Get yourself a largeish 24V transformer, I use an old 8A Stancor: http://www.glitchwrks.com/images/dec/pdp1110_psu_repair/5411086_under_test.jpg
The AC input can be between 20-30V so it's not critical. Plenty of other "control transformer" type units would do fine. You shouldn't need a lot of current on the 15V rail. Thanks, Jonathan ------- Original Message ------- On Wednesday, January 26th, 2022 at 19:22, Rob Jarratt via cctalk <cctalk@classiccmp.org> wrote: > > -----Original Message----- > > > > From: W2HX w...@w2hx.com > > > > Sent: 27 January 2022 00:11 > > > > To: r...@jarratt.me.uk; Rob Jarratt robert.jarr...@ntlworld.com; General > > > > Discussion: On-Topic and Off-Topic Posts cctalk@classiccmp.org > > > > Subject: RE: Testing H745 Regulators > > > > Any chance you have a second supply you can parallel with the one you're > > > > using? Some bench supplies are dual supplies and have a parallel mode so > > > > you can benefit from both sides of the supply and they can track the same > > > > voltage. Or just put two supplies in parallel with the same voltage set on > > both > > It is already a twin PSU, I am using one half to power the AC input and the > > other half to power the +15V input. > > I do have a separate bench PSU I could use for the +15V and twin up the > > actual twin PSU, so I might try that next. > > > 73 Eugene W2HX > > > > Subscribe to my Youtube Channel: https://www.youtube.com/c/w2hx- > > > > channel/videos > > > > -----Original Message----- > > > > From: cctalk cctalk-boun...@classiccmp.org On Behalf Of Rob Jarratt via > > > > cctalk > > > > Sent: Wednesday, January 26, 2022 6:42 PM > > > > To: General Discussion: On-Topic and Off-Topic Posts > > > > cctalk@classiccmp.org > > > > Subject: Testing H745 Regulators > > > > I am trying to test a couple of H745 regulators with a DC bench PSU and I > > am > > > having some problems with testing them. > > > > My bench PSU is a twin unit so I can supply the +15V required as well as > > the > > > "AC" input using 20VDC from the other half of the bench PSU. The problem > > is > > > that I don't think the bench PSU can supply enough startup current to > > allow > > > the regulator to run. It can only supply 5A max. > > > > I have seen with the H744s that if I put too big a load on them, then they > > > > can't start because of the heavy startup current required. I can start > > them > > > with a lower load and then add load once the regulator is running without > > > > breaching the current limit of the PSU. > > > > With the H745s I have tried reducing the load to see if I can get them to > > start, > > > but a 10R load appears to be too much and the regulators draw the full 5A > > > > without outputting -15V. > > > > I have two H745s, both exhibit the same behaviour. I suppose they could > > > > both have the same fault, but I am inclined to think that perhaps they > > need a > > > higher startup current than I can supply. Can anyone confirm this? > > > > Thanks > > > > Rob
