New 5E3 build - great sound; at unamplified guitar level...

[loudthud]

There doesn't seem to be any capacitor across the V1 cathode resistor (820 ohm). When one channel is used, an out of phase signal comes out of the other channel at slightly reduced volume. Make sure the volume control on the un-used channel is turned all the way down to prevent signal cancellation.

Try to route the wires that go to the volume and tone controls away from the input jacks as much as you can.

[Intergalactic Tourister]

as Sleeve and Switch are jumpered together and thus both at ground potential.

You said it better than I.

The symptom to me sounds like all your signal is bleeding out to ground

The switch (on the input jack) is positive. And you have it jumpered to the sleeve? All your signal is going from the switch (which touches the large positive tip when your cable is connected) directly to ground.

You have the resistor (on the input jack) connected from the positive switch lug (where yellow wire and the resistor connect) to the other positive tip lug (where the black jumper wire and resistor connect). The resistor is redundant connecting positive switch to positive tip.

The resistor should connect positive switch lug (where yellow wire is connected) to negative sleeve lug on the input jack. Its a grid leak resistor I would think.

At least that is what I'm seeing from here.

And I'm speaking only about the input jack. Don't worry about any connections after it (like V1 or tube pins).

[Intergalactic Tourister]

Also, look at what big_teee replied.

The first .pdf link at triodestore shows the resistor connected from positive switch lug to negative sleeve lug.
That is a good layout that should help.

[Intergalactic Tourister]

Just in case:

On the input jack... there is one negative lug and two positive lugs.

You should not have a black jumper wire connecting the negative lug to any of the two positive lugs.

[Intergalactic Tourister]

It also appears like the switch on the input jack is bent. It doesn't look like the switch will ever make contact with the positive tip once your guitar cable is inserted into the jack.

[FreddieRay]

Hello all,

Now that I'm back, let's pick this up again. I carefully reread every reply you guys posted, now I would like to summarize everything we got so far.

I recommend You wire both Jacks and both 68k resistors like the layout. Then if it doesn't work go from there.

That is how I started: with both jacks wired, using the Weber layout as a guideline. And this wiring gave me the exact same problem as I have got now (which from the start made me assume that there was nothing wrong with the input jack wiring). So I rewired the inputs, hoping that would solve my problem - it didn't.

Then loudthud suggested me to check input resistances, this is what I read:

With no cable plugged in:
- Pin 2: 67K to ground
- Pin 7: 77K to ground

With an open ended cable plugged in:
- Pin 2: 1348K to ground
- Pin 7: 1246K to ground

Cable tip to ground: 1286K.

Cable tip to pin 2: 67K.
Cable tip to pin 7: 77K.

He said this was ok. If my input wiring had been wrong, had he not seen wrong resistance values here? Then I started thinking with my limited knowledge of electronics, and I came up with this quick drawing. On the left, my input wiring, on the right, how it should have been according to the Triode layout that big_teee posted (with and without jack inserted). Am I right if I conclude that there is no electrical difference between left and right? Would that be confirmed by the correct resistance values I read when performing loudthud's tests?



Then I considered this:

There doesn't seem to be any capacitor across the V1 cathode resistor (820 ohm). When one channel is used, an out of phase signal comes out of the other channel at slightly reduced volume. Make sure the volume control on the un-used channel is turned all the way down to prevent signal cancellation.

But turning one volume control down and the other one way up still didn't solve anything.

I guess we're back at the low heater voltage thing again now: 2,8V at 4/5 and 9 etc which gives me a total of 5,6V. Would this really be too low for the tubes to properly turn on? The preamp tubes don't get really hot, and they glow quite dimly (although this could be normal, I have limited experience with tubes).

Any more ideas? I'm thinking about giving up, pulling everything out and redoing the entire amp more neatly and with all the wires on top of the board, taking care to keep cable lengths at an absolute minimum and dressing them properly. Would that make sense or should I keep looking until I have found the problem?

Thanks again for all your help

[big_teee]

With the good B+ voltages, the rectifier heater voltages must be plenty good.
It runs off it's own 5V AC Heater circuit.
So the Heater voltage in question is the 6.3V AC.
I wouldn't rip it apart, but I would rewire and tight twist the Heater Circuit.
In the process I would check the heater voltage at the source, with the heater chain disconnected, and all the tubes removed.
I would finish wiring the other jacks, add the capacitor at the end and make it complete.
The Fender site has the 57 reissue detailed Schematic with test points, and voltage readings.
Dig In.
We all have issues and hard to find probems at times.
Good Luck,
Terry

[FreddieRay]

Hello everyone,

It's been a while since I last posted in this thread. I had put this project aside for some time, but last week I picked it up again, and decided to redo all the wiring inside the amp, and make some adjustments for my circuit to again match the original schematic.

Outcome: I still get the same low volume from the amp (a bit louder than an unamplified electric guitar).

What we have now is this:

- For the board itself and the connections to the tubes, I followed the original fender layout without any modification.
- The input jacks are wired like this:


- The output jacks are wired like this (forgive me the quick drawing but I think it should be clear):


- The heaters are wired like this: green&green from PT secondary, each to a lug on the lamp socket, then on to the rest of the circuit. The green/yellow from PT secondary is connected to the last ground point on the board (more precisely, the negative side of the last 25µF cap). Heater voltage is fine now: I measure a steady 6V (that's not too low now is it?) across the 2&7 and 4&5/9.

