Blues Junior trace be gone

[shortcircuit]

I just got this in , no sound , powers up , all tubes are lit , slight hum from the speaker . First suspect the cheesy input jack , get access to the back of the board surprise trace taken out by the output transformer mounting screw ?. After cleaning it off a bit , I can't quite tell if there were 2 traces side by side ? It's a silver panel, so I don't believe it to be a Junior III. Always appreciate your input


Fender-Blues-Junior-Schematic highlight.pdf
https://www.thetubestore.com/lib/the...-Schematic.pdf

If I'm following the schematic correct I'm thinking I can run jumpers as such , yes? D12 R34 R36 all survived

[nevetslab]

I just got this in , no sound , powers up , all tubes are lit , slight hum from the speaker . First suspect the cheesy input jack , get access to the back of the board surprise trace taken out by the output transformer mounting screw ?. After cleaning it off a bit , I can't quite tell if there were 2 traces side by side ? It's a silver panel, so I don't believe it to be a Junior III. Always appreciate your input

[ATTACH=CONFIG]54026[/ATTACH][ATTACH=CONFIG]54027[/ATTACH]
[ATTACH]54028[/ATTACH]
https://www.thetubestore.com/lib/the...-Schematic.pdf

If I'm following the schematic correct I'm thinking I can run jumpers as such , yes? D12 R34 R36 all survived
[ATTACH=CONFIG]54036[/ATTACH]

Yes, there are two traces. I've shown them in RED, adding them to your photo below:

[shortcircuit]

Thank You nevetslab !!!!

[The Dude]

Do grind out any of the charred circuit board before adding the jumpers. Once burnt that circuit board can become conductive.

[shortcircuit]

Do grind out any of the charred circuit board before adding the jumpers. Once burnt that circuit board can become conductive.

Thanks Dude , I was going to ask what others would do to deactivate the remains

[The Dude]

I usually just scrape/cut it away with an x-acto knife if it's not too bad. Sometimes it requires a dremel tool. Get it down to where you no longer see charring.

[nevetslab]

Thanks Dude , I was going to ask what others would do to deactivate the remains

A recent PCB trace burn repair done on an Aguilar DB 751:



After having scraped away all of the chared remains, which took going down a full level of the fiberglass layer, I had coated the area with Corona Dope, two coatings, just to put a seal on it. That's mostly for areas that are carrying high voltage. I haven't looked at the Blues Jr to see just where this damage is.

[shortcircuit]

I usually just scrape/cut it away with an x-acto knife if it's not too bad. Sometimes it requires a dremel tool. Get it down to where you no longer see charring.

Do you use any sealer of any kind after ?? I see nevetslab mention the Corona

[The Dude]

I'm not positive what those traces are for, but I see a brown and blue wire nearby. Maybe OT leads? If so, they will have B+ on them. A little Corona Dope wouldn't hurt. That said, if you clean the burnt board out well, I don't think it's necessary. What's left won't be any more conductive than it was to start with. And, it goes without saying, don't forget to do something about the screw that started the whole mess. (I know,......Mr. Obvious)

[Pedro Vecino]

Be careful with the contamination in that area. From left to right:
D12 - diode between EL84 plate and ground.
R34 - input grid resistor
R36 - screen grid resistor
R32/31 - bias feed resistors

Requires total isolation between these components. The corresponding EL84 could have also some problem...

[shortcircuit]

[ATTACH=CONFIG]54042[/ATTACH]

Be careful with the contamination in that area. From left to right:
D12 - diode between EL84 plate and ground.
R34 - input grid resistor
R36 - screen grid resistor
R32/31 - bias feed resistors

Requires total isolation between these components. The corresponding EL84 could have also some problem...

Yes critical area , that's why I'm looking for a sealer, but I only need a fingernail polish bottle not a quart /and have found but shipping. V5 El84 tested great (Russian Groove tube) , socket pads look iffy , so maybe trans screw was just an easy blame at first.

[g1]

Yes critical area , that's why I'm looking for a sealer, but I only need a fingernail polish bottle not a quart /and have found but shipping.

You might find 'liquid tape' at a hardware store. It's not as good and may take a couple layers. The important spec. is dielectric strength in V/mil, corona dope is around 4000, liquid tape more like 2000 or less.
Check to be sure, some of them are just basically for waterproofing.

[drewl]

I've had to drill out bc sections of fried boards.

After cleaning check for any stray resistance before coating in your substance of choice.

[shortcircuit]

You might find 'liquid tape' at a hardware store. It's not as good and may take a couple layers. The important spec. is dielectric strength in V/mil, corona dope is around 4000, liquid tape more like 2000 or less.
Check to be sure, some of them are just basically for waterproofing.

Thanks for the info G1 , because of where this is on the board, I'll opt for the Corona.

[nevetslab]

Corona Dope source

Thanks for the info G1 , because of where this is on the board, I'll opt for the Corona.

The source for the MG Chemicals Super Corona Dope P/N 4226-55ML is Mouser Electronics, their P/N 590-4226-55ML @ $11.06 55mL bottle.