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| Common Hookup
info for my layout diagrams |
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This drawing shows common
hookup info codes used on my layout diagrams. Notes:
Blue parts are usually 3 watt, 5 watt or 10 watt.
A Blue .1 cap can be a 250V cap.
See the
parts listing for each project. No
connect is a pin on a tube that is not connected internally. You can use
these pins as terminal connectors since they just dead end and do not
enter the tube. |
| Removing the
death cap |
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The purple
.047 cap in this drawing is know as the "Death cap". Many a guitar
player has been shocked on a microphone because of this cap. If you have a 3 prong grounded power cord and it is installed properly, you
do not need, or you can remove the purple parts from your amp. The green power cord ground
wire must be grounded to the metal chassis so that your amp is tied to ground properly. The
parts you do not need are the ground switch and the cap that is connected to this switch.
Many people use the ground switch hole on a chassis
for a standby switch. |
| Input jack
wiring |
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Hi/Lo jacks:
This is a diagram of a Hi/Lo jack pair.
One pair usually goes to valve one, Pin 2.
The other pair usually goes to valve one, Pin 7. |
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Hi/Lo jacks:
The photo to the left shows a Hi/Lo pair of jacks. Two Switchcraft 12A jacks are
arranged with the solder tabs lined up. The red dots indicate where there will be solder
connections made.
The #1 jack on the right is the High input jack.
The #2 jack on the left is the Low input jack.
Note: I do not solder the joining tabs outside the amplifier because they may not
line up with the amplifiers holes properly. I solder the tabs in place inside the amp
itself. |
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Single input jack:
You can also just use one input jack, you do not have to have a Hi and Lo input.
The 68K can be other values like 33K, 47K, etc. |
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<- Click on the image to see a larger image. Diagram, courtesy of Sluckey |
| Heater hookup |
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| The 6.3 volt heater wires come out of
the power transformer and they go right to a light bulb fixture to power the
pilot lamp. This is a common arrangement on Fenders. The lamp is a convenient terminal on the way to the power tubes.
From the lamp you can then run a twisted pair of 18 Gauge wires over to the first power
tube. Pins 4 and 5 are jumpered together on 12A*7 type pre amp tubes. 20 Gauge wire is
fine for the pre amp tubes. If you do not
have a heater center tap on your power transformer, you must run two 100 ohm 1/2 watt
resistors to ground to create an artificial center tap. If you do not have a center tap,
you will get 120 cycle hum. Each 100 ohm resistor is soldered to one of the heater wires.
The other ends of the 100 ohm resistors are twisted together and then soldered to ground.
If your power transformer has a center tap wire, solder that to ground. Most power
transformer heater center tap wires are green with a yellow stripe.
The heater wires are usually run up in the air,
above the tube sockets in a twisted pair. Twisting the heater wires cancels hum. This is
why phone line wires are run in twisted pairs. The twisted pair wires drop down and get
soldered to the tube socket pins. The twisted pair continues down the line to every tube
in the chain.
Keeping the wires in phase helps with hum
sometimes. In other words, pin 7 on one power tube goes to pin 7 on the next power tube.
Pin 9 on a pre amp tube goes to pin 9 on the next pre amp tube. EL84 power
tubes heater connections are pins 4 and 5. Most other 8 pin power tubes use
pins 2 and 7. |
| Power transformer hookup and rectifier info |
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| Note: I am
not showing any bias windings or bias taps on any of the above diagrams. |
| Half wave rectifier
circuit - This circuit is found on the old 6G15 Fender stand alone reverb units.
It produces very rough DC voltage and needs lots of filtering to smooth it out. The
transformer does not need a 5 volt tube rectifier filament winding since there is no tube
rectifier. It is very cheap to set up but all you save is 3 diodes and the DC is so rough
that you have to filter the crap out of it. |
Full wave diode
rectifier circuit - This circuit produces DC voltage that is twice as smooth as
the half wave circuit. It requires a center tap on the high voltage winding. The
transformer does not need a 5 volt tube rectifier filament winding since there is no tube
rectifier.
If you measure the AC voltage across the two Red AC windings you will usually see about
700 volts AC. You may end up with roughly 400 plus volts DC coming off the rectifier,
depending on the winding current spec's for the high voltage winding. The larger the
current rating, the less of a voltage drop you will get under load. |
Full wave tube
rectifier circuit - This circuit produces DC voltage that is twice as smooth as
the half wave circuit. It requires a center tap on the high voltage winding. The
transformer requires a 5 volt tube rectifier filament winding to heat the tube rectifier
filament.
If you measure the AC voltage across the two Red AC windings you will usually see about
700 volts AC. You may end up with roughly 400 plus volts DC coming off the rectifier,
depending on the winding current spec's for the high voltage winding. The larger the
current rating, the less of a voltage drop you will get under load. |
Full wave bridge
rectifier circuit - This circuit produces DC voltage that is 2 times as smooth as
the half wave circuit. It needs way less filtering than a half wave circuit and has the
added advantage of not needing a center tap on the high voltage winding. The transformer
also does not need a 5 volt tube rectifier filament winding.
If you measure the AC voltage across the two Red AC windings you will usually see about
350 volts AC. You may end up with roughly 400 plus volts DC coming off the rectifier,
depending on the winding current spec's for the high voltage winding. The larger the
current rating, the less of a voltage drop you will get under load.
NOTE: Notice that the high voltage winding AC voltage is roughly half
that of the full wave rectifier. |
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| Making a 4 power tube board |
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| The blue
parts have been doubled in the diagram above. |
| You can make a 4 power
tube version of any board. I don't sell 4 power tube mask because it's easy
for you to make a 4 power tube board if you already own a two power tube
mask. You must own my drilling template and a mask to be able to do the
procedure described here. Basically,
all you are doing is adding two more 1 ohm cathode
resistor spots and two more screen resistors spots to your board.
You must plan ahead by making your board longer by 4 more lug places
horizontally. You can also just drill the board and then trim it to length
after you are done. This is the foolproof method. As
you are drilling the board left to right or from the pre amp end towards
power tube end, you must stop when you get to the area where the 1 ohm
cathode resistors and screen grid resistors are. You go ahead and drill the
normal 4 spots it takes for a two power tube board. Then you just shift the
mask to the right four places. Once the mask has been moved you can drill
the 1 ohm and screen grid resistor holes again. Now you should have 4 x 1
ohm resistor spots and 4 x screen grid resistor spots.
You can leave the mask where it is and
drill the remaining holes to the right. If there is a bias pot on your
board, the template should be correct because I designed it to be able to
do two or 4 power tube versions of the boards.
If your board has negative feedback,
you will have to change the value of the feedback resistor to two times the
normal value. Example: a 50 watt Marshall has a 47K feedback resistor and a
100 Watt Marshall has a 100K feedback resistor. |
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