5F2A Little to no noise.

[makingnoise88]

Hey guys I'm building a 5f2a from a hoffman kit for a buddy and got it all together and have double checked everything but cranked it is barely audible!
So I have been trying to find the voltages for a 5f2a but don't see any on the schematic.
Anyway here are my voltages so far.

V1 12ax7
1. 177
2. 0
3. 1.5
4&5 6.3ac
6. 261
7. 0
8. 0.25
9. 6.3ac

V2 6v6
1. 19.8
2. 6.3ac
3. 344
4. 315
5. 005 MV
6. 005 MV
7. 6.3ac
8. 19.8

Let me know if you notice anything off thanks.

[shooter]

V1b pin 8 seems low to me, I would expect something closer to pin 3
check that you have 1.5k and not a 150ohm.
do you have NFB hooked up?

[makingnoise88]

I thought the same!
So the first thing I did was check and make sure I had NF hooked up and I did have a 1.5k installed and I do. So both of those are correct.

[sluckey]

I agree that V1-8 voltage is too low. And the voltage on pin 6 is too high. Both those readings indicate that half of the tube is barely conducting. Be sure the resistor on pin 6 is a 100K. Oh, and try a different tube.

I'm betting there is a wiring error or bad connection.

Check the input and output jack wiring carefully. Click on the link in my signature line below this reply and follow the instructions to verify the amp is wired correctly. Post some good pics so we can help you look.

[PRR]

My 2 cents says a half-bad 12AX7. (Maybe an OK tube and a bad socket.)

Or one side of the heater is not *really* getting power. Bad solder on the 4-5 strap.

Or just mistakes in the readings. I've learned that this can happen.........

But a mis-wire might be the problem, and is certainly a very popular problem.

[makingnoise88]

I reflowed solder swapped out the 12ax7 double and triple checked the diagram for input and output. Is there a way to test the socket?

[makingnoise88]

When reading V1 pin 6 it makes a sparking Noise! No spark just very noisy while i'm testing it.

[makingnoise88]

replaced the v1 tube socket and nothing changed!

[John]

On your input jack, it looks like the 1M grid leak resistor is between ground lug and shorting lug.

[makingnoise88]

The 1m grid leak is on the ground lug and tip of the 1st jack and the sleeve of the second.

[sluckey]

The 1m grid leak is on the ground lug and tip of the 1st jack and the sleeve of the second.

You say "sleeve" of the second. Do you really mean "switch" of the second? Hoffman's labels for the jacks are G=ground, S=switch, and T=tip.

It's easy to miswire the Fender hi/lo jacks. Not saying that yours are miswired but if they are then you may not be able to get a guitar signal through. Here's a quick and easy way to verify that your jacks are wired correctly...

Connect your ohm meter to V1 pin2 and chassis.

1. With no plug in either jack, resistance should read about 34KΩ.

2. Insert a plug (may use a guitar cable but don't connect a guitar) into the "HIGH" jack. Resistance should read about 1MΩ.

3. Now insert the plug into the "LOW" jack. Resistance should read about 68K.

If any of these 3 resistance readings are incorrect, the jacks are not wired correctly.

[makingnoise88]

Ok I'll try this when I get home to double check but it looks to be correct according to the other amps I've built with the high low jack.