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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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10th May 2020, 2:58 pm | #21 |
Triode
Join Date: Apr 2020
Location: Northallerton, North Yorkshire, UK.
Posts: 36
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What is this 1980's surface mount package called?
While troubleshooting I've picked out all the soft rubber potting compound hiding these sparse components but I'm wondering what the circled package type is called and am I actually looking at the semiconductor material. Its probably a power Darlington and despite my efforts may still be working, at first I thought I had clumsily pulled the top off the package but there were still fragments of the rubber stuck to the surface. I've had a good search but can't find anything that looks like this, only the inside of a TO3 Darlington which has the same pattern etched on it but with the leads attached within the pattern. As its about the same size as a TO-218/TO-247 perhaps its just a regular device without the case?
Chris Last edited by AC/HL; 10th May 2020 at 3:57 pm. Reason: Threads merged |
10th May 2020, 3:17 pm | #22 |
Heptode
Join Date: Feb 2013
Location: Yarm, North Yorkshire, UK.
Posts: 535
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Re: What is this 1980's surface mount package called?
I may be way off course, but those markings remind me of an antenna for something like bluetooth level of signal. What is the unit it is in?
Colin |
10th May 2020, 3:54 pm | #23 |
Nonode
Join Date: Jan 2016
Location: Stafford, Staffs. UK.
Posts: 2,532
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Re: What is this 1980's surface mount package called?
I suspect you are right, a semiconductor. I also suspect you have removed the bond wires that link from the connections to the substrate.
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10th May 2020, 4:12 pm | #24 |
Nonode
Join Date: May 2016
Location: Cornwall, UK.
Posts: 2,336
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Re: Reverse engineering Lumenition optical switch
I bet it's T3/T4 in the patent application circuit diagram you posted, so yes a power darlington. Presumably the pink left wire is the 12V in, with the film resistor between it and the red wire to the optical switch (7.5V) and the bottom red object is the Zener Z1. The black wire(s) look like they're on an earth link, which has the small red diode between ground and the base of the Darlington pair.
Seem legit? |
10th May 2020, 4:17 pm | #25 |
Nonode
Join Date: Jan 2016
Location: Stafford, Staffs. UK.
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Re: Reverse engineering Lumenition optical switch
It looks like what I think is known as a bare die package. In other words, it's what's normally inside your metal can or plastic moulding. I suspect you have removed the bond out wires along with the potting compound. There appears to be some evidence of them on two of the three areas, just tiny circular marks where the bonds will have been welded. If you have a digital microscope, or a cmaera with a macro function you could probably get a decent photo of just that area.
Last edited by duncanlowe; 10th May 2020 at 4:19 pm. Reason: Thought my previous answer had gone, and wanted to add more detail |
10th May 2020, 4:19 pm | #26 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Re: Reverse engineering Lumenition optical switch
That's a power darlington transistor pair, you can see the main transistor, and its smaller driver in a corner. It looks to be mounted on a ceramic insulator to stop the collectors connecting to the heatsink.
It is possible that this ceramic is simply Alumina, aluminium oxide, which is safe, BUT there is also the possibility that it could be beryllium oxide BeO, which is very dangerous if chipped, cracked, ground or drilled. Units from this era usually didn't have warning labels about BeO. It is good practice (IE it might save your life) to treat ceramics in this sort of position as dangerous unless proven innocent. It should be safe so long as there is no risk of dust being created. As Duncan says in removing the silicone rubber, you've likely removed the bond wires linking base and emitter on the die to their respective metal areas on the ceramic and the connection pins. Do you have a microscope? But I don't know anyone with a ball/wedge bonder that could replace the bond wires. As an alternative, there are power transistors of the necessary ratings in pachkages similar to that. The problem comes in insulating the collector-connected tab. You need to pass heat efficiently, but electricity not at all. David
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10th May 2020, 4:29 pm | #27 |
Nonode
Join Date: Jan 2016
Location: Stafford, Staffs. UK.
Posts: 2,532
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Re: Reverse engineering Lumenition optical switch
Yes, this photo of the insides of a Darlington show quite well, where the two bond wires go when inside a metal case. The third connection in this case is the metal can. In your case, the bond wires would go to the two gold stripes at either end of the ceramic.
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10th May 2020, 4:34 pm | #28 |
Nonode
Join Date: Jan 2016
Location: Stafford, Staffs. UK.
Posts: 2,532
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Re: Reverse engineering Lumenition optical switch
With care, I would think a heatsink isolation mount kit comprising an insulating but heat conducting 'tab' and an insulator for the screw hole, after drilling and tapping the heatsink. I seem to remember there are even self adhesive versions around.
