Fender Blues Deville Speaker Jack Connections too close to chassis

[mikeydee77]

Removed as mistook cardboard protection for metal of chassis. Red Faced symbol

[52 Bill]

Basically there are two open switchcraft style jacks for the speaker connection, surrounded by a metal shroud. On this amp the shroud is about just a tiny distance (less than a millimetre) from the tip of the speaker jack when inserted. Also I noticed that the shroud is bent away from the jacks a little as the metal is slightly distorted - perhaps deliberately.

I have not seen one with a metal shroud around the speaker jacks, that may be something particular to export models. Perhaps you could post a photo.

In any case, I'm not sure that I would believe that a shorted speaker jack would cause the fuse to suddenly blow. I would clean and service both jacks being especially careful to clean the extension jack switch contacts. If these get oxidized they can cause the speaker line to open circuit, which could cause the amp blow. I'd also be sure that the shroud is clear of the jacks.

Have the output tubes been tested?

[soundguruman]

You can fix this with a hammer.

[mikeydee77]

Hi 52 Bill,

Thanks for you comments.

just after the original post I decided to measure the gap with a set of feeler gauges and perhaps get some photos. It was lest than .0012" and in making the measurement I realised that had made a mistake in my post. It turns out that the shroud is not metal at all, but cardboard! It just looks very much like the chassis. So as a result I deleted the original post in case it became misleading.

However your comments on speaker jacks are relevent to the original fault. Any suggestions on cleaning narrow areas of metal such as these. I have often wondered if a nail file could be adapted to fit the contacts on the the black "cliff" sockets that you get on Marshall, AC30 etc.

The power tubes sound fine and with the fault not repeating regualrly so it is one of those tricky situations where it's more elimination than deduction. I think I will change the power tubes and see if the fault re-occurs then.

[Enzo]

That cardboard is a special kind of cardboard, we call it "fishpaper." If you are interested, just gogle the term fish paper.

[52 Bill]

Any suggestions on cleaning narrow areas of metal such as these. I have often wondered if a nail file could be adapted to fit the contacts on the the black "cliff" sockets that you get on Marshall, AC30 etc.

I'm not a big fan of using highly abrasive substances or tools on contact points in audio jacks. Once the plating is damaged it leads to even deeper corrosion, etc.

I use Caig Deoxit on jacks. You can spray just a little between the two contacting leafs and then manually move the two parts together, causing the contact areas to burnish themselves clean.

On really tough cases, I cut a thin strip of heavy paper that is the width of the leaf and insert it in between the two contact points. Then letting the contact pressure do most of the work I pull out the strip, allowing the surface of the paper to burnish both contact points. I tend to use this method a lot on the Cliff style jacks as there is no simple way to move the contacts to burnish themselves.

[Enzo]

I use a little strip of business card - it's sturdier than plain paper.

I appreciate wanting to protect any plating on the connector, but having been in field service on relay based gear for years, I use burnishing tools. Like a small file, but diamond dust instead of abrasive grooves. I see no damage, and once cleaned with the burnisher I almost never see a jack come back. I have several sizes, but the small 1/8" one fits neatly in the groove of Cliff-style jacks

I use the GC9337. Google the number for an interesting collection of the item and other things with the same number.

MCM sells them.
GC Electronics Fine Grade Burnishing Tool | 9337 | GC Electronics

As do others like Frys.
FRYS.com | GC Thorsen

[52 Bill]

I use a little strip of business card - it's sturdier than plain paper.

Yeah, I cut strips off of our repair tickets which are printed on a similar weight stock.

I have used the diamond dust burnishers on big relay contacts, especially when they have become pitted. All of the modern jacks that I see now seem so cheaply plated that I hate to risk any real abrasive.

[Enzo]

I also sometimes recommend a brass brush (end bristles) in my Dremel to spin into jacks. It polishes the inner face of the bushing as well as the tip contact. I get chastized that it will take off the plating. MY counter to that and to the burnish-deniers is that any plating that was so loose as to come off that way was ALREADY loose and was probably contributing to the problem as it was.


I find the burnishers impresive. I have done a lot of relay work, and carried point files and emory boards. You can smooth a pitted contact with a file, but those burnishers leave it as smooth as a baby's bottom.