trinityamps.com

Hi. I have constructed the lightning that a sound well, the only problem is that raising the potentiometer of master and the volume the amplifier it hisses, like entered in resonance; also without input signal.

http://img103.imageshack.us/my.php?image=mod18tq.jpg

http://img120.imageshack.us/my.php?image=mod20wk.jpg


The 2° photo is a filter on a filaments central tap secondary.

I need help!!!!

P.S. I'm Italian and my English is not well, i hope you understand me.

Try this first - just unsolder and reverse the two wires that go from the output transformer to the two output tubes pin 7.

Don't change anything else for now.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thank you...
It works well!!!
Beautiful clean sound, and good punch.

WOW!!!



WONDERFUL AMPLIFIER

Glad it all worked out for you. This is a fairly common problem in tube amps.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Hi
This is my first post, thanks for a great forum, I've been reading
posts on this forum for a while now gathering ideas on what to
build.

The output resonance and hiss problem fixed by reversing the wires to the output transformer, it solved the problem but why?
Can someone please explain it to me?

The push and pull configuration is driving the positive and negative
halves of the signal in the transformer input, the output of the transformer is isolated from the input, the magnetic field is the only
thing connecting the two. Where can this resonance come from?

Espen:

Reversing the output transformer leads can work because one of the primary leads is in phase with one of the secondary taps. In a high gain amp, this phase relationship needs to be maintained.

So this is simply maintaining a phase relationship on the trasnformer/output stage.

Squealing/Feedback usually occurs when there is coupling between the input and output stages. The positive feedback causes the amp to become an oscillator. Vary the volume and tone controls to see if it affects the oscillation. That will tell you if the coupling is occurring before or after the control. Sometimes the problem can be solved by minor changes to the wiring (moving output wires away from input wires, shortening excessively long wires, etc.).

Here are some other tips that are in our assembly manual:

Use shielded wire on the input jack to help a hum or squealing problem.

Ensure the shielded wire goes on top of the board, not underneath it.

If you've built a TMB-MV 18, you may have a squeal when you turn up the Volume & Master Volume together. Try the following to eliminate it:

1. Move the 470K grid stopper resistor to attach directly to pin 2 of V3.
2. Use shielded wire from the TMB Volume pot wiper to the resistor.
3. Connect wire shield to the socket, or chassis at V3; some people prefer to attach to the potentiometer.
4. Reduce the 470K value (to 68K min.) until the squeal goes away; 68K will give you a nicer impedance, but if you are going for gain, just bypass that resistor with shielded wire and enjoy.
5. If all that doesn't work reverse the output transformer leads on pin 7 on V4, V5.
6. If step 5 was necessary, you might be able to return to 470K grid stopper resistor value. Note: If you are looking for gain, you could omit the grid stopper or bypass it with a cap. If not, you should try to leave it in there. This point in the design happens to have the most effect on gain.

In extreme cases, you may need to ground the output jacks to the chassis.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thank you 'coco' I gained some insight on the OT transformer issues
that can lead to resonance.

On another note, how close is the Trinity 15 schematic to the
Matchless Lightning, in terms of component values?
Of course component placement/wiring is different due to
point-to-point versus eyelet/turret board layout.

I've got 2 versions of the Matchless Spitfire schematic '2-9-94' with
5 DC filter caps and 250uF cathode cap. The other one
with 25uf cathode cap and 4 DC filer caps, which one is correct
, or is both correct? just Matchless that changed the circuit
over the years?

Has anyone got the what can be called a 'correct' schematic for the
Matchless Spitfire & Lightning?


Espen / EHansen(on the 18watt forum)

espen,

See viewtopic.php?t=500

This is the correct schematic. I have a new one I will post with a cut control.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps