[GreenKeys] What an Idiot!

Tue May 28 18:09:09 EDT 2013

Someone I asked who is not on this list suggested the transistor is a germanium one and that I should try an OC28.  I suspect swapping germanium to silicon might not work, but I don't know enough about the circuit to know.

Regards

Rob

> -----Original Message-----
> From: Chris Elmquist [mailto:chrise at pobox.com]
> Sent: 28 May 2013 18:04
> To: robert.jarratt at ntlworld.com
> Cc: greenkeys at mailman.qth.net
> Subject: Re: [GreenKeys] What an Idiot!
> 
> I was curious about the transistor too so I've looked at a few prints and parts
> lists and they sure keep the details of that puppy a secret.
> 
> I think the "7339" you've found marked on it is indeed a date code as others
> have pointed out.
> 
> The Teletype part number is 181675 which was sometimes marked on the
> device (house numbering).
> 
> Some indications are that it was a Motorola device...  MJE family.
> 
> It is pretty much a general purpose PNP switch with no spectacular
> requirements I don't think.  Appears to see about 20v across it from -20V
> supply to ground with the selector magnet as the load.
> 
> I've attached one page of M33 schematic set where the two transistors and
> power supply in the unit are shown.
> 
> I would be tempted to try a modern, readily available device such as
> MJ2955 and see how that works in the event your device is truely smoked.
> The package and pinout appear to be the same so should be an easy swap.
> 
> For reference,
> 
> http://www.digikey.com/product-detail/en/MJ2955/497-6712-ND/1038920
> 
> I'd also check the -20 and -4.7V supplies to make sure those are still correct.
> If you had 2X the input voltage at T1, the zener ZD1 was potentially also at
> risk.
> 
> Chris N0JCF
> 
> On Monday (05/27/2013 at 12:32PM -0400), Teletypeparts wrote:
> >
> > Rob,
> >
> > I have never delved deep into the SMD card or the 500 MA transistor that
> sits behind it.  Probably because I never needed to so I cant be of much help
> there.
> >
> > I do have some power (500 MA) transistors that are new or good and a
> couple of SMD cards on hand if you think you need them.
> >
> > Look some more to make sure the kybd break key is not causing the
> trouble or any other obvious issue.
> >
> > I dug out the books and checked more for you.
> >
> > I measured the input (pins 1 and 2) to the large power tranformer and it is
> not open, its about 8 ohms, the book says 29 ohms, but I suspect what I got is
> correct as I checked it on a spare transformer and on the transformer in my
> spare UCC-6.
> >
> > I think you have a burned out primary in your transformer.  I am attaching 4
> pics.  The first two are FS-1 receive.  The second two are the SMD card print.
> Print them and cut off the edges on the second sheets and you can carefully
> line them up and tape them together.  Real cut and paste.
> >
> > Sorry I couldnt fit them into the scanner any better but I think they will help
> you.
> >
> > Wayne
> >
> >
> >
> > -----Original Message-----
> > From: Robert Jarratt <robert.jarratt at ntlworld.com>
> > To: 'Teletypeparts' <teletypeparts at aol.com>; info <info at drukknop.nl>;
> > greenkeys <greenkeys at mailman.qth.net>
> > Sent: Mon, May 27, 2013 7:30 am
> > Subject: RE: [GreenKeys] What an Idiot!
> >
> >
> >
> > I checked the transformer underneath the fuses. The resistance across the
> wires going into the primary and the secondary sides appears to be infinite,
> which I believe is a good thing. The resistance across the two input wires and
> the across the two output wires is zero. All these things would seem to be
> good to me.
> >
> > I assume the power transistor is the one under a plastic cover mounted on
> a large L-shaped piece of metal behind the SMD PCB marked 181675. I am not
> sure of the pinout of this transistor, but, after removing it from the circuit, I
> used my diode tester to measure across the terminals in all combinations and
> directions, I got readings of 0.14V, infinite, 0.91V, infinite, 0.15V, infinite. I
> suspect this transistor is damaged. What is the spec for it?
> >
> > There appear to be two transistors on the SMD card. My desoldering skills
> are very poor so I would rather not desolder them for testing at this point
> unless I have to.
> >
> > I am not sure which coil is being referred to, so I have not tested that,
> unless it the transformer. I cannot see any burned wires.
> >
> > Regards
> >
> > Rob
> >
> >
> >
> > From: greenkeys-bounces at mailman.qth.net
> > [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Teletypeparts
> > Sent: 26 May 2013 18:45
> > To: info at drukknop.nl; greenkeys at mailman.qth.net
> > Subject: Re: [GreenKeys] What an Idiot!
> >
> >
> >
> > Rob,
> >
> >
> >
> > Check the 3 fuses in the UCC-6 first.  They are on top of the UCC-6 toward
> the back.  Hopefully one is blown.
> >
> >
> >
> > After that, could be anything.  The SMD card, the power transistor
> mentioned by Simon, the large transformer under the fuses, burned wires.
> >
> >
> >
> > Look for the easy fix before you dig too deep.
> >
> >
> >
> > How did you manage to plug a 120 VAC style end into the 220 UK?  I
> thought they were very different in style.
> >
> >
> >
> > Wayne
> >
> >
> >
> >
> >
> >
> > -----Original Message-----
> > From: Simon Claessen <info at drukknop.nl>
> > To: greenkeys <greenkeys at mailman.qth.net>
> > Sent: Sun, May 26, 2013 1:26 pm
> > Subject: Re: [GreenKeys] What an Idiot!
> >
> > probably the switching transistor. the thing on the big cooling metal.
> > also the connected pcb might contain some blown transistors as well.
> > fortunate the documentation is readily downloadable but extensive. You
> > may want to look at doc 574-100-103TC page 20 for a schematic. also
> > check the power supplies and measure the coil resistance. if it is
> > infinite, the coil sould be replaced as well as the transistors.
> >
> > good luck!
> >
> > On 25-05-13 20:50, Robert Jarratt wrote:
> > > I mistakenly plugged my ASR33 directly into the UK mains (240V/50Hz)
> > > rather than via the 110V transformer. It blew two fuses in the plug
> > > before I realised what I had done wrong.
> > >
> > > The machine now runs open (i.e. “chatters”) even in LOCAL mode.
> > >
> > > What might I have damaged?
> > >
> > > Regards
> > >
> > > Rob
> > >
> > >
> > >
> > >
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> > --
> > Met vriendelijke Groet,
> >
> > Simon Claessen
> > drukknop.nl
> >
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> 
> 
> 
> 
> >
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> 
> --
> Chris Elmquist