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#2
Ok is your 6.3V tap of the PT going to the heater then to all the tubes? Do you have a centre tap, is it ground? If you don't have a CT you need to create an artificial one with two 100R resistors. I can explain more if you don't have a CT.

Are you getting a high AC voltage on your secondary? Is this HV getting to the rectifier? Is the recto giving your your DC B+?

A bit more info is needed. Preferably in diagrams/schematics.


Your amp looks great though! Really nice work. Looks like it was all handmade yourself, no prefabs.
#3
Interesting idea, the video...

#1) can you get close up pictures of the sockets? Like, a decent digital camera on Macro (the flower shape thing) or something similar? Meaning, not a cell phone...

#2) remove all tubes, get a multi-meter, turn it on, and read the voltages on every pin of every tube socket, and post those if you could please. That usually goes a long way to explaining things...
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#4
Quote by kurtlives91
Ok is your 6.3V tap of the PT going to the heater then to all the tubes? Do you have a centre tap, is it ground? If you don't have a CT you need to create an artificial one with two 100R resistors. I can explain more if you don't have a CT.

Are you getting a high AC voltage on your secondary? Is this HV getting to the rectifier? Is the recto giving your your DC B+?

A bit more info is needed. Preferably in diagrams/schematics.


Your amp looks great though! Really nice work. Looks like it was all handmade yourself, no prefabs.



6.3V center tap isn't required for operation, only for quiet operation...sounds like he's getting nothing at all...
Quote by kcdakrt
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#5
I did test the tubes with a multimeter; they all work fine.

I'll try to get some pics up for you ASAP.
#6
One thing that i notice immediately... it looks like your only using 1 wire to connect the heaters from the pilot light to the tubes?

Post a few more pictures and take voltage readings on each of the pins.
#7
Quote by tbc4491
I did test the tubes with a multimeter; they all work fine.

I'll try to get some pics up for you ASAP.



Cool with the pics...

What I mean with voltages is, put the ground of the meter on the chassis, and then read the voltage on every pin with the positive probe. Use DC for all the pins except the heater pins (4,5,9 on the preamp tubes, 2 and 7 on the power amp tubes), use AC for those. With the tubes out.

If everything looks good there, we put the tubes back in and reread the voltages.
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#9
Man, the Harvards had some stoopid heater wiring...wow.

NEways, waiting on the closeups....that wiring diagram helped a ton though, thanks!
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#10
Also, at this point, also based on what I saw in the zoomed out pic, I think the problem is in your heater wiring. Post those closeups, don't worry about voltages yet...
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#13
Crap...hard to tell.

Actually, not. Look at the layout...upper left, one of the greens goes to ground...yours doesn't do that (as far as I can tell). that'd be your problem.

EDIT: going into further detail...you need a complete circuit...with that one not going to ground, you have no complete circuit.

That heater wiring is contrary to every heater wiring in the last 50 years, so you're kindof working from the wrong playbook.

Also, where it goes to the 12AX7, that heater wire should go to pins 4 and 5, and then 9 should be grounded to the chassis...
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Last edited by DLrocket89 at Oct 1, 2009,
#14
Quote by DLrocket89
Crap...hard to tell.

Actually, not. Look at the layout...upper left, one of the greens goes to ground...yours doesn't do that (as far as I can tell). that'd be your problem.

EDIT: going into further detail...you need a complete circuit...with that one not going to ground, you have no complete circuit.

That heater wiring is contrary to every heater wiring in the last 50 years, so you're kindof working from the wrong playbook.

Also, where it goes to the 12AX7, that heater wire should go to pins 4 and 5, and then 9 should be grounded to the chassis...


gotcha on the 12ax7; that made sense.

With the green going to ground, would that be the green from the power cord or one of the greens from the pilot light? I have one wire which is a green/yellow mix to ground, but I don't even think I need that one.
#15
OOOOOOOOOOOOH, I get it.

Step 1 - contact the manufacturer, ask them to confirm that the green/yellow wire coming from the PT is indeed the 6.3V heater winding center tap. Maybe you got a diagram with it? If you did, post a pic of it or a link to it.


