Please help with my first build 5F1 with no sound

[icy_wind500]

ok....so I've spent the last 3-4 hrs re-doing everything
I made sure all the nodes on the board is good, made sure every joint is solid, placed a layer of insulation under the board.... I've shortened all the wires and made it look neat....
All hopes are high, plugged it in and got nothing ......
I'm about to burst into tears......

[Steve Conner]

Oh, stop blubbing. Does the pilot light come on? Do all of the tubes light up? Any sound at all from the speaker? (Humming, hissing, etc)

[icy_wind500]

pilot light comes on
tubes all glow !
no sound at all

[Bruce / Mission Amps]

Do you have a voltmeter so we can check a few first order things, like determining if the tubes are biasing up?
Measure the DC voltage on the cathodes of both triodes and the power tube to see if there is anything working.
Not important yet, unless you accidentally grounded the signal path, but your shielded audio cable from the volume pot is grounded incorrectly for most current schemes.

[icy_wind500]

Do you have a voltmeter so we can check a few first order things, like determining if the tubes are biasing up?
Measure the DC voltage on the cathodes of both triodes and the power tube to see if there is anything working.

Yep, ok but which pin do I measure? and do i measure to ground?
Thx!

[tubeswell]

Has your voltmeter arrived yet? (as suggested in the telecaster forum, you need to provide all the idle voltages of the filter cap nodes, plates, screens, grids, and cathodes, and also check the DC connections with your R-meter for continuity)

[g1]

Sorry to start with the obvious but have you verified the speaker is working?

[icy_wind500]

Ok I started taking voltages with the new meter

from left to right on the turret board

16uF cap : 357V
8uF cap : 184V
8 uF cap : 158V
25 uF cap : 7.55V
node between 1.5k and 22k resistor : 0.77V
0.022uF cap : 102.5V
0.022uF cap : 93.4V
25uF cap : 0.965 V

So seems like some are different to what weber suggests in the diagram

[icy_wind500]

Sorry to start with the obvious but have you verified the speaker is working?

yes I did that too

[icy_wind500]

Here are my findings

[tubeswell]

Ok I started taking voltages with the new meter

from left to right on the turret board

16uF cap : 357V
8uF cap : 184V

What (dropping) resistance have you got between the 16uF and the 8uF filter caps? The Fender 5F1 schematic says 10k (but you could easy halve that). The screen voltage could be a wee bit higher. (you want about 300V there) Or did you put the 22k in there by mistake? (instead of the 10k?)

8 uF cap : 158V

Check that the dropping resistor connecting to this cap is 22k. (160ish is kinda low - You want about 250V there)

25 uF cap : 7.55V

This is way too low. You should have about 18-19V. Check that you have a 470 Ohm cathode resistor in parallel with the 25uF cap.

node between 1.5k and 22k resistor : 0.77V

This is too low as well. This should be about 1.5V. This may come right when you check/correct the the dropping resistors in the supply rail

0.022uF cap : 102.5V
0.022uF cap : 93.4V

THese are a bit on the low side, they want to be around 150V each. This should come up when you check/correct the dropping resistors in the supply rail

25uF cap : 0.965 V

So seems like some are different to what weber suggests in the diagram

Again this is low. You want about 1.5V here (same at the other pre-amp cathode resistor)


Double-check that you have the correct supply resistors in the filter cap chain.

Double check that you have all the correct connections in the signal path - input to grid of V1, plate of V1 to coupling cap and then to input of Vol pot, wiper of vol pot to grid of V2, plate of v2 to coupling cap and then to grid of 6V6. test the connections for DC-continuity with your R-meter

Refer to the layout below

[tubeswell]

Can you post some decent resolution gutshot pics of the chassis?

[icy_wind500]

Sorry I dont know how to comment between a qoute so I will just bold them :P

What (dropping) resistance have you got between the 16uF and the 8uF filter caps? The Fender 5F1 schematic says 10k (but you could easy halve that). The screen voltage could be a wee bit higher. (you want about 300V there) Or did you put the 22k in there by mistake? (instead of the 10k?)

The resistor across there is 9.96k so I think its right




Check that the dropping resistor connecting to this cap is 22k. (160ish is kinda low - You want about 250V there)

That cap is 21.7k so I think its ok too

This is way too low. You should have about 18-19V. Check that you have a 470 Ohm cathode resistor in parallel with the 25uF cap.


the cathode resistor is 466 ohms

This is too low as well. This should be about 1.5V. This may come right when you check/correct the the dropping resistors in the supply rail



THese are a bit on the low side, they want to be around 150V each. This should come up when you check/correct the dropping resistors in the supply rail

Which one is the dropping resistor?

Again this is low. You want about 1.5V here (same at the other pre-amp cathode resistor)


Double-check that you have the correct supply resistors in the filter cap chain.

Double check that you have all the correct connections in the signal path - input to grid of V1, plate of V1 to coupling cap and then to input of Vol pot, wiper of vol pot to grid of V2, plate of v2 to coupling cap and then to grid of 6V6.

Refer to the layout below

[ATTACH=CONFIG]18906[/ATTACH]

ok I'll double check with that diagram

[icy_wind500]

The heater wire doesnt look the same in the layout....

[überfuzz]

All hopes are high, plugged it in and got nothing ......
I'm about to burst into tears......

If you're planing on building more amps... get use to it. ;-)

I see that you've probed some stuff in the preamp. Here's some thoughts about that. You state that you get noting, I take it you mean no sound what so ever, not even a hum. This would suggest gnarlys in later stages in the amplifier. (Possibly even the speaker connection.)