SSE blowing fuse - could it be the xformer ??

[HawkeyM]

I've been running my SSE for 4+ years. Always solid. I just moved the rack, powered up and it worked for two days. Then the next time powered on - the fuse blows right away. Strange, replaced it and pop again.

So started trouble shooting, nothing obvious - burnt or smoking. Worked backwards and finally I'm only left with the Hammond 274BX hooked up to the fuse and power switch - all it's secondaries disconnected from the PCB. Flip the switch and the fuse blows. I can't find any shorts other than the primary is reading zero ohm across the 110V in - was expecting at least a few ohms. I've never heard of a transformer going bad over time, but I just don't know what else it could be - very strange.

Anyone seen this before? My next step is to order a replacement as I don't know how else to debug any further. Thanks for any and all feedback.
Michael

 

[cogitech]

It sure sounds like a bad transformer, based on your troubleshooting.

My 274BX went bad after 4 days, so 4+ years is a long run, based on my direct experience. 🙂

 

[HawkeyM]

Thanks for the quick reply. Was is the same, primary was shorting? Did you buy another Hammond or source someone else?

 

[rayma]

Transformers definitely can go bad and short. Cut off all the leads and chuck it.

 

[cogitech]

Thanks for the quick reply. Was is the same, primary was shorting? Did you buy another Hammond or source someone else?

Nope, was the 5V winding on mine that went. I cut the yellow leads off and might use it in the future for a project that doesn't need that winding (like an SSE or a guitar amp with SS rectification maybe).

My 274BX was replaced by Hammond (under warranty) for free, but I am not using the replacement in my SSE. While I was waiting for an answer from them, I decided to order an Allied 6K7VG. It has been working great (and running way cooler than the 274BX was) so far.

The Allied one is about 1/4 inch wider through the plate stack and is a bit heavier, but I was able to get it installed in the exact same holes as the 274BX.

The Allied is also considerably cheaper. Hammond Manufacturing - 6K7VG - TRANSFORMER, PRI:110-120V, 50/60HZ, 750VCT @150DCMA, 5V @3A, 6.3A @ 5.0A, LEADS - Allied Electronics & Automation

It is made by Hammond and actually branded "Hammond" now, but it is definitely not a re-badged 274BX.

 

[cogitech]

Note: All the leads on the 6K7VG come out one side of the transformer, unlike the 274BX which are split about 50/50 on each side, so I did have to drill one of the lead holes in the chassis a little larger and install a larger grommet.