5F1 build - green wire voltage only 2.5?????

[leevc5]

I'm back with yet another 5F1 problem. The previous amp is y'all helped me with is working terrifically. So I figured why not build another

This time the green wires are only reading 2.5V at the light and at the filaments. I swapped out the Classic Tone Pwr Xfmr that had this problem with a Weber Xfmr and same problem. The result of course is a 5F1 that is about as loud as a ceiling fan, sounds good and clean but of course want it to do its 5W thing.

Is there anything I could have done in wiring up the thing that would cause this problem?

[labb]

measure ac voltage from green wire to green wire and see what you get..You will have to give a little more info. as what xformer are you using. Is the filament center taped, how do you have it wired.

[leevc5]

Across green is 6.3V.
Weber W022772 transformer.
Pic of wiring attached.

[drgonzonm]

I looked the specs on the weber transformer.  green wire to green wire should be about 6.3v as you reported.

For others the filament portion of the transformer is center tapped. 

[leevc5]

Thank you for looking. So the filament voltage is the cause of the quiet 5F1??? What else might it be?

[labb]

6.3 volts ac is the correct voltage for the filament. Hard to tell from the picture but you should have one of the green filament wires going to one terminal of the pilot light and the other green filament wire going to the other terminal  of the pilot light.  From there to your tubes.The green/yellow wire should go to ground.  Measure the voltage pin 3 of the 6V6. Should be about 350 vdc. Measure the voltage at pin 8 of the 6V6. Should be about 18 vdc. Measure the voltage at pins 1 and 6 of the 12ax7. Should be around 150 vdc. Measure the voltage at pins 3 and 8 of the 12ax7. Should be about 1.5 vdc. Take a look at this. It should help you check your wiring...https://www.tedweber.com/media/kits/5f1_layout.jpg

[leevc5]

Thank you, all the voltages checked out. I will go through your link tomorrow.
Thanks again.

[John]

If you have 6.3 vac across the heater pins at each socket, then you have a wiring error somewhere else.
Check your pots: make sure the ground lug is actually showing 0 ohms to ground.
Make sure the cathodes of each tube are going to ground through their cathode resistor. If you measure each cathode pin to ground, your preamp tubes should show in the 1.5K range (depending what resistors you used) Your power tube should show about 470 ohms.
If you installed the NFB resistor, make sure it's 22K and not 2.2k
Make sure your 220K grid leak on the power tube isn't reading 22K.


Make sure the volume pot on your guitar isn't dodgy. Don't ask why I  know to ask. 
.

[drgonzonm]

I compared your layout versus the published layout from Fender, the layouts are different, (probably to avoid a copyright problem).

If you have a copy of the layout as provided by the manufacturer of your kit, Sluckey has some advice, on tracing the wiring.  I would suggest getting a couple of copies of the layout, a few highlighters and tracing out the build versus what the manufacturer has.  I would even verify each resistor by its color code and if possible determining its value. 

In the picture, that resistor above the 16 microfarad cap does not too healthy, (color).

A kind of dumb question, you did ground the filament center tap didn't you? You might have a hum problem if you didn't.  (That assumes you create the artificial tap with a pair 100 ohm resistors. 

[sluckey]

It's a Hoffman board. No need to compare to Weber layout or the original layout.

[drgonzonm]

It's a Hoffman board. No need to compare to Weber layout or the original layout.

Thanks,
I found the layout on this forum under Hoffman Turret Boards (the layout or picture upside down  )

[leevc5]

Thank you all for sharing your troubleshooting expertise. After following the steps amp has a steady buzz and volume at 12 is probably 25% of what it should be. I have:
Verified the wiring matching layout to amp and marking with highlights to make sure I got it all;
Checked the voltages at P90 I points identified and they matched within tolerance;
Checked resistors and they are all where they should be;
Went back and reflowed the solder at all ground points.
 
Anybody have any ideas?

[pompeiisneaks]

I think a few more pics from the top down on the input jacks and pot wiring as well as from the tubes down would help, it's kind of difficult to see what wires go where in the direct down shot. 

Buzz could be a ground loop issue, did you make sure to follow the grounding schemes from the layout?  Lowered output could be something wired wrong on the volume etc, but I can't make out the wiring very well at this angle from your one pic.

