GA-5 circuit installed In Boot Hill Amps 5F1 Kit

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-21 All components shown are included in Boot Hill Amps 5F1 Champ (GA-5 Option) Kit.
Builder must install nylon machine screw before securing the first and second filter caps. Three 22uF 450V filter caps are on tap.
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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-21
Primary differences between the 5F1 and the GA-5 amplifier circuits are found in the preamp section resistor values.

Hybridized Boot Hill design is based on Champ Layout, Original GA-5 component values, Hoffman's Schedule 40 GA-5 project and Boot Hill Amps parts on hand.
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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-20
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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-20
Hoffman's build uses an EL34 power tube and it's requisite parts. My build utilizes a 6V6 power tube as shown in the original GA-5 schematic. I chose to stay with the 6V6 because my chassis are punched for the larger diameter 6V6 tube in the V2 position.

Missing a couple of filter caps there???

when you finish i'd like to hear some sound clips of the two to hear the differences.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-22 After populating the board, and remembering to install nylon machine screw under the big filter caps, put a dab of silicone glue over the screw head. Position the first and second filter caps on the board.

Solder all the ends of the turrets where component leads have been wrapped around their respective turrets. Clip the ends of the leads so that they make aprox 3/4 of a turn around the turret. That way, strength of the solder joint and ease of removal are both employed.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-22
After the joints have been soldered along both sides of the board, the top of the board joints are ready to be soldered along with lengths of hook up wire and a ground bus.

"he likes to keep his fire engine clean, it's a clean machine"
Does anyone know an HTML trick to make musical notes :)

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-23 Top mounted components are soldered in place along with 3 1/2 inch sections of hook-up wire where indicated. You may use any color wire you like wherever you want to use it. Yellow wire is a traditional color for preamp side. Red is a traditional color for power side. Using different colors helps you to distinguish where wires should connect. Also helpful in avoiding confusion.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-23 Back of board wires. The first orange wire is connected to input resistors which will be soldered to pin 2 V1. The next orange wire connects to V1 pin 8. It is part of the negative feedback circuit. The shorter wire of the two red wires connects the positive output of the third filter capacitor (preamp's HV power supply) to the plate resistors (in this amp, these are 200K ohm resistors).
The long red wire that is fed through the holes in the board will later connect the wiper (center lug) on the volume pot to pin 7 (grid) on V1.

Nice.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-24
Install Ground Bus as shown.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-24

Using a home-made Cardboard Template insures correct alignment so that connections can be soldered outside the chassis.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-24

Bend Bus Wire to fit right side jack ground tab. The jack itself will provide the means to grounding the preamp side of the circuit.

If using Cliff jacks, you can drill a hole in the chassis and make a dedicated grounding point. By soldering a ring terminal to the end of the bus, bolt the bus to the chassis. You could instead bolt a terminal strip to the chassis and solder the end of the bus to that terminal strip.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-24

Pencil line on template aligns with cathode resistor's turret to indicate positioning of controls and jacks as they relate to the board. Check fitment in chassis.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-24
To install 1M resistor to switched jack, insert resistor lead through ground tab and into switch tab. Leave sufficient length so that you can bend the resistor around so that the body of the resistor makes no contact with any part of the jack.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-24

The hot tab of the high jack gets two wire leads. One (orange here) goes to its input on the board (ultimately to the grid - pin2 on V1). The other wire (yellow) goes to the switch tab on the low jack.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-24

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-24

Begin making connections between the board and controls and input jacks.

Daaaaave!
(sorry had margaritas). You didn't see my post on wiring jacks :). That's a lot o wire!!

Good thread with lots of photos, this junkie loves it! Hey I am really hoping my 5F2A transformers and chasis arrive this week so I can finish up my Boothill kit. My last Trinity kit did not utilize the shared copper wire ground as shown above. I don't know much about it. Seeing as it is shown so well here, I thought it would be a good place to discuss it. It appears to be a solid, shared common ground. I assume it is there to help quiet the circuit? Sorta along the same lines as the brass plate I see in the Weber kits? I see the blue shield on there also. To help protect it aginst touching any jack connections that my come close during chasis assembly? A Your guidance appreciated. It looks great by the way. Keith

Thanks, Keith. Here's the set up: The ground bus puts all the preamp grounds on the input side of the chassis to one point away from the PT.

The alternative brass plate makes ground at many points along the chassis face. Everywhere the plate gets pinched by a potentiometer and everywhere the plate gets pinched by the input jacks makes ground. It works, obviously, but IMHO, it is easier to use a bus wire and get a more efficient grounding scheme.

All my builds have been quiet and hum free, so I know this way works very well.

Bus is short for omnibus, BTW.

The PT center tap, the heater circuit center tap, the AC ground wire and the power supply filter caps get their own ground on their end of the chassis which you will see happen later on here.

The bit of blue insulation I left on the bus is not necessary, but there was neither any need to remove it.

Think of the ground bus as a river with the smaller ground wires connected to it as tributaries. The river dumps into the sea which is the chassis.

I bogarted this analogy from someone else, but it's a good one, I think.

The stock Gibson filter caps were 20-10-10. Less filtering on the preamp sounds more "lively" and is still quiet. Bumping the 20uF up to 30 helps the amp produce clean bass without farting out.

The stock Gibson filter caps were 20-10-10. Less filtering on the preamp sounds more "lively" and is still quiet. Bumping the 20uF up to 30 helps the amp produce clean bass without farting out.

That sounds like a winner. Hoffman did his this way with three 20's. I'll try your suggestion also.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-27
Board is ready to install

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-27
Number 6 screws thread into the mounting holes for the Output Transformer. Some OT's for these single-ended amps are large and some are small. There are a few holes in these chassis so they can accomodate the different size transformers that are available.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-27
The key point here is to install the OT mounting screws into the chassis before installing the board. One of the screws is under the board.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-27
Here is where this Weihai Tech 8 ohm OT will be mounted. It has a ding from shipping, but it is OK.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-27
Nuts on the nylon machine screws serve as standoffs for mounting.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-27
Electrical tape provides added insulation for security.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-27

One jack makes zero voltage aka ground. It gets a 3/8" star washer. The other jack gets a 3/8" fiber washer sandwich. The green jumper grounds the ground-isolated jack to its neighbor. This is probably overkill, but it is not a tremendous undertaking and it might help quiet the amp a bit.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-27

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-27

Board is home.

Coming Soon:
tube sockets and wiring.
It is easier to do these next steps without big ol' honkin' transformers bolted to the chassis. They won't be needed until the tube sockets are wired up. Keep it Light, My Friends.

looks cool, but wow, it's basically a 5f1 with a power switch vs on the pot! well not exactly, but you know what i mean . . . :grin:

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-30
Install tube sockets and wire them according to typical layout. Pin 9 of 6N2P preamp tubes goes to ground.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-30
This old power transformer has no heaters for rectifer tube. Here is a diode rectifier module and an inrush current limiter aka thermistor.

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-30

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-30

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-31 Twisted pair of heater wires begin at preamp tube socket and connect to pin 2 and 7 on power tube socket.
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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-31 These two-holes-per-pin tube sockets included in my kits make it easy to connect heater wires.
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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-31
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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-31
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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-31
Twist a pair of 100 ohm resistors to create an artificial center tap for heaters.
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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-31

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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-31
Put about 18v DC on the 6.3v AC heaters by connecting the wire to cathode of power tube.
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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-31
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By boothillamps (http://profile.imageshack.us/user/boothillamps) at 2012-03-31