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Post by oldgeezer on Aug 8, 2017 8:18:39 GMT -5
The Cobra Cam 88 does not perform well with US or Russian manufactured 6BQ5 tubes for the RF power output. Typically those tubes produce 2 to 2-1/2 watts and modulate to 5 watts with the Cobra Cam 88 modulation opened up. The old, but good Hitachi 6BQ5 makes 3.5 watts and modulates to 10 watts with the modulation opened up. So, without tuning you need a Japan made Hitachi 6BQ5. And, tuning the final requires a plastic IF can type special tool. (Most radios have fixed inductor & two variable capacitors). Plus, the USA made tube may not tune to proper power output.
This Japanize tube has two very small parallel plates welded at top of tube. The tube can be bought at Brent Jessee in Chicago. Phone number is 847 496-4546. Tube is $15 for new old stock.
He may state he has Japan made tubes, but unsure of the Hitachi brand. Just ask for that tube with the two small plate & he will find it. Also state many Mullards has the same small plate & he will clearly understand. (You cannot use Mullard brand).
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