Slide resistor

[Radio Fixer]

Hi Lawrence

http://dx.com/p/uni-t-ut70d-3-lcd-digital-multimeter-red-deep-grey-1-x-9v-6f22-196589?tc=GBP&gclid=CP_amLLVoLsCFZQctAodKmsAKw

This is a superb meter as it can read True RMS with DSP, I needed this for one project and I'm pleased with it

Gary

[pwdrive]

Cheers.

Lawrence.

[AlanBeckett]

Or alternatively .....

   

Alan

[Bushbaby]

Hi all
Thanks for your help and guidance. The amp specifies a 3.2ohm speaker in this instance.
I have wired the resistor as per Ed Dinnings instructionas and I beleive that it must be more than 15ohms as I have the slide about an inch in from one side.

Regards

Rob

[Bushbaby]

Hi all,
I am very confused with this slide wire. I have tried to undertake fine adjustments with the slider to get to 3.2ohms. I am aware that the resistance will change with the output but the idea is just to apply a dummy load and see whether I am getting the same voltage readings as per the Fender schematic.
However, as I make fine adjustments with the slider, the resistance is not stable. The reading on multimeter shows 3 to 4ohms in one instant and then into k ohms or even M ohms in the next instant. At present, I dont feel that I could trust placing the resistor across the output transformer.

Any thoughts?

Regards

Rob

[pwdrive]

You could always use some fixed resistors of a suitable wattage rating ie: three 10 ohm resistors in parallel would give you 3.33 ohm.

Lawrence.

[AlanBeckett]

Rob,

I don't think you can just slide it about. You'll have to tighten it down using the screws to get a decent contact on the Resistance Wire.

Alan

[Bushbaby]

Hi Alan,
Apologies as I should have made this clearer, each time I have moved it I have ensured that the slider was parallel to the end and screwed down. Could dirt between the windings be a problem (it doesn't look that clean)??

Regards

Rob

[Joe]

I must be missing something but why not use a speaker? That's the exact sort of load it will ultimately be driving so would, I would have thought, be a fairer test. Of course a resistor isn't going to deafen you.

- Joe

[AlanBeckett]

Perhaps he can't stand the horrible distortion

Most Resistance Wire will have an Oxide film. You could give it a bit of a rub with Glasspaper - not Emery.

Alan