UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Re-claiming a leaky UL41

kalee20 · 3rd Jul 2009, 2:15 pm

I have richrussell's UL41 now. While the gettering is a bit dull, with plenty of rainbow colours at the fringes (indicative of prolonged high-temperature working), it measures rather well on leakage.

Grid to all electrodes reads >30M so I was comfortable enough to put in my DAC90a.

Switching on, the grid voltage is 30mV which I am very comfortable with. And it performs fine!

The only suspect pin is Pin 4, which is theorectically isolated. This measured 8.6M to heater. So, in a 'normal' DAC90a where this pin is used as a convenient grid-circuit anchoring tag, there would be significant hum injected. I've isolated Pin 4 in my DAC90a for this reason.

Anyway, as I seem to have a perfectly useable valve, I'm not qoing to zap it! But any unuseable ones, I would be grateful for - postage will be refunded!

3rd Jul 2009, 2:15 pm	#13
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,088	Re: Re-claiming a leaky UL41 I have richrussell's UL41 now. While the gettering is a bit dull, with plenty of rainbow colours at the fringes (indicative of prolonged high-temperature working), it measures rather well on leakage. Grid to all electrodes reads >30M so I was comfortable enough to put in my DAC90a. Switching on, the grid voltage is 30mV which I am very comfortable with. And it performs fine! The only suspect pin is Pin 4, which is theorectically isolated. This measured 8.6M to heater. So, in a 'normal' DAC90a where this pin is used as a convenient grid-circuit anchoring tag, there would be significant hum injected. I've isolated Pin 4 in my DAC90a for this reason. Anyway, as I seem to have a perfectly useable valve, I'm not qoing to zap it! But any unuseable ones, I would be grateful for - postage will be refunded!