Detectron Geiger Counter
in [Repair]
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From: Chris F. on 24 Apr 2010 10:51 > I'll stand on my comments that your clip lead and external power > supply kludge is probably causing problems. Find some suitable > electrolytics and place them across where the battery would normally > connect. The idea is to reduce the impedance that the counter sees in > the direction of the power supplies. That should reduce the > motorboating (oscillation). I tried putting a 100uF cap in that area, the result was that it greatly increased the frequency of the stray clicks.... I wonder if a row of 10 9-volt batteries would work?
From: Jeff Liebermann on 24 Apr 2010 12:52 On Sat, 24 Apr 2010 07:51:13 -0700, "Chris F." <zappyman(a)hotmail.com> wrote: >> I'll stand on my comments that your clip lead and external power >> supply kludge is probably causing problems. Find some suitable >> electrolytics and place them across where the battery would normally >> connect. The idea is to reduce the impedance that the counter sees in >> the direction of the power supplies. That should reduce the >> motorboating (oscillation). > >I tried putting a 100uF cap in that area, the result was that it greatly >increased the frequency of the stray clicks.... Did you figure out where the yellow electrolytic in the photo was connected? Power supply filter or meter integrator? Find an oscilloscope that can tolerate some high voltage (i.e. 100x probe). Look at the power supply line. Got pulses? If so, get rid of them with a filter cap. Old carbon composition resistors tend to change value with age (and moisture). With the power off, you might walk though the pile and see if there are any that are radically off value. I don't think this is causing the problem, but it might be contributory. >I wonder if a row of 10 9-volt batteries would work? Probably, but rather expensive. It should work with your external power supplies, but due to the apparent lack of power supply filtering, it might be oscillating. If all else fails, trace out the schematic. It doesn't look all that messy and you can probably use the DG-9 schematic as a guide. The author of the web site where we found the DG-9 schematic is the founders son. Send him email asking if he has a DG-7 schematic or if he knowns anyone that can help. -- Jeff Liebermann jeffl(a)cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
From: Jeff Liebermann on 24 Apr 2010 13:03 On Sat, 24 Apr 2010 09:02:32 +0100, "N_Cook" <diverse(a)tcp.co.uk> wrote: >Does USA "kludge" = UK "bodge" ? I think so. Also sometimes spelled kluge. <http://en.wikipedia.org/wiki/Kludge> -- Jeff Liebermann jeffl(a)cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
From: Chris F. on 24 Apr 2010 13:45 > Did you figure out where the yellow electrolytic in the photo was > connected? Power supply filter or meter integrator? It's connected across the meter. > > Find an oscilloscope that can tolerate some high voltage (i.e. 100x > probe). Look at the power supply line. Got pulses? If so, get rid > of them with a filter cap. Already tried that.... or are you talking about the AC line feeding my transformer/rectifier/cap power supply? > > Old carbon composition resistors tend to change value with age (and > moisture). With the power off, you might walk though the pile and see > if there are any that are radically off value. I don't think this is > causing the problem, but it might be contributory. Checked them all, and all are well within their specified tolerances. > >>I wonder if a row of 10 9-volt batteries would work? > > Probably, but rather expensive. It should work with your external > power supplies, but due to the apparent lack of power supply > filtering, it might be oscillating. > > If all else fails, trace out the schematic. It doesn't look all that > messy and you can probably use the DG-9 schematic as a guide. The > author of the web site where we found the DG-9 schematic is the > founders son. Send him email asking if he has a DG-7 schematic or if > he knowns anyone that can help. > I might do that. Can't think of anything else it might be, as it's really a rather basic circuit. BTW that small tube with the 2 leads I mentioned is a 5841 (voltage regulator), and I don't have a sub for it.
From: tm on 24 Apr 2010 14:33
"Chris F." <zappyman(a)hotmail.com> wrote in message news:4bd32e4e$0$12423$9a566e8b(a)news.aliant.net... > >> >> >> >> If all else fails, trace out the schematic. It doesn't look all that >> messy and you can probably use the DG-9 schematic as a guide. The >> author of the web site where we found the DG-9 schematic is the >> founders son. Send him email asking if he has a DG-7 schematic or if >> he knowns anyone that can help. >> > I might do that. Can't think of anything else it might be, as it's really > a rather basic circuit. BTW that small tube with the 2 leads I mentioned > is a 5841 (voltage regulator), and I don't have a sub for it. > Check this out: http://www.dvq.com/geiger/heath_rc1.pdf Googleing says it is a 900 volt regulator. maybe a stack of 150 volt zeners would work. I did see some replacements available. |