12XXX Build 05/2010

[Vegard]

Does George have this hum in his builds as well?...

[vanhalen5150]

Does George have this hum in his builds as well?...

PM'd him.

[Tone Slinger]

Shannon, what tubes you got in that thing.

[plexified]

what a cool thread . By the time a few more weeks pass this babys is going to be screaming .

VHjunkie was such a cool read helping you out and everyone for that matter .

I would agree that baby is going to be on the bench for a while . At least until your smiling enough .

Use small aligator clips like the small copper micro ones from radio shack for good heat sinks on both sides of parts being soldered . Install or remove . Heat kills parts .

I like to use my variac with my iron to control heat . You can tone down a 30 watt iron or use a 15 watt to start . The big puddle solder jobs need the huge solder gun . Its just a huge problem with with the radiation from that gun . Don't use it . Use mechanical grounds . Steves ground system is a killer . Use the washers to solder wires to and not the back of the pot . It cooks the pots !

I also would clip the wire ties and unbind the ac rail . It sounds like you have an AC issue like VHjunkie had mentioned . AC hum is usually radiation . Your heaters are cool wound and close to the chassis . The green pre amp wires should be above the chassis on the sensitive side of the preamp under power . You can use a wood chopstick and one hand in your pocket to probe wires and parts while under full power and NO INPUT . HERE you can hear noises and their origionation . Tap caps , resistors and tubes for signs of noise . As you chase the signal from front or input to the output you should find a stage with issues . The stand by hum is a true AC issue as only the heaters are on technically .

You can use an aligator clip on the main ground from the ac in lug and jump to different ground points to hear any 'improvement'. This should be done under standby , and then under full power without input . I start with the volume reasonable and if I find no issues , I turn her up full blast and do the same , chase the noise .

The bridge diode ground can be moved to the main power filter ground point or just to the back of the amp .

Your prescence wires usually purple can also be very sensitive to noise depending on the amout of feedback you desire to use .

Lastly you will be tuning the amp and keep in mind high end is very much an irritant . I would suggest tune from a super bass circuit and go from their adding high end as you go . Not adding high end in one area , but experimenting to see what type of high end you want and and where in the stages of the ciruit you want it .

Simple areas are always overlooked like screen resisitor values , grid resistor circuit changes and value changes , and your prescence circuit .

Awesome build and you should be tweaking on the bench with the headbox collecting dust in no time .

Cool , I can't wait for clips , David

Almost forgot , in regards to the ouput trans wires being twisted , The origional iron had a cloth braided high gauge solid wire . This is not only a noise potoential area , but also an area of engineering that is never duplicated for the wrong reasons .

[plexified]

jeez forgot again , so busy , Mechanical locality is very critical to the origional tone it has an interaction . A 3-D plane of radiation and reaction . So that is good to keep in mind .

The most you should have in terms of noise is a sssshhhhhh . A hum is very different .

If you get the ac ironed out and still have noise , record a good long track of the noise bothering you and attach that track to your guitar track pre effect . And here you run it out of phase and EQ to cancel all that BS .

Now you can git your pant legs flappin and your arm hairs tickling as the entire house resonates with your rig at full blast !

[plexified]

alzheimers must be kickin in . The ac could use a polarity flip too just like the old heads had , never know the home ac line is an inspect what you expect kind of thing . Be safe and put the meter in the wall and monitor what you got while your at it . Its usually all over the place from 105-135 believe it or not . If you have a variac regulate it . I'm sure we can git her ironed out , I gotta jet ....

[Sral68]

I never figured out what the problem was... I wonder if other 12series builders have had this problem too

My 12.000 series has this problem also

[vanhalen5150]

Shannon, what tubes you got in that thing.

Mullard 12ax7's and El 34's.

[vanhalen5150]

what a cool thread . By the time a few more weeks pass this babys is going to be screaming .

VHjunkie was such a cool read helping you out and everyone for that matter .

I would agree that baby is going to be on the bench for a while . At least until your smiling enough .

Use small aligator clips like the small copper micro ones from radio shack for good heat sinks on both sides of parts being soldered . Install or remove . Heat kills parts .

