Merlin's heater wiring scheme.

[lord preset]

I recall when I saw Merlin's recommended heater wire routing I thought it was even more difficult, fiddly and anal retentive than other schemes I had seen and rejected it outright. I have primarily done overhead heater wires which has the advantage of being able to procrastinate and leave heater wiring to the end of a build. But this time I am waiting for parts so I decided to try Merlin's scheme.

It turns out that for me it was WAY easier than any other method I have tried and went very fast. It was easier to see where to trim wires to size and running the wires to pin 9 between pins 4 and 5 tended to hold the wires in place while fitting and soldering. Note that I am using teflon wire - fatter PVC wire might make this less fun. No idea yet whether this method "works" better but it sure was faster.

[xtian]

Looks great. Helpful to see this again. I had been pinching 4+5 together and running 9 along side. This is better. Just need to be careful not to melt insulation on 9 when soldering 4+5.

[lord preset]

Looks great. Helpful to see this again. I had been pinching 4+5 together and running 9 along side. This is better. Just need to be careful not to melt insulation on 9 when soldering 4+5.

And that's why telfon wire is magical. All traces of hamfisted clumsy soldering technique disappear.

If I didn't have teflon wire I would have to learn to solder properly. Boring.

[Phil_S]

You should be changing your handle to Slick. That is some fine wiring job! BTW, always do the heaters first. It makes the whole build go a lot better.

Also, if you aren't sure about the heater winding, you can socket the tubes and see what the heater voltage is before you commit to the rest of the work. This is particularly useful if you are recycling an older PT (which I often do) the 6-8% line voltage differential is jacking up the heaters too high. You can then easily figure what value resistor to put in line to tame the voltage a few tenths of a volt.

[Firestorm]

I do Merlin's thing too. You've got to angle the sockets right to make it easier.

[andyfromdenver]

on twin triodes, it's even easier to spin the socket and enter to the 4&5 through the gap.
super tidy

[rp]

If I didn't have teflon wire I would have to learn to solder properly. Boring.

Even worse, I have to chose btwn fixing my mistakes or leaving it pretty. Teflon makes me look capable.

BTW, always do the heaters first. It makes the whole build go a lot better.

With most tasks never save the worst part for last, get it over when you’re fresh, and it would be a drag to have an amp almost all set to go but have to sit there and trudge through the heaters before you can fire up.

My 5G9 will have flying heaters, I just wanted to try it. Any idea, I assume Fender did these last? They’d be in the way if I did them first.

[Firestorm]

If I didn't have teflon wire I would have to learn to solder properly. Boring.

Even worse, I have to chose btwn fixing my mistakes or leaving it pretty. Teflon makes me look capable.

BTW, always do the heaters first. It makes the whole build go a lot better.

With most tasks never save the worst part for last, get it over when you’re fresh, and it would be a drag to have an amp almost all set to go but have to sit there and trudge through the heaters before you can fire up.

My 5G9 will have flying heaters, I just wanted to try it. Any idea, I assume Fender did these last? They’d be in the way if I did them first.

I'll bet you're right about Fender wiring the heaters last. They were meticulous about lead dress (pre-CBS) EXCEPT for heaters, which sometimes had the polarity cockeyed.

[pdf64]

I'll bet you're right about Fender wiring the heaters last. They were meticulous about lead dress (pre-CBS) EXCEPT for heaters, which sometimes had the polarity cockeyed.

Except for p-p power tubes, I can't see that makes a theoretical / noticeable / measurable difference?
Surely if Fender thought it important, they wouldn't have used the same colour wire on both 'sides'?
They must have thought it an improvement over their previous heater arrangement (using the chassis as a heater conductor) which at least ensured consistent polarity!

[John_P_WI]

Nice Job!

I despise preamp heaters so much that I have told myself that I will only use the SLO buss style and DC heaters in the future.

[John_P_WI]

I'll bet you're right about Fender wiring the heaters last. They were meticulous about lead dress (pre-CBS) EXCEPT for heaters, which sometimes had the polarity cockeyed.

Except for p-p power tubes, I can't see that makes a theoretical / noticeable / measurable difference?
Surely if Fender thought it important, they wouldn't have used the same colour wire on both 'sides'?
They must have thought it an improvement over their previous heater arrangement (using the chassis as a heater conductor) which at least ensured consistent polarity!

Hmmm, that's a big assumption. We're talking about the same Fender that tacked random grounds throughout the chassis right?

[Firestorm]

Even the P-P power tube polarity doesn't make much difference in a Fender amp. Probably the random ground thing. Plus you can't actually hear the hum, its just added to the signal and creates ghost notes. The amps were under filtered anyway, so that's a given. The idea to ground one side of the heaters is a) easier and b) actually works to guiet SE amps, which were Fender's first designs.

[sabredude]

If you are already re-orienting the sockets, why not do the Soldano heater technique of a bus wire down each side?

[Gainzilla]

Ive seen someone make a jig so you can wire the heaters outside the amp. Just drill the appropriate sized holes in a board with the same layout as the chassis. Once you've got all the heaters wired, you just drop the "harness" into the chassis. keep meaning to try that.

[xtian]

Ive seen someone make a jig so you can wire the heaters outside the amp. Just drill the appropriate sized holes in a board with the same layout as the chassis. Once you've got all the heaters wired, you just drop the "harness" into the chassis. keep meaning to try that.

That would be awesome...if any two of my amps were the same...