Fender Blues Deluxe won't power up

[Tim Aladyetz]

I bought a used Fender Blues Deluxe last fall. The pilot lamp didn't work, but the amp worked fine, and I finally got around to replacing it this week.

When I wiggled it in the socket it turned on, then off. I took the back off the amp to access the lamp holder and attempted to squeeze the holder to seat the bulb more securely. Bulb lit on and then off as I handled the holder, then simply stayed off. I put the back on again and discovered now the amp didn't work at all. I could hear a slight hum from the transformer, but the tubes did not light up and no sound (hum or otherwise) came through the speakers.

I checked the fuse, which was fine. I checked continuity through the lugs on the fuse holder, which was fine. I checked the transformer primary resistance and found 4 ohms. I checked the main secondary and found 43 ohms. I checked continuity across the power switch, which was fine. I checked the resistance across the blades of the AC cable (unplugged) with the switch on and got 20 ohms. I removed all tubes and checked the resistance between the heater pins on the preamp tubes and found 3 ohms, which seems okay.

Any ideas on what to consider next?


Also, the channel switch LED illuminates, so there's power in there somewhere.

[Enzo]

Yes, my suspicion is you shorted out the 6vAC supply while fussing with the bulb socket, and that blew the heater fuse. But then do these even have a heater fuse? Are the tube heaters lighting up?

Since you get some sort of light, we can assume all the primary side stuff is working. Nothing in the primary or the primary wiring would allow one power supply to come on but not another.

Do you have the Blues Deluxe, or do you have the BLues Deluxe Reissue?

A wire could be broken free or cracked of solder, don't the heater power wires go direct to the tube socket boards?

[The Dude]

On the Blues Deluxe, I'm pretty sure the heater wires do go directly to the socket board and then are sent to the lamp from that board. I'd check those connections. I agree with Enzo. I don't think it's an overall power problem, but a filament supply problem. Check voltage at filament wires from the PT and make sure it's getting to the socket board. If this one does have the fuse (reissue), have fun with that. It's not easy to get to.

[Tim Aladyetz]

Thanks guys. Amp's still not going, but this has been really helpful. It's a reissue, from 2019. I was looking at a 2004 schematic, which didn't have a heater fuse. But this amp has a heater fuse, and no, the tubes weren't lit at all. I pulled out the fuse and it looks intact but doesn't show continuity. So I need to get a replacement.

I checked voltage on the heater wires. One was .6v and the other 0. That seems bad? I was expecting 3.5v from each...

Enzo, I had burst of recognition when I saw your name pop up. You used to work on my amps when I lived in Lansing.

[The Dude]

Check heater voltage by checking across the heater winding (2 green wires)- one probe on each wire and not to ground. It will be AC volts.

[Tim Aladyetz]

Thanks, dude. That's exactly the mistake I made. Heater wires have 6.3v. Hopefully, a new heater fuse will do the trick.

[Enzo]

You should have two resistors to ground, 100 ohms R80, R81. Whatever took out the heater fuse probably burnt open one of those resistors. They are what centers your 6v around zero. If one opens, then you get 6 and zero rather than 3 and 3. Simple test, measure resistance to ground from one side of the heater string.. if you get about 100 ohms I am right. If both 100 ohm resistors are OK, then you read about 50 ohms.

Hi Tim, I hope I did a good job on them. I finally had to retire when I could no longer keep mental focus.

[Tim Aladyetz]

I replaced the heater fuse and it works perfectly now. I think I maybe when I was messing with the lamp socket I caused a short that blew the fuse. Thanks for your help.

Enzo, yes. You always did a great job. I moved out of Michigan ten years ago and haven't had a dependable tech since. When this broke I thought, "geez, I wish I could just take it down to Enzo." And then here you were.

[Enzo]

Thanks for the kind words.