5F1 Build thread - by a first timer.

[sluckey]

You funny ace.

[Meteorman]

Took the plunge and finally installed all tubes and hooked up the dim bulb rig.
Hooked up the speaker cab.
Turned on the juice.
Fairly anticlimactic.
Pilot light on nice. Dim bulb was dark at first.
After about 90 seconds bulb filament glowed orange and stayed that way for the duration of the approx 10-min power up.
Zero hum out of speaker.....   As in, disturbingly silent.
As in, maybe something is wrong silent.
Didn't plug in guitar.
Turned everything off, unplugged, and off to gym to burn off some anxiety.
Later tonite will re-power and try guitar.

[Meteorman]

well, it's official - no sound.
no buzz, hum, hiss, squeal or gurgle.
bummer.

I've chopsticked it  - all looks correct.

here is my speaker switch wiring - this looks ok doesn't it ?
the black from the OT is "common" - I put that on the common switch pole, and jumped it over to the jack tip (with the NFB red).
yellow green and gray are the 4,8,16 ohm taps. 

the jack green is grounded on the chassis.

my speaker cab has a non-switched jack, i.e. just a tip and and sleeve post.  That's not a problem is it ?

thanks for any tips..  Bummed.

[Paul1453]

You grounded the tip?  Why?

You have a switched ground jack, the ground should be connected there not the tip.   
OK, maybe I miss read your post.  But I would expect that black wire to connect to the green on the jack.

Double check your switch wiring.  Can you post the OT's switch wiring diagram?

Those other wires should be soldered better once you verify their connections.   

You're close, don't worry you will get her done soon.

And it will sound great to your ears!   

[Willabe]

DON'T turn on that amp again, you have wired the OT as a direct short. 

Wait for someone to show you how to wire it correctly.

What OT do you have? We need to see the OT's diagram showing the wires and there colors.

[Meteorman]

I have the Classic Tone 40-18031 output transformer.
The schematic is this:


NOTE:  the red wire to my switch (photo in previous post) is NOT repeat NOT the primary red from the OT. 
That red wire above comes from middle lug of my NFB pot - feedback circuit.

The red OT primary goes into chassis to pin8 of my rectifier.
The blue OT primary goes into chassis to pin 3 of my 6v6.
The brown primary is capped with shrink tube and goes nowhere.
The black wire exiting the top of the photo in previous post is the OT secondary "common".

The switch is a 1-pole 3 position switch
http://www.mouser.com/ProductDetail/NKK-Switches/HS13Y/?qs=sGAEpiMZZMvNbjZ2WlReYmUduk%252by82OaZkUdP2yPJTY%3d
You can see the wiper currently contacting the grey lug.
It rotates to the green & yellow and back again.
The lug with the black wires is the common - the wiper doesnt go to it.

With this info, have I still direct shorted the OT?
I did pass the dim bulb test, I believe.

Thanks!!!!
/mik

[Meteorman]

OK, i believe I see the problem now.
The black "common" from the OT should go directly to the jack ground.  And NOT to the switch.
Yes?

[Willabe]

The black "common" from the OT should go directly to the jack ground.  And NOT to the switch.
Yes?

Yes.

But where does that red wire and green wire come from/go to on the speaker jack?

[Paul1453]

Yes, I think if you swap the red and black wires on the switch, that may fix it.   

Maybe not.  Maybe the red wire should go where the black wire is and the black wired should connect to the green wire on your jack.

The black jumper from the switch to the tip stays.   

[Willabe]

Yes, I think if you swap the red and black wires on the switch, that may fix it.   

No.

[Paul1453]

Yes, I think if you swap the red and black wires on the switch, that may fix it.   

No.

I think you are right.  That won't do it, same issue, no path through the speaker.

Modified my earlier suggestion.   

[Meteorman]

Yes.

But where does that red wire and green wire come from/go to on the speaker jack?

The red wire is my negative feedback wire.
It goes to the jack tip, as per Hoffman diagram.

