UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Solartron CD 1400 Oscilloscope Refurbishment

Chris55000 · 2nd Jul 2020, 7:23 am

Hi!

Further to the above, a perusal of the CX1443 standard T.B. module circuit diagram reveals that two auxiliary lower voltage h.t. lines of +220V and +160V are obtained from the two triode cathode–followers V7a and V7b, (the horizontally mounted ECC88 on the small sub–chassis) whose grids are connected to a chain of three resistors across the main +320V h.t. line, the resistor values worked out to give the correct potential voltages needed on V7a and V7b grids.

(N.B! The two cathode–followers V7a and V7b are only provided to enable low–wattage h.t. dropping resistors to be used, they do NOT provide any h.t. stabilization!)

Now I think Solartron's intention may well have been to originally obtain the +160V from the main chassis, hence the original inclusion of R108 & C109 on Board 1, with the lead off from Tag 15 of Board 1 going to either pin 1 or pin 2 of SKTA, SKTB and SKTC (the plug–in module connectors) – these two pins on each connector plug/socket are annotated in my moth–eaten Tech. Manual as "Reserved for Solartron Development".

Chris Williams

2nd Jul 2020, 7:23 am	#23
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,864	Re: Solartron CD 1400 Oscilloscope Refurbishment Hi! Further to the above, a perusal of the CX1443 standard T.B. module circuit diagram reveals that two auxiliary lower voltage h.t. lines of +220V and +160V are obtained from the two triode cathode–followers V7a and V7b, (the horizontally mounted ECC88 on the small sub–chassis) whose grids are connected to a chain of three resistors across the main +320V h.t. line, the resistor values worked out to give the correct potential voltages needed on V7a and V7b grids. (N.B! The two cathode–followers V7a and V7b are only provided to enable low–wattage h.t. dropping resistors to be used, they do NOT provide any h.t. stabilization!) Now I think Solartron's intention may well have been to originally obtain the +160V from the main chassis, hence the original inclusion of R108 & C109 on Board 1, with the lead off from Tag 15 of Board 1 going to either pin 1 or pin 2 of SKTA, SKTB and SKTC (the plug–in module connectors) – these two pins on each connector plug/socket are annotated in my moth–eaten Tech. Manual as "Reserved for Solartron Development". Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! Last edited by Chris55000; 2nd Jul 2020 at 7:31 am.