3 Mar
2016
3 Mar
'16
12:33 a.m.
Morning folks (other timezones are available)
One of the casualties in my expiring VT100 PSU last weekend was a 2W
resistor named R22, or at least it seems more dead than its twin at R47
which gives a steady reading on my DMM. Seems that they're surprisingly
difficult to find these days with none of the main parts stockists having
any.
Anyone got one or two lurking in a bits box somewhere?
Cheers!
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
3 Mar
3 Mar
1:27 a.m.
On 03/03/2016 08:33, Adrian Graham wrote:
Morning folks (other timezones are available)
One of the casualties in my expiring VT100 PSU last weekend was a 2W
resistor named R22, or at least it seems more dead than its twin at R47
which gives a steady reading on my DMM. Seems that they're surprisingly
difficult to find these days with none of the main parts stockists having
any.
Anyone got one or two lurking in a bits box somewhere?
No, sorry, but Farnell do:
http://onecall.farnell.com/webapp/wcs/stores/servlet/Search?catalogId=15001…
--
Pete
Pete Turnbull
1:33 a.m.
On 03/03/2016 08:33, Adrian Graham wrote:
Morning folks (other timezones are available)
One of the casualties in my expiring VT100 PSU last weekend was a 2W
resistor named R22, or at least it seems more dead than its twin at R47
which gives a steady reading on my DMM. Seems that they're surprisingly
difficult to find these days with none of the main parts stockists having
any.
Anyone got one or two lurking in a bits box somewhere?
No, sorry, but Farnell do:
http://uk.farnell.com/webapp/wcs/stores/servlet/Search?catalogId=15001&…
The URL I posted before was for OneCall, which you might not be able to use.
--
Pete
Pete Turnbull
2:25 a.m.
Hi Pete,
Must admit Opencall didn't come up yesterday in all my Farnell searching,
my google-fu failed somewhat. The culprit in question looks like this:
On 3 March 2016 at 09:33, Pete Turnbull <pete at dunnington.plus.com> wrote:
On 03/03/2016 08:33, Adrian Graham wrote:
--
adrian/witchy
Owner of Binary Dinosaurs, the UK's biggest home computer collection?
www.binarydinosaurs.co.uk
Morning folks (other timezones are available)
One of the casualties in my expiring VT100 PSU last weekend was a 2W
resistor named R22, or at least it seems more dead than its twin at R47
which gives a steady reading on my DMM. Seems that they're surprisingly
difficult to find these days with none of the main parts stockists having
any.
Anyone got one or two lurking in a bits box somewhere?
No, sorry, but Farnell do:
http://uk.farnell.com/webapp/wcs/stores/servlet/Search?catalogId=15001&…
The URL I posted before was for OneCall, which you might not be able to
use.
--
Pete
Pete Turnbull
2:30 a.m.
and my premature-enter-key is catching this morning too :)
Link:
http://onecall.farnell.com/international-resistive/sph-1-0-5/resistor-2w-1r…
The only difference (and I know the pictures are for example only but...)
the one I'm looking for has a blue band too.
http://f0p.co.uk/r22.jpg
The printset has it as 'fuse'.
Cheers!
On 3 March 2016 at 09:33, Pete Turnbull <pete at dunnington.plus.com> wrote:
On 03/03/2016 08:33, Adrian Graham wrote:
--
adrian/witchy
Owner of Binary Dinosaurs, the UK's biggest home computer collection?
www.binarydinosaurs.co.uk
Morning folks (other timezones are available)
One of the casualties in my expiring VT100 PSU last weekend was a 2W
resistor named R22, or at least it seems more dead than its twin at R47
which gives a steady reading on my DMM. Seems that they're surprisingly
difficult to find these days with none of the main parts stockists having
any.
Anyone got one or two lurking in a bits box somewhere?
No, sorry, but Farnell do:
http://uk.farnell.com/webapp/wcs/stores/servlet/Search?catalogId=15001&…
The URL I posted before was for OneCall, which you might not be able to
use.
--
Pete
Pete Turnbull
6:36 a.m.
On 03/03/2016 10:30, Adrian Graham wrote:
and my premature-enter-key is catching this morning
too :)
Link:
http://onecall.farnell.com/international-resistive/sph-1-0-5/resistor-2w-1r…
The only difference (and I know the pictures are for example only but...)
the one I'm looking for has a blue band too.
Nearest I can find is a 1R 0.5W fusible in a pack of 10 from RS (so I
suppose you could use 4 in series-parallel in a pinch):
http://uk.rs-online.com/web/p/through-hole-fixed-resistors/2671660/
--
Pete
5:03 a.m.
No, sorry, but Farnell do:
http://uk.farnell.com/webapp/wcs/stores/servlet/Search?catalogId=15001&…
The original resistor (as mentioned in the Subject: line) was one of those safety fusible
resistors. AFAIK none of the ones that Farnell stock are.
It appears Digikey do them, but only to special order with a large (thousands)
minimum order quantity
-tony
6:29 a.m.
On 03/03/2016 13:03, tony duell wrote:
The original resistor (as mentioned in the Subject: line) was one of those safety
fusible
resistors. AFAIK none of the ones that Farnell stock are.
