Help needed on kt88 WAD amplifier

If they glow, this is the place to be
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bostod
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#1 Help needed on kt88 WAD amplifier

Post by bostod »

Not sure if this is a problem or not. I know very little about valves. On my WAD KT88 power amplifier there are the 4 big kt88 valves along the back and 4 small valves at the front. My potential problem is with one of the small valves. The one at the end glows brighter than the others when first switched on before dimming back down to match the others.
Is this normal or is there a problem. When the tube is warm and the amp is switched off and back on again, the tube looks normal. The problem seems to happen only when the tube is cold.
At present it is having no impact on the sound.
On a separate note my friend borrowed the amp for a short while. He could not get rid of a rather loud hum. On my system there is no noise at all. What might this have been.
Any advice would be greatly appreciated,especially about the valve potential problem
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Nick
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#2 Re: Help needed on kt88 WAD amplifier

Post by Nick »

The glow on startup is normal, its caused by a bit more of the heater sticking out the end of the cathode than the other valves.

The hum is probably a earth loop, I would check your amp case is connected to earth (just for your safety). And see if your signal ground is connected directly to the case ground. Or it may be through a small resistor. If it is via a small resistor then I would make sure that resistor is not open circuit which would cause your signal ground to float and be earthed by the connected equipment.
Resistance isn't futile it's V / I.
bostod
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#3 Re: Help needed on kt88 WAD amplifier

Post by bostod »

Thanks for the reassurance Nick. Very much a novice here but trying to learn
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Nick
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#4 Re: Help needed on kt88 WAD amplifier

Post by Nick »

No problem.
Resistance isn't futile it's V / I.
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