RE: H7861 PSU issues

; Chiappa via cctalk > Sent: 02 November 2017 16:24 > To: cctalk@classiccmp.org > Cc: j...@mercury.lcs.mit.edu > Subject: Re: H7861 PSU issues > > > From: Rob Jarratt > > > when I replaced it and powered on there was a big bang > > What went 'bang'? (I

Re: H7861 PSU issues

> From: Rob Jarratt > when I replaced it and powered on there was a big bang What went 'bang'? (I assume if there was a loud noise, it mus have left visible damage somewhere.) Noel

RE: H7861 PSU issues

cmp.org > Cc: j...@mercury.lcs.mit.edu > Subject: Re: H7861 PSU issues > > Thanks! It was very satisfying and not the worst thing to go wrong for a > beginner. > > I was also quite surprised that such a simple component would die, and what I > find more confusing is that it died while I was u

Re: H7861 PSU issues

>I was also quite surprised that such a simple component would die, >and what I find more confusing is that it died while I was using >the machine. A 555 can also take a Commodore PET down because it's solely in charge of the RESET circuit, and no RESET == no PET. On 2 November 2017 at 14:22,

Re: H7861 PSU issues

Thanks! It was very satisfying and not the worst thing to go wrong for a beginner. I was also quite surprised that such a simple component would die, and what I find more confusing is that it died while I was using the machine. Aaron. Noel Chiappa via cctalk wrote: >

Re: H7861 PSU issues

> From: Aaron Jackson > Picked up a few 555s and sockets and now it works! Congratulations! It's odd that a 555 failed, but sometimes there's no rhyme or reason to what fails. E.g. I was fixing some broken M7859's (KY11-LB Programmer's Console), and on one of them a 7493 (4-bit counter)

RE: H7861 PSU issues

t.me.uk > Cc: 'General Discussion: On-Topic Posts' <cct...@classiccmp.org> > Subject: Re: H7861 PSU issues > > Picked up a few 555s and sockets and now it works! I am very happy. Going > from not knowing how switch mode power supplies work, to watching some > YouTube

Re: H7861 PSU issues

nt: 31 October 2017 21:26 >> To: cct...@classiccmp.org >> Subject: Re: H7861 PSU issues >> >> Just had another look after watching a video about how switch mode power >> supplies work On the small control board connecting to J4, there are > two >> D44Q1 transi

Re: H7861 PSU issues

; > Jackson via cctech > > Sent: 31 October 2017 21:26 > > To: cct...@classiccmp.org > > Subject: Re: H7861 PSU issues > > > > Just had another look after watching a video about how switch mode power > > supplies work On the small control board conne

RE: H7861 PSU issues

not sure if this is a sign of any kind of problem. Regards Rob > -Original Message- > From: cctech [mailto:cctech-boun...@classiccmp.org] On Behalf Of Aaron > Jackson via cctech > Sent: 31 October 2017 21:26 > To: cct...@classiccmp.org > Subject: Re: H7861 PSU issues > &g

Re: H7861 PSU issues

Just had another look after watching a video about how switch mode power supplies work On the small control board connecting to J4, there are two D44Q1 transistors. As expected, there is about 65KHz going into the base of the transistor for the 5V side. However, there is no signal going into

H7861 PSU issues

Hi everyone, I've been trying to figure out what is wrong with the 12V rail on my H7861 (BA11-S) power supply. It's showing about 4.2V. The 5V rail is spot on. Page 39 of the following schematics is the main part board of the PSU. http://bitsavers.org/pdf/dec/qbus/MP01233_BA11-S_schem_Mar81.pdf