Re: DEC H7140 (11/44) power supply revisions and general advice?

> From: Mattis Lind > Very nice and clear description on what is required to have relay to > activate! Indeed! Thanks, Brent, for that wonderful writeup - I'm sure I'll find it immensely useful when the time comes to work on my 11/44. I'll have to carefully save a personal copy in a

Re: DEC H7140 (11/44) power supply revisions and general advice?

2015-10-11 5:44 GMT+02:00 Josh Dersch : > On Sat, Oct 10, 2015 at 2:38 PM, tony duell > wrote: > > > > > > > From a quick glance at the schematic I think that this part is related > to > > > the fan driving circuitry. The diodes look like some kind

RE: DEC H7140 (11/44) power supply revisions and general advice?

> > The bias voltage is generated by the chopper on page three in conjunction > with T1 and some rectifying diodes on the motherboard. Then it is feed back > to the bias board on J2:2 to produce the 5V. (page 2) Yes... It's not totally obvious at first glance, but this is yet another SMPSU with

RE: DEC H7140 (11/44) power supply revisions and general advice?

> > I'm slowly coming to terms with the schematic but I'm not quite clear where > these two voltages are being generated. I note from the block diagram that > the +15 and +12 are rectified on the motherboard (backplane) -- which > should make it GREAT fun to probe. So it looks like some careful

Re: DEC H7140 (11/44) power supply revisions and general advice?

On 2015-Oct-10, at 8:44 PM, Josh Dersch wrote: . . . > Thanks for the explanation. I tacked on some wires to the bias board (to > bring them out for safe probing); the wires are connected to the 5V logic > supply and the +12V bias supply and I get nothing at all out of them when > the H7140 is

RE: DEC H7140 (11/44) power supply revisions and general advice?

> > Am I missing something? - is there anywhere in that doc that explicitly > declares the > association between the 2-dozen connectors, for example, that Line Supply P1 > & P2 > connect to Motherboard J5 & J4, and that Bias and Interface Board J1 & J2 > connect > to Motherboard J7 & J6? Not

Re: DEC H7140 (11/44) power supply revisions and general advice?

On Sun, Oct 11, 2015 at 12:07 PM, Brent Hilpert wrote: > On 2015-Oct-10, at 8:44 PM, Josh Dersch wrote: > . . . > > Thanks for the explanation. I tacked on some wires to the bias board (to > > bring them out for safe probing); the wires are connected to the 5V logic > >

Re: DEC H7140 (11/44) power supply revisions and general advice?

On 10/11/15 6:19 PM, Josh Dersch wrote: On Sun, Oct 11, 2015 at 12:07 PM, Brent Hilpert > wrote: On 2015-Oct-10, at 8:44 PM, Josh Dersch wrote: . . . Note that the "+13V" supply must also be present, and it's generated and

Re: DEC H7140 (11/44) power supply revisions and general advice?

lördag 10 oktober 2015 skrev Josh Dersch : > > > On Oct 10, 2015, at 2:15 AM, tony duell > wrote: > > > >> > >> Once again, I find myself in over my head debugging a power supply, this > >> time an H7140 from a PDP-11/44. Here's the

Re: DEC H7140 (11/44) power supply revisions and general advice?

> On Oct 10, 2015, at 2:15 AM, tony duell wrote: > >> >> Once again, I find myself in over my head debugging a power supply, this >> time an H7140 from a PDP-11/44. Here's the skinny: > > That doesn't surprise me, the H7140 is one of the most complex PSUs you are >

RE: DEC H7140 (11/44) power supply revisions and general advice?

> > From a quick glance at the schematic I think that this part is related to > the fan driving circuitry. The diodes look like some kind of protection Yes. > diodes which is good to have when switching inductive loads. I have really > no idea why they have been removed. But I don't think it

Re: DEC H7140 (11/44) power supply revisions and general advice?

On Sat, Oct 10, 2015 at 8:44 PM, Josh Dersch wrote: > On Sat, Oct 10, 2015 at 2:38 PM, tony duell > wrote: > >> > >> > From a quick glance at the schematic I think that this part is related >> to >> > the fan driving circuitry. The diodes look like

Re: DEC H7140 (11/44) power supply revisions and general advice?

On Sat, Oct 10, 2015 at 2:38 PM, tony duell wrote: > > > > From a quick glance at the schematic I think that this part is related to > > the fan driving circuitry. The diodes look like some kind of protection > > Yes. > > > diodes which is good to have when switching

RE: DEC H7140 (11/44) power supply revisions and general advice?

> > Once again, I find myself in over my head debugging a power supply, this > time an H7140 from a PDP-11/44. Here's the skinny: That doesn't surprise me, the H7140 is one of the most complex PSUs you are likely to come across... > When power is applied (plugged in, breaker switch flipped to

Re: DEC H7140 (11/44) power supply revisions and general advice?

And as I just noted after Jay's response, the subject line should say "11/44" not "11/40." Corrected... - Josh On 10/9/15 8:42 PM, Josh Dersch wrote: Hey all -- Once again, I find myself in over my head debugging a power supply, this time an H7140 from a PDP-11/44. Here's the skinny: I