Need 5E3 Build Troubleshooting Help

Pete Farrington

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I mean to measure the heater resistance of the valve itself, not the voltage on its socket. ie I expect just an ohm or 2 between pins 2 & 8.
 

william vogel

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Between pin 4 and 6 I get 680VAC, between pins 2 and 8 I get 5VAC, everything reads as it should on the rectifier socket.
Look for a 6087 or a 5Y3WGTB. These tubes are indirectly heated cathode, allowing a slow controlled warmup that’s easy on the amp and allows you to stay away from the standby switch. If you get one of these, just leave standby in play mode. They have the same voltage drops and current capacity, everything as a 5Y3 but warm slow. No more 500 volt startups on the reservoir cap or hot switching.
 

paul-e-mann

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Look for a 6087 or a 5Y3WGTB. These tubes are indirectly heated cathode, allowing a slow controlled warmup that’s easy on the amp and allows you to stay away from the standby switch. If you get one of these, just leave standby in play mode. They have the same voltage drops and current capacity, everything as a 5Y3 but warm slow. No more 500 volt startups on the reservoir cap or hot switching.
I removed the standby awhile ago and put a ppimv in the hole. I did order a 5Y3WGT, hopefully have it in a week.
 

paul-e-mann

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I mean to measure the heater resistance of the valve itself, not the voltage on its socket. ie I expect just an ohm or 2 between pins 2 & 8.
yeah it measures 1 ohm, does this indicate a bad tube? If it were a good tube it would measure higher?
 

william vogel

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I dont know, how do I check this?
Measure the voltage of the output on the red wire at the rectifier socket. Pin 8 to ground ground. Switch on the amp and watch the DC voltage rise and then fall as the tubes warm.
 

paul-e-mann

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Measure the voltage of the output on the red wire at the rectifier socket. Pin 8 to ground ground. Switch on the amp and watch the DC voltage rise and then fall as the tubes warm.
It went to 120VAC then back down.
 

william vogel

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It went to 120VAC then back down.
Pin 8 of the rectifier is the DC output. At fully warmed idle it should be about 350-370 volts DC. As the rectifier warms up but before the other tubes begin to conduct you’ll see pretty high voltage 490-500 because the power transformer should produce around 350-0-350 AC.
 

paul-e-mann

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Pin 8 of the rectifier is the DC output. At fully warmed idle it should be about 350-370 volts DC. As the rectifier warms up but before the other tubes begin to conduct you’ll see pretty high voltage 490-500 because the power transformer should produce around 350-0-350 AC.
Ok, so it the rectifer tube is dead then no warm up and no voltage correct? Basically when I turned it on it went to 120 then back down to 0 and just stayed there.
 

Pete Farrington

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If the rectifier heater resistance measures around 1ohm, then it should pass current and get hot.
May be there’s a bad solder joint, or bad socket contact, preventing current passing.
 

paul-e-mann

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If the rectifier heater resistance measures around 1ohm, then it should pass current and get hot.
May be there’s a bad solder joint, or bad socket contact, preventing current passing.
Hmm... I chopsticked around inside and didnt see anything loose

I'll have a new tube in a couple days, we'll see if it fires up or not.
 

Pete Farrington

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He may be using a hot switching standby, and measuring the extreme HT rectification ripple (at twice mains frequency) in standby mode.
If not, something is wrong.
 

paul-e-mann

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Pin 8 should be DC. What do you see there? Pins 4 and 6 are AC. Where are you seeing 120 AC?

He may be using a hot switching standby, and measuring the extreme HT rectification ripple (at twice mains frequency) in standby mode.
If not, something is wrong.
Lets make sure I'm doing this right, the bad tube is still installed, measured pin 8 to ground is 1 VDC. The 120 VAC was when I measured pin 8 to ground with power off then flipped it on, the initial surge went to 120 then back to 0. Measured pin 4 to 6 is 680 VAC. Measured pin 2 to 8 is 4.6 VAC. I have no standby switch.

lGfFwAC.jpg
 
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Chris-in-LA

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You should have about 380v DC at pin 8. If you only have 1v DC, that’s the problem. I would assume that a new tube would fix that.
 


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