2009年7月10日 · The sudden change in bias indicates something's wrong. Try to find out where the glow is coming from exactly. See if you can look inside the tube, through the round holes in the anode. Can you see if the grid wire inside the tube is glowing? Is the glow situated below or above the upper mica disc? Regards, Ray

JJ KT88 tubes glowing bright yellow. Not open for further replies. I bought a matched pair of JJ KT88 tubes to use in my SET amp. It has no bias adjustment. I was using a matched pair of reissue GL kt88, but wanted to try the JJ tubes as I was impressed with the look of the build quality and weight.

2015年3月25日 · It's heater glow. If you don't have a tube tester can you get a 6.3 volt supply, a octal relay socket and some kind of ammeter? Check it for current pull and check the others to see if it is different. Maybe it's just how it was assembled.

2011年5月26日 · There is no 'lightning', just a blue glow at the very top of the KT88. No sound issues, no popping or any other anomalies. No volume drop. Help! Fitzgig tempts me in from remission. It's kind of interesting actually.

2022年9月2日 · Another possibility to consider is that the 12AX7 driver tube for the channel affected (V4 or V7) failed with a heater cathode short. It can and does happen. When it does, it effectively removes all bias voltage from the output tube served and will then cause it to glow cherry red in no time.

2022年10月13日 · Check the coupling cap on that channel for leakage at the grid of the output tube, check the grid resistor on that output tube and make sure it isn't open. I'd also check the triode/UL switch and make sure it hasn't failed. Monitoring the plate voltage of the driver won't tell you much. You need to check the cathode current on the output tube.

2025年1月19日 · He also has a picture at beginning that shows some tubes with different heater filament glow levels (I tried to post a picture were the failed tube spot V6 glows brighter than the rest but its blurry) and indicates this is fine. He said a good way to check the tube was swap it which I did, and it blew the fuse.

2021年3月24日 · The KT88 tube base width is slightly wider than the 6550. Sound wise, the 6550s have that true Ampeg "punch in the gut feel" and the KT88 sound is less in your face. If I had a choice for hifi, I would use the KT88's as they sound neutral.

2019年1月7日 · I've been really busy but have wanted to build the Kegger se kt88 for awhile now and after seeing blueglows youtube videos I'm sold. I enjoy my 5 watt se builds but have a party coming up this spring and need more power so am ready to get started but have a few questions.

A sudden sharp crack lasting only a second at start up or shut down may be one of the large power output tubes (EL34, KT88, etc). This is more serious than a noisy small signal tube. If you hear this, keep a close watch on the power output tubes to see if any flash, and immediately turn your amp off and replace any bad tube.