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FERNSEH · 15th Jul 2014, 1:09 am

There is a quick method to establish if the boost capacitor has failed, that is gone short circuit. Disconnect the top cap of the boost diode, if the EHT returns, the capacitor is SC.
Negative volts greater than 40 at the control grid of the PL36 indicates the line drive is present.
As the PL36 is biased by grid current, lack of line drive will result in the valve drawing excessive current. The anode can glow red hot. The failure of the line output transformer can cause the same effect.
I examined the circuit of the line output stage and sure enough it is very similar to the later DR1 series. So if the line output transformer is faulty the set is a candidate for a jellypot conversion.
The scan coils can fail although it is uncommon. disconnect them and see what happens.

DFWB.

15th Jul 2014, 1:09 am	#14
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: End of my beloved DR101 There is a quick method to establish if the boost capacitor has failed, that is gone short circuit. Disconnect the top cap of the boost diode, if the EHT returns, the capacitor is SC. Negative volts greater than 40 at the control grid of the PL36 indicates the line drive is present. As the PL36 is biased by grid current, lack of line drive will result in the valve drawing excessive current. The anode can glow red hot. The failure of the line output transformer can cause the same effect. I examined the circuit of the line output stage and sure enough it is very similar to the later DR1 series. So if the line output transformer is faulty the set is a candidate for a jellypot conversion. The scan coils can fail although it is uncommon. disconnect them and see what happens. DFWB.