PT thermal breaker

[Leevi]

I got a PT for Blues Junior and wonder the thermal break wires.


https://www.tubeampdoctor.com/en/mains-transformer-for-fender-blues-junior-pro-junior-230v


Do you think I should do something for that or just leave those disconnected?


/Leevi

[PRR]

Do you use seatbelts in your car?

[Leevi]

Yes, I use. Just thinking if  it is overkill to implement this protection. One issue is that I don't have idea how it should be implemented. I suppose there is some kind of thermal fuse inside the PT?
/Leevi

[kagliostro]

Connection with Board labeled 1998 REV B and REV C:
Primary:
Thermo Pink wire to CP 5 (formerly  unused)
Thermo Pink wire to CP 7 (formerly unused)
0V Violet wire to CP 8 (formerly black)
230V Grey wire to S2B (formerly  white)
 
Secondary:
HV Red To CP 12 (formerly red)
HV Red To CP 13 (formerly red)
Bias Brown To CP 16 (formerly brown)
0V Brown To CP 17 (formerly brown)
6,3V Green To CP 18 (formerly green)
0V Green To CP 10 (formerly green)
 
Connection with Board labeled 2001, 2002, 2003, 2010 (Blues Junior III)
Primary:
Thermo Pink wire to P4
Thermo Pink wire to P7
0V Violet wire to P 8
230V Grey wire to S2B

Reading the PT spec (that say to connect those pink wire on some points on the board), seems that there is a component that interacts with the circuit, not a simple temperature fuse, something like an NTC/PTC

Franco

[Leevi]

I'm building a Blues Junior conversion from scratch, no PCB.
/Leevi

[shooter]

I suppose there is some kind of thermal fuse inside the PT?

not sure about your case, in automotive wiring you'll find a bunch of "fused links", basically wire that's designed to "burn open" when overloaded, PITA to find in a wiring harness 

last count, I contributed ~ $800 to the govm't oversight of my behavior 
I was fortunate enough to be there to cut 3 ppl from their seatbelts while the cars burnt, or sank.

[2deaf]

Yes, I use. Just thinking if  it is overkill to implement this protection. One issue is that I don't have idea how it should be implemented. I suppose there is some kind of thermal fuse inside the PT?
/Leevi

P4 is connected to the fuse, so one pink wire connects to the fuse (1A SLO-BLO).  P7 is connected to P8, so the other pink wire is connected to the violet wire from the transformer.  The grey wire from the transformer connects to the other side of the DPST switch which isn't connected to the fuse.

[2deaf]

I noticed that Fender gives no choice with the thermal fuse in the 120V version, but the export version gives the option of going through the thermal fuse or not.  I also noticed that Fender is calling for a fast 1A fuse.  I would still use a slo-blo.

Is it easy to replace a blown thermal fuse?  If it's not easy or impossible, I would use the thermal fuse initially on the export versions.  Then if something went wrong and it overheated the power transformer, I could fix whatever went wrong and still be able to use the PT by changing the connections. 

[sluckey]

Yes, I use. Just thinking if  it is overkill to implement this protection. One issue is that I don't have idea how it should be implemented. I suppose there is some kind of thermal fuse inside the PT?
/Leevi

The link you posted for that PT tells you how to hook it up. Just scroll down almost to the bottom of the page.

If you are scratch building this amp then just connect the pink wires between the power switch and fuse. This would be a quick easy and neat way to do it. The thermal fuse will simply be in series with the mains fuse.

[2deaf]

I should have asked you what voltage you have where you live before I told you to use the grey wire.  Good thing Sluckey mentioned looking at the link you posted.

[Leevi]

I should have asked you what voltage you have where you live before I told you to use the grey wire.  Good thing Sluckey mentioned looking at the link you posted.

230v mains. The instructions you proposed make sense thanks.


/Leevi

[PRR]

The regular fuse protects against over-Current. The thermal fuse protects against over-heating. Some faults will over-heat the transformer without pulling excessive current. An overheated transformer may burn, start a fire. In a crowded club, it may start a panic.

I have not "needed" my seatbelt in many decades. However when I was small a drunk driver T-boned us, we didn't have seatbelts (1956 Plymouth), we were OK, but next day my dad was drilling the car for seatbelts and we were trained to use them every time.

I know PT thermal fuses have a habit of false-blowing. And I have had PTs "burn" with little fuss. And the house is full of transformers without thermal fuses. But I have also seen a whole school emptied-out by a transformer fire. I have mixed feelings, but I'd tend to use it unless it was "only me" and "only out in the open".