The fat green wire is a wire I added and is grounded on the chassis.
I did this because the jack itself will not be mounted to chassis (and thus not grounded the normal way).
The jack will be mounted on a separate plate (the brass one you see) on my wooden head cab.

As soon as this Big 10 tourney game is over, I'll go move the OT black secondary to the jack ground.
It will join the fat green ground wire there.

And see what happens. Thanks so much fellas. 
This is why they say don't do mods as a noob! 

[Willabe]

The red wire is my negative feedback wire.
It goes to the jack tip, as per Hoffman diagram.

Ok, that's fine.

(Edit; that's wrong, see reply #66. Willabe)

The fat green wire is a wire I added and is grounded on the chassis.
I did this because the jack itself will not be mounted to chassis (and thus not grounded the normal way).
The jack will be mounted on a separate plate (the brass one you see) on my wooden head cab.

That's fine too.

Remember to leave the black jumper from rotary switch to speaker jack.

[Paul1453]

The switch does add some complexity.

The NFB is designed to always come off the same tap, but moving to where I suggested it will change with the switch.

If the NFB wire is designed to come off the 8 ohm tap, then I think it should be connected to that 8 ohm tap wire on the switch.

Does that sound better Willabe?   

[Paul1453]

More confusion on my part.   

Now I'm thinking the NFB wire must come off the 4 ohm tap instead of the 8 because of the switch.

Or does that not matter because the entire secondary winding is energized regardless of the tap used to power the speakers?   

[Willabe]

The NFB is designed to always come off the same tap, but moving to where I suggested it will change with the switch.

If the NFB wire is designed to come off the 8 ohm tap, then I think it should be connected to that 8 ohm tap wire on the switch.

Now I'm thinking the NFB wire must come off the 4 ohm tap instead of the 8 because of the switch.

Or does that not matter because the entire secondary winding is energized regardless of the tap used to power the speakers?   

Sorry guy's I missed that.

Yes, the NFB should be hooked up to the 4 ohm tap just like Fender had it. (That is to say Fender only had a 4 ohm tap.)

The NFB voltage divider resistors values were calculated with that 4 ohm tap and it's voltage output. The NFB won't change by switching the rotary switch, it will remain constant. Because that 4 ohm taps acv is what it see's.

[Meteorman]

If the nfb is hooked to 4-ohm tap (yellow) on switch, wouldn't that result in no NFB when switched to the 8-ohm or 16-ohm taps? (Now see your edit above....)

So I swapped the OT black to jack ground.
We now have moderate hum.
Unfortunately, I also now have piercing, immediate-headache-causing high-pitched squeal.
Guitar strings did not register at all thru speaker.
I'm guessing this might be a lead dress issue?  or the NFB issue? but I'm all ears....
When I slowly turned up NFB pot during squeal, it got louder than started to break up bad - I didnt do much of that.

[sluckey]

Unfortunately, I also now have piercing, immediate-headache-causing high-pitched squeal.

Swap the OT primary wires.

[Paul1453]

Well the good news is that I think you now have the OT portion of your circuit wired properly.

The bad news is, remember earlier in the thread there was a comment about the placement of your NFB pot?

With your mod you also have OT signal wires running more places then if it were un-modded.

Sometimes it is best to start with the basic design 1st, ensuring that it functions as expected.

Then proceed to make your modifications.

This has the added benefit of knowing what the original sounds like,
and how the sound has changed because of your modification.

It appears you now have an oscillation issue to deal with, not fun.

Maybe you could consider completing the build as designed 1st?
Making sure it functions properly as designed.
Then moving to implement any mods 1 at a time to know where problems are introduced?   

Your NFB connected to the 4 ohm tap will function as designed regardless of the tap used to drive the speaker. 

[tubeswell]

Always that little pang of anticipation firing up a new build for the 1st time - no matter how many builds you've done.


So how did it go?

[Meteorman]

Swap the OT primary wires.

10-4, Steve - will give this a try as fix #1. Thanks.

