- Vintage transistors and tin whiskers - 5 Updates
- DPF Cleaners - 2 Updates
| Cursitor Doom <cd@not4mail.com>: May 17 02:15PM Gentlemen, I have some old OC171 transistors from an old Eddystone short wave radio I'm restoring. The problem is I suspect they've developed whiskers, as the resistance readings from e,c and b to the screen connection are all far too low (sub 10 ohms). A colleague has suggested blasting the whiskers by tying the ecb leads together and zapping them against the screen with a 500nF cap charged to 500VDC. Now this seems a bit counter- intuitive to me and I'd have thought higher current lower voltage would be safer for these delicate germanium devices, but WTF do I know? Is it feasible to remove the whiskers by this sort of method or any other? Thanks, CD |
| DecadentLinuxUserNumeroUno@decadence.org: May 17 02:51PM Cursitor Doom <cd@not4mail.com> wrote in > remove the whiskers by this sort of method or any other? > Thanks, > CD Put it in your ten below freezer for an hour and let the cold disintegrate the non alloyed tin. Then give it a nice hard rap to break it all loosed like we used to do to the old tube type TVs to get them going again. Kidding of course... except for the TV thing. That worked. So did taking the back off it and re-seating all the socketed tubes and components. Worked every time. It is almost always a mechanical connection. |
| Pimpom <nobody@nowhere.com>: May 17 08:26PM +0530 On 5/17/2020 7:45 PM, Cursitor Doom wrote: > Is it feasible to remove the whiskers by this sort of method or any other? > Thanks, > CD I don't know about the whiskers but Ge transistors have high leakage and no sharp knee at low currents. I wonder if 10 ohms is too low depending on the voltage applied by your meter. I have a few of the later AC188 types. I'll dig them up tomorrow and measure their resistances. For quick go-no go checks of transistors, I prefer analog MMs. The static forward resistance depends highly on the current applied through the probes. I used to have some OC71s and OC72s a long time ago. They made neat phototransistors with the paint scraped off from their glass enclosures. |
| Pimpom <nobody@nowhere.com>: May 17 09:06PM +0530 On 5/17/2020 8:26 PM, Pimpom wrote: > I used to have some OC71s and OC72s a long time ago. They made > neat phototransistors with the paint scraped off from their glass > enclosures. OK, I got the AC188s. With a DMM they measure 25-50 ohms forward and a few Ks in the reverse direction. |
| Cursitor Doom <cd@not4mail.com>: May 17 04:34PM On Sun, 17 May 2020 21:06:23 +0530, Pimpom wrote: >> enclosures. > OK, I got the AC188s. With a DMM they measure 25-50 ohms forward and a > few Ks in the reverse direction. I think you've misunderstood the problem here, Pimpom. The leakage in question is between the case ("screen") and the die and significantly pre- date the black-painted phototransistors we all fondly recall from 50 years ago. :-) |
| Cursitor Doom <cd@not4mail.com>: May 17 11:14AM Hi all, Does anyone have any experience of this stuff? /Wynns Professional Off Car Diesel Particulate Filter DPF Flush Cleaner/ Supposedly the next best thing to an actual physical DPF replacement. Anyone tried it? |
| Cursitor Doom <cd@not4mail.com>: May 17 02:17PM On Sun, 17 May 2020 11:14:02 +0000, Cursitor Doom wrote: Sorry guys, wrong group - please ignore! |
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