If the answer to step 1 is yes (and it probably is) do this:

You have two wires going to the pilot light. Go from the pilot light to pins 2 and 7 of the first output tube. From there, go to pins 2 and 7 of the second output tube (it'll be quieter if you wire pin 2 from the first tube to pin 7 of the second tube, and 7 and 2 respectively). From there, send one of them to pins 4 and 5 of the 12AX7 and the other to pin 9 of the 12AX7. From there, send one to pin 3 of the 6AT6 and the other to pin 4.

The yellow/green will stay to ground (if the above answer is yes)
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#16
Quote by DLrocket89
OOOOOOOOOOOOH, I get it.

Step 1 - contact the manufacturer, ask them to confirm that the green/yellow wire coming from the PT is indeed the 6.3V heater winding center tap. Maybe you got a diagram with it? If you did, post a pic of it or a link to it.


If the answer to step 1 is yes (and it probably is) do this:

You have two wires going to the pilot light. Go from the pilot light to pins 2 and 7 of the first output tube. From there, go to pins 2 and 7 of the second output tube (it'll be quieter if you wire pin 2 from the first tube to pin 7 of the second tube, and 7 and 2 respectively). From there, send one of them to pins 4 and 5 of the 12AX7 and the other to pin 9 of the 12AX7. From there, send one to pin 3 of the 6AT6 and the other to pin 4.

The yellow/green will stay to ground (if the above answer is yes)


Here is the only diagram that I can find. Straight from the website.

http://www.magneticcomponents.net/40-18027_Rev_B_Stock.pdf
#17
Quote by tbc4491
Here is the only diagram that I can find. Straight from the website.

http://www.magneticcomponents.net/40-18027_Rev_B_Stock.pdf



*DING DING DING* we have a winner.

Do what I stated before and you should have a functional amp.

Basically, the old Fender amps didn't have a center tap on the 6.3V winding. That transformer does, and it changes everything on how you have wire it up.

BTW, if you do get this thing running, and it's making a horrible 60Hz hum or 120Hz buzz, there's a workaround for that. What you do is from the B+ supply on the screens, have two resistors in series going to ground, like this:

B+ screen node > Resistor 1 > Resistor 2 > Ground

Make resistor 1 something like a 1 watt 470K resistor, resistor 2 a 1 watt 100K resistor. Bypass the 100K resistor with a 10uF/200V capacitor (bypass = put the cap in parallel with it).

Instead of connecting the green/yellow wire to ground, connect it to the junction of resistor 1 and resistor 2. That will go a long ways towards eliminating the hum/buzz.

With as low of a gain amp as that is though, it might not be a problem. I wouldn't bother with trying unless it is a problem.

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#18
DLrocket89, you have been a blessing in disguise. Thank you for putting up with my questions and problems, as i'm sure i will have more coming.

I will tackle that when I wake up later today (fresh eyes will help me out A LOT right about now.

One more question, this amp asks for a 3/4 amp fuse. I have only been able to find 1/2 amp fuses and everything above 1 amp. What should I do, or (maybe better question), where can I find these fuses? I've checked my local Home Depot/Lowes, and little electronics shops around.
#19
Quote by tbc4491
DLrocket89, you have been a blessing in disguise. Thank you for putting up with my questions and problems, as i'm sure i will have more coming.

I will tackle that when I wake up later today (fresh eyes will help me out A LOT right about now.

One more question, this amp asks for a 3/4 amp fuse. I have only been able to find 1/2 amp fuses and everything above 1 amp. What should I do, or (maybe better question), where can I find these fuses? I've checked my local Home Depot/Lowes, and little electronics shops around.



Glad I could help.

I usually get little parts like that from Radio Shack. If not, www.tubedepot.com and www.tubesandmore.com will both have them.

