British 18watt Kit Tremolo Noise

[Shadrock2]

Hi ALL... This is my first post. I've visited this site for years but only now have I been able to register successfully.

So I just completed a Mojotone British 18watt kit for a friend of mine and everything works pretty well except...

There is a loud motorboat sound if the dual foot switch is not plugged into its stereo jack.
This can't be normal can it?
Noise is within normal limits if the foot switch is plugged in. And the tremolo works works reasonably well except that the intensity is very sensitive to adjust. If the pot is up past about 10 O'clock it has completely cut off the dry signal.
Is that normal?
I have run a shielded cable over to the grid of V3. The layout diagram shows no connections to the switched side of the jack, but after the first couple of start ups I connected the tip switch to the shield which is grounded. This cut the the volume of the buzz in half when the foot switch plug is removed.

This is my first attempt at assembling a kit amp though I've fixed a few and designed one from scratch.

[g1]

Does the motor-boating match up to the speed of the tremolo? Do any other controls affect the frequency of the motor-boating?

[g1]

Looking again, I'm not sure why there are 2 separate switches for the trem. What are they each supposed to do?

Edit: Never mind, I see that one switch is hi/lo speed for trem.

[Shadrock2]

Thanks for the reply.
The tremolo controls have only the slightest of effect.
I understand the basic amplifier circuits but not the tremolo circuit so if anyone can give me a few clues or point me to a link with a circuit description I would appreciate.
Also with my DVM grounded, touching any component attached to pin 7 of V3 will cause the noise to stop.

I'll see if I can post some photo's tomorrow.

[Shadrock2]

I finally got a few pics of the build.

[Shadrock2]

Just wanted to add a follow-up note:

I tied all the switched lugs on the Tremolo stereo jack together so that both the speed and intensity switch connections are grounded when the foot switch is unplugged. This stopped the Tremolo related motor-boating. These connections were not indicated on the layout sheet that Mojotone provided

The works really well now with the caveat that the Tremolo intensity control is very sensitive with usable effects provided with Intensity control between 8 & 10 O'clock.

[LarsonLE]

Hey I'm a new member and just saw this post but I am in the process of building an 18 watt from mojotone as well. One thing I noticed just by quickly looking over your photos is that the filter cap near the PT/OT (the 16 uF 475V cap) is supposed to be tied to ground if I am not mistaken.