5F1kit voltage between ground and 16uF cap 366 s/b 475

[leevc5]

Checked wiring until I am going blind.  Switched rectifier out.  What is the trouble shooting path I need to follow?

[sluckey]

Checked wiring until I am going blind.  Switched rectifier out.  What is the trouble shooting path I need to follow?

Please explain what you are saying in your subject line. Give us some more info. Click on the link in my signature line at the bottom of this reply.

[leevc5]

I do not know how to make it more clear Re: 5F1 amp kit.
When I put my voltage probe on the positive lead of the 16uF cap and the negative probe on ground I get a reading of 366 volts.  The data I have says it should be 475 volts.  The wiring is correct and I have switched out rectifiers.  I would like some opinions on what may be causing this low voltage.  The end result is obviously I have very little and very distorted volume on my amp.

[DummyLoad]

data you have is wrong. original 5f1 layout says 340V at 16uF main filter.


http://el34world.com/charts/Schematics/files/fender/Fender_champ_5f1-layout.png



--pete

[leevc5]

Thank you Pete,

If the voltage is right do you have any suggestions on where I should begin to check and see why my volume is so low and distorted?  I have gone over the wiring a dozen times and swapped out the 6V6 and 12AX7 tubes.

-Lee

[sluckey]

5F1kit voltage between ground and 16uF cap 366 s/b 475

Your abbreviation for "should be" didn't register with me. I was trying to think of some electrical term. Who's data do you have that says the voltage s/b 475? If you are using Hoffman's board and documents then maybe you saw 475V written on the big blue filter cap. That's just the max voltage rating of the cap and does not imply you will actually have 475V at that point. Highest voltage in a champ is more like 350V.

When a new build amp kit does not work the most likely problem is a wiring error or a wrong value component. The link in my sig line points to a very good method to verify wiring and component values. Hi rez pics often make it easy for us to spot a problem. Voltage readings on all pins for every tube are also very helpful in troubleshooting.

[leevc5]

"Voltage readings on all pins for every tube are also very helpful in troubleshooting."

Where do I find what the voltages should be for every tube pin?

-Lee

[sluckey]

Post your measured voltage readings and we will tell you if they look reasonable. I'm still betting on a wiring error at this point.

[HotBluePlates]

5F1kit voltage between ground and 16uF cap 366 s/b 475

Your abbreviation for "should be" didn't register with me. ...

I thought the title meant, "366v on 16µF cap, but 475v in 'standby'".

And then I was wondering why you added a standby to a 5F1... Then realized Sluckey already asked for clarification & figured I'd keep my mouth shut.

Where do I find what the voltages should be for every tube pin?

Dummyload posted a layout earlier; it has voltages for every pin (near-enough) for the 6V6 and 12AX7. The thing to learn is these are not ultra-critical targets; rather, you need a feel for what looks reasonable or wrong.

For example, the layout shows 12AX7 pins 3 & 8 at 1.5v. Something between 1-2v (or close) is probably "right". 10-100v (or dead-zero volts) would be wrong.

The layout doesn't show voltages for 6V6 pin 5, or 12AX7 pins 2 & 7. Those should be 0vdc.

The layout shows 150v for 12AX7 pins 1 & 6. Those could be 100-200v and be fine. Or the 200v could be a bad sign if pins 3 or 8 were also 0v. There's a fair amount of unstated background informing that judgement...

Same is generally true of the 6V6 voltages, but its voltages are on a different scale.

... The wiring is correct and I have switched out rectifiers.  ... I have very little and very distorted volume on my amp.

... I'm still betting on a wiring error at this point.

Be sure not to interpret the above as a slight. 99% of the time (or more) when a new build doesn't work, it's because of a wiring or part-value error. I make occasional wiring errors, too. But it's always hard to see the mistake in your own work, unless you remember the phrase, "if it was wired right, it would be working now." So when my stuff doesn't work, I know I messed up something somewhere and set about looking for the error.

[DummyLoad]

Thank you Pete,

If the voltage is right do you have any suggestions on where I should begin to check and see why my volume is so low and distorted?  I have gone over the wiring a dozen times and swapped out the 6V6 and 12AX7 tubes.

-Lee

follow HBP and slucky's lead. they will assuredly help you sort this amp out. posting some hi resolution shots resized to 1024 x 768 will help immensely.

as HBP pointed out: the layout i linked to has the needed voltages, admittedly a couple are hard to read so i made a table of the values: view it below.

--pete

12AX7
pin 1 +150V
pin 2 grid - not measured
pin 3 +1.5V
pin 4 6.3VAC
pin 5 6.3VAC
pin 6 +150V
pin 7 grid - not measured
pin 8 +1.5V
pin 9  tied to ground. 

6V6
pin 1 - tied to ground
pin 2 - tied to ground
pin 3 +340V
pin 4 +295V
pin 5 grid - not measured
pin 6 - no connection
pin 7 6.3VAC
pin 8 +18V

[HotBluePlates]

Be aware we don't do heaters like the 50's anymore.

You probably have a grounded center-tap, so you should see 3.15vac (or thereabouts) to ground from either pin 7 or 2 of the 6V6, and pins 4/5 or 9 of the 12AX7.

[leevc5]

Thanks Pete!  I really appreciate the table.

-Lee

[drew]

Dummyload posted a layout earlier; it has voltages for every pin (near-enough) for the 6V6 and 12AX7. The thing to learn is these are ultra-critical targets; rather, you need a feel for what looks reasonable or wrong.

You meant are not ultra-critical targets, right?

[HotBluePlates]

Right. Edited the post from earlier.