Quick(?) question....

[tylerrussell]

...my first 5e3 build came out fine after a grounding issue was resolved with this forum's help. My second build is a duplicate of the first, the only difference is a 22uf as the first filter cap instead of the usual 16uf. The other filters are 16uf. Fired it up with the light bulb limiter~so far so good. At full volume it's really quiet and crunchy. After checking and re-checking the only thing I'm finding is 6-7mvdc on the negative side of the first (22uf) filter cap. There are zero mvdc on the second and third filter caps. Is this an issue that would cause such low output?

[sluckey]

The first filter cap negative lead should have a good mechanical/electrical connection to the chassis. Voltage should be zero on the negative terminal. Resistance from the negative lead to chassis should be zero ohms.

[tylerrussell]

OK, thank you. Will re-check that ground. Could that be the cause of "low output"?

[sluckey]

OK, thank you. Will re-check that ground. Could that be the cause of "low output"?

A bad ground on that cap would more likely cause loud hum. Low output can be caused by many things. And measuring 6-7mV on the ground side of that cap could be just because of a poor connection with your meter probe, not really a big concern but needs to be checked.

Measure and post the voltage readings on all the filter caps. Then measure the voltage on all tube sockets. Post those readings too.

[tylerrussell]

Thank you so much for your time.
5y3: 4: 322    V4: 1:  1             V3:  1: 1.0      V2:  1: 139      V1:  1: 150
        6: 322         2:  2.0                  2: 2.6             2:                   2:
        2: 346         3:  340                 3: 341            3: 2.0              3: 1.9
        8: 346         4:  306                 4: 306            4: 2.6              4: 2.5
                           5: 5.6mv?            5: 4.7             5: 2.6              5: 2.5
                           6: 5.6mv?            6: 4.7             6: 177             6: 151
                           7: 2.7                  7: 2.7             7: 3.1              7:
                           8: 40.8                8: 40.8           8: 10               8:  1.9
                                                                           9: 2.2              9: 2.2

Filter caps:  22uf:  346    16uf: 307   16uf: 232

Thank you once again. 

[tylerrussell]

Also, the PT is a Hammond 290AX. The OT is a Hammond 1750E

[sluckey]

V2 pin 8 should be about 40V. Be sure you have correct value resistors in that circuit. Turn the amp off and measure resistance from V2-8 to chassis. Should be about 57KΩ.

V3 and 4 pins 8 should be about 20V. 40V implies the tubes may be running way too hot. Verify you are using a 250Ω resistor on pins 8. Also, V3 pins 5 and 6 are showing 4.7V. Maybe you forgot to call it 4.7mV? Should be zero but 4.7mV is close enough. That's probably just a meter thing.

All your filament voltages are low. Recheck those. Don't measure with reference to chassis. Put both your meter probes directly on the tube sockets. For the 6V6 sockets one probe goes to pin 2, the other goes to pin 7. For the little tubes, one probe goes on pin 9 and the other goes on pin 4/5. Be sure pins 4 and 5 are tied together.

[tylerrussell]

V2 pin 8 to chassis is: 59k. Resistor pin8 V 3 is: 248.
Yes, V3 pins 5/6 are mv; sorry.
V3 and 4   across pins 2/7 is 5.8
V2 across pins 9 and 4/5 is 5.8
V1 across pins 9 and 4/5 is 0.
Seems like v1 needs some looking into.
Thank you. I'll be back.

[tylerrussell]

OK. Re-touched V1 solder joints @ pins 9 and 4/5. Have 5.8 there solidly.  Unfortunately, she's still very quiet and distorted.
  I'll go over input and output jack wiring (for the 16th time) Actually, no. I'm confident there!

[tylerrussell]

V3 and 4 pins 8 should be about 20V. 40V implies the tubes may be running way too hot.

Since 40V at pins 8 on the 6v6's is high; is that related to the cap with the resistor? 250ohm 5W/25uf 50V Cap. That cap is oriented the same as the large filter caps. Where's the additional 20V coming from?

[sluckey]

It's coming from the excessive current flowing thru the 250Ω cathode resistor. 40V across 250Ω means 160mA is flowing thru that resistor! That current splits and hopefully half flows thru each tube. That's 80mA. And with 300v between plate and cathode means each tube is burning at 24W at idle. A 6V6 is only rated for 14W! I would think the plates would be red. Those tubes won't live very long. I'd replace that 250Ω cathode resistor with a 500Ω resistor for now just to protect the tubes. The tubes may already be dead and could be a factor in your low volume.

The voltage on V2-8 is still an issue.

[tylerrussell]

Ooops. Is pin 8 on V2 DC? On DC it reads 44.6.     Also, pin 8 on the 6V6's are 18.8DC. I apologize for the mis-understanding of the AC/DC thing. Hopefully, this makes more sense now? Does that 250ohm/25uf 50V resistor/cap play into this?

[Willabe]

I'll go over input and output jack wiring (for the 16th time)

Here's a great way to recheck a build;

http://el34world.com/Forum/index.php?topic=17701.msg178630#msg178630


             Brad   

[tylerrussell]

Thanks for that. I'll (once again) go over all of this in the next few days. It's gotta' be something, right? I truly appreciate all of the input from you guy's. I'll be back.

[tylerrussell]

The whole problem was my printer! Actually, I printed the layout in greyscale~and since I'm apparently blind in one eye and can't see out the other, the blue wire from the .022 to the 1M (and ultimately to V2 pin7) was           omitted. Very sorry for the unnecessary questions and all. She sounds very good so far. Looks like "color" printing is in order. Thank you all again.

[Willabe]

Hey, glad you found it Tyler!     

Very sorry for the unnecessary questions and all.

Not unnecessary at all, amp wasn't working right.   

We have ALL missed things for 1 reason or another.

Actually, I printed the layout in greyscale~and since I'm apparently blind in one eye and can't see out the other, the blue wire from the .022 to the 1M (and ultimately to V2 pin7) was omitted. Looks like "color" printing is in order.

Sorry to hear that. And if printing in color works better for you, then by all means, do it.


                          Brad     

[HotBluePlates]

... blind in one eye and can't see out the other ...

And a Jerry Reed fan? 

Good job catching the missing jumper. I think we've all learned the hard way a poorly-functioning new-build generally has some simple build-error floating around somewhere.