Make sure you get the right fast/slow blow style too. Probably want a slow blow...
Quote by kcdakrt
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#20
I've rewired the heaters and the rest of the tube sockets, grounded what i needed to, and so on so forth. When I try to turn it on though, I get nothing. I use to get the pilot light on before but now not even that comes on anymore. What more am I doing wrong? I'll post the updated pics that I have of it.
#22
Quote by tbc4491
I've rewired the heaters and the rest of the tube sockets, grounded what i needed to, and so on so forth. When I try to turn it on though, I get nothing. I use to get the pilot light on before but now not even that comes on anymore. What more am I doing wrong? I'll post the updated pics that I have of it.


When you say you've grounded what you needed to, you aren't grounding either side of the heaters anymore are you?
#23
Quote by end_citizen
When you say you've grounded what you needed to, you aren't grounding either side of the heaters anymore are you?


Here's what I have grounded:

  • the 12ax7 socket from pin 9
  • the yellow green wire from the pt
  • red-yellow wire from the pt
  • both red-white wires from pt
  • red-black wire from pt
  • brown wire from pt
  • green wire from my power cord
  • the .01 cap connected to the fuse holder


When you say the heaters, are you refering to the green wires? cause if so, I have the two green wires connected to the pilot light, then from there one is connected to pin 2 on the first 6v6 socket, and then the other wire went to pin 7 on the same socket. Then I basically followed what Dlrocket86 had suggested.
#24
you should have one green wire to pins 4 and 5 of the 12AX7, the other one to pin 9. right now your heaters are 3.15V
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#25
I have to run to the doc's right now, I'll draw up a diagram when I get home and post that...
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#26
Since DL is off right now, I'll try to help out.

Here's a really simple amp that uses a 12AX7 and an EL34. It was a very nice looking layout on the last page of the pdf file. The heaters are the white wire attached to Pin 9 on the 12ax7 and pin 2 on the EL34 and the green wire attached to pin 7 on the EL34 and pins 4&5 on the 12AX7.

A 12ax7 is actually spec'd to run on 12.6v AC heater voltage, but it is center tapped on pin 9 so you can run it on 6.3v AC. Right now, you've essentially grounded your heater voltage.

Since pins 4 & 5 are both attached to pin 9 (with very little resistance), you've got both leads of your heaters grounded.

http://ax84.com/static/p1x/AX84_P1x_080623.pdf

Pins 4&5 should be connected to each other, and have 1 of the heater leads going to that connection. The other heater lead should go to pin 9.

Also, you'll notice in that layout, that the heater wires are twisted together. This is not necessary, but it will help cut down on noise/hum. Something you might keep in mind when you get it fired up if it's a bit noisy.
Last edited by end_citizen at Oct 1, 2009,
#27
You also should look at the 20 watt push pull poweramp under the core series...it shows poweramp stuff a bit bettter.
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#28
ok...what about my power cord? it has a black wire, a white wire, and a green wire. Currently, I have the white wire to the fuse, the black wire to ground, and the green wire to the AC switch. Any changes to that?
#29
Here's what I have grounded:

  • the 12ax7 socket from pin 9
  • the yellow green wire from the pt
  • red-yellow wire from the pt
  • both red-white wires from pt
  • Meadows
    Quote by Jackal58
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    #30
    Quote by tbc4491
    ok...what about my power cord? it has a black wire, a white wire, and a green wire. Currently, I have the white wire to the fuse, the black wire to ground, and the green wire to the AC switch. Any changes to that?
    You need to test with a meter.

    Normally the Green wire of a power cord is Ground
    White is "neutral"
    Black is "hot"
    Meadows
    Quote by Jackal58
    I release my inner liberal every morning when I take a shit.
    Quote by SK8RDUDE411
    I wont be like those jerks who dedicate their beliefs to logic and reaosn.
    #31
    i don't have an ohmmeter on me right now. all that is with my friends house at the moment.

