UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Quad 22 KT66 to 6L6 with Cathode resistor increase?

Marconi_MPT4 · 16th Sep 2022, 2:54 pm

I ran into this issue when using original spec 6L6G in a Williamson amp. The grid bias had to be increased so the combined anode and screen dissipation when strapped as a triode was no higher than 21.5W. Also gave reduced power output.

6L6GC has a higher anode and screen power rating of 30W and 5W respectively. It also has a higher anode and screen voltage rating which is comparable to KT66. Suitability depends on circuit configuration. Compare RCA data for 6L6/6L6G and 6L6GC.

https://frank.pocnet.net/sheets/049/6/6L6GC.pdf

https://frank.pocnet.net/sheets/049/6/6L6.pdf

I have had the misfortune to buy a batch valves marked 6L6GC only for them to fail prematurely. Most likely remarked 6L6GT.

Rich

16th Sep 2022, 2:54 pm	#6
Marconi_MPT4 Heptode Join Date: Mar 2011 Location: Dorset, UK. Posts: 522	Re: Quad 22 KT66 to 6L6 with Cathode resistor increase? I ran into this issue when using original spec 6L6G in a Williamson amp. The grid bias had to be increased so the combined anode and screen dissipation when strapped as a triode was no higher than 21.5W. Also gave reduced power output. 6L6GC has a higher anode and screen power rating of 30W and 5W respectively. It also has a higher anode and screen voltage rating which is comparable to KT66. Suitability depends on circuit configuration. Compare RCA data for 6L6/6L6G and 6L6GC. https://frank.pocnet.net/sheets/049/6/6L6GC.pdf https://frank.pocnet.net/sheets/049/6/6L6.pdf I have had the misfortune to buy a batch valves marked 6L6GC only for them to fail prematurely. Most likely remarked 6L6GT. Rich __________________ To an optimist a glass is half full; a pessimist half empty; an engineer twice as big as need be!