>
> There were two VT220 designs (I think), using either an onboard or
> offboard flyback. The part number of the onboard flyback is 16-26299-01,
> and there are some available on eBay if you are feeling rich.
>
I don't want to hijack Rob's thread too much :-)
I actually have one of each design
osts' ; 'Mattis
> Lind'
> Subject: RE: VAXmate PSU fixed, but no video
>
> It is not my design, Tony Duell sent it to me and I think he got it from a
> magazine many years ago. I will try to find it.
>
> Regards
>
> Rob
>
> > -Original Message-
> >
n-Topic and Off-Topic Posts ; 'Mattis
> Lind'
> Subject: Re: VAXmate PSU fixed, but no video
>
> On 2020-04-18 11:09 AM, Rob Jarratt via cctalk wrote:
> > I checked Q6 (in circuit), it is not shorted. I have already checked all the
> electrolytic capacitors for a bad ESR
arning to design a pwm flyback controller which is
more or less the same thing in principle?
--Toby
>
>
> Regards
>
>
>
> Rob
>
>
>
> From: Mattis Lind
> Sent: 18 April 2020 13:31
> To: r...@jarratt.me.uk; Rob Jarratt ; General
> Discussion: On-T
I don't have an LCR meter but I think it might be a good idea to get one.
Regards
Rob
> -Original Message-
> From: cctalk On Behalf Of Aaron Jackson
via
> cctalk
> Sent: 18 April 2020 15:13
> To: Peter Coghlan ; General Discussion: On-Topic
> and Off-Topic Posts
>
circuit some years ago). I don’t think you can do ring tests in
circuit can you?
Regards
Rob
From: Mattis Lind
Sent: 18 April 2020 13:31
To: r...@jarratt.me.uk; Rob Jarratt ; General
Discussion: On-Topic and Off-Topic Posts
Subject: Re: VAXmate PSU fixed, but no video
Den
> -Original Message-
> From: cctalk On Behalf Of Peter Coghlan
via
> cctalk
> Sent: 18 April 2020 12:57
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: VAXmate PSU fixed, but no video
>
> >
> > Some of you may recall seeing me p
>
>
> One approach to testing flyback transformers seems to be to use a circuit
> that causes them to ring and observing whether the ringing is damped by
> shorted turns. I've never got around to trying this myself.
>
>
I have a VT100 that failed with some smoke coming out of the center of the
>> 1. If the EHT lead was not properly connected to the CRT anode, could
>> that cause problems?
>
> Possibly. I have VT220 terminal which was making a smell of ozone when it was
> running which I should have done something about but never got around to.
> This could have been due to corona
Den lör 18 apr. 2020 kl 13:26 skrev Rob Jarratt via cctalk <
cctalk@classiccmp.org>:
> Some of you may recall seeing me post about the VAXmate PSU failure. Thanks
> to members of this list I found the failed part in the PSU and the PSU is
> now working again. However, it looks like
>
> Some of you may recall seeing me post about the VAXmate PSU failure. Thanks
> to members of this list I found the failed part in the PSU and the PSU is
> now working again. However, it looks like the PSU failed because of a
> failure on the monitor board. There is a burning sm
Some of you may recall seeing me post about the VAXmate PSU failure. Thanks
to members of this list I found the failed part in the PSU and the PSU is
now working again. However, it looks like the PSU failed because of a
failure on the monitor board. There is a burning smell coming from
On Fri, Apr 10, 2020 at 10:14 AM Rob Jarratt via cctalk <
cctalk@classiccmp.org> wrote:
> D12 is an MBR3045PT. It tests correctly as a common cathode diode network.
> However, the forward voltage seems to be 0.19V. The datasheet (
>
Rob Jarratt via cctalk wrote:
> Thanks Eric, I had a private reply that said pretty much the same thing.
>
>
>
> Last night I replaced the shorted diode and another electrolytic capacitor
> and the PSU started up on the bench, powering a load board and an RD53 hard
> disk. Ripple was good
:05
To: r...@jarratt.me.uk; Rob Jarratt ; General
Discussion: On-Topic and Off-Topic Posts
Subject: Re: VAXmate PSU
On Fri, Apr 10, 2020 at 10:14 AM Rob Jarratt via cctalk mailto:cctalk@classiccmp.org> > wrote:
D12 is an MBR3045PT. It tests correctly as a common cathode diode network.
H
Lind
Sent: 10 April 2020 15:16
To: r...@jarratt.me.uk
Cc: General Discussion: On-Topic and Off-Topic Posts ;
Matt Burke
Subject: Re: VAXmate PSU
I have found the problem and a possible other problem too.
But that is great!
I have discovered that D24 is shorted (no visible damage
>
>
> I have found the problem and a possible other problem too.
>
But that is great!
>
> I have discovered that D24 is shorted (no visible damage), although its
> twin D23 is not. I will replace both. I know it is shorted because I lifted
> one end.
