Hi All-
thanks to those that assisted with the WHY a 1% 5000pf in the Z axis circuit.( most likely it was what was most expedient in stock)...my solution is a 5100pf (3%) ordered 10 and chose one 5040pf...close enough! cap looks like it belongs there.
replaced that and the series 1.6k...raster has returned and is working just fine with a couple of exceptions....
item one.
Arcing- problem where the anode lead enters/attaches to the CRT the silicone covering has a gap allowing sparking to occur to the shield at that entry point hole. time was not kind to the silicone from the pressure of the HV lead pushing to one side
solution so far remove CRT and shield, clean with alcohol...still arc. so I placed a piece of insulation between (over the edge of the) shield and entry point...so far a temporary fix. ran for an hour. only a couple of pops..whoo hoo! (which led to #2 during testing)
So suggestions for a permanent fix?? more Silicone? ( generally it will not adhere to itself) this may have been part of the above cap failure- arckle sparkle is a no no....
there used to be a "play dough for high voltage" to assist in preventing coronas is that stuff still available?
item two-
does anyone have the specs on Beckman Helipot 82-4-2 ( specifically pin spacing and temp coef) this is R47 on the A10 board...looks like a PAIN to change.? 250K 10% 0.5W...I am looking at a Bourns 3339H as a replacement.
what it does is something mechanical -touch it and channel 1 voltage pops back to correct displayed value on the CRT ( using 2v cal signal it drops 0.2V. consistent over multiple ranges.) ( btw- channel 2 is fine)
I fidgeted with it and no matter the setting same unreliable issue...so it must go unless other solution prevails...possible solder issue but IF I take A10 board out i will replace it....are these trim pots a known failure item?.....I may change the small 'lytics too.? cute scope! more portable than my 465 or 475.....
Thanks for the assistance.
搁别苍é别, K6FSB
