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Old 17th Jan 2021, 12:08 pm   #1
richieyork's Avatar
Join Date: Dec 2010
Location: York, North Yorkshire, UK.
Posts: 183
Default Knight 600C Valve Tester advice sought

Hi all

I recently took the plunge and bought my first valve tester - a Knight 600C. I believe this was likely the last model of this range and dates back to around 1970. These were sold as kits and the standard of the soldering suggests it was home built though its perfectly adequate and the joints are solid enough.
It was supplied with lots of original documentation and lots of charts so i'm happy with that.

So, i'm just getting to grips with this device having never had a valve tester before. The vendor has replaced out of spec resistors with quality metal film types and capacitors of which there are few thankfully so all good there.

I've carefully followed the instructions ad tested dozens in my box of valves, initially just to familiarise myself with its operation but not surprisingly I found quite a few week/dud valves. I also have a few new stock valves and tested these and happy to report they test as they should so i'm pretty sure it's all good.

There are a couple of things I want to query with you folks:
The vendor has fitted a new step down mains transformer (240 - 115v??) as these were for the USA market. It's about 3ins x 2ins. With the tests I've done so far (predominantly on 6.3v valves) I 'think' the filaments aren't glowing 'quite' as brightly as I'd expect to see in a typical wireless. Not miles out just not as bright unless it's my old eyes. I located the calibrating information and using the steps suggested and it was pretty close to correct, measuring 6.3v on the octal socket set for a 6V6. However I'm wondering if the mains transformer isn't beefy enough? When a valve is tested the panel lights dim slightly as the valve filament supply switch is enabled. Is this typical behaviour? If the general suspicion of you guys is that it would benefit from a larger step down transformer i'd appreciate your advice as to one you'd suggest and the costs. Otherwise i'll just live with it and be happy!

Looking forward to hearing from you!
Kind regards
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Old 17th Jan 2021, 4:08 pm   #2
David Simpson
Join Date: Mar 2008
Location: Aberdeen, UK.
Posts: 2,349
Default Re: Knight 600C Valve Tester advice sought

Rich, can you monitor the 115V O/P from the transformer with a multimeter ? Just to make sure its OK . Likewise, can you monitor the heater supply whilst a valve is working ?

Regards, David
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Old 17th Jan 2021, 7:01 pm   #3
Join Date: Jan 2007
Location: Bristol, UK.
Posts: 1,021
Default Re: Knight 600C Valve Tester advice sought

David's advice is spot on for a quick check, what you have is a basic emissions tester very much like the Heathkit series. By the time the 600C was introduced I believe the parts were from Japan. There is nothing wrong with emissions testers as long as you remember that they were designed for servicemen to quickly screen out bad valves, the readings as you have discovered are relative between good and bad valves but are not comparable with readings from AVO or Hickock types testers and as such you don't need to worry about anything other than line adjust and filament voltages.
Good luck and have fun checking your valves.
Chris Wood
BVWS Member
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