Might have tasted a little humble pie today

brooom · May 2019

Sure I agree, in the context/perspective of the total amount of units sold. Yes not really super common, but a lot of them do show up in such a state (again quite possibly because there are lots of them out there). It was a bit of an overstatement, but not totally untrue.

ICBM · May 2019

brooom said:

Sure I agree, in the context/perspective of the total amount of units sold. Yes not really super common, but a lot of them do show up in such a state. It was a bit of an overstatement, but not totally untrue.

Yes, and considering how consistent the area of the arcing is and how simple it would be to fix it by redesigning the board layout at very little cost, it's still not good that they haven't fixed it.

It's actually a really stupid flaw - the EL84 is a well-designed valve which purposely has the high-voltage pins on one side of the base, separated from each other and from the low-voltage pins by spaces to prevent arcing. So what did Fender do? Ran one of the low-voltage traces straight between the high-voltage pins! Totally defeating the point of the valve design...

For anyone unfamiliar with this, this is how it starts - or sometimes between the lower right pin and the trace parallel to it roughly where there is a tiny black spot on the edge of the trace:

And this is how it ends:

brooom · May 2019

Perfect example... and I think they updated to phenolic brown tube sockets. I think for some time they were much lower quality. I've seen example where the actual socket melted and you couldn't even pull out the el84 anymore.

Not that it fixes the underlying issue as you pointed out.

Keefy · May 2019

ICBM said:

brooom said:

Sure I agree, in the context/perspective of the total amount of units sold. Yes not really super common, but a lot of them do show up in such a state. It was a bit of an overstatement, but not totally untrue.

Yes, and considering how consistent the area of the arcing is and how simple it would be to fix it by redesigning the board layout at very little cost, it's still not good that they haven't fixed it.

It's actually a really stupid flaw - the EL84 is a well-designed valve which purposely has the high-voltage pins on one side of the base, separated from each other and from the low-voltage pins by spaces to prevent arcing. So what did Fender do? Ran one of the low-voltage traces straight between the high-voltage pins! Totally defeating the point of the valve design...

For anyone unfamiliar with this, this is how it starts - or sometimes between the lower right pin and the trace parallel to it roughly where there is a tiny black spot on the edge of the trace:

And this is how it ends:

Holy crap!

A friend has a Mk IV Blues Junior with Jensen, and it does sound glorious. I wouldn't want to risk something like this happening though. Neither of my gigging guitar amps use PCBs, they are built on turret board and/or tag board.

ICBM · May 2019

Keefy said:

I wouldn't want to risk something like this happening though. Neither of my gigging guitar amps use PCBs, they are built on turret board and/or tag board.

The problem is *not* PCBs, it's poor design. There are many extremely high-quality amps that use PCBs and do not, and never will, suffer from problems like this because their designers were more careful.

Conversely, this is a fire that happened in a Fender Custom Shop Twin-o-Lux... which is a tag-board amp. (After removing the burned wiring loom from the socket.)

The common factor is poor design - in this case not fitting the amp with an HT fuse, which is also a fault in the Blues Junior. That one step would have prevented this completely.

That isn't to say Fenders are unusually poorly-designed either - in fact I would put them slightly above average for a mass-production company.

crunchman · May 2019

p90fool said:

crunchman said:

chrisj1602 said:

I’m tempted by the Blues Jr tweed quite often, but then think I could get a 68 Princeton used for not much more than the new BJr so might go down that route.

The 68 Princeton benefits from a speaker change as well. I've put a WGS Veteran in mine - a lot better than the stock Celestion. I don't know why Fender persist in putting budget Celestions in their amps. They really do sound better with "American" style speakers.

I thought the same, but put the stock Celestion back in my 68 custom Princeton when I sold it to the other guitarist in my band.

Six months of flat out gigging later and I suddenly noticed it sounded better than when I had it, and two years later it sounds awesome.

That's running the amp on nine or ten for about six hours a week though.

I got mine second hand so I don't know how well broken in the speaker was. I'm not sure the original owner used it a lot at high volume, but I didn't change it out right away. Based on my experience I definitely prefer the WGS.

Keefy · May 2019

ICBM said:

Keefy said:

I wouldn't want to risk something like this happening though. Neither of my gigging guitar amps use PCBs, they are built on turret board and/or tag board.

The problem is *not* PCBs, it's poor design. There are many extremely high-quality amps that use PCBs and do not, and never will, suffer from problems like this because their designers were more careful.

Conversely, this is a fire that happened in a Fender Custom Shop Twin-o-Lux... which is a tag-board amp. (After removing the burned wiring loom from the socket.)

The common factor is poor design - in this case not fitting the amp with an HT fuse, which is also a fault in the Blues Junior. That one step would have prevented this completely.

That isn't to say Fenders are unusually poorly-designed either - in fact I would put them slightly above average for a mass-production company.

Fair enough!

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Might have tasted a little humble pie today

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