Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Papa Jim on April 04, 2019, 09:34:35 am
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Pull a live tube and amp gives no sound until I power down ac, drain the ps filters and power ac back up. I don't intentionally do this but if it happens it takes this every time. Is this normal, even though all the filaments and B+ Voltages are present even.
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Pull a live tube and amp gives no sound until I power down ac, drain the ps filters and power ac back up. I don't intentionally do this but if it happens it takes this every time. Is this normal, even though all the filaments and B+ Voltages are present even.
I'm a little slow this morning. What exactly are you saying? Of course if you pull a live tube in an amp such as a three tube 5F2A, you will lose the sound. And turn it off and power back up without that tube you will still have no sound. Plug the tube back in and the sound returns.
But I think you are trying to say something different? An I just don't get it? :w2:
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Yes when you put that or any other tube back in no sound. Leave everything as is power down and drain the B+ Caps, Power back up and sound comes back. Hold your answer though because I just discovered a wire that was broke inside of some heatshrink. I will be back.
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Well that may be the case for your amp but not any of my amps.
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Ok here's what I found a minute ago. Although the amp was coming back on after doing what I described it quit altogether a bit ago after posting this thread. The resistor lead broke on the 220k from the opt 6v6s pin 5 grid to ground. I think I will leave well enough alone pulling a hot tube unless you don't think it will hurt. Otherwise I will just leave it as a mystery. What do you think Sluckey.
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I've pulled thousands of hot tubes in my life. There are even tools to help doing this so you don't burn your fingers. My favorite tool for small tubes is tongs...
https://www.ebay.com/itm/GC-Electronics-Electron-Vacuum-Tube-Extractor-Coated-Prongs-5092-NOS/352614865344?hash=item52197bd9c0:g:j8EAAOSwzd5cXfwh
Asbestos gloves work well for handling bigger hot tubes.
I worked around a lot of equipment that it was unfeasible or impossible to turn the power off just to change a little tube. You do have to be careful reinserting the tubes. I've bent a few pins because I had a hard time aligning the tube, but you get good enough to get it right almost every time. :icon_biggrin: We also had pin straighteners mounted on every scope cart.
https://www.ebay.com/itm/RARE-Original-NOS-No-8655-GC-Electronics-7-9-Pin-Vacuum-Tube-Pin-Straightener/173858475923?epid=1403921356&hash=item287ac5cf93:g:3bcAAOSwsupcmK1h
I'm not advocating that you should pull hot tubes in a little amp, but I'm saying that I do. If there's a STBY switch I usually kill the B+, but I don't mind pulling a little tube even with B+ on it. I don't do this with power tubes though.
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Ok. Sounds good. I'm not scared either to do the preamp tubes like that. I will try that test later and see what happens now that I found that broken resistor lead. Last time I will do a point to point. This is about the 4th parts lead that has broken.
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I don't do this with power tubes though.
:icon_biggrin:
some wing-nut in tech School managed to take the 120kv anode lead outta the X-ray tube HOT :think1:
he wound up in shipping n receiving :icon_biggrin:
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I don't do this with power tubes though.
:icon_biggrin:
some wing-nut in tech School managed to take the 120kv anode lead outta the X-ray tube HOT :think1:
he wound up in shipping n receiving :icon_biggrin:
:huh: :l2:
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When you plug the cold tube back in, you have to wait 11 seconds for the cathode to get hot again.
If you did, and it didn't come back, and it is an ordinary guitar amplifier, I'll go with "intermittent wire fault". It's not the tube out/in, it is the gremlins messing with your mind.
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Yep I'll go with gremlins. I waited long enough. Tomorrow gonna test it again now that I have repaired the broke lead.