk's modifications?

    The_equalizer's build is based on the modified schematic which can be found here
     
  11. Narwhalius
    Quote:

    Originally Posted by tomb /img/forum/go_quote.gif
    You took some great pics awhile ago. Can you take a couple that show the entire PCB, top and bottom? Also, it would help to get a view of the wiring to the backplate and the terminal block at the pot.



    Alright, no problem.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  12. Juaquin
    Some of those joints, particularly the ground ones, look cold. For example, in the third pic from the bottom, that joint in the middle. You can tell because it is not a smooth mound and doesn't look like it's all flowed together. If you want to be sure, grab the DMM and check the resistance between a lead that should be connected to ground, and a ground point elsewhere. It should be almost exactly 0 (less than an ohm, preferably lower).
     
  13. the_equalizer
    Quote:

    Originally Posted by timmyGCSE /img/forum/go_quote.gif
    equalizer I'm having trouble with the tube pinout mappings from this picture:



    Hello timmyGCSE

    Ok, I'll try to address your questions one by one. What we need to do when substituting the tubes is wire the connections to the equivalent pins, that is, if a wire connected to the 19J6's grid, we now need to find the 12AU7 grid pin and run the wire to that instead.

    So here's the pinout mapping again with a description added

    ______________19J6 12AU7
    ------------------------------
    Plate 1 -------- pin 1 = pin 6
    Plate 2 -------- pin 2 = pin 1
    Heater --------- pin 3 = pin 4
    Heater --------- pin 4 = pin 5
    Grid 2 --------- pin 5 = pin 2
    Grid 1 --------- pin 6 = pin 7
    Cathode ------- pin 7 = pin 3, pin 8

    About pins 3 and 8, even though both the 19J6 and the 12AU7 contain two triodes in a single bulb, the 19J6 has only one cathode for both triodes, whereas the 12AU7 has an individual cathode for each triode.

    Finally, remember that we want to wire the triodes in each 12AU7 in parallel.

    Quote:

    Originally Posted by timmyGCSE /img/forum/go_quote.gif
    right, talking about the 12AU7 pinouts here -
    pin 1 => pin 2 - thats fine, pin 1 connects to pin 6 and they both go off to the 4-terminal, so in effect pins 1&2 on the 19J6 (this is how it looks..or is it going into 5 in which case I'm totally lost)




    These are the tube plates. I see the confusion, the pic does look unclear on that point. Indeed, pin 1 in the picture connects to pin 6 through the orange wire.


    Quote:

    Originally Posted by timmyGCSE /img/forum/go_quote.gif
    pin 2 => pin 5 - also cool, this is in effect joining pin 5&6 from the 19J6 and taking it to the RCA's



    Pins 2 and 7 in the 12AU7 are the grids. Again this must be wired together. That's what the white wire does.


    Quote:

    Originally Posted by timmyGCSE /img/forum/go_quote.gif
    pin 3/8 => pin 7 - got it, in effect pin 7 from 19J6 with a 2K resistor to ground, clearly visible in pic. But then where's the cap come from that also looks like its soldered to pin 3??



    The cap IS soldered to pin 3. Pins 3 and 8 in the 12AU7 are the cathodes. You need to wire them together, that is done by a gray wire, barely visible in the picture at pin 8. Since the two pins are wired together, the cap and resistor (which is also barely visible behind the cap) can go to ground from either one of them; I chose to do it at pin 3.


    Quote:

    Originally Posted by timmyGCSE /img/forum/go_quote.gif
    pin 4 => pin 3 - now we get confused.. as per your pinout mappings, pin four should be pin 3 from the 19J6, which has the 150uF cap then to the 4-terminal ready for the output. but in your picture it shows as pin 4 going to ground!....which brings us to..

    pin 5 => pin 4 - I expected this to go to ground since pin 4 on the 19J6 goes directly to ground.. but from the picture, well I'm not sure where that wire goes to! and then you have the 150uF cap into that pin as well..it looks to me as if that should be pin 3 of the 19J6 but ooh god I'm so confused...




    Pins 4 and 5 are the tube heater; now the heater has no polarity, so you can wire either pin 4 to ground and pin 5 to the MOSFET or viceversa. I chose the former, indeed.

    I hope this helps with the confusion. Feel free to post or PM me if you have more questions.

    cheers!
     
  14. Narwhalius
    Quote:

    Originally Posted by Juaquin /img/forum/go_quote.gif
    Some of those joints, particularly the ground ones, look cold. For example, in the third pic from the bottom, that joint in the middle. You can tell because it is not a smooth mound and doesn't look like it's all flowed together. If you want to be sure, grab the DMM and check the resistance between a lead that should be connected to ground, and a ground point elsewhere. It should be almost exactly 0 (less than an ohm, preferably lower).



    Which other ones do you think could be cold? And could this possibly be my volume pot?
     
  15. Juaquin
    My internet is crap at night so I'm having trouble loading the pictures at the moment, but look for any like that one. Even if they aren't the source of the problem, they may become a problem later on. Also, it looks like the wires going to your LEDs (this picture) have cuts in them that aren't heatshrinked or covered with electrical tape? If those ever touch each other you'll short 48V to GND and have big problems.
     
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