2022年4月4日 · On the 12SQ7, in many radios, there is often a mica capacitor hanging on the plate of the triode section- which can and does sometimes become problematic, causing the issues you described. HI-no I did not touch the mica caps in the set,

2013年10月6日 · or, the drugstore was out of 12SQ7's at the time, the owner looked in the sub book on the counter beside the tube tester, and purchased a 12SR7 so he could listen to the big game that evening. all i know is when i subbed that 14AF7 tube in place of an original Philco XXD, as all tube sub books stated, that radio squealed like a pig.

2011年8月11日 · Hi guys, I am having some troubles with pin reading on my 12SQ7 tube. I checked nostalgia air for the diagram, and found the diagram there was quite differen… Get a better experience by installing our free app!

2023年11月23日 · Re: Testing 12sq7 Post by Chris108 » Nov Sun 26, 2023 1:12 pm The problem with 12SQ7s, 6SQ7s, and related types like the 6Q7/12Q7 is the design of the detector diode plates which are right against the cathode.

2011年12月24日 · 12SQ7's are cheap and available, and other than a burned out filament, or microphonics in the triode ...

2025年2月14日 · I had 53 volts on pin6 of the 12sq7. It should be 30 volts. The resistor R9 was 470k. I increased this to a 3.3 Meg. That brought the plate voltage to 30 volts. My problem is that the grid voltage on the 12sk7 and the 12sq7 are off. 12sk7 pin 4 should be zero volts. It reads -.43 volts. The 12sq7 pin 2 should be -.2 volts and it reads -.6 volts.

2024年12月18日 · While looking for my 12SR7, I found a 12SQ7 and tried it. Solved that issue. I then noticed the problem some triodes dual diodes like the 12SQ7 can have which is audio making it to the triode portion from a diode. Since I had an extra unused tube socket I put the bad 12SQ7 there and just used one of the diodes.

2025年1月9日 · Tube lineup: 12SA7, 12K7, 12SQ7, 35L6, 12SQ7, 35L6, 35Z6. Late 30s, maybe? Steel needle phonograph. BTW, I can't seem to get to the Mallory-Yaxley web site. Every time I type the web address into my google browser, it inserts the "S" behind the HTTP and says the site is not found. Anyone have any help for me there? Best Mike

2025年1月12日 · That is a dual pole single throw switch, the AGC line should be grounded and plate voltage should be applied to the BFO tube when the switch is in the code position. So if the 12SQ7 plate voltage position is wrong, check the AGC section since it should also be reversed. Has the switch been replaced? Rodger WQ9E

2025年2月16日 · Double check the values of the two replaced resistors (3.3meg, 470K), the one's Sams calls number 28 and 24. Since you are at least getting a station, but have no hum when you touch the middle volume control terminal (make sure shaft is tuned to center) the issue seems to be between the volume control and the output tube (since you hear a hu