5E5A Speaker jack output mod

[russmanr]

Hi there,

I have a Weber 5E5A (head only), and would like to change
the output speaker jacks, such that I have a 4-ohm output and
an 8-ohm output. The layout calls for only 1 output, with an extension
speaker jack tied to it.

https://taweber.powweb.com/store/5e5a_layout.jpg

I think I just need to disconnect the link between the 2 jacks
(tip to tip connection), and then just wire the 2nd output from the
OT to the 2nd speaker jack. Does that sound right?

Thanks,
Rich

[MWJB]

Yes, but you also need to disconnect the switch to ground link on the main 8ohm speaker jack, otherwise the OT secondary will be shorted if you plug into the 4ohm tap. In brief, neither your 4ohm tap, nor your 8 ohm tap should have shorting jacks.

[russmanr]

OK, thanks! The confusing thing for me was the connection from the 100K resistor to the primary jack.
Once I make the mod, it seems that won't be linked to the 2nd jack at all; because I am disconnecting
the tip-to-tip connection between the two jacks.

[jmaf]

Hi russmanr, that sounds right.

Just unsolder the T terminal and solder the 8 ohm OT wire to it. Leave the negative feedback and other wiring on the other jack, as that resistor has been calibrated for the voltage coming from the 4 ohm out.

[jmaf]

MWJB is right, you should unsolder the switched terminal as well. A disadvantage is that removing that switch will remove the protection against flyback in the OT in case someone pulls the plug from it while you're playing.

[russmanr]

Thanks very much. I will get on it now.

[MWJB]

The 100K NFB resistor is still connected to the 4ohm jack via the OT secondary winding. So you still have NFB irrespective of which jack you use...you might want to experiment with a compromise value that works with both output taps...if you are not happy with the tone from the 4ohm jack. I'd try 56K, or something between that value and 100K.

[Wittgenstein]

I'm not sure how feasible it would be for you, but you might consider adding an additional 3/8" hole for a on/on (DPST) switch. That way you can leave the second jack hooked up as a external and select from 4 or 8 ohms with the switch. I added two additional jacks to my chromed out 5E3 chassis so I could do this with 4, 8, or 16 ohm for the most amount of options.

[russmanr]

OK, so am going to go with the impedance switch option.

In the meantime, however, I decided to wire up the 8 ohm
tap ONLY. I left the 4 ohm tap disconnected.

When I turn the amp on, I get terrible low-frequency
feedback, as soon as I hit a note on the guitar.
I swapped out the pre-amp tubes with no change.

Yikes, I guessed I messed something up... any ideas to start
my troubleshooting journey?

[Wittgenstein]

OK, so am going to go with the impedance switch option.
In the meantime, however, I decided to wire up the 8 ohm
tap ONLY. I left the 4 ohm tap disconnected.
When I turn the amp on, I get terrible low-frequency
feedback, as soon as I hit a note on the guitar.
I swapped out the pre-amp tubes with no change.
Yikes, I guessed I messed something up... any ideas to start
my troubleshooting journey?

Could you explain further what you mean by low-frequency feedback? Does it only happen when a guitar is plugged in and playing? Does the volume or tone knob effect the feedback? Does it sound worse when you play certain notes vs others?

Without further information, it sounds to me like a microphonic tube. I see that you swapped out the pre-amp tubes, which is a good start, but did you try a new rectifier?

If it is more of a high pitches squeal that is present without guitar and independent of the volume, then you should swap the two output transformer secondaries (wire to B+ & center tap to ground).

[russmanr]

Thanks for the quick update. Maybe the correct term was "oscillation".
I reversed the 2 output transformer wires to the power tubes and it
seems to have fixed it.

[Wittgenstein]

Woot, glad to hear it! I had to do the same on my 5F1 Champ on fire-up. When wired backwards is was providing positive feedback (oscillation, squealing, etc...) instead of negative feedback (lower gain/distortion).

[russmanr]

Great.. can I just say that this is the greatest amp in the known world?
I have it running into a 2x12 cab with Eminence RedCoat Man-O-War's,
and I can dial up anything from The Beatles to Black Sabbath with my
guitar's volume control alone!