26-02-2017, 05:57 AM
(This post was last modified: 26-02-2017, 06:06 AM by Diabolical Artificer.)
Tidied up the layout of the pre/driver stage as it was abit of a bird's nest. I used the traditional tag strip, an old one I found in the shed. I also rejigged the CCS to get better impedance by replacing the bottom LED on the circuit below with a 6V8 zener and 1N4148. Switched on, LTP PS cathode rose to 200v, what the...!? Out with the zener LED back in, after adjustment
PS cathode at 11v, one anode at 80v the other at 225v! After investigation I found the "input" grid at +12v, the tag strip had gone conductive.
After some thought I remembered I had some turret tags in the shed. Didn't want to use the old paxolin or other similar old boards so used new ish fiberglass single sided copper clad board. This works out well because you end up with a cross between a PCB and tag board. I used a dremmel to cut out the traces on the underneath leaving a wide copper free gap between traces carrying HT and grounded traces. I'm quite chuffed with this idea and think it has potential.
Prior to this I found a nasty square ish signal on the cathode. Was this what you refering to Trevor? Morgan Jones mentions it, see below last para bottom of page. He used a current regulator diode in place of R1, but at £10- 15 a pop I'll see if one of those adjustable current source IC's like this one - http://uk.farnell.com/nxp/pssi2021say-11...dp/1758034 ( this probably no good as it's PNP and not if max voltage ok) will do the job.
Andy.
PS cathode at 11v, one anode at 80v the other at 225v! After investigation I found the "input" grid at +12v, the tag strip had gone conductive.
After some thought I remembered I had some turret tags in the shed. Didn't want to use the old paxolin or other similar old boards so used new ish fiberglass single sided copper clad board. This works out well because you end up with a cross between a PCB and tag board. I used a dremmel to cut out the traces on the underneath leaving a wide copper free gap between traces carrying HT and grounded traces. I'm quite chuffed with this idea and think it has potential.
Prior to this I found a nasty square ish signal on the cathode. Was this what you refering to Trevor? Morgan Jones mentions it, see below last para bottom of page. He used a current regulator diode in place of R1, but at £10- 15 a pop I'll see if one of those adjustable current source IC's like this one - http://uk.farnell.com/nxp/pssi2021say-11...dp/1758034 ( this probably no good as it's PNP and not if max voltage ok) will do the job.
Andy.