Maybe you could consider completing the build as designed 1st?
Making sure it functions properly as designed.
Then moving to implement any mods 1 at a time to know where problems are introduced?   

Your NFB connected to the 4 ohm tap will function as designed regardless of the tap used to drive the speaker. 

Thanks Paul.  if OT lead swap doesn't help, I will move towards this strategy.

Always that little pang of anticipation firing up a new build for the 1st time - no matter how many builds you've done.

So how did it go?

well... let's just say it wasn't flawless. posts above chronicle the issues.

[Meteorman]

     
It's Miller Time!!!.... I may even upgrade to Pabst Blue Ribbon.
I swapped the OT primaries, moved the feedback wire to the 4-ohm tap and re-routed it away from OT primaries,  said a prayer to the ghost of Leo Fender, and plugged it in.
I had also stuck in a "vintage" RCA 5Y3GT i got off eBay and left the SovTek on the sidelines.
No squeal, a low non-intrusive 60-cycle hum, and the guitar comes through like Jimmy Page.   
OK, that last part is a lie, but it comes through clear, fat, and loud.
Right now, the hum is not an issue for me - it disappears when NFB pot is up over half way.
Couldn't be happier, and can't thank you guys enough. 
Now....  back to work on the custom head box for it.
Thanks again for all the help on this!!
/mm

[p2pAmps]

   
It's Miller Time!!!.... I may even upgrade to Pabst Blue Ribbon.
I swapped the OT primaries, moved the feedback wire to the 4-ohm tap and re-routed it away from OT primaries,  said a prayer to the ghost of Leo Fender, and plugged it in.
I had also stuck in a "vintage" RCA 5Y3GT i got off eBay and left the SovTek on the sidelines.
No squeal, a low non-intrusive 60-cycle hum, and the guitar comes through like Jimmy Page.   
OK, that last part is a lie, but it comes through clear, fat, and loud.
Right now, the hum is not an issue for me - it disappears when NFB pot is up over half way.
Couldn't be happier, and can't thank you guys enough. 
Now....  back to work on the custom head box for it.
Thanks again for all the help on this!!
/mm

It's official, you have the amp building bug.  You do realize this is the first af many to come LOL...  Great job.  Building an amp and having it work is quite the accomplishment.  Don't disappear from the forum 

[Shack]

Awesome

[Paul1453]

Congratulations!!!

I knew you could do it.  But it doesn't end there.

Now that you know you can make your own great sounding amp,
there will be more where that came from.   

Upgrading your tubes can really sweeten the sound.
I seem to like the Mullard 12AX7 best, but most old Amperex 12AX7s sound good too.
A vintage 6V6GT can help, but the premium 12AX7 seems to make the most noticeable difference to me.

All amps sound better to me, if I can say "I built that".   

[PRR]

> If the NFB is hooked to 4-ohm tap (yellow) on switch, wouldn't that result in no NFB when switched to the 8-ohm

The winding taps are a lever.

Stand a 8-foot stick straight up, then move the top over 2 feet.

The 4-foot point of the stick moves over 1 foot. Exact proportion.

(Actually a transformer is an imperfect, not-utterly-stiff, stick. But within the audible band an audio transformer will be lever-enough for all practical purpose.)

[Meteorman]

Finished up the head unit, except for a nameplate I'm workin on. 
The speaker cab is a 1x12 with a Hellatone 25.
Thanks again for all the help!
/mike

[Popsleigh]

Well done your rig looks awesome.

[Paul1453]

No doubt, that is a fine looking amp!

I'm sure your nameplate will be a great finishing touch.

Your friends might not believe you made that yourself,
as you did such a professional looking job!   

[FranciscoPerez]

Wow congrats!! Looking really good!!
I wish my first build had looked half as good! 
I think it'd look even better if you'd lacquer the tweed. It'd also match the guitar better 

[pompeiisneaks]

Very nice!  I wish I was that good at building cabinets, mine take TOO long :)

~Phil