UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - AVO CT 160 Improved Anode Current Measurement

David Simpson · 24th Sep 2019, 12:13 pm

The thing is, Karsten, back in the day(for CT160 usage) - late 1950's to the 1970's the UK Military bases & ships would have had better stable AC supply sources than the general public & business premises. These days, CT160's are just owned by private vintage radio enthusiasts, & a number of audiophools with high expectations & deep pockets. Folk have their workshops/shacks in garden sheds/garages/lofts/etc. either sharing their house's ring mains or on a spur. So supply fluctuations are a common occurrence. Problems relating to the UK's sinusoidal accuracy & domestic interference from a multitude of switch-mode appliances have been well discussed Forum-wise(see "Search").
From my experiences back in the 60's - servicing & repairing CT160's, and more recent ownership of a couple, I reckon that accuracy beyond 10 to the minus 1 for Gm & a couple of % for Ia is more than can be expected for these 60 odd year old valve testers even if they are kept in good calibration. Particularly as the don't give a decent meter indication of Ia - like a MK3 or MK4(after all, the CT160 is more or less just a MK3/4 squeezed into a clamshell).
There might well be a handful of experimental/design folk who require true & accurate static valve parameters, or even venture beyond Barkhausen's Law & study dynamic properties - to these folk I say - build a pure DC Tester. From what Martin Forsberg tells me - the RoeTest is extremely accurate. As is the VCM163, and the "Sussex", as other Forum folk tell me. And I've heard that Tektronix made a super accurate Curve Tracer back in the 70's/80's, which is hellish expensive to acquire these days.
Me(an old analogue guy), & quite a number of Forum/Vintage Radio folk, are now of pensionable age. So we have to consider very carefully what we spend, regarding expensive test equipment. Hence, in my experience, building a decent DC tester out of redundant/surplus parts/equipment, was a very attractive project - coming in at less than £200. Some folk ask 4 times or more than that amount these days for a CT160! Jesus - a genuine AVO 10K RV2 or a 30uA meter can cost £200!

Regards, David

24th Sep 2019, 12:13 pm	#13
David Simpson Nonode Join Date: Mar 2008 Location: Aberdeen, UK. Posts: 2,858	Re: AVO CT 160 Improved Anode Current Measurement The thing is, Karsten, back in the day(for CT160 usage) - late 1950's to the 1970's the UK Military bases & ships would have had better stable AC supply sources than the general public & business premises. These days, CT160's are just owned by private vintage radio enthusiasts, & a number of audiophools with high expectations & deep pockets. Folk have their workshops/shacks in garden sheds/garages/lofts/etc. either sharing their house's ring mains or on a spur. So supply fluctuations are a common occurrence. Problems relating to the UK's sinusoidal accuracy & domestic interference from a multitude of switch-mode appliances have been well discussed Forum-wise(see "Search"). From my experiences back in the 60's - servicing & repairing CT160's, and more recent ownership of a couple, I reckon that accuracy beyond 10 to the minus 1 for Gm & a couple of % for Ia is more than can be expected for these 60 odd year old valve testers even if they are kept in good calibration. Particularly as the don't give a decent meter indication of Ia - like a MK3 or MK4(after all, the CT160 is more or less just a MK3/4 squeezed into a clamshell). There might well be a handful of experimental/design folk who require true & accurate static valve parameters, or even venture beyond Barkhausen's Law & study dynamic properties - to these folk I say - build a pure DC Tester. From what Martin Forsberg tells me - the RoeTest is extremely accurate. As is the VCM163, and the "Sussex", as other Forum folk tell me. And I've heard that Tektronix made a super accurate Curve Tracer back in the 70's/80's, which is hellish expensive to acquire these days. Me(an old analogue guy), & quite a number of Forum/Vintage Radio folk, are now of pensionable age. So we have to consider very carefully what we spend, regarding expensive test equipment. Hence, in my experience, building a decent DC tester out of redundant/surplus parts/equipment, was a very attractive project - coming in at less than £200. Some folk ask 4 times or more than that amount these days for a CT160! Jesus - a genuine AVO 10K RV2 or a 30uA meter can cost £200! Regards, David