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Old 28th October 2017, 05:02 PM   #1
Mark Fugate is offline Mark Fugate
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Default TSE 300B Initial checkout problems. Help please.

I am building a TSE with 300B tubes and the initial checkout is not going well.

My B+ 457 Volts, 5842 plate voltage is also 457 Volts, and R5 (270 Ohm 2W) glows red.

My power transformer is an Edcor XPWR131-120 with the following wiring
W 330 V CT T1-1
Y2.5 V T1-2
Y 2.5 V T1-3
R 330 V T1-4
O 330 V T1-5
BR 3.15 V T1-6
WBR 3.15 V CT T1-7
BR 3.15 V T1-8
Thanks much in advance for any and all assistance.
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Old 28th October 2017, 05:10 PM   #2
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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R5 is your negative bias supply and only feeds C6 and R6. Check C6 is the correct way around.
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Old 28th October 2017, 08:03 PM   #3
Mark Fugate is offline Mark Fugate
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C6 and C7 are correctly oriented,

Any other thoughts?
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Old 28th October 2017, 09:15 PM   #4
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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To make R5 heat up there is obviously a heavy load. The resistor following is 10k so it is either a solder bridge on C6 end, or it is magic. Nothing else can cause that.
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Old 28th October 2017, 09:18 PM   #5
Mark Fugate is offline Mark Fugate
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Maybe a bad C6?

I replaced the 270 ohm resistor, powered things up, and C6 started smoking.
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Old 28th October 2017, 09:20 PM   #6
Mark Fugate is offline Mark Fugate
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Could a shorted C6 cause me to see full B+ (450+ Volts) on the 5842s?

Thanks much for your comments.
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Old 28th October 2017, 09:23 PM   #7
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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If C6 is short, you will have no negative bias and the output valve will complain by getting extremely hot very quickly.
Full HT on the anode of the 5842s is a bias issue on those valves. If they are not biased correctly, (turned off) full HT will be on the anodes.
Sort out your -ve bias voltage first. One step at a time.
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Last edited by JonSnell Electronic; 28th October 2017 at 09:25 PM.
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Old 28th October 2017, 09:26 PM   #8
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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Have you got -200volts roughly on C6?
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Old 28th October 2017, 09:43 PM   #9
Mark Fugate is offline Mark Fugate
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-508 which seems impossible. I will recheck. Confirmed.

The voltage across R7 is 0

Last edited by Mark Fugate; 28th October 2017 at 09:53 PM.
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Old 28th October 2017, 10:04 PM   #10
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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Check your wiring, C6 must have no more than about 220v ish, certainly not 508!
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