11-08-2014, 03:43 PM
Originally built in the early 1970s, this PSU has undergone a number of revisions and re-works since then - including a replacement HT mains transformer. That's why the internal wiring and general appearance is a bit scruffy.
The case originally housed an ancient Murphy signal generator that was given to me in the early 1960s. As the years went by, that was superseded by other generators that were a bit more comprehensive - so the case was eventually put to a good use.
First, a block diagram:
[attachment=11039]
And secondly, the cct. diagram:
[attachment=11040]
Overall, the design is quite conventional but a few features need some comments. Upon switching on the incoming a.c. mains, the heaters of the valves inside this unit and those external, receive 6.3 v.a.c. immediately. A timer then starts which runs for approx. 30 seconds before the a.c. HT from two transformers is applied to the internal valves.
Apart from the 6.3 v.a.c. output, there are four HT outputs: HT1 is an unregulated supply (approx. 650 v.); two independent, regulated, adjustable HT outputs, HT2A and HT2B, each adjustable from 100 → 400 v.; a regulated, adjustable HT negative output, adjustable from -30 to - 90v. A facility is provided for HT2A and HT2B to be electrically connected in parallel with an independent output voltage adjustment for that mode. The front panel features a switch appropriately labelled 'HT 2 mode: S / P' (separate or parallel).
An indication of the current drawn from HT2A and HT2B is provided (front panel meters) and a front panel voltmeter, with a selection switch, enables any output voltage to be inspected. Each HT output is connected to its corresponding output terminal by a switch and a neon for each output which is illuminated when that supply is present at the output terminals. This feature is included as a safety feature: accidentally putting oneself across a regulated supply of 350v.+ from a source that will deliver approx. 100 mA is not to be recommended!
As for the construction, a 'two-tier' style has been adopted. The upper deck is hinged at the rear, enabling access to the components beneath that deck and the components on the lower deck. This arrangement can be seen in the attached photos. Two fans are fitted: one for inlet and one for exhaust. The case has its original carrying handle and that handle is needed: this item is heavy!
For anyone who needs a regulated, adjustable HT PSU, a simplified version could easily be built by eliminating one of the independent HT outputs (i.e. HT2B), the HT- supply, (possibly) the current and voltage monitoring and the timer: two separate switches could be used: i.e. a manual delay. However, the removal of an 'HT output' switch and warning neon I would not recommend.
Finally, I do not claim that this design is perfect in all respects or without some design short-comings. All I can say, in summary, is that it has met my various needs for a comprehensive adjustable, regulated, multi-output HT PSU for many years.
[attachment=11041] [attachment=11042] [attachment=11043]
[attachment=11044] [attachment=11045] [attachment=11046]
[attachment=11047] [attachment=11048]
Al. / Skywave / Aug. 11, 2014 //
The case originally housed an ancient Murphy signal generator that was given to me in the early 1960s. As the years went by, that was superseded by other generators that were a bit more comprehensive - so the case was eventually put to a good use.
First, a block diagram:
[attachment=11039]
And secondly, the cct. diagram:
[attachment=11040]
Overall, the design is quite conventional but a few features need some comments. Upon switching on the incoming a.c. mains, the heaters of the valves inside this unit and those external, receive 6.3 v.a.c. immediately. A timer then starts which runs for approx. 30 seconds before the a.c. HT from two transformers is applied to the internal valves.
Apart from the 6.3 v.a.c. output, there are four HT outputs: HT1 is an unregulated supply (approx. 650 v.); two independent, regulated, adjustable HT outputs, HT2A and HT2B, each adjustable from 100 → 400 v.; a regulated, adjustable HT negative output, adjustable from -30 to - 90v. A facility is provided for HT2A and HT2B to be electrically connected in parallel with an independent output voltage adjustment for that mode. The front panel features a switch appropriately labelled 'HT 2 mode: S / P' (separate or parallel).
An indication of the current drawn from HT2A and HT2B is provided (front panel meters) and a front panel voltmeter, with a selection switch, enables any output voltage to be inspected. Each HT output is connected to its corresponding output terminal by a switch and a neon for each output which is illuminated when that supply is present at the output terminals. This feature is included as a safety feature: accidentally putting oneself across a regulated supply of 350v.+ from a source that will deliver approx. 100 mA is not to be recommended!
As for the construction, a 'two-tier' style has been adopted. The upper deck is hinged at the rear, enabling access to the components beneath that deck and the components on the lower deck. This arrangement can be seen in the attached photos. Two fans are fitted: one for inlet and one for exhaust. The case has its original carrying handle and that handle is needed: this item is heavy!
For anyone who needs a regulated, adjustable HT PSU, a simplified version could easily be built by eliminating one of the independent HT outputs (i.e. HT2B), the HT- supply, (possibly) the current and voltage monitoring and the timer: two separate switches could be used: i.e. a manual delay. However, the removal of an 'HT output' switch and warning neon I would not recommend.
Finally, I do not claim that this design is perfect in all respects or without some design short-comings. All I can say, in summary, is that it has met my various needs for a comprehensive adjustable, regulated, multi-output HT PSU for many years.
[attachment=11041] [attachment=11042] [attachment=11043]
[attachment=11044] [attachment=11045] [attachment=11046]
[attachment=11047] [attachment=11048]
Al. / Skywave / Aug. 11, 2014 //
