R78, R79 in a Hot Rod Deluxe III

[Tone Meister]

I know this topic has been discussed in some detail, but I'm starting a new thread to differentiate between the older model HRD and the new Hot Rod Deluxe III. I've seen some debates as to whether any version of the HRD ever came with 330 ohm power resistors, or not. The consensus seems to be that a 470-ohm 5-watt is a better choice here, no matter what values actually came in the amp.

Well, I have a nearly new HRD III and R78, R79 are indeed 330-ohm, even though the schematic clearly shows them to be 470/5-watt. One of the leads is broken off the board, so I plan to replace them both with 470 5-watters. Is there anything different about the new design that would make the 330 ohm a better choice, or was this just an oversight at Fender?

Suggestions?

[Jazz P Bass]

Those two resistors are not the same.
It appears that the amp was worked on before you got it?

[52 Bill]

Those two resistors are not the same.
It appears that the amp was worked on before you got it?

I agree, is the second hidden resistor 330 ohms as well?

If I remember correctly, some of the earliest versions of the Deluxe series came with 330 ohm resistors installed. These were changed by Fender to the current 470 ohm value after the overheating problems started showing up. The 330 ohm value has not been used by Fender for years now, so that one is not original to the amp. The original Fender part is a Dale CP-5-3 series part and is usually marked as such.

The DeVille series of amps use the 330 ohm value in their 16 volt supplies, but they are using a separate power transformer tap for this which produces a lower voltage than the bias supply tap that the Deluxe series amps use to make the low voltage supplies.

[Tone Meister]

Those two resistors are not the same.
It appears that the amp was worked on before you got it?

According to the owner, it hasn't been worked on, and he has owned it since new. But the resistors are different, indeed, and even the mounting style is different. That said, I've replaced them both with 470's.

[Enzo]

Yes, there definitely were some that came with 330, but 470 works and generates less heat, so...


Open the HRD3 file you posted, it covers deVille and Deluxe, the 330 and 470 both appear on the power supply page.

[Tone Meister]

Agreed, but on the power supply page the amps are in separate sections and the Deville portion shows 330's while the Deluxe shows 470s'. Furthermore, footnote #9 on the first page indicates the values are different for R78 and R79. I went with the norm, and now it's already buttoned up and on its way home.