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Post by nicholas on Dec 1, 2019 9:52:38 GMT -7
So the other day I was rocking out (at ear bleed volume - so glorious he he) when I got a whiff of that electrical burning smell. In my experience that smell is usually followed by letting the magic smoke out of something So I tilted the amp forward and looked at the tubes. One of the power tubes had gone south and was badly redplating. I pulled the chassis to have a look see and all I notice is what I think is the grid resistor. Soldered between pin 1 & 5. It also happens to be the same socket of the failed tube. It has definitely gotten got. I poked it with a toothpick and was able to crumble some of the coating off. I'd think this is a good spot to start. Any other ideas? I did install a fresh set of tubes and brought it up on a variac. It still works fine. So I think I caught it in time. But seems best to replace it before it blows on me down the road. Can anyone confirm these are the correct replacements? Or a link to a better substitute? Thanks in advance!
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Post by Chilly Gibbons (Todd T.) on Dec 1, 2019 15:43:11 GMT -7
Yep, looks like the tube failure took the grid stopper with it
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Post by Chilly Gibbons (Todd T.) on Dec 1, 2019 15:45:21 GMT -7
It will still work fine, grid stopper are used to cut Rf interference. If you live close to an AM radio station you might pick up some of the signal. Super easy fix though and I’d recommend replacing it.
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Post by zpilot on Dec 2, 2019 4:19:09 GMT -7
I would not go with 1/4 watt resistors. Minimum value should be 1/2 watt. Personally I prefer 1 watt when using metal film types. I get mine from Antique Electronic Supply.
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Post by nicholas on Dec 2, 2019 9:02:21 GMT -7
Thanks guys. I found some 1/2w resistors. I tested the other three and found another one open, even though it looks ok. So I'll just change all 4 while I'm in there.
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Post by nicholas on Dec 7, 2019 8:22:18 GMT -7
I would not go with 1/4 watt resistors. Minimum value should be 1/2 watt. Personally I prefer 1 watt when using metal film types. I get mine from Antique Electronic Supply. I had ordered a few different wattage resistors. I went with the 1 watt like you suggested. They also looked closest in size to what Z used. The 1/2 watt was much smaller ( below the old ones in the picture ). I changed them all out. Went well. It's easy working on such a cleanly laid out amp. When I turned it on to try out one of the tubes was redplating within seconds? I was scratching my head for a while! Tested a bunch of stuff. Then I noticed one of the socket terminals pushed through and wasn't making contact with the actual tube pin. I pushed it back in place and re-tensioned all the terminals on all 4 sockets. Working perfectly now I have to say, whatever sockets Z uses are really good. After 10 years and many, many tube changes I've only had to re-tention them this once, and they are easy to re-tension the way they are designed. For the first few years I was almost obsessively trying different tubes. I can't believe this is the first time I've had to do any maintenance on them.
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Post by Chilly Gibbons (Todd T.) on Dec 7, 2019 9:14:46 GMT -7
Beautiful! Nice work Nicholas. They are an amp techs dream to work on. Easy to get to all of the components and solidly built.
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Post by nicholas on Dec 7, 2019 13:03:13 GMT -7
Beautiful! Nice work Nicholas. They are an amp techs dream to work on. Easy to get to all of the components and solidly built. Thanks man. It's nice having something serviceable this day in age. I like how he keeps the the turret board clear of all the tube sockets so they are easy to get at. I've had a few "other brand" hand wired amps, and very high end PCB amps that cover the tube sockets with the board, which make testing and inspecting a pita. Now I'm back in action with it for another 10 years! 4 dollars spent. Love this amp.
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Post by premiumplus (Dave) on Dec 7, 2019 18:55:45 GMT -7
One of tube amplifer's fine benefits is they're easy to work on. Especially now that my eyes are starting to get worse! Good job, Nicholas, it looks great.
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Post by nicholas on Dec 8, 2019 5:35:12 GMT -7
One of tube amplifer's fine benefits is they're easy to work on. Especially now that my eyes are starting to get worse! Good job, Nicholas, it looks great. Thanks. And yeah, lol, about the eyes! I have to wear a magnifying headband to see what the he!! I'm doing anymore! I look like such a dork.
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Post by premiumplus (Dave) on Dec 8, 2019 8:02:32 GMT -7
The worst part about the magnifying headbands is that they don't cover my expanding bald spot!
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Post by zpilot on Dec 8, 2019 18:59:27 GMT -7
One of tube amplifer's fine benefits is they're easy to work on. Especially now that my eyes are starting to get worse! Good job, Nicholas, it looks great. Thanks. And yeah, lol, about the eyes! I have to wear a magnifying headband to see what the he!! I'm doing anymore! I look like such a dork. After seeing photos of Leo Fender wearing a magnifier many years ago I don't let it bother me at all.
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