Anyone got a Variac transformer?

[Spur07]

Hi all

Wasn't sure where to put this request, but thought DIY might be the best option.

Does anyone living in the Surrey area have a variac transformer they could kindly lend me for an hour?

I got some old tube amps I need to bring back from the dead and don't really want to buy one especially for the task.

No worries if not.

Cheers.

P

[Firebottle]

If you can't beg borrow or steal one the next best thing is to wire a standard 60W incandescent light bulb in series with the mains input.

[Spur07]

If you can't beg borrow or steal one the next best thing is to wire a standard 60W incandescent light bulb in series with the mains input.

Hi Alan

Keep hearing about this but never done it before, is there an explanation / guide somewhere on how to do this?

Cheers

[struth]

It works as a current limiter.

[Spur07]

It works as a current limiter.

Something like this dim bulb tester?

https://antiqueradio.org/dimbulb.htm

[Spur07]

I've replaced all the resistors and capacitors save for 2 original electrolytes associated with the rectifier tube and the transformer which I want to keep. The tubes have been tested as strong.

[Firebottle]

Something like this dim bulb tester?

https://antiqueradio.org/dimbulb.htm

That's it.

[Spur07]

That's it.

But does this method mean the transformer gets the full whack of mains at once though?

[Spur07]

Ok I just read somewhere that the resistance of the light bulb limits the voltage that will reach the equipment. By increasing the bulb (wattage?), you can increase the power to the equipment.

[walpurgis]

Ok I just read somewhere that the resistance of the light bulb limits the voltage that will reach the equipment. By increasing the bulb (wattage?), you can increase the power to the equipment.

Yup!

[Audio Al]

Thats a bright Idea :)

[spendorman]

It must be incandescent

[struth]

often called rough service bulbs now to get round the ban. most are useless. dare say you will be able to buy decent ones somewhere still.

[Spur07]

often called rough service bulbs now to get round the ban. most are useless. dare say you will be able to buy decent ones somewhere still.

Thanks all. I got myself one of these:

https://s2.gifyu.com/images/s-l160052bd703979ff613f.jpg

[willbewill]

https://www.thelightbulb.co.uk/light-bulbs/incandescent

[Spur07]

https://www.thelightbulb.co.uk/light-bulbs/incandescent

Thanks for the link Malcolm

[killie99]

https://www.youtube.com/watch?v=wRFRwOnLsZI

[Spur07]

So now I got my DBT and a variety of different wattage bulbs does anyone have any tips with regard to procedure?

I've been reading up on the web (and asking a few friends) for advice.

I want to see if I can use the DBT as a form of variac with the different wattage bulbs as I have 2 original electrolytes in place relating to the transformer, (as well as guard against shorts). The rest of the circuit has been replaced with new resistors and caps.

I'm thinking, with the circuit exposed for visual / smell inspection:

1. No valves - DBT 25W / 40W / 60W / 100W

2. Rectifier in place - DBT 25W / 40W / 60W / 100W

3. All valves, Output, rectifier, power, in place and dummy load - DBT 25W / 40W / 60W / 100W

4. Full mains and play music

Probably overkill I guess :) The amp output is 15 - 20W.

P

[M6NTL]

I have a Variac I'd be happy to loan you, but I'm in Leicester. I could post it, but it isn't lightweight...

Sent from my G8441 using Tapatalk

[Spur07]

I have a Variac I'd be happy to loan you, but I'm in Leicester. I could post it, but it isn't lightweight...

Sent from my G8441 using Tapatalk

Thanks for the offer, that's very kind of you. Yes, maybe it's a bit too far, probably cost £30 there and back via courier.

[lilolee]

Just saw this. Where in Surrey?

[Spur07]

Just saw this. Where in Surrey?

Thank for the response Lee. I'm in Weybridge, down the A3.

I got my amps up and running now using my dim bulb tester. They seem to be ok.

Where are you based out of interest?