Oops, I missed that part of the subject line. It'll be fusible for a
reason, so should be replaced with the same type. Moreover, if it's
gone, there's probably something else wrong too, so maybe Adrian needs a
pair ;-)
--
Pete
7:21 a.m.
The original
resistor (as mentioned in the Subject: line) was one of those safety fusible
resistors. AFAIK none of the ones that Farnell stock are.
Oops, I missed that part of the subject line. It'll be fusible for a
reason, so should be replaced with the same type. Moreover, if it's
gone, there's probably something else wrong too, so maybe Adrian needs a
pair ;-) 
7:34 a.m.
On Mar 3, 2016, at 9:21 AM, tony duell <ard at p850ug1.demon.co.uk> wrote:
I know rather more about this than Adrian has said, so I might as well
let on. It's from a VT100 power supply board, it's in the chopper circuit.
The chopper transistor has failed short-circuit B-C and open B-E and this
took out the resistor (as far as I can tell).
Knowing how chopper circuits behave (or don't!) I agree this must be replaced
by a fusible resistor. Otherwise next time the chopper fails it might be
spectacular
Speaking from complete ignorance, could it be a normal resistor and a fast-acting fuse in
series? Aussuming the correct fusible resistor is not easy to locate and that there is
room to hang a fuse holder off of the circuit board there?
The original resistor (as mentioned in the Subject:
line) was one of those safety fusible
resistors. AFAIK none of the ones that Farnell stock are.
Oops, I missed that part of the subject line. It'll be fusible for a
reason, so should be replaced with the same type. Moreover, if it's
gone, there's probably something else wrong too, so maybe Adrian needs a
pair ;-) 
8:19 a.m.
On 03/03/2016 07:34 AM, Tapley, Mark wrote:
Speaking from complete ignorance, could it be a normal
resistor and a
fast-acting fuse in series? Aussuming the correct fusible resistor is
not easy to locate and that there is room to hang a fuse holder off
of the circuit board there?
Not a bad question, in my own humble opinion. No need for a fuse
holder, either. A Picofuse in series with an appropriate resistor
shouldn't take up much more space than the original.
However, many fusible resistors also feature a strong positive
temperature coefficient which serves to limit current as the load
increases before the device releases its magic smoke.
If you do take the fusible resistor route, be careful to pay attention
to the *type* of fusible resistor. Some are wirewound; others are
composition--the former may well exhibit a stray inductance that doesn't
sit well in a chopper circuit.
For whatever it's worth,
Chuck
8:28 a.m.
On Mar 3, 2016, at 11:19 AM, Chuck Guzis <cclist at
sydex.com> wrote:
...
If you do take the fusible resistor route, be careful to pay attention to the *type* of
fusible resistor. Some are wirewound; others are composition--the former may well
exhibit a stray inductance that doesn't sit well in a chopper circuit.
Out of curiosity, what does a "fusible resistor" look like? What are the specs?
I hadn't heard of any such thing before today.
In my experience, film resistors (i.e., the conventional carbon or metal film resistors)
are "fusible" -- if you overload them significantly they will release magic
smoke and stop conducting. Is that adequate?
paul
9:10 a.m.
On 03/03/2016 07:03 AM, tony duell wrote:
Also check Mouser. I don't know about 1W, but I use a 10W
Ohmite fusible (or at least flame-proof) resistor.
That is the 40J25RE, and I get them from Digi-Key.
Jon
No, sorry, but
Farnell do:
http://uk.farnell.com/webapp/wcs/stores/servlet/Search?catalogId=15001&…
The original resistor (as mentioned in the Subject: line) was one of those safety
fusible
resistors. AFAIK none of the ones that Farnell stock are.
It appears Digikey do them, but only to special order with a large (thousands)
minimum order quantity
6:27 p.m.
Have you looked at the various flameproof resistor offerings? Flameproof
types are frequently used as a fusible element - it's by virtue of the fact
that they abruptly go open-circuit under overload, that they fail to reach
smoke / ignition temperature.
Check some datsheets and see what kind of specs they publish for that
service.. might be an ideal way to go.
On Thu, Mar 3, 2016 at 11:10 AM, Jon Elson <elson at pico-systems.com> wrote:
On 03/03/2016 07:03 AM, tony duell wrote:
No, sorry, but Farnell do:
(or
at least flame-proof) resistor.
That is the 40J25RE, and I get them from Digi-Key.
Jon
http://uk.farnell.com/webapp/wcs/stores/servlet/Search?catalogId=15001&…
The original resistor (as mentioned in the Subject: line) was one of
those safety
fusible
resistors. AFAIK none of the ones that Farnell stock are.
It appears Digikey do them, but only to special order with a large
(thousands)
minimum order quantity
Also check Mouser. I don't know about 1W, but I use a 10W Ohmite fusible
3214
days inactive
3215
days old
13 comments
9 participants
participants (9)
-
ard＠p850ug1.demon.co.uk -
binarydinosaurs＠gmail.com -
cclist＠sydex.com -
drlegendre＠gmail.com -
elson＠pico-systems.com -
mtapley＠swri.edu -
paulkoning＠comcast.net -
pete＠dunnington.plus.com -
witchy＠binarydinosaurs.co.uk