unijunction needed

A

alp soandso

Guest
Looking for a part made by ssi.

MSU 112-2

I need one. Will a few more if absolutely necessary and price is low. Not
looking to buy $200 minimum.

I live in Canada.

you can contact me by email by removing the first alp in the address.
 
alp soandso wrote:
Looking for a part made by ssi.

MSU 112-2

I need one. Will a few more if absolutely necessary and price is low. Not
looking to buy $200 minimum.

I live in Canada.

you can contact me by email by removing the first alp in the address.

I can't seem to find a spec on that part? Maybe if you knew some more
Click to expand...
information on it, like the Peak Voltage, valley etc on the emitter one
could be dropped in.

I have some unijunctions in my drawers and as far as know, they didn't
make to many different types.

Jamie
 
"alp soandso" <alpalpsoandso@gmail.com> wrote in message
news:rlXeq.27134$eS.14198@newsfe03.iad...
Looking for a part made by ssi.

MSU 112-2

I need one. Will a few more if absolutely necessary and price is low. Not
looking to buy $200 minimum.

I live in Canada.

you can contact me by email by removing the first alp in the address.
Click to expand...
As someone else pointed out there's no spec coming up for that part #, but
it has the look of the type of number you might find on a PUT.

If that's the case and you only want 1, its easy to re-construct the same
effect as the 4-layer device with a cross coupled complimentary pair of
BJTs.

If you can put a schematic somewhere like A.B.S.E it may be possible to work
out whether the circuit for a conventional unijunction can be modified for a
PUT (or 2-BJT equivalent).
 
There's a few links here might be helpful:


http://www.onsemi.com/pub_link/Collateral/HBD855-D.PDF

http://www.alliedelec.com/Images/Products/Datasheets/BM/NTE_ELECTRONICS/935-6198.PDF

http://encyclobeamia.solarbotics.net/articles/put.html

http://baec.tripod.com/DEC90/uni_tran.htm

http://www.allaboutcircuits.com/vol_3/chpt_7/8.html
 
I don't know anything about the device. I have a delay timer/relay that
is supposed to activate a cryogenic compressor after a roughing pump has
run for about one minute. It suddenly stopped working. I opened the timer/
relay.

It is a Potter Brumfield CUF-41-30120.

It has very few components wired up between 8 contacts or so. I have
replaced the capacitors (two of them) and the diode checked out fine, but
I put a new one in anyway. The resistors look fine, I have not tested
them yet nor did I plan to. I believe the coil is fine, but I will have
to unsolder a few parts to make sure I am not reading this wrong. The
prime suspect right now is the MSU 112-2, which I have been told is a
UJT, perhaps a PUJT (PUT). I wouldn't know where or how to measure the
peak voltages/current..... I would be poking around inside a relay with
240 v and several amps behind it. Not something I want to do with the
part installed on the device and the device running.

Ian, thanks for the links. If I study hard and long enough I will be
able to come up with a replacement of my own manufacture. I doubt I have
long enough to live however (I joke, but in reality my capacity to learn
new stuff has dropped off significantly over the last couple of years).
They should at least get me pointed in the right direction if I have to
try (and don't wish to pay the 200-300 bucks for a new timer/relay).

Thanks
all.

Alp
 
On 09/26/2011 08:33 PM, alp soandso wrote:
I don't know anything about the device. I have a delay timer/relay that
is supposed to activate a cryogenic compressor after a roughing pump has
run for about one minute. It suddenly stopped working. I opened the timer/
relay.

It is a Potter Brumfield CUF-41-30120.

It has very few components wired up between 8 contacts or so.
If this is just a stock delay relay module, why don't you just replace
Click to expand...
it with a new stock relay? Much easier than trying to source a part
that has been obsolete for 40 years! If there's another reason that you
have to repair this module, why not put a 555 or similar timer in there?

Jon
 
Jon Elson wrote:

On 09/26/2011 08:33 PM, alp soandso wrote:


I don't know anything about the device. I have a delay timer/relay that
is supposed to activate a cryogenic compressor after a roughing pump has
run for about one minute. It suddenly stopped working. I opened the
timer/
relay.

It is a Potter Brumfield CUF-41-30120.

It has very few components wired up between 8 contacts or so.

If this is just a stock delay relay module, why don't you just replace
it with a new stock relay? Much easier than trying to source a part
that has been obsolete for 40 years! If there's another reason that you
have to repair this module, why not put a 555 or similar timer in there?

Jon
COST!!!!
Click to expand...

Jamie
 
On Tue, 27 Sep 2011 14:14:00 -0500, Jon Elson wrote:


Yes, Jamie is correct, the cost of the device is ridiculous.

I would be able to build something (hack) if I could figure out how this
circuit works. With all the pdf links I got from the other newsgroup
posting I should be able to figure something out.

Thanks again
!
Alp
 
alp soandso wrote:
I don't know anything about the device. I have a delay timer/relay that
is supposed to activate a cryogenic compressor after a roughing pump has
run for about one minute. It suddenly stopped working. I opened the timer/
relay.

It is a Potter Brumfield CUF-41-30120.

It has very few components wired up between 8 contacts or so. I have
replaced the capacitors (two of them) and the diode checked out fine, but
I put a new one in anyway. The resistors look fine, I have not tested
them yet nor did I plan to. I believe the coil is fine, but I will have
to unsolder a few parts to make sure I am not reading this wrong. The
prime suspect right now is the MSU 112-2, which I have been told is a
UJT, perhaps a PUJT (PUT). I wouldn't know where or how to measure the
peak voltages/current..... I would be poking around inside a relay with
240 v and several amps behind it. Not something I want to do with the
part installed on the device and the device running.