Edit: forgot champ has no tone :D and I just built one last month.

~Phil

[pompeiisneaks]

Oh I was just looking at it again, and I'm pretty sure I see something that doesn't make sense to me.

I'm attaching a pic I have a red arrow to what looks like either pin 3 or pin 7 to me, I can't tell from the angle, and it's a green heater wire that's jumpered to the next pin (4 or 6?) This would not work.  I'm not sure i"m seeing it right, though, you should have pins 1,2,3 as the first triodes anode, grid and cathode in some order (I don't recall off the top of my head). and then 4/5 are jumpered for the heaters.  Maybe it's just the picture?

~Phil

[pompeiisneaks]

Another thing I can't seem to make out well, I'm seeing possibly a green and a yellow wire connected to the speaker jack, and it seems they may be to the ground point, but I'm not sure.  Also I don't even see the black grounding wire that's required as well. 

See attached.  Red arrow points to the connection I'm trying to understand.

~Phil

[leevc5]

Green heater wire is to pins 4 and 5 like layout.
Speaker ground wire is correct just a color difference.
I ran guitar input to pin 7 ( second stage of 12AX7) and buzz went away and volume increased. So something is wrong between guitar input and 12AX7 first stage signal path. I have changed the cap and swapped 12AX7s but still something a miss in that section of the amp.

[sluckey]

You have already built one of these amps and the first one works. Put them side by side and you should be able to quickly see what is wrong with the second amp.

[leevc5]

Followed stage one of the 12AX7 signal path and found my stupid mistake = I did not instal the wire between turret 100k resistor and 022 cap ...put the wire on there as it should be and BINGO!!! I have a beautiful clean 5F1 that I can crank into a screaming demon at 12.

THANKS gang your keeping me searching was really the path to the answer.

With respect, Lee

[John]

Verified the wiring matching layout to amp and marking with highlights to make sure I got it all;

Let this be a lesson to you! 

[leevc5]

Yeah, who'd a thunk it...wiring the turrets is a no brainer right? NOT!!!

[pompeiisneaks]

Yeah like I said, it's kinda hard to tell in the picture,  glad you got it working!

[sluckey]

I did not instal the wire between turret 100k resistor and 022 cap

I would expect that to have zero sound, nothing like "about as loud as a ceiling fan, sounds good and clean but of course want it to do its 5W thing."

[leevc5]

I did not instal the wire between turret 100k resistor and 022 cap

I would expect that to have zero sound, nothing like "about as loud as a ceiling fan, sounds good and clean but of course want it to do its 5W thing."

Yes, that is strange, very strange indeed. But the picture clearly shows (after the fact) the missing connection. I didn't make a sound sample but it really was a very quiet little amp somehow. Maybe a quantum anomaly or sumthing :w2:weird...

[kagliostro]

Just a verify

is the OT connected correctly (right impedance taps I mean)

Franco

[leevc5]

Just a verify

is the OT connected correctly (right impedance taps I mean)

Franco

I don't know. It works, doesn't that mean it's connected correctly?

[kagliostro]

Reading the thread I've understand that you have low output power (am I wrong ?)

if there aren't other problems (like a bad ground, wrong component value, etc. etc.), one of the possible trouble is a wrong impedance match at the power tube and one reason for this can be a wrong OT connection

I'm not saying that you have this problem (bad OT connection) but only to verify your connections

But I didn't read all your post, so I'm missing something (your post #17 ), my bad english, in junction whith the fact that Steve
in one of his last post say >> ....  but of course want it to do its 5W thing. << made me mistake about the problem thinking that it was still present

Franco

[drgonzonm]

Just a verify

is the OT connected correctly (right impedance taps I mean)

Franco

I don't know. It works, doesn't that mean it's connected correctly?

  As Franco explained in many words, If you hook up an 8 ohm or 16 ohm cab to a 4 ohm tab, the amp will not be as loud as matching impedances on the taps.  In addition to feeding the speaker a lower voltage, the reflected impedance of OT will not match the power tube as well, also reducing how the loud the speaker sounds. 

[leevc5]

That part I did get right, not through technical know how but by default - the OT has only 8 Ohm output so I could mess that up.