• Disclaimer: This Vendor's Forum is a paid-for commercial area. Unlike the rest of diyAudio, the Vendor has complete control of what may or may not be posted in this forum. If you wish to discuss technical matters outside the bounds of what is permitted by the Vendor, please use the non-commercial areas of diyAudio to do so.

DIY Tubelab SSE build keeps blowing fuses when turned on.

Link to amp build / blown fuses:
Imgur: AMP & BLOWN FUSES

I just wired up my newly delivered transformers to my Tubelab SSE build & switched it on for the first time a few days ago and ran it for a few hours. It played wonderfully - that is, until I lightly bumped a few wires that connect the power entry module to the power transformer... That's when I heard a fuse pop and that was that. The next day I re-soldered all my connections in that area and replaced the fuses. I turned it on and everything seemed to be fine. I turned it off and on again and popped another set of fuses. I checked everything and tried again and again with no luck, just more popped fuses. Trying to problem solve and narrow down the issue, I removed the power tubes and turned it on... more popped fuses. Finally I kept the power tubes out and added a jumper where the Solid State mode switch would be to see if it was the rectifier tube. It popped the fuses on turn-on but the fuses popped much less aggressively. All the other popped fuses where black (as seen in the picture) but this time there were little to no burn marks in the glass fuses (also seen in the picture). I'm at a loss. How do I problem solve such an issue? I am going to rewire everything tonight from scratch to be sure... But ff I cannot turn it on, I don't know how to problem solve.
 
Last edited:
But ff I cannot turn it on, I don't know how to problem solve.
Build yourself a test lamp socket to safely power the amp. This will let you run it while troubleshooting. The lamp should not light when there's no short. Depending on the particular amp, sometimes a very dim glow may be ok. Typically use a 75 or 100 watt bulb.
 

Attachments

  • DimbulbSketch.jpg
    DimbulbSketch.jpg
    39.1 KB · Views: 217
  • test bulb.jpg
    test bulb.jpg
    79.7 KB · Views: 220
  • TestSocket.jpg
    TestSocket.jpg
    13.7 KB · Views: 216
Build yourself a test lamp socket to safely power the amp. This will let you run it while troubleshooting. The lamp should not light when there's no short. Depending on the particular amp, sometimes a very dim glow may be ok. Typically use a 75 or 100 watt bulb.

This seems like an interesting idea. I am not sure if I understand it entirely though. Will the lamp preserve my fuses? Or are you suggesting to power it with this configuration without the fused power entry module? Thanks for your reply!
 
Connect things up as normal with the lamp in series with the main power. The lamp acts as a current limiter. Fuses will not blow and it allows you to make tests.

This sounds like a great solution! I am going to wire everything up tonight from scratch / recheck everything. If that doesn't solve it I am heading to home depot to build this device. Thanks again :)
 
If you have the rectifier diodes installed, as it sounds like you do, I would suspect that both are shorted.

Win W5JAG

Hmm, by rectifier diodes are you referring to the HEX FRED diodes? I do have these installed. Do you recommend that I remove these? When I installed them I was uncertain of their purpose, but then I read that they might be the SS alternative to the rectifier tube, is that correct?
 
If you have the rectifier diodes installed, as it sounds like you do, I would suspect that both are shorted.

Win W5JAG

Ok, so I just said F-it and went ahead and snipped off my hex freds...being under the impression that these diodes are for the SS option that I don't plan on using and now thinking that these are also what is shorting out my amp. It now is running again! Was this the right decision? Can I just leave those out? It was a rash decision without having all the knowledge but I went for it and now my amp is playing beautifully again.
 
Was this the right decision? Can I just leave those out?

Yes. The hexfreds are optional and used for the solid state rectifier option only.

As you found out any silicon device can not handle even a momentary over voltage surge. You probably have (or had) a loose connection in the transformer circuitry, or even a loose line cord in the power entry module. The transformer is a big inductor and a momentary loss in power followed by a rapid restart can generate a large voltage surge. The hexfreds are the most likely device to be damaged, but I have seen 5AR4's blown in the same situation.

It should be standard procedure with any tube amp, and some big solid states amps not to turn the amp off and then right back on. Wait at least a minute or so before restarting it.