Hi everyone,
I built a Tubelab SSE about a month ago (first amp built ever) and have been really enjoying it.
I've been experimenting with different tubes, trying KT88s and EL34s (I prefer the sound of KT88s so far), and I've also tried different input tubes.
The amp has been running for 4 hours a day during the week and much more during the weekends.
Then one day, I turned on the amp and noticed that the tubes were glowing brighter than usual
I checked the B+ voltage at the end of R4, which normally reads around 440V. However, this time, the multimeter kept climbing way above 500V, and eventually maxed out 😱
I turned off the amp, and after a few seconds, the voltage started dropping from 500V to nearly 0.
Suspecting a faulty JJ rectifier tube (they have a reputation for reliability issues), I replaced it with a new Sovtek tube, but the problem persists.
I've also carefully checked for bad solder joints and loose connections, but everything seems to be fine.
The amp is currently configured in triode mode without CFB or ultra-linear feedback.
Here are the specifications:
Output Transformers: Hashimoto HC-507U (using the 4-ohm output)
Power Transformer: Hashimoto PT-165R
Choke: Hashimoto CC-10-200W
Tube rectification only (no D1 & D2)
Coupling capacitors: 0.22uF
Supplemental capacitor: 47uF + 47uF
Does anyone have any idea why I'm suddenly getting such high voltage readings?
Are there any specific components I should check?
Thanks for your help
I built a Tubelab SSE about a month ago (first amp built ever) and have been really enjoying it.
I've been experimenting with different tubes, trying KT88s and EL34s (I prefer the sound of KT88s so far), and I've also tried different input tubes.
The amp has been running for 4 hours a day during the week and much more during the weekends.
Then one day, I turned on the amp and noticed that the tubes were glowing brighter than usual
I checked the B+ voltage at the end of R4, which normally reads around 440V. However, this time, the multimeter kept climbing way above 500V, and eventually maxed out 😱
I turned off the amp, and after a few seconds, the voltage started dropping from 500V to nearly 0.
Suspecting a faulty JJ rectifier tube (they have a reputation for reliability issues), I replaced it with a new Sovtek tube, but the problem persists.
I've also carefully checked for bad solder joints and loose connections, but everything seems to be fine.
The amp is currently configured in triode mode without CFB or ultra-linear feedback.
Here are the specifications:
Output Transformers: Hashimoto HC-507U (using the 4-ohm output)
Power Transformer: Hashimoto PT-165R
Choke: Hashimoto CC-10-200W
Tube rectification only (no D1 & D2)
Coupling capacitors: 0.22uF
Supplemental capacitor: 47uF + 47uF
Does anyone have any idea why I'm suddenly getting such high voltage readings?
Are there any specific components I should check?
Thanks for your help
Attachments
The soldering on the tube sockets looks insufficient, almost non existent.
The stress of removing and inserting tubes may have caused cracks and the tubes are no longer drawing current to pull the power supply down.
Also, check the screw terminal connections are tight. Thermal cycling can cause them to lose tension.
Just a thought.
Win W5JAG
The stress of removing and inserting tubes may have caused cracks and the tubes are no longer drawing current to pull the power supply down.
Also, check the screw terminal connections are tight. Thermal cycling can cause them to lose tension.
Just a thought.
Win W5JAG
A completely unloaded 380-0-380 volt transformer can make about 530 volts of DC. This is with zero load. Reality is generally much lower than that, especially with a tube rectifier. Before going much farther verify that the meter is correct. Measure your line voltage, is it close to 230 volts? Many low cost digital meters will read high when their battery gets low. I once spent quite some time trying to find out why my power supply put out more voltage every day. A fresh battery made everything good again.
If your tubes appear to be too hot, I would expect a lower than usual B+ voltage due to increased current draw.
If your tubes appear to be too hot, I would expect a lower than usual B+ voltage due to increased current draw.
Thank you both for your help and advices 👍
@Tubelab_com, actually it's my multimeter that's faulty, I thought the tube were brighter than usual then freaked out 🤣
Tried with a spare multimeter and everything is ok
@w5jag I was very happy with my soldering work on the resistors and capacitors, but it's true that I could have done (much) better on the sockets 😆
@Tubelab_com, actually it's my multimeter that's faulty, I thought the tube were brighter than usual then freaked out 🤣
Tried with a spare multimeter and everything is ok
@w5jag I was very happy with my soldering work on the resistors and capacitors, but it's true that I could have done (much) better on the sockets 😆
Attachments
Nice amp!
Glad this issue was so easily resolved. This is great information for others. I know I would have panicked and would have never suspected the meter was faulty.
Glad this issue was so easily resolved. This is great information for others. I know I would have panicked and would have never suspected the meter was faulty.