12 Feb
2014
12 Feb
'14
12:02 a.m.
I have a box of them, used, along with the monitor boards and almost all
vt1xx logic boards. I have some of the boards handy, but the rest I won't
be able to dig out for a while due to more pressing personal priorities. I
will post when I find them.
Thanks, Paul
On Tue, Feb 11, 2014 at 4:54 PM, Jarratt RMA <robert.jarratt at ntlworld.com>wrote:
I am away from home all week. I have the files with me
but I don't have the
system with the software on it to check I actually have the right files. I
will reply privately with the files because I don't think the list accepts
attachments.
Regards
Rob
On 11 February 2014 21:49, Andreas Holz <aswood at t-online.de> wrote:
Ohms.
will
Rob,
thank you, would be nice to get your stripboard design.
Also thanks to Tony to justify my naive attempt to check the transformer
by measuring its resistance.
I'm just checking sources to get replacement transformers. There aren't
much left. Will try to get some transformers as spares.
Andreas
> Am 11.02.2014 um 22:22 schrieb Jarratt RMA <
robert.jarratt at
ntlworld.com
:
Tony sent me a circuit design for a ringing tester. I converted this
into a
> TinyCad drawing from which I was able to create a stripboard design. If
> anyone wants this I can send it to them.
>
> Regards
>
> Rob
>
>
> On 11 February 2014 20:49, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
>
>>>
>>> I measured the resistance of the flyback transformer as of four >>
From my point of view this is a proper value.
>
> Unofrtunately DC resistance measurments on a flyback transformer tell
you
> very little. A single shorted turn in that
winding will not change the
DC
> resistnace enough to see. A shorted turn in
anotehr windign will not
> change the resistance at all. But either will extract enough energy to
> prevent the flyback from resonating, will cause the primary currnet to
go
>> very high and will damage the output transistor.
>>
>> The only useful test is a ringing test. Basically, you resonate the
>> widnidng with a capacitor 9arounf 100nF IIRC), then apply pulses to it
>> (the nromal way is a nopen-collect drier using a BU406 or similar
>> trasnsitor) and look at the waveform on a 'scope. A good flyback will
>> show many osciallations before they decay to 'invisible', a bad one
>
probably not oscillate at all.
>
> -tony
>