This is a multi-part message in MIME format. ------=_NextPart_000_0196_01C81292.30ADF090 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Can someone please suggest a fix to this problem. In the diagram, the 220R 0.5W gate resistor keeps showing me how much smoke it can blow out I plug this in, wait a couple of seconds, then press a pushbutton, which makes a 12F675 send a 10us to the opto-triac. The pulse is OK, checked that on a scope What will happen is that the flash will go off, then the 220R starts slowly burning. The power gets turned off, maybe a second later, before the resistor actually goes open I've tried a large-value resistor pull-down on the SCR gate, but that makes no difference. It's presently 2 x 560k (some resistors in this circuit are series pairs, for the voltage rating) Tried several values for a pull-down, from 1M to 5M, in the position shown, but the 220R burns up just the same. I feel like General Haig sending them over the top, poor little blighters Must be on the wrong track with a pull-down. Can't see where that power is coming from. I figured that for all but a very brief time, the resistor is isolated from any PD across it. Something is obviously not turning off, and making it dissipate a lot more than it should need to. The only candidates, AFAICS, are the tube, the SCR or the opto I don't think anything else is suffering. My logic being that the flash will go off with a new 220R Plan A - replace the 220R after every flash, but I'm pretty sure that's not how the pros do it ;-) Plan B - ask you guys TIA ------=_NextPart_000_0196_01C81292.30ADF090 Content-Type: image/gif; name="pic_flash.gif" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="pic_flash.gif" R0lGODlhvQHJAIAAAAAAAP///ywAAAAAvQHJAEAC/oyPqcvtD6OctNqLs968+w+G4kiW5omm6sq2 7gYgwGzEh/3mujLbPR3o1WQqHC44TCqRSuPumfhJp9TqERp11pxarLfYBSK7lOv3DLWq1xFzWYiO y+XuuT1Xz+Tzd5iJLwJIRNfXIPhxOJEIsSixVwhCFsmy2EipeDN4SObjuGL5ALo2StUGqREDyhSk qqpXRngaZToUFjrJUEe6+yOLOMshefsJm1mbKfbnO5jimmuIcdXZeWJEzcS5ujn1peYg3bTKw8xI Yits/PrCB8dqDb7gHA+9jLV5I8+c77Vv7rfOqNc7T+WuFWvzjgYXZOnqNaQlDtOWENdSNRTUqJ87 /nwDyXm0oPFNO2UFl0h0uCNkOJQfvwEbw1DlPFTPNDGMOO6jxXDSrEWD6QqjR2oKpz10KNMkS5z0 4uRL2lJpi3Y7N55EuVNSUplQ8Vw98/TlES3wojL196vmUoBr/yQz9NZeXJAkZcwNdBfk3a5t6Z4c uyVZR6t9CcI8hlgqLrSBCjt+LAswZLMduvKdjDmzX8VpKtfVDDq06AplRxJW2o/dP7VVLaZSeBMb 0JWja48+ZyxviYRUS3HsdZqzYdvEi9du/XKJmdQuaRp/Dj1606MXVDuXjj17dua7tXv/Dj68+PHk y5s/jz69+sLngK+PFBe5FLZZc9uP/T6/frm8/vr7/w9ggAIOyIY2iFz2V0z47XfdQgtVx2BnHjyi l2BZWJFOGAR6s9uGHn4ohi2BgTgfbbxxY+JvJBII34eNzUTcZQgmN4xTpkh2mEs4VlVOEYutFsx0 oAGi0oyU0dgNVhDpQuSPF3KITjRGpuSeJShmdAlEdnU05ZQv1kNhhDlN1SMPIe7lHow1UhRmmMvs MRIQZB1VpJAJRsRXib2VhSdHdlKHgpffVLHmY4Ie6eQzPB7UnHDHIQRcK3oGWZGBlqpVJgxxVnop oF9VQ2hTi2oJzWCkqsfdn6ck4saDOX4G4YV+BjYiRqF2V1JQmY4F2zFnHspYoiyxakdYuKqp/k9s 9Z01zLKk7QcVsMdmChaQncLjLGfSzpTtp28OpZs65FUyh7HBIjltkJiKyW5mMo6wbbvNIpthYohV GmWSnjJ6KXLVwJqWvAKzJVxPGKZYK4fWsjlblfUmPHDEZO5LDLqb0fvsK25KzLFns3rmWp8bM8uv xd5S3HHK3xn8ZJq0upOmuSrPbJurBmVjcsmIFkpzz9B6fK7PQq+XKrxDH4100kovzXTTTj/dcYj4 xSudzQbiGOhbXM7ismlQZ3k1yimLGLaj/hBVbzZUf81225CUpunabscy91BiZ6wDbofJHZ3e3Z5c d87DYRzolg/x3bfhJjmDuH51rrtksjyT/tx0qxMObja6jfuyFeSTd0pt5uIaXfGpsQr+eaM7t0Su jwEvrO6YNQNMu+f2OIKtIrnrHPR1sI+OOmbvlh46PwHBARiRkRLRejPCng687LcR7nvhmBuPFPGx f5Vv9JDxmTrezl9/e/Zl+kv544TDjUq4fZXCuNempxt+3kpCig/o/9o+8GshiQI2nsHNIKQDE6h8 U73VxSNmCjSU9lTVu+lYbVRf+hZryvaqPr0ueLeQD2M8aC8M6k91BKPe4kSYHGJ9MDe6ecqK+iMq rqXNhBfjIN2YN0MVZc5yKYGeOHxAQRo2kFG98trBxBfA/XVQRSUS4nia5LphucsrUdSR/ug4WBE5 7WlE79Od+3j3k5dZBXwK1MgEF0RGJD7wggDMVRh7hC9ljdCCaiSN/GIVR57Ub4gxxKEepVfDrDXx gnMMXsh8iKrfOdFGgOvh9prxRaBZkXL8u4jFNldB2GEykJ6rkpwoqcji2c1V6QMUr7YWlQLl6I6V VA4wJugy81HEMViS1cuMVDQ+WQ1jushhw0CZk7/N7zzRoiX5yofITPKxO4fkJHqKyZ5GOjJ6RmSg JVt5iWbWkXNaieQ2EyjFYz5BZnNs5qJGRj9wXrFciUljKLHTPDSQc5bY3KAiN/k2YkrTfu/8nZfU B8jACXSP6izoQA96h+EpE6GeYF87/mWzHNmEMKHLXJd8YrlQe16OoW9ckInQJ9FV9gFr1RFIpD55 N+9pVJIc5RhJxySUgFYxo5ojYUsj9lKx6CyeKt2ot/B50ymmdGL9NGhQn4ZAmLESYEWTaSM/6aBX grA+3TuqvM4kMjs11YaVfE3+tDkRIO7oYVZ9Dvr8tdRXJoFsL4UiExU2z7JCzW8gtV6t/qSnrhVV rnw102C2qA8UAZIXQ11kXw/rxx/KLqKP5KphEQvZBG61ooWNrGVLNtnKOvaynE2mM33a2dDSc68d Fa1pT4va1Kp2taxtrWtfC9vYyna2tK3tQE9516UBdowYtS3n+qXYpGlFhF3KUB7l/kgb1/qNaTh7 ELCkxqk5eRS2egOmS+/zR+tOYj7VTZ5vv6sHrX1MOaZJa4x0WlKggpejDiXtesd3W/SuNIBCwJp6 Q4Nb+3q2be2d77+WS0ChnRWi66Ss0+LnVqJGdaJDww0pwXjQ1FgHbNLVbP8e5s5hRvh52n0vS1vK lXrKV4weduqGR+tYshUsq247Z4cXKBRwkEvG+fHmyayELGLROIKgPSD+aLLjCsEiyCVJ7KCK61/d ZRTHubAxFXlcQFFKyIAzda9NG1vgLqZzy49NYnO4WwwwQxjFWN5vaS28FoXCV8rjvJFaS7k7Fa65 zJ/d7325/OHadXmNb25CTHdU/ss5WxmCb7iyaIKYZzxvtsp9ZDCMvCtOMg9axDAm6GQybFRJE3qa dLRroklY1TNPj9KR1jSpvbwq3E341Ja2W5Zb7UA2fzPKsEZ1Ps8XtgTTuZeSo7PwCovpTZt6z4y+ dY0GbGhRK6a/Xqyaxpz86p6y2tO/xTUQqXPEnt45zZOqkNRKzWETc7raVCZ2jc3bZDHvM9zYliOS y93pRRMtfyCbNU2l50mjKDHeerazuHZpHGimVFBMxiBYaR2ZI38MeTQCqLyXtzezEjXZCNfqr9Ya vqVum3+PqDBje2xgX013Qhe/ZQr9Wud98xK5JsupuDXmS3QWIi/DrW7IWx7e/uFSG62WDPW0aarr iwoG4hpuEMtfXmuSxxDgZ3H4zcctUntV2KZ8a4V8Ee1yc+OaFYWMq6AV/c2Nq4npJOWUTOMlqfqe NIPCRvNIn0xtRb1a7PKkeMUT/usSqlzuuqIF3ft9wkf+/efmuNWYwZ7kdtq4Et01eFt0DO1SOcXw Wke5GBnuamkDHsNiuweiLY22ZDH9fsf7thcFonTHZ5in2raUMLwedzam/F5mvibmsYHSFzPyyKiX ElX8cFyzG9aMhwMuDzWPl0E++sWen/vPnsW44OS8V1Fnuw2J/1CcId3u8Optr9ENyoODWzyBLnCw N7NbsxVcX5lOfrFlSGJZ/o/L126HOl5Ljkv6Q3nYOOy76tw5ePYGOAG4M7zmS5tHde42NXDEZ/Bn dWuyO2Ogb7pXdxtEgNcHU1czI/KwaiKlfIu1QDHHdRPhF8Ikf8lTRApoTLN0gdt3TR5IgesmQFfX dWeXNgwnfm72edwHM2YSVhI4XuHEf/zWdnoHPdx1Ujdjg8uXfbPRbIpXfvN2b0TogkZ4ePeEKYAV enSRg/L3RHcnS15ohTLYeuVjgkmnHQL3eGQ4cbWHhWYYUldIfmAIb2j4dfyic47nKY0TMv5HejEo gG6Id0XHT8DDCZjXLTLXfUfUGtkmb0mihNFmh0VobGLoAuQUJeakQZUX/ogDmGYPtSUvtCIrSIhw h0i/RxhkpIhTGHafSILJlXiJM36XOGme+H7+5jj6NIttOHsF9U8c1oL2Bx6shz21eD2/OF/BmDei yIzN6IzPCI3RKI3TuAsldlUIaI20pWbZiFQlx1vg137It17ehFUYlwXZdWeCJXjEtXfsNo44QUHO 1YO0VwvgWIiA6GryGHux6FsfaIATWI/1dXQ3tA+6NJB0qH/vxWzNJV6XF3kTp4yTWIrcOH8oY4/s h5AUWR5Zt4nzQGS2BnLj8JEaOTv7cn4htIP1J4kTiZL4SJLkRkkXmZCWKIgvOYxPl5EsWZM26R0c mU1F4T8boXZBOZRC/jmTckd4PEmQ7HSUZuZVueaDYpUi3qeUN/mIlAF7qreJPHdIPleVWOETwOUo mRWS9JYVYHVtbEVWX/k9v2RkSEKW+NiBbHloKgZkTjhySamSPEiXJamVorOF5dWQSkVzLWN6IReR fRkwZEclGudX3siPinloisN1UplEadUqvzKYyiaZDBVTMKWOTdmZudiEoIganyaXo0kzuVcanxmO nKmaF2aXrnSVJmmMsUlM+JeENEmJO4mbwlWFhJaVv9liqCmaxNlgQgmUykmUy1mUBYmcnmmctxmd Ajadr1mdunWd4pidzLWdsNmdwqUwduSM4dlioWme2SiT6cme7emeB+8JnwxSAAAAOw== ------=_NextPart_000_0196_01C81292.30ADF090 Content-Type: text/plain; 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