>
Well, sometime there are no visible damage
> -Original Message-
> From: Rob Jarratt
> Sent: 09 April 2020 20:34
> To: r...@jarratt.me.uk; 'Rob Jarratt' ; 'General
> Discussion: On-Topic and Off-Topic Posts' ; 'Matt
> Burke' ; 'Mattis Lind'
> Subject: RE: VAXmate PSU
>
> > -Original Message---
> -Original Message-
> From: cctalk On Behalf Of Rob Jarratt via
> cctalk
> Sent: 09 April 2020 19:52
> To: 'Matt Burke' ; 'Mattis Lind' ;
> 'General Discussion: On-Topic and Off-Topic Posts'
> Subject: RE: VAXmate PSU
>
>
>
> > -Original Mess
> -Original Message-
> From: cctalk On Behalf Of Matt Burke via
> cctalk
> Sent: 09 April 2020 09:40
> To: cctalk@classiccmp.org
> Subject: Re: VAXmate PSU
>
> On 08/04/2020 22:24, Rob Jarratt via cctalk wrote:
> > I will look at all the suggesti
On 08/04/2020 22:24, Rob Jarratt via cctalk wrote:
> I will look at all the suggestions, particularly of a failure on the
> secondary side. Something must have burned up, because there was a distinct
> burning smell after the initial failure, although I have never been able to
> see any
: VAXmate PSU
torsdag 9 april 2020 skrev Rob Jarratt mailto:robert.jarr...@ntlworld.com> >:
I did use a faster timebase, 10us, triggering on the negative edge of channel
2, and it looked identical to this:
https://rjarratt.files.wordpress.com/2020/04/primary-side-shutdown-detail-2.png
annel 2 negative slope.
>
>
>
> /Mattis
>
>
>
> Thanks
>
>
>
> Rob
>
>
>
> *From:* Mattis Lind
> *Sent:* 08 April 2020 07:42
> *To:* r...@jarratt.me.uk; Rob Jarratt ;
> General Discussion: On-Topic and Off-Topic Posts
> *Subject:* Re: VAXma
in, but there was no difference, the result was identical.
Regards
Rob
From: Mattis Lind
Sent: 09 April 2020 05:52
To: r...@jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts
; Rob Jarratt
Subject: VAXmate PSU
onsdag 8 april 2020 skrev Rob Jarratt mailto:robert.jarr
arratt.me.uk; Rob Jarratt ;
> General Discussion: On-Topic and Off-Topic Posts
> *Subject:* Re: VAXmate PSU
>
>
>
>
>
>
>
> Den ons 8 apr. 2020 kl 00:34 skrev Rob Jarratt via cctalk <
> cctalk@classiccmp.org>:
>
>
>
> > -Original Message-
>
; General
Discussion: On-Topic and Off-Topic Posts
Subject: Re: VAXmate PSU
Den ons 8 apr. 2020 kl 00:34 skrev Rob Jarratt via cctalk
mailto:cctalk@classiccmp.org> >:
> -Original Message-
> From: cctalk <mailto:cctalk-boun...@classiccmp.org> > On Behalf
Den ons 8 apr. 2020 kl 00:34 skrev Rob Jarratt via cctalk <
cctalk@classiccmp.org>:
>
>
> > -Original Message-
> > From: cctalk On Behalf Of Brent Hilpert
> via
> > cctalk
> > Sent: 06 April 2020 21:07
> > To: General Discussion: On-Topic an
> -Original Message-
> From: cctalk On Behalf Of Matt Burke via
> cctalk
> Sent: 08 April 2020 01:25
> To: cctalk@classiccmp.org
> Subject: Re: VAXmate PSU
>
> On 07/04/2020 23:34, Rob Jarratt via cctalk wrote:
> > I have seen the suggestions to study
On 07/04/2020 23:34, Rob Jarratt via cctalk wrote:
> I have seen the suggestions to study the waveforms at a much higher
> resolution. What I am doing is setting the overall timebase in the 100ms
> range so that I can trigger on when the 555 starts to oscillate and capture
> the whole period of
> -Original Message-
> From: cctalk On Behalf Of Brent Hilpert
via
> cctalk
> Sent: 06 April 2020 21:07
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: VAXmate PSU
>
> On 2020-Apr-05, at 11:12 PM, Rob Jarratt wrote:
> >>
&g
On 2020-Apr-05, at 11:12 PM, Rob Jarratt wrote:
>>
>>> I have obtained a scope trace as you suggest. R32 is still lifted so
>>> the
>>> UC3842 is powered by the bench PSU, but I am using the full 240VAC (no
>>> variac). The channels are:
>>> 1. Ch1. 555 timer.
>>> 2. Ch2. D19 Anode
>>> 3. Ch3.
iscussion:
> On-Topic
> > and Off-Topic Posts
> > Subject: Re: VAXmate PSU
> >
> >
> > Switching power supplies are, to coin a phrase, voltage/current-ratio
> power
> > translators.
> > They will attempt to adjust the (cycle-averaged) input-current
> I would agree that a check for shorts in the output stages can be of interest.
> Possibly disconnect one output stage at a time and see if that make a
> difference.
>
>
I like this idea, I will have to see how best to do that.
