Bugera 333XL Transformer Clip Fix
This is that little bugger that has been causing so many so many head aches...and well...it happened to my 333XL today. Powered everything up, and no power tube glow. I knew what was wrong almost immediately. Sure enough, the filament lead coming off the transformer arc'd and melted the plastic clip connected to the preamp board.
So,I hopped in my car and took it in to the local TV/Electronics repair shop in my small little town to get a "second" opinon and I had to twist Bob's arm to accept $5.00 for his 7 minute fix.
Here's what we found:
Primary Transformer Lead Clip location.
Shure enough...that bugger sparked from a loose connction.
1. Unplug the clip and clean the posts by scraping with a screw driver. The lead that arc'd will have oxidization on it that you got to get off there or the solder won't stick to it. With a soldering gun "wrap" some solder around the burnt post.
2. Cut only the burn lead off the clip. Strip it back a few .mm and wrap some solder around it, then solder it diretly onto the post.
3. Repeat steps one and two, only cut the wire you are getting ready to solder so you don't screw up the correct order of the wires. Bend the posts away from each other a bit just for space.
That's it...you're done and ready to rock!!
Should look something like this when you're done.
Close up of torched Clip
***Ok folks, a little update about that burnt molex transformer clip fix....
It's been about three years since I cut off that clip and soldered the leads directly to the pins. Well I had another failure and I suspect that pin 1 got torched enough to eventually stop transfering current.
Symptoms with pin 1 out:
The standby light shuts off and there will be NO sound. The amp acts as if it is "stuck" in standby mode. The tube heaters stay on, and all other electronics seem to work.
1. Draw yourself a little schematic of the preamp PCB wires and mark all those tiny little clips so you can reassemble them correctly.
2. Remove the preamp PCB.
3. Unsolder the burnt pin and solder in a GOLD pin instead of the cheap TIN stuff that comes stock. Resolder you lead.
4. Reassemble. Hopefully you marked well and took good notes from step 1.
***Another option is to remove all the pins and solder all the OT leads directly to the PCB.***
I've yet to go thru the procedure myself, but my ohm meter tells me pin 1 is toast. I will let you all know how its goes.
As it turns out, the OT leads/posts where fine. What I found was a dislocated solder joint on the preamp PCB. The white table-top looking resistor where the factory had wires stretched over the top and it broke loose. It took more time removing all the glue and clips from the PCB, than it did resoldering it up. After reassembling, it fired right up!!