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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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5th Mar 2017, 4:26 pm | #21 |
Retired Dormant Member
Join Date: Oct 2016
Location: Syracuse, New York, USA.
Posts: 1
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Re: Sencore Mighty Mite VII / TC162 Valve Tester runs hot.
The Mighty Mite has a very marginal transformer. It was made for service calls where light weight and small size were important, and will overheat easily even on 60 cycles. Try operating it on 110 volt at 50 cycles, or better yet, see if anyone makes a switching type power converter that takes 240 volts in and delivers 60 cycles or higher out. Make all the settings first before plugging in the valve, and make the test quickly. Bruce , KA2IVY
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6th Mar 2017, 8:53 am | #22 | |
Heptode
Join Date: Oct 2008
Location: Aalborg, Denmark
Posts: 903
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Re: Sencore Mighty Mite VII / TC162 Valve Tester runs hot.
Quote:
Thank you for your input and welcome to the forum. I wish I'd known before bidding on eBay. Sencore specifies the transformer for use with 50Hz but that's something they obviously didn't check out. I can say that I'm someone who makes a 240VAC/50Hz to 117VAC/60Hz power-converter, read earlier postings |
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13th Mar 2017, 1:48 am | #23 |
Heptode
Join Date: Oct 2005
Location: Olympia, Washington, USA.
Posts: 664
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Re: Sencore Mighty Mite VII / TC162 Valve Tester runs hot.
A quick test for the transformer is to disconnect the PRIMARY completely and tape the wires. Then set the fil selector to 6.3 V and run 6.3VAC into that winding.
Basically you are back feeding the transformer. I thought this out on audio servicing where open Pri. were really common here on the cheap stuff; (Especially after a power surge/outage), and I had to check out the rest of the unit for functionality. But Bruce is correct. They were the "low end" Not well designed (or even supported) after a short time. Like most of their products, based on my own experiences.) I believe they were designed primarily for the "tube swapper" to use in the home. Now IIRC, Dick Smith Co in OZ made a "universal" tube tester transformer back in the 80's. One of those might work. I would suggest measuring the transformer voltages, and maybe putting 1 or 2 out of other equipment in it to replace the existing transformer. I don't remember what the transformer voltages feeding the semiconductor section were. Not pretty, but better than sending it to the rubbish bin. Best of luck. --Oh you might try adding a "pancake" cooling fan & vent holes to the tester also. That wouldn't hurt at all. Maybe mount the fan on the outside of the case, as I doubt there is room inside. |
13th Mar 2017, 8:08 am | #24 |
Heptode
Join Date: Oct 2008
Location: Aalborg, Denmark
Posts: 903
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Re: Sencore Mighty Mite VII / TC162 Valve Tester runs hot.
Thank you for suggestions but let me remind you of my findings.
The transformer runs absolutely fine when fed 117VAC/60Hz. At 50 Hz the core saturates and the transformer idle (secondaries disconnected) current is excessive. About 3/4 amp. when fed 117VAC/50Hz. Obviously this smells disaster, literally ! The tester will either need a new transformer dimensioned for 50Hz or I'll have to feed the original transformer 60Hz as per experiments, see posting #17. |