Those little twiddly things used to close lastic bags, superseded by

The ziplock bag

The HMV gramophone, superseded by
The Dansette record player, superseded by
The compact cassette player, superseded by
The Compact disc player, superseded by
The Digital Video Disc player, now superseded by
The BluRay disc player.

Whatever next ? ? ?

Dyson products
The wheelie bin
That classic hifi amp who's name I've forgotten

Got it . . . Quad

All parts of the Apollo space programme

The Land Rover

Concorde

Cat's eyes (1933).

First off, what do you mean by adjustable voltage? If you mean adjustable output, it is the flash duration that is adjustable, not the voltage.

To achieve your goal, you'll need either:-

A manual flash with adjustable output on the camera to trigger . . .
one or more slave flashes with adjustable output and slave sensors. The onboard flash will not work properly to trigger anything other than a P-TTL capable flash, so don't waste time trying. Or . . . you'll need

A radio trigger setup like the Cactus V4 devices, and as many old manual flashes of any make as you want. This is by far and away the best solution as it means you don't have to have a flash mounted on the camera. You have total control.

Arguably the best value for money flash to suit your needs is the AF500FTZ. It has adjustable output power ad is very powerful.

Oggy,

Did you not read the part of my previous post where I wrote "ALL Pentax flashes are safe to use on ALL Pentax SLR's, film and digital"?

The oldest flashes I have used on several Pentax DSLR's are probably the AF160, AF240T, AF280T and the AF400T. The latter 2 have analogue interfaces to the hot shoe, very old-tech. Current flashes from, I don't know when, use a digital interface, including the AF140FC that Jack has now sold.

I had one and got some great images from it and my *istD, *istDS, K10D, K20D. I only sold mine when I got the AF160FC.

The 'High Trigger Voltage' phobia is only really relevant to third party makers like Vivitar etc. And only then, applies to there older kit.

Of course there is Oggy, but no Pentax flash will exceed it.

High trigger voltages are usually found in very old flashes from mostly independent makers.