Regards
Rob
> -Original Message-
> From: Brent Hilpert
> Sent: 06 April 2020 00:12
> To: r...@jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts
>
> Subject: Re: VAXmate PSU
>
> On 2020-Apr-05, at 2:53 PM, Rob Jarratt wrote:
> > I have obtained a s
Den sön 5 apr. 2020 kl 22:18 skrev Brent Hilpert via cctalk <
cctalk@classiccmp.org>:
> On 2020-Apr-05, at 6:05 AM, Rob Jarratt via cctalk wrote:
> > I found time to follow Mattis’s suggestion today and I got some
> interesting results.
> >
> > I powered the UC3842 with about 16V from a bench
On 2020-Apr-05, at 2:53 PM, Rob Jarratt wrote:
> I have obtained a scope trace as you suggest. R32 is still lifted so the
> UC3842 is powered by the bench PSU, but I am using the full 240VAC (no
> variac). The channels are:
> 1.Ch1. 555 timer.
> 2.Ch2. D19 Anode
> 3.Ch3. D19 Gate.
> 4.
> -Original Message-
> From: cctalk On Behalf Of Brent Hilpert
via
> cctalk
> Sent: 05 April 2020 21:18
> To: Rob Jarratt ; General Discussion:
On-Topic
> and Off-Topic Posts
> Subject: Re: VAXmate PSU
>
>
> Switching power supplies are, to coin a phras
On 2020-Apr-05, at 6:05 AM, Rob Jarratt via cctalk wrote:
> I found time to follow Mattis’s suggestion today and I got some interesting
> results.
>
> I powered the UC3842 with about 16V from a bench power supply. I lifted R32
> so that the transformer would not supply it. I then used an
Discussion: On-Topic and Off-Topic Posts'
Subject: RE: VAXmate PSU
Thanks, I do have an isolating transformer as well, so I will use that. I have
done previous tests with a bench PSU on the UC3842 and found it needs 16V to
get going. I just checked the Technical Description and it says
On Sun, 29 Mar 2020, Rob Jarratt via cctalk wrote:
Thanks Mattis. I do test it with a load, although to be honest I forgot
to do this when I took the measurements yesterday. I use a modern-ish
IDE disk and a load board from a MicroVAX 2000 as the dummy load. I
don’t know if that is sufficient.
> -Original Message-
> From: cctalk On Behalf Of Matt Burke via
> cctalk
> Sent: 29 March 2020 10:41
> To: cctalk@classiccmp.org
> Subject: Re: VAXmate PSU
>
> On 29/03/2020 08:50, Mattis Lind via cctalk wrote:
> > Hello Rob,
> >
>
point me at? One of the things I have tried to do, but
clearly not very successfully, is to minimise the lengths of the wires.
Regards
Rob
From: Mattis Lind
Sent: 29 March 2020 08:51
To: r...@jarratt.me.uk
Cc: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: VAXmate PSU
On 29/03/2020 08:50, Mattis Lind via cctalk wrote:
> Hello Rob,
>
> söndag 29 mars 2020 skrev Rob Jarratt :
>
>> Thanks Mattis. I do test it with a load, although to be honest I forgot to
>> do this when I took the measurements yesterday. I use a modern-ish IDE disk
>> and a load board from a
gt;
> *From:* Mattis Lind
> *Sent:* 29 March 2020 06:39
> *To:* r...@jarratt.me.uk; Rob Jarratt ;
> General Discussion: On-Topic and Off-Topic Posts
> *Subject:* Re: VAXmate PSU
>
>
>
> Hello Rob,
>
> lördag 28 mars 2020 skrev Rob Jarratt via cctalk :
>
> I
...@jarratt.me.uk; Rob Jarratt ; General
Discussion: On-Topic and Off-Topic Posts
Subject: Re: VAXmate PSU
Hello Rob,
lördag 28 mars 2020 skrev Rob Jarratt via cctalk mailto:cctalk@classiccmp.org> >:
I have posted here a couple of times because I have a failed VAXmate PSU. I
have just
Hello Rob,
lördag 28 mars 2020 skrev Rob Jarratt via cctalk :
> I have posted here a couple of times because I have a failed VAXmate PSU. I
> have just posted a little bit more information here:
> https://robs-old-computers.com/2020/03/28/further-
> analysis-of-the-vaxmate-h7
>
I have posted here a couple of times because I have a failed VAXmate PSU. I
have just posted a little bit more information here:
https://robs-old-computers.com/2020/03/28/further-analysis-of-the-vaxmate-h7
270-psu-failure/ with some scope traces and a greatly improved schematic.
Although
> The UC3842 datasheet does show you can draw up to 20 mA from the Vref pin,
> which should certainly power up a 555. But, this is a 5 V regulator, and
may
> not be working properly. it may be that driving several mA to the 555, E2
and
> other components has cooked it over time. With the 555
On 02/15/2020 12:17 PM, Rob Jarratt via cctalk wrote:
A little while back I posted here because I needed help with analysing the
failure of the PSU from my VAXmate. Since then I have had some comments on
the reverse engineered schematic which I have now improved and which is
here:
A little while back I posted here because I needed help with analysing the
failure of the PSU from my VAXmate. Since then I have had some comments on
the reverse engineered schematic which I have now improved and which is
here:
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