Down the rabbit hole it goes,
having taken on board your suggestions I rebuilt the multiplier , tested with signal generator and got more out than I put in thus drawing the ire of the long arm the laws of thermodynamics and cheers from the free energy horde .... nah not really, it just seemed to be fit for purpose once more. That was number 1 in the high voltage section schematic attached.
So that was a go, but no go. Rooted about and found the dead drive transistor (2n3906) in box number 2 , poor little thing flogged it's guts out trying to make the voltages better ... to no avail. Powered up and watched a tiny firework display dancing around the enclosure surrounding the HT board , the ceramic 500pF caps in box 3 were covered in craze patterns from arcing .
As an aside That board is rev B , the donor scope had a rev A board and this seemed to be a common issue with them. At some stage someone had smeared ( best description)a lacquer all over the board and applied tape over the section of the casing where most of the arcing across had occurred. I assumed common since , fearing a dead transformer , I started looking around for a replacement board and on
www.sphere.bc.ca I found a picture of a rev A board ( sold already , argh !... Yet fortunate it turns out). It too was likewise rudely adorned in the same brown goo ,was It HP themselves or a travelling lunatic complete with sweeping brush and bucket of goo to be applied with ? Pics below if you want a look.
Back to the plot , with no love lost between me and the sparkling caps the whole lot were given their marching orders and replaced by jelly bean replacements fresh off the ebay. Success , no , but now I switched on and when I got up from under the bench witnessed no light show allowing things to warm for about 30 seconds only to hear whistling. Not having an excess of protein in my diet I knew I wasn't the source and the medly was soon cut short by the popping of the primary DC fuse.
I blamed it on wheezing electrolytics on the low voltage supply board. Not wanting to point any fingers the whole lot went the way of the crazed ceramics. So they were gone , switch on ( but standing now , only slightly hunched ... at an oblique angle to the device) no sparks, HT probe on the cathode 1.9kV ,grid 2.1kV - tweaked the HT adjust and the intensity limit BINGO in spec!
But alas , trace find came back empty handed . Nothing on the screen. While observing the screen and going through the controls desperately looking for a glimmer of life some bugger started whistling again! The bastards are back I mused , it was another swansong but this time the mains input fuse died. This time the only remaining was the 2000uF reservoir cap lurking beside the diode bridge , sling your hook was the order and off he went. Currently it stays alive until I probe the cathode voltage , whereupon it promptly goes piff and another main fuse dies, though I only have quick blows and the orginal is a slow blow resistor fuse. I can't put all the blame on the speed of fusing can I ? Next task is to remove and clean the CRT end cap (plug ?) and have a look for cause among it's connections.
The struggle goes on, but I won't let the bastards get me down.Have Hakko FR-301 ( love that machine), will travel through the schematic until I find my nemesis if the 20kV doesn't get me first. Yup the post accelerator seems to be alive and kicking as it now gives a farewell burp on the screen every time the machine is shut off , or shuts itself off.
Regards and happy mondays, make that tuesdays now.
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