    I also have a brown-white cord too. right now it is connected to the 6800 resistor, since i don't have a white wire from my PT. Is that right, and if not, then what wire should I use?
    #32
    I also have two black wires: one is solid black, the other a black/white mix. right now, I have the black/white mix connected to the power switch. Is that right as well, or does that need to be switched too?
    #33
    Quote by tbc4491
    i don't have an ohmmeter on me right now. all that is with my friends house at the moment.
    Don't be in a rush. Get what you need to do the job correctly.
    Quote by tbc4491
    I also have two black wires: one is solid black, the other a black/white mix. right now, I have the black/white mix connected to the power switch. Is that right as well, or does that need to be switched too?
    Black-white and Brown-white should be connected together. These two wires connect to either the power switch or the fuse.

    IF the Black-white and Brown-white are connected to the power switch,
    Then the Red-Black connects to the fuse.

    IF the Black-white and Brown-white are connected to the fuse,
    Then the Red-Black connects to the power switch.


    Btw, I did some calculations. Your B+ voltage is gonna be high. Very high.
    Meadows
    Quote by Jackal58
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    Quote by SK8RDUDE411
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    #34
    Quote by SomeoneYouKnew
    Don't be in a rush. Get what you need to do the job correctly.

    Understood.

    Black-white and Brown-white should be connected together. These two wires connect to either the power switch or the fuse.

    IF the Black-white and Brown-white are connected to the power switch,
    Then the Red-Black connects to the fuse.

    IF the Black-white and Brown-white are connected to the fuse,
    Then the Red-Black connects to the power switch.


    Btw, I did some calculations. Your B+ voltage is gonna be high. Very high.



    Then what about the connection to the 6800 resistor? I used the diode instead of the rectifier to keep my good health, so what wires need to go there?

    And what can I do to get the B+ level down?

    Btw, i do really appreciate the help I've been given.
    #35
    SYK - thanks for picking up where I left off, and for double checking the wiring on the PT...


    TS: there's a semi-decent chance your PT is toast...proceed like it's fine, but keep it in the back of your mind that it might not be...grounding the secondaries like that...yikes. that makes PTs melt down (literally, there's wax inside, it can melt and run out).
    Quote by kcdakrt
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    #37
    so I did the brown-white & black-white connection to the fuse holder, and the red-black wire to the pilot light. I still have the white and black ends of my power cord unattached as well as the solid black wire on the PT unattached. I also ungrounded the green-yellow connection on the board as SYK did suggest. What next?
    #38
    Addon: I also still have to conynect the negative and positive wires to the circuit board. What should I do with that?
    #39
    Quote by tbc4491
    Then what about the connection to the 6800 resistor? I used the diode instead of the rectifier to keep my good health, so what wires need to go there?
    That's for your grid bias supply. Normally that's connected to a tap that's around 30~50v. You can connect that to the same winding as one of the plates of your rectifier tube. But the resistance value will have to be much higher.

    Quote by tbc4491
    And what can I do to get the B+ level down?

    Btw, i do really appreciate the help I've been given.
    Your B+ (using the red wire calculates out to around 460v, minus whatever you drop across the 5Y3 tube. Roughly 60v, I reckon. Way high.

    Using the Red-whites, 385v minus 60v would give you 325. High, but not horrible.

    EDIT:I just checked the specs on a 5Y3. Should drop more like 80v.
    So your B+ should be about right, using the Red-whites.

    Srsly, though. I would pull your rectifier tube and not even connect the 6800 ohm resistor just yet. I think you should focus on the transformer primary connections and the heater circuit.
    Meadows
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    Last edited by SomeoneYouKnew at Oct 2, 2009,
    #40
    Quote by SomeoneYouKnew
    That's for your grid bias supply. Normally that's connected to a tap that's around 30~50v. You can connect that to the same winding as one of the plates of your rectifier tube. But the resistance value will have to be much higher.

    Your B+ (using the red wire calculates out to around 460v, minus whatever you drop across the 5Y3 tube. Roughly 60v, I reckon. Way high.

    Using the Red-whites, 385v minus 60v would give you 325. High, but not horrible.



    Ok, so you're saying that I should use the red-whites instead of the red solid wires. If so, what should I do with the solid red wires?

    and how high of a resistance are we talking? Do I need ro replace anything on the board?