SE Plexi build fail

[HighFlyingV]

  Schematic :

Traced everything no luck. It has voltage at all B+ and plates , no sound. Checked input chord, guitar. changed the russian tubes.

[shooter]

check all DC voltages at cathodes.  plates provide the potential, cathodes show how well the tubes are conducting .

[PRR]

_NO_ sound?

Or a tiny hiss/hum with your ear in the speaker?

_NO_ sound suggests a short or open between OT and speaker.

[HighFlyingV]

Will do this afternoon , thanks for the reply. I built this as everyone might notice from Seward and had a lot help but currently the forum is down for a week.
I built this amp in a different configuration and did not like the result.
So I ordered a few things and reused the toroidal mantel with a different OT.
That build do not work but I thought is was because of a wrong tube that was shipped.
So this really the 3rd build with different schematics.
I am not electronics student or I wasn't until I joined a forum. Lol

[HighFlyingV]

_NO_ sound?

Or a tiny hiss/hum with your ear in the speaker?

_NO_ sound suggests a short or open between OT and speaker.

it actually has a little hum but I should have said it does not pick up a input signal or get it to the speaker. Normally an amp when plugged in to just a Cable will generate some noise. It does not.
I checked the speaker and input jack.

[eleventeen]

Are you quite sure of the pinout; eg, basing diagram of the 6P1P output tube? (I am completely unfamiliar with Russian tubes)


As I poke around, I see the 6P1P cited as "equivalent" to a domestic 6AQ5, a 7-pin tube. You understand that two tubes can be "equivalent" (which would mean; they have the same heater volts, the same mu, the same ability to dissipate heat, the same ability to handle (say) 350 volts on the plate, the same ability to put out (let's say) 5 watts given 3 volts of drive; and etc; etc; without being pin-compatible or socket-compatible. We speak of a 6AQ5 (7-pin) and a 6V6 (octal = 8 pin) and a 6BQ5 (9-pin) being 'almost the same tube'.

But you obviously cannot place a 7 pin tube in an octal socket. Nor can any of the other tubes I mentioned be exchanged because they are mechanically, physically incompatible. ELECTRONICALLY, they are considered "the same tube". They are "the same tube IF AND ONLY IF the user accomodates the different sockets they use by "translating" the plate is ____ on tube A and the plate is ___  on tube B. The cathode is ____ on tube A and ____ on tube B. For each and every tube element.


You show the input signal going to pin 7 on grid #1 aka "control grid". Just like a 6AQ5.
You show the plate being pin 1, or pin 6. You mean; you can connect to either one? Well that can't be right. (there ARE tubes that do this, but not in this case) So maybe this 6P1P is more like a 9-pin 6BQ5. OK! Let's go check that out.


Let's start over.


You show the input signal going to pin 7 on grid #1 aka "control grid". Wait a minute. Pin 7 on a 6BQ5 is da plate!!
That's enough to obliterate any possibility of this working right there.


My opinion is: The pinout you have (and from which you presumably wired up the amp) of the output tube is completely buggered.

[sluckey]

The pinout is correct on the 6P1P tube. It agrees with the pinout link from Duncan.

[sluckey]

That schematic is workable. Maybe you have a wiring error? Click the link in my signature line at the bottom of this reply for a good method to verify your wiring.

[PRR]

Do volume or tone controls change the sound any?

[HighFlyingV]

check all DC voltages at cathodes.  plates provide the potential, cathodes show how well the tubes are conducting .

Good call , no voltage on the gain stage cathodes !
The power tube has 14v at the cathode.
Perhaps I have made an error and just over looked it.

[HighFlyingV]

I think I fixed the ground on the cathode 2nd stage so I have 1.5v first stage cathode and very low .5 on the 2nd cathode . The volume does change the hum but still no input signal coming through.

[HighFlyingV]

Are you quite sure of the pinout; eg, basing diagram of the 6P1P output tube? (I am completely unfamiliar with Russian tubes)


As I poke around, I see the 6P1P cited as "equivalent" to a domestic 6AQ5, a 7-pin tube. You understand that two tubes can be "equivalent" (which would mean; they have the same heater volts, the same mu, the same ability to dissipate heat, the same ability to handle (say) 350 volts on the plate, the same ability to put out (let's say) 5 watts given 3 volts of drive; and etc; etc; without being pin-compatible or socket-compatible. We speak of a 6AQ5 (7-pin) and a 6V6 (octal = 8 pin) and a 6BQ5 (9-pin) being 'almost the same tube'.

