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Old 2nd June 2012, 10:02 PM   #1
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Default Matchless Hotbox Layout problems

Hi
Ive allways wanted to build the matchless hotbox high voltage tube preamp pedal, but have been hesitating because the projects on genrealguitargadgets are a bit tricky to read/understand.

Ive tried redrawing the layout using software found on the internet, But I still have doubts. I think there are some components in the schematic, not showing in the layout?
The third resistor from the right side of the board (maybe a 2,8k??) I cant read what it says in the original layout? And unfortunately still a bit of a beginner when it comes to reading schematics.

What about the three places on the upper side of the board that says "point B"... Where is point B? Maybe it is obvious? But Im unsure.
The original layout has the pin numbering on the tubes in revers order on V2. i have tried to turn it around in my layout?

So tell me what you thinK. Does this redrawn layout get me closer to a succesful build, or should I let it go.
Have built several tubeamps from verified layouts succesfully, and I know how to discharge caps and work safe around highvoltage... but Im still a paintbynumbers kindaguy....

Link to original ggg layout:
http://www.generalguitargadgets.com/...s/hotboxlo.jpg

Link to ggg schem:
http://www.generalguitargadgets.com/...s/hotboxsc.gif

Link to ggg Bill of materials:
http://www.generalguitargadgets.com/bom/hotboxbm.txt
Attached Files
File Type: pdf Hotbox layout pdf.pdf (45.0 KB, 99 views)
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Old 3rd June 2012, 12:08 AM   #2
kevinkr is offline kevinkr  United States
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This belongs in Instruments & Amplifiers forum per forum policy.

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Tubes / Valves All about our sweet vacuum tubes Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum
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Old 3rd June 2012, 12:37 AM   #3
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Sorry... I Will correct my mistake
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Old 3rd June 2012, 01:06 AM   #4
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If you look at the schematic you will see the B+ power supply voltages marked A and B. Simply connect all the points marked A together and all the points marked B together.
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Old 3rd June 2012, 07:38 AM   #5
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Ahh, I see
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Old 7th June 2012, 02:10 PM   #6
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Default Hotbox Layout Problems

I've built 2 of these and am about to start a third. It is a challenging build. The first one is huge and ugly, the second one my friend borrowed and won't give back so I am building a third.
The resistor is 2200 or 2.2k.
The B+ voltages A and B are labeled reversed on the layout from the schematic but the voltages are correct'
On the layout the "Clean Vol" and "VOL CH2" pots are shown wired from the front or backwards.
I'm not sure about the layout of the tone stack wiring. It caused me grief on the first one. I fixed it by trial and error and used a 3 way FMV tone stack on the second build
On the layout, tubes V1 and V2 are labeled opposite the schematic.
On the layout the pins of V2 is labeled and wired incorrect. Renumber V2 clockwise.
Change the lead going to the pin labeled 7 to 2, 8-3,6-1,1-6,2-7,3-8 and 9 is unused.
I built 3 "Real McTube II"s before trying the Hotbox. They all sound great and are an excellent first project. It's designed by the late Fred Nachbauer and a step by step build and theory guide comes with it. It's on dogstar.dantimax.dk
The power supply from the "Real McTube II" can be modified for the "Hotbox" and is a huge upgrade in AC hum reduction and a huge cost savings in transformer and capacitors prices.
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Old 21st June 2012, 08:45 AM   #7
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Hi. Thanks for the excellent and very helpful reply! I didnt see it until today, infortunately.
Ive also built the Real Mctube, and I like it, and Im also going to try the back to back transformer powersupply in this build, to save some money. Ill correct the mistakes in my layout, and upload it later, so others can use it, if they are interested.
-Kasper
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Old 21st June 2012, 09:03 AM   #8
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Here it goes...
Attached Files
File Type: pdf Hotbox - corrected.pdf (53.1 KB, 180 views)
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Old 17th July 2012, 07:19 PM   #9
Niquel is offline Niquel  Spain
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Quote:
Originally Posted by Tubed View Post
The power supply from the "Real McTube II" can be modified for the "Hotbox" and is a huge upgrade in AC hum reduction and a huge cost savings in transformer and capacitors prices.
I'm trying to build my own Hotbox and i have taken a look to the Real McTube but have some questions.

I don't understand the ground connections from the Real McTube between the second and first rectifier bridge, I thought that both negative pins had to be connected and the pin 9 from each tube not used as it is suposed to be 12V. What values did you use for filter Caps and R in the power supply?

Thank you,
Miquel
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Old 17th July 2012, 07:56 PM   #10
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Since the first bridge is floating, pin 9 just provides a center tap to give a ground reference. This balances any ripple noise between pins 4 and 5. If you twist those wires together, the noise will tend to cancel when it trys to bleed into the signal.
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