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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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29th Mar 2006, 2:11 am | #41 |
Octode
Join Date: Mar 2006
Location: Watford, Hertfordshire, UK.
Posts: 1,270
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Re: Motorboating
Hi Neil, I have been comparing your circuit with that of a radio made by Champion in 1953 namely model 820. It uses the ECL80 and confirms that the output transformer primary is around 10k Ohms. Big noticeable differences are:-
1) Grid leak resistor on pin 9 is 680k, yours is 330k. 2) Cathode resistors are 150 Ohms each with the bypass capacitor at 470uF, much higher than your present 47uF. 3) The 1M resisistor between pin 2 and the cathode centre tap is in fact a 1M volume control, the wiper is connected to pin 2, one end to the cathode centre tap, the other end is the signal input via a 10nF capacitor. 4) Your triode anode load resistor of 47k+3k3+22uF Capacitor is 220k on the Champion circuit, quite a difference and there is no 22uF de-coupling capacitor except for a 100pF mica to earth which may prevent the RF oscillation as previously mentioned. 5) Also as mentioned above, there is a 3M3 resistor connected between both anodes for stability. Not sure how to get photos on here but I will try pasting one in and hope it works. Good luck with the project, getting these things sorted out is part of the fun. |
29th Mar 2006, 2:17 am | #42 |
Octode
Join Date: Mar 2006
Location: Watford, Hertfordshire, UK.
Posts: 1,270
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Re: Motorboating
BIG P.S. Can you spot the mistake? They have pins 7 & 8 incorrectly labelled. The scren grid is pin 8 not pin 7, their mistake not mine. I had spotted it earlier but forgot to warn you in my previous. Your pin outs are correct!
All the best Neil. |
29th Mar 2006, 6:31 pm | #43 | |
Retired Dormant Member
Join Date: Mar 2006
Location: Alhaurin de la Torre, South of Spain, near Malaga
Posts: 3
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Re: Motorboating
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