My Little 5W Dragon

Nicholas-L

So along with all my other projects I've been trying to get this little 5 Watter done. Finally have everything( yay ). So this is how it started and progressed so far.

Blank Board

Getting the holes drilled

Turrets and components on

Yay!!! Got the blank chassis.

Finally got all the holes done.

Checking where the Trafo's should go.

Time to get some color on that chassis..... mmmm Primer.

Oooooh Massey Ferguson Red.... ? or tractor red ?

singemonkey

Looking great.

Nicholas-L

:'( process came to a halt because the fuse holders keep breaking... New ones on there way... so maybe by Saturday I'll have it done ? ? :?

makepeace

looking good! very funny you mention that! i've had the same problem. are they bakelite? i think they are inherently hard but brittle..

now.. on to what you're building ?

its not a standard tweed princeton or champ.. and i don't think its a take on either either. so lets have it eh ? looks funkeh with lots of switch options

Nicholas-L

yeah I think they are made of bakelite :-\ ( i got what i paid for I guess :roflmao: )

The only switching options will be on/off and standby. It is based off of the AX84 P1. Single ended 5W running on a 12AX7 and an EL84. The only thing I have changed so far is the tone stack... Changed it from the marshall-ish style to a fender style with quite a few value changes which will hopefully give quite a unique style to it, so I have no idea what it's going to sound like ?

Nicholas-L

So finished building..... ??? Time for the test and what happens ma'se Buzzzzzzzzz. Time to trouble shoot tonight.

makepeace

Pics or it doesn't exist ?

MikeM

Let us folk have a peek, maybe we can spot something fishy

Gearhead

My vote is for automatic fuse, hands down. You are not fusing a production amp that's tried and tested, you are trying and testing something you produced that may also be used as an amp. If you're not blowing the fuse at least three times, you are not moving fast enough 8)
Forget about bakelite and wire, get an ETA.

Nicholas-L

Was listening carefully. I'm hearing a popping noise under all the buzz as well.

Nicholas-L

Adjusting volume doesn't really effect the Buzz, but there is a slight change during turning of the volume pot.

Gearhead

Did you earth the center of the filament supply? If your tranny does not have, you can make one by putting one 100Ohm resistors from earth to each side of the supply.
If those green wires are the filament supply, you need to twist them together a lot more and never let each go either side of the socket...

Nicholas-L

GH the green wires are the Heater Filament wires and there is a center tap to earth for them... I will clean up the wiring a bit more especially those green ones. Thanks

Gearhead

I found that using coaxial wire between input and first tube, grounding the shield on one side, helps a lot in keeping the noise floor down.

Nicholas-L

That's actually a good idea ? .... I also found that the buzz only occurs when the output tube is in and I've tried two different ones.... Guess I'll have to open the gram radio and steal one of those for a test :roflmao: as I know they work.

makepeace

I'm assuming that you've gone over all the DC's with a MM, I would guess that you are missing a signal or ground connection somewhere. I would doubt that its a tube already (assuming they're all new). Plus, you wouldn't get much signal going to your speaker without an output tube ???, so there shouldn't be a buzz unless your filtering is a shocker. Recheck against layout/schem and then poke at your joints with a wooden dowel and other hand behind your back. Check your input jack, output jack and OT are wired correctly. +1 re the coax. I find that all signal carrying lines that aren't on the board should be coaxial with grounded shield. Also, I've discovered metal films ?. I don't care how much snake oil carbon comps come with, that noise is no where near worth it..

Nicholas-L

So the circuit I was working from said to connect the heater voltage between the cathode and the cathode resistor of the EL84 output tube ???.... The layout supposedly works.... I decided then to cut the link between the cathode and the heater voltage ? and voila!!!!! :applause: :dance: :woohoo: :goodtimes: ?arty: :sorry: ? :-[

bottledtone

The heater ct was connected to cathode of el84 because it is a DC reference. The slo100 has something similar but the dc refernce comes from using a potential divider from the ht supply.
GH is right. Your heater wires should be twisted more. Also your ouput jacks should be moved over to the siide where you have your output transformer. Now you have high current wires running a length right past your preamp valve. And shorter lengths of wire from board to valve sockets is best.
Popping is normal a sound related to arching... Did you have the ct connencted to cathode and ground same time?
Oh and don't twist your ht dc wire with the wire from the el84 anode that goes to the output transformer. Twisting should only be used when current is equal in both wires, and in this case, you don't want ac in duced into your dc supply.

Nicholas-L

Thanks guys for the help. Will do some cleaning up on the wiring. Run it this morning quickly before work and it sounds awesome. Quite a nice raw drive from the preamp. Will eventually see what the power tube drive sounds like. The tone stack I changed can go quite bright but it sounds awesome.

shaunf

Well done! Nice project. One day when I'm big....