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10th May 2020, 4:40 pm | #29 |
Nonode
Join Date: Aug 2010
Location: Resolven, Wales; and Bristol, England
Posts: 2,609
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Re: Reverse engineering Lumenition optical switch
Here's a later power module:
The three-legged component on the right tests as a power darlington but I don't remember if I managed to find a part number. There are several thick-film resistors on the substrate and there were several conventional leaded components within the silicon pottage.
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10th May 2020, 4:52 pm | #30 |
Nonode
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Location: Resolven, Wales; and Bristol, England
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Re: Reverse engineering Lumenition optical switch
Here's another picture with the wires still attached, compare this with the photo above and the circuit in the Patent application to make sense of the whole:
Connections are: RD power from ignition RD to opto module (7.5V) BLU to opto module (signal) BK to opto module (GND) BK to chassis (GND) BN to coil
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10th May 2020, 6:19 pm | #31 |
Nonode
Join Date: May 2016
Location: Cornwall, UK.
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Re: Reverse engineering Lumenition optical switch
BBC Sounds has a few cracking dramatisations of 'The Saint' with Paul Rhys on at the moment. And I see the sun is just over the yardarm, so a gentle task like digging away the potting compound for the LED appeals. Indeed it is the orange-ish example of the TO-46. The markings indicate an OP133, which I see is a 100mA, 935nm IR emitter. 18 degree viewing angle and a 1.75V forward voltage drop.
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11th May 2020, 12:19 am | #32 |
Nonode
Join Date: May 2016
Location: Cornwall, UK.
Posts: 2,336
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Re: Reverse engineering Lumenition optical switch
We have success! Here's the circuit I've knocked up to test, which fires reliably each time the gap is broken.
Next question: can I make this in a small enough space to fit into the optical switch housing, and what do I pot it in with? Is there anything that is rather more easily removable than the stuff originally there that required some serious time with little drills and scrapers? |
11th May 2020, 12:47 am | #33 |
Moderator
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Re: Reverse engineering Lumenition optical switch
Non-acetic silicone.
David
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11th May 2020, 12:50 am | #34 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,642
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Re: Reverse engineering Lumenition optical switch
Brilliant. Once fettled you won't need to get at it, and sealing will be the most important criteria. It will be in a somewhat hostile environment.
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11th May 2020, 10:58 am | #35 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Reverse engineering Lumenition optical switch
I found that one of the most important things with these was routing the sensor's connecting wires, make sure to allow for any movement due to advance/retard etc, I fitted one of these 25 years ago, it was still going strong last time I saw it a few months back.
Lawrence. |
11th May 2020, 5:07 pm | #36 |
Nonode
Join Date: May 2016
Location: Cornwall, UK.
Posts: 2,336
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Re: Reverse engineering Lumenition optical switch
Thanks. I'll look into the silicone. I assume it doesn't shrink away from the edges of the recess. What is a good general purpose compound? I have never potted anything before. Chris's experience above suggests a soft material in the power module, whereas in the switch I would have said it was a pretty rigid epoxy.
Am I best off manufacturing a new circuit board and using the little SOT packages as in the original (and some replacement for the thin film resistors), or using the through-hole parts I am familiar with (which could possibly fit in nearly the same space as the circuit doesn't have too many parts)? I suppose heat is the enemy here, so do either of these options have thermal advantages? |
11th May 2020, 7:26 pm | #37 |
Moderator
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Re: Reverse engineering Lumenition optical switch
non-acetic silicone rubber. It's significantly more expensive than the bathroom variety, but that stuff exudes acid which rots metal.
The one I;ve used in the past is by GE (General Electric of America) and is grey coloured. Is works very well and survives terrible environments. David
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11th May 2020, 8:42 pm | #38 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,642
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Re: Reverse engineering Lumenition optical switch
We used something called Plast2000 for waveguide and coax cables, also a grey silicone sealer. Getting it retail may be a problem though.
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11th May 2020, 9:15 pm | #39 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Re: Reverse engineering Lumenition optical switch
Farnell or RS
David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
11th May 2020, 9:42 pm | #40 |
Nonode
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 2,350
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Re: Reverse engineering Lumenition optical switch
I have been using Loctite 5920 for around 10 years for sealing, potting etc and it has been faultless. A couple of years ago it seemed to have gone off the market, with a few tubes on Ebay at high cost. However it seems to have been replaced by an identical compound (5990) in slightly smaller tubes st higher cost. It is copper coloured and often referred to as "copper silicone plastic" or similar. If your potting is deep, then apply in thinnish multiple layers, or its setting time will be rather extended. This really is a "master of all trades" in my book. No worry about corrosion, electrical leakage, or high temperatures. Don't get it on your lenses, it is pretty opaque!
Les. |