But you obviously cannot place a 7 pin tube in an octal socket. Nor can any of the other tubes I mentioned be exchanged because they are mechanically, physically incompatible. ELECTRONICALLY, they are considered "the same tube". They are "the same tube IF AND ONLY IF the user accomodates the different sockets they use by "translating" the plate is ____ on tube A and the plate is ___  on tube B. The cathode is ____ on tube A and ____ on tube B. For each and every tube element.


You show the input signal going to pin 7 on grid #1 aka "control grid". Just like a 6AQ5.
You show the plate being pin 1, or pin 6. You mean; you can connect to either one? Well that can't be right. (there ARE tubes that do this, but not in this case) So maybe this 6P1P is more like a 9-pin 6BQ5. OK! Let's go check that out.


Let's start over.


You show the input signal going to pin 7 on grid #1 aka "control grid". Wait a minute. Pin 7 on a 6BQ5 is da plate!!
That's enough to obliterate any possibility of this working right there.


My opinion is: The pinout you have (and from which you presumably wired up the amp) of the output tube is completely buggered.

You might be over thinking this but in amp knowledge you got me. point being the 6p1p has been used by many folks successfully and this schematic was drawn for use of the 6p1p and not any other tube. It works as described but don't ask me why or why mine is not working. Lol

[kagliostro]

Go on verifying the circuit

Franco

[HighFlyingV]

Do volume or tone controls change the sound any?

I now have the volume controlling the hum so it works in that department.

[Tone Junkie]

Check the link at the bottom of Sluckey page . Trace down start to finish crossing off every wire as you go. Has helped me many times finding a problem.
Thanks Bill

[John]

Make sure you haven't done something silly like have your coupling cap on the wrong side of your plate load resistor. Try bypassing the pots (one at a time), maybe 1 is dodgy/sending signal to ground, maybe a hair thin piece of solder is grounded. It's almost got to be something really simple. At least, most of my mistakes are.


Oh yeah, if you've used shielded wire, make sure there's no continuity between shield and conductor wire. That's driven me nuts a couple times.

[shooter]

I have 1.5v first stage cathode and very low .5 on the 2nd cathode

you're there, almost, follow the link Sluckey uses and you'll be jamming soon,
 n smarter - Bonus

[HighFlyingV]

Make sure you haven't done something silly like have your coupling cap on the wrong side of your plate load resistor. Try bypassing the pots (one at a time), maybe 1 is dodgy/sending signal to ground, maybe a hair thin piece of solder is grounded. It's almost got to be something really simple. At least, most of my mistakes are.


Oh yeah, if you've used shielded wire, make sure there's no continuity between shield and conductor wire. That's driven me nuts a couple times.

Good advice John thanks. I have been following the tips from Sluckery but I do think you are on to something here John.
 I do feel it is something simple. Every time I have a light bulb moment it's seems to not be significant . I thought I had it with the ground. I wish I knew a little more about these circuits.
I have the pre-amp book from Valve Wizard  but that is like reading a dictionary. Lol
I gave up for today , back at it tomorrow. I have lost a lot of playing time with this obsession but it's fun.

[HighFlyingV]

Do volume or tone controls change the sound any?

It seems now that I fixed one ground it does work . Still just hum but it controls the hum up or down so I guess that is good.

[tubeswell]

Have you got the wiring to the plate and cathode pins mixed up on the pre-amp tube socket?

[HighFlyingV]

You made me look again, lol. No but I am trying bypassing the tone stack.

[tubeswell]

Go through the amp with your R-meter and check for DC-continuity between all the ground-sides of the component leads and the chassis, especially the ground-sides of the ilter caps, the cathode resistors, and the pots . (Just to check that you haven't omitted a ground return wire/connection somewhere)

[HighFlyingV]

I got it  It must have been the tone but I think I had the Volume and gain pots goofed up.
I looked at the 5F1 champ layout on another site and finally un-buger it 
Oh , I forgot. Thanks to everyone for your help. !

[HighFlyingV]

The result :