- The voltages:

V1
pin 1: 131 V
pin 2&7: 0 V
pin 3&8: 2 V
pin 6: 119 V

V2
pin 1: 121 V
pin 2: 0V
pin 3: 1,8 V
pin 6: 179 V
pin 7: 5,7 V (that's normal, right?)
pin 8: 62 V

V3 & V4
pin 3: 396 V
pin 4: 352 V
pin 8: 22 V

V5
pin 2&8: 402 V
pin 4&6: 328 V

- There is a crackling noise when turning the bright volume pot; I measured for DC leakage and got a 25 mV reading. Is that problematic? While I was at it, I checked the other caps for DC on the wrong side - there was none (except on the .02 µF cap, but that's normal, right?).

Then, I took the Fender schematic big_teee was talking about in his last post, and started testing, comparing my voltages with the ones indicated. In doing this, I found one consistent anomaly: the AC signal levels were all way low (as I have no formal knowledge of electronics, I can't know if this matters, but it is the only thing I found that differed):

- 1,4 V into both volume pots, instead of the specified 3,79 V
- 8 V into the second half of V2, instead of the specified 17,4 V
- 8 V into both power tubes, instead of the specified 16,7 V

That's about it. Any further suggestions? I tried with another speaker, I tried with different tubes (but not power tubes; should I swap those?), I tried with different cables, different guitars, etc... Hell I feel like I tried anything Should I just take it to an amp tech?

Thanks in advance!

Fred

Edit: One more thing came up today. With both power and standby switched on and the volume/tone controls to zero, the behavior of the amp is not always the same. Sometimes it puts out a faint 100Hz hum, sometimes it puts out nothing (dead silence). Slightly turning the scratchy pot up and down brings the hum back/makes it go away. All this has no effect on the volume nor the sound characteristic of the guitar coming through.

[MWJB]

V2 pin 7 should be much more than 5.7vdc. It should be 62vdc at pin 8 less cathode voltage drop accross the 1.5K resistor at pin 8...so in the region of 60.5vdc.

Voltages at V1 suggest that you have a 12AY7 in V1? This could be why your AC voltages do not match the Fender schem. Please stop posting digrams of what you have done, we need to see what you ACTUALLY have done, not a translation of that, or what you INTENDED to do. AC voltages suggest inputs are correct, show pics of tube socket wiring & speaker jack wiring.

Voltage at V2 pin 1 seems low, do you have a 12AX7 here? List the voltages at the "+" of the 3 filter caps.

[FreddieRay]

Hello MWJB, thank you very much for your reply.
I didn't think the V2 pin 7 voltage would be an issue, as pointed out by loudthud earlier in this thread:

Normally V2 pin 7 will not measure correctly. But pin 8 shows an acceptable voltage which indicates there is no problem on pin 7.

I assume this is correct?

I put in two 12AT7's during an earlier testing phase, to rule out bad preamp tubes as a possible problem. I had those lying around and I was sure they were good, that's why I put them in.

The voltages at the + side of the filter caps are 406 V, 358 V and 252 V.

You can find detailed pictures of the insides of my amplifier here. Hope this helps pointing towards my error(s)!

[MWJB]

You measure the voltages at V2 pin 7 & 8 right at pin 8 of the tube socket, then at the juction of the 1M, 1.5K & 56K resistors, rather than right at pin 7.

If you use different mu tubes to those on schematics & layouts you will not get meaningful voltages as each type draws more or less current, throwing out the voltages. To compare to the Fender 57 Deluxe schem you must use 2x12AX7.

[MWJB]

Can't see the output jack wiring in your pics, things aren't helped by you using the same colour wires for grids, plates, cathodes & heaters.

[MWJB]

"Then, I took the Fender schematic big_teee was talking about in his last post, and started testing, comparing my voltages with the ones indicated. In doing this, I found one consistent anomaly: the AC signal levels were all way low (as I have no formal knowledge of electronics, I can't know if this matters, but it is the only thing I found that differed):

- 1,4 V into both volume pots, instead of the specified 3,79 V
- 8 V into the second half of V2, instead of the specified 17,4 V
- 8 V into both power tubes, instead of the specified 16,7 V"

VAC you get at the OT secondaries? Apply your 100mVAC at the input, tone pot & unused vol at 12o'clock now turn up the used volume until you see 11VAC at the OT secondaries? Report back.

[MWJB]

Don't use a GZ34 with the stock 250ohm cathode resistor, rebiasing with a 330-400ohm resistor would be better, or stick to NOS 5Y3.

[FreddieRay]

You measure the voltages at V2 pin 7 & 8 right at pin 8 of the tube socket, then at the juction of the 1M, 1.5K & 56K resistors, rather than right at pin 7.

Measuring like this gives me a correct reading of 60 V.

Can't see the output jack wiring in your pics, things aren't helped by you using the same colour wires for grids, plates, cathodes & heaters.

I'm sorry about the picture quality. Here's a better one.

VAC you get at the OT secondaries? Apply your 100mVAC at the input, tone pot & unused vol at 12o'clock now turn up the used volume until you see 11VAC at the OT secondaries? Report back.

Now for this... By turning tone pot & unused volume to 12 o'clock and increasing the used volume to about 9 on the dial, I get VAC readings a little closer to the schematic (knowing I got the wrong tubes in there):

- 3V into the volume pots
- 10V into the second half of V2
- 15 V into V3 \

difference ok or suspicious?

- 11 V into V4 /

The bad thing is, I don't get any voltage reading on the OT secondary (I assume that is the green wire connected to the tips of the output jacks). Maybe it's just too low and I'm unable to read it (my multimeter goes down only to 1V in AC measurement), but that would still be a bad thing, no?

I know the GZ34 is not really a good option here. I'll track down a NOS 5Y3 as soon as I got the amp working. I have a new 5Y3 (Sovtek), but that won't make that much of a difference, will it?