I like to use my variac with my iron to control heat . You can tone down a 30 watt iron or use a 15 watt to start . The big puddle solder jobs need the huge solder gun . Its just a huge problem with with the radiation from that gun . Don't use it . Use mechanical grounds . Steves ground system is a killer . Use the washers to solder wires to and not the back of the pot . It cooks the pots !

I also would clip the wire ties and unbind the ac rail . It sounds like you have an AC issue like VHjunkie had mentioned . AC hum is usually radiation . Your heaters are cool wound and close to the chassis . The green pre amp wires should be above the chassis on the sensitive side of the preamp under power . You can use a wood chopstick and one hand in your pocket to probe wires and parts while under full power and NO INPUT . HERE you can hear noises and their origionation . Tap caps , resistors and tubes for signs of noise . As you chase the signal from front or input to the output you should find a stage with issues . The stand by hum is a true AC issue as only the heaters are on technically .

You can use an aligator clip on the main ground from the ac in lug and jump to different ground points to hear any 'improvement'. This should be done under standby , and then under full power without input . I start with the volume reasonable and if I find no issues , I turn her up full blast and do the same , chase the noise .

The bridge diode ground can be moved to the main power filter ground point or just to the back of the amp .

Your prescence wires usually purple can also be very sensitive to noise depending on the amout of feedback you desire to use .

Lastly you will be tuning the amp and keep in mind high end is very much an irritant . I would suggest tune from a super bass circuit and go from their adding high end as you go . Not adding high end in one area , but experimenting to see what type of high end you want and and where in the stages of the ciruit you want it .

Simple areas are always overlooked like screen resisitor values , grid resistor circuit changes and value changes , and your prescence circuit .

Awesome build and you should be tweaking on the bench with the headbox collecting dust in no time .

Cool , I can't wait for clips , David

Almost forgot , in regards to the ouput trans wires being twisted , The origional iron had a cloth braided high gauge solid wire . This is not only a noise potoential area , but also an area of engineering that is never duplicated for the wrong reasons .

Wow, thanks for the extra info Dave, Im going to try this stuff this weekend.

[vanhalen5150]

I have a feeling putting that ground bus wire on the pots may have damaged them. I had to do them twice. The first time I could pull the solder off by hand. If put a tester on each pot a move the dials, can I tell if I have a bad pot?
Im not familiar with the term AC rail? What does that refer too?

[vanhalen5150]

alzheimers must be kickin in . The ac could use a polarity flip too just like the old heads had , never know the home ac line is an inspect what you expect kind of thing . Be safe and put the meter in the wall and monitor what you got while your at it . Its usually all over the place from 105-135 believe it or not . If you have a variac regulate it . I'm sure we can git her ironed out , I gotta jet ....

Thats a good point. I have a variac as well. Ill try lowering the wall voltage, and check the wall output. I never thought this would be easy. Messing around with the thing, getting it to do what, is as much fun as the build itself.

[vh junkie]

Aw Geez! I almost forgot about this thread! I hate the way its been sinking in the VH Forum. How is it going? Are there any diagrams of the power section of these amps? Are the power caps wired in parallel?

[vanhalen5150]

Naw...got no diagrams..nothing. Things are well so far, still letting everything settle. Had it dim'd for an hour straight out in an iso room. Bias went slightly up but after rebias has held steady. Great woody plexi tone, and thats straight out of the box with no tweak.

Thanks VJ! Much appreciated, as well as everyone else. Nobody knows it all, so no head swelling....

Yeah, the VH forum is now a bit brutal. Yes, I add some B.S as well at times, but come on, it's an amp forum. Stick to that at least for basics. I'm digging back 2 years in posts to find a simple solution, that should be at my fingertips on a forum like this. I type in "Variac" and I get like 20 references to "POD Variac settings"........

There was a ton of great guys here with great insight...where's Goodguest? Where's that dude Mike, with the layouts...where's.....mmmm....guy's who knew shit and actually helped? Where's Ralle? Where is the guy that pretended he was Rudy.L ?.....At least he was entertaining.

Exhale............

[vanhalen5150]

Forgot about the thread?


That would make you a deadbeat dad?

[Strat78]

I haven't forgot, but I'm still waiting for my kit (been waiting 10 days, is that normal?). Meanwhile I've prepared my entire basement for the damn things arrival. Where can I get a good biasing kit?