Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: Sadamson on February 22, 2019, 01:26:28 PM

Title: 240 to 120 conversion
Post by: Sadamson on February 22, 2019, 01:26:28 PM

Is anyone able to recommend a replacement power supply  (SR or not)? I built a crack several years ago and have modified it with an alps blue / bigger caps / speedball but have recently moved to Canada, where my 240v transformer isn't much good. I was thinking of rebuilding it anyway whilst also adding a few more mods and tidying up the job. I sent an email to BH asking if they would sell me a new one but the response was firmly negative - "use a step-up" being the only suggestion. 🤔

Title: Re: 240 to 120 conversion
Post by: Paul Birkeland on February 22, 2019, 01:54:46 PM

The replacement 240V transformer is NLA.  The new universal transformer won't fit the old transformer hole easily and isn't all that straightforward to wire up.

Title: Re: 240 to 120 conversion
Post by: 2wo on February 22, 2019, 04:39:09 PM

The step-up, step-down actually, is a good cost effective solution.
Hell, buy two and say you're working on a balanced power set up 😎...John

Title: Re: 240 to 120 conversion
Post by: Sadamson on February 23, 2019, 04:14:13 AM

Thanks for the replies - I actually have a couple of step-ups that I use for other things but a) want  a less unsightly solution and b) am most likely rebuilding it anyway, so would prefer to change the transformer at the same time, for a 120v one. Modifying the top plate (or even making a new one) shouldn’t pose too many issues, I simply have little knowledge about transformers and their specifications so need a bit of help to find a replacement. Anyone?

Ps thanks mods for moving the post, I had to sign up again to be able to login so assumed that I wouldn’t be able to start new threads for a bit.....

Title: Re: 240 to 120 conversion
Post by: Paul Birkeland on February 23, 2019, 07:25:34 AM

The only other transformers that fit the hole pattern don't have enough current on the 6.3V winding to heat a 6080.

There are larger transformers that could be used if you enlarged all the holes on the chassis a lot, but they all have much higher voltage B+ windings, so you would need to also use a choke input filter with critical inductance or redesign the circuit for higher voltage operation.   

Title: Re: 240 to 120 conversion
Post by: Sadamson on February 26, 2019, 06:30:43 AM

Thanks Paul, that's starting to sound a lot more complicated than the sim swap that I was hoping for. Anyone got a spare, original 120v transformer that they'd like to get rid of...😬