DIY Mic Pre Kits, Lunchbox Mic Preamp Kits, Power Supply Kits

Please only use an 18-0-18, or 20-0-20 transformer...

at *most*, a 22-0-22 transformer will work, but the regulators will also get too hot than it needs to be, then you'd need a bigger heatsink and bring all other problems and all that... so just stick to 18-0-18 or 20-0-20 and be done with it.

Use of anything higher than what I listed above, and you run the risk of going over the voltage ratings of the capacitors in the PSU.

Don't just buy any transformer you found on a surplus store because it's cheap or what. Use the right transformer to avoid damaging your psu or preamp.

I sell transformers on my site too, and these are the same transformers I use personally. If you don't want to buy transformers from me, buy the correct rating transformer from somewhere else. But plzzzzz... use the right one.

and most of all, BE SAFE! When in doubt, STOP!

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I purchased a PSU-2448mks with the power transformer a couple years ago (red board). I finally put it to use. It works well, powering a couple of api 312s and a gssl buss compressor in a single unit. I noticed the voltage regulators were really hot to the touch. When I jumped on this forum and read this post, it raised some concern. My kit has a 22-0-22 transformer.
My secondary is 22VAC. Post rectifiers, I'm measuring +-27VDC at the power caps. Post voltage regulators, the 312s and the gssl are all reading +-16VDC at the proper points and 48VDC at the 312s as well. The unit sounds and operates great. My only concern is the voltage regulators are really hot.

Update: the power transformer with the kit is a Avel Y236104. According to their website this is rated for 18-0-18 V. I measured the transformer disconnected from the PSU and it measured 22VAC as wired per your directions (orange/red together). I'm assuming the higher measured voltage is due to no load (not connected to the circuit)?