Tracing out the ciruit

[nomad100]

confused! i trying to trace out the circuit on my modules, but pin 1 on v1 does not seem to be connected, which is the load for that tube stage. further i went the more confused i got. the circuit does not seem to be using the tubes in a traditional way. Anyone have some insight?

 

[SacredGroove]

Pins 1 and 5 on the tube board are not used and pins 4 and 5 (heaters) on the tube are not used. V2 is a little different and I don't have the layout with me right now. Maybe this (below) will help.

PCB--V1
1--OPEN
2--plate 2, tube pin 6
3--grid 2, tube pin 7
4--cathode 2, tube pin 8
5--OPEN
6--cathode 1, tube pin 3
7--grid 1, tube pin 2
8--plate 1, tube pin 1

 

[fearnloathing]

depends on the module. Some dont use the first side of tube 1. All the high gain modules use all 4 gain stages though. If you hold the module up to a light with it removed you can see the traces are layered so some are invisible unless viewed with a backlight. Hope the helps

 

[nomad100]

how does it work if both sides of the tubes heaters are not on

 

[SacredGroove]

I wonder if it's setup that way too help eliminate hum, and that enough heat is produced from the plate to conduct? It's just a guess. I don't know enough about tubes yet.

 

[JKD]

The heater is the thing that glows on the 12ax7 tube right? If you look at a module...you'll find them lit up like tubes in any old amp as far as I recall.

 

[fearnloathing]

Yes that is what you see glowing. V1 A and B are both hot with 6.3 volts what Sacred Groove described above would result in a module that doesnt work if I am understanding what he wrote correctly.

 

[nomad100]

16v on the heaters would hurt the tube, as well

 

[nomad100]

definatly making me wonder if the tubes are even being used for tone.

 

[fearnloathing]

definatly making me wonder if the tubes are even being used for tone.

Sorry about that I made a typo in my above post and didnt realize it. Its 6 volts not 16volts. 12ax7 can operate between 6.3volts and 12.6 volts on the heater filaments. Why would wonder if the tubes are used for tone? Dont take this the wrong way but try googling some basic tube amp theory and do some reading. I think you will find most the answers you are looking for. I would recommend checking out www.tubenewbie.com as a pretty easy to follow description of how these circuits work. If you know how to read schematics which I assume you do since you wanted to trace the circuit I have most of the modules already traced out and would be happy to send them to you.

 

[nomad100]

that would be awesome to have the schematics. The reason i'm confused is because on my blackface module, which is the only one i've had a chance to look at. seems like plate and heater connection are not made. I'd like to compare the modules to the original circuits and possibly mod a little bit.

 

[nomad100]

cap cad is very poorly written program and is a pain to view the images with. Do you have them as pdf's?