Ian, thanks for the links. If I study hard and long enough I will be
able to come up with a replacement of my own manufacture. I doubt I have
long enough to live however (I joke, but in reality my capacity to learn
new stuff has dropped off significantly over the last couple of years).
They should at least get me pointed in the right direction if I have to
try (and don't wish to pay the 200-300 bucks for a new timer/relay).

Thanks
all.

Alp
Click to expand...
Yep, >$200 is horrible. If you know the function(s) the relay
must deliver, you can build a circuit to do it using current
parts.

Some issues to determine concerning the function(s):
You say that the relay must operate after the roughing pump
has run for about 1 minute.

* What is the relay supposed to do if the roughing pump runs for
less than 1 minute?
* Once the relay activates, how/when is it supposed to de-activate?
* How much current at what voltage must the relay switch?
* How many poles must the relay switch?

If you have room in the machine, and are willing to re-wire a bit
if necessary, delivering the functions you need with an external
circuit is a piece of cake, provided of course that you know those
functions. OTOH, if you must create a drop-in replacement for (or
repair of) the bad part, that can be a PITA.

Ed
 
"alp soandso" <alpalpsoandso@gmail.com> wrote in message
news:OJ9gq.3992$WF1.2916@newsfe01.iad...
I don't know anything about the device. I have a delay timer/relay that
is supposed to activate a cryogenic compressor after a roughing pump has
run for about one minute. It suddenly stopped working. I opened the timer/
relay.

It is a Potter Brumfield CUF-41-30120.

It has very few components wired up between 8 contacts or so. I have
replaced the capacitors (two of them) and the diode checked out fine, but
I put a new one in anyway. The resistors look fine, I have not tested
them yet nor did I plan to. I believe the coil is fine, but I will have
to unsolder a few parts to make sure I am not reading this wrong. The
prime suspect right now is the MSU 112-2, which I have been told is a
UJT, perhaps a PUJT (PUT). I wouldn't know where or how to measure the
peak voltages/current..... I would be poking around inside a relay with
240 v and several amps behind it. Not something I want to do with the
part installed on the device and the device running.

Ian, thanks for the links. If I study hard and long enough I will be
able to come up with a replacement of my own manufacture. I doubt I have
long enough to live however (I joke, but in reality my capacity to learn
new stuff has dropped off significantly over the last couple of years).
They should at least get me pointed in the right direction if I have to
try (and don't wish to pay the 200-300 bucks for a new timer/relay).
Click to expand...

The PUT was much touted as being more stable and better for long delays than
the old style 2-base unijunction.

You stand a better chance of getting hold of a PUT these days - and if you
can't, its easy to do the same thing with a complementary pair of
transistors.

The circuit is easier to design as well, while the old style unijunction has
a set trigger point (subject to inevitable device tolerance) the PUT is
basically a thyristor with the gate at the anode end instead of the cathode
end.

Basically you set the trigger point where you want it to be (within reason)
by connecting the gate to a potential divider across the supply, the anode
goes to the C/R as did the "emitter" of the old style unijunction.

As the C charges up to the trigger point; the anode becomes positive wrt the
gate and the PUT fires and develops a pulse across the cathode resistor.
 
The PUT was much touted as being more stable and better for long delays
than the old style 2-base unijunction.

You stand a better chance of getting hold of a PUT these days - and if
you can't, its easy to do the same thing with a complementary pair of
transistors.

The circuit is easier to design as well, while the old style unijunction
has a set trigger point (subject to inevitable device tolerance) the PUT
is basically a thyristor with the gate at the anode end instead of the
cathode end.

Basically you set the trigger point where you want it to be (within
reason) by connecting the gate to a potential divider across the supply,
the anode goes to the C/R as did the "emitter" of the old style
unijunction.

As the C charges up to the trigger point; the anode becomes positive wrt
the gate and the PUT fires and develops a pulse across the cathode
resistor.
Click to expand...
Thanks for taking the effort to explain. I managed to download a bunch of
files explaining this sort of thing as well, but my main background is
chemistry, not electronics. I know what the words mean, but they don't
make much sense right now.
Maybe I'll get lucky and find out it was the tantalum capacitor that went
bad.

Alp
 
"alp soandso" <alpalpsoandso@gmail.com> wrote in message
news:bx8nq.10058$UI7.3197@newsfe11.iad...
The PUT was much touted as being more stable and better for long delays
than the old style 2-base unijunction.

You stand a better chance of getting hold of a PUT these days - and if
you can't, its easy to do the same thing with a complementary pair of
transistors.

The circuit is easier to design as well, while the old style unijunction
has a set trigger point (subject to inevitable device tolerance) the PUT
is basically a thyristor with the gate at the anode end instead of the
cathode end.

Basically you set the trigger point where you want it to be (within
reason) by connecting the gate to a potential divider across the supply,
the anode goes to the C/R as did the "emitter" of the old style
unijunction.

As the C charges up to the trigger point; the anode becomes positive wrt
the gate and the PUT fires and develops a pulse across the cathode
resistor.

Thanks for taking the effort to explain. I managed to download a bunch of
files explaining this sort of thing as well, but my main background is
chemistry, not electronics. I know what the words mean, but they don't
make much sense right now.
Maybe I'll get lucky and find out it was the tantalum capacitor that went
bad.

Alp
Click to expand...
Tantalum caps can throw the odd curveball!

Any reverse voltage applied can make them go leaky, so apparently can rapid
DV/Dt that can occur in some SMPSU applications.

Tants attract their share of discussion in these groups.

If the capacitance isn't very high - say 10 to 15uF; you can get multilayer
ceramic chip capacitors that far exceed the quality of tants, readily
available as SMD parts but if you search for them they can be found as resin
dipped leaded types.
 
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