'67 Deluxe Reverb Rectifier change

[award70]

Hi Fender People,

I have a '67 deluxe reverb and the B+ is around 450vdc. I'd like to bring that down a bit so I am considering swapping the GZ34 rectifier for a 5U4GB. Does anyone know if the power transformer (part 025130) can provide the 3A of heater current needed for the 5U4GB?

TIA

Alan

[martin manning]

I would pull the rectifier tube out and measure no-load voltage on the 5VAC winding, then plug in a 5AR4 and measure 2A load, then repeat with a 5U4GB. If the voltages drop is ca. 7-8% from the no-load voltage with the 5U4GB, I think it will be ok.

[award70]

I would pull the rectifier tube out and measure no-load voltage on the 5VAC winding, then plug in a 5AR4 and measure 2A load, then repeat with a 5U4GB. If the voltages drop is ca. 7-8% from the no-load voltage with the 5U4GB, I think it will be ok.

Makes sense Martin. I'll do the tests later today. Thank you.

Alan

[award70]

No load 5.64 Vac
5AR4 5.37 Vac
5U4GB 5.27 Vac

Looks I’m ok at around 6%.

[martin manning]

Yes, I agree.

[Stevem]

You might want to check out a 5V4 also.

At least it’s indirectly heated like the 5AR4 is.

[award70]

You might want to check out a 5V4 also.

I may do that. The 5U4GB is a spare I had.

[B Ingram]

I have a '67 deluxe reverb and the B+ is around 450vdc. I'd like to bring that down a bit so I am considering swapping the GZ34 rectifier for a 5U4GB. ...

You might want to check out a 5V4 also.

The 5V4 doesn't achieve award70's goal.

- The 5AR4/GZ34 has a lower voltage drop than 5Y3, but it can manage 250mA of output current (page 2 of the data sheet).

- The 5Y3 will only manage about half the output current, at 125mA (page 2 of the 5Y3 data sheet).

- The 5V4 is capable of a 5Y3-like output current of 175mA (Page 1 of the 5V4 data sheet). In this case that's probably okay because with only a pair of 6V6s, the Deluxe Reverb isn't pulling enough current to necessitate all a 5AR4 or 5U4 can manage.


But along with being indirectly-heated, the 5V4 has its plates very close to its cathode, and so has very low voltage-drop akin to the 5AR4/GZ34. On that point, it does not accomplish the increased voltage-drop that made award70 look for a different rectifier-type.

[award70]

Good point B Ingram. https://300guitars.com/articles/rectifi ... rop-chart/

[Stevem]

That chart is all well and good, but A DR only pulls about 120 ma at idle depending on your bias voltage on the outputs .

[Stevem]

Here’s some empirical results with four different rectifier tubes in my 1954 Gibson GA77 which is cathode biased with 6L6GT outputs

The tube complement is 2-12AX7s, (1) 6SL7, (1) 6J5 and a 5V4.

All the recto’s I used tested out strong on my Hickok 600.

The first two columns here are the percentage of how each plate in the recto tested out.

Next is the idle current

Next is the B+ seen.

All the tubes heater voltage other then the 5U4 was 5.09, the 5U4 dragged that down to 4.92.

5AR4
78////80////159ma////412

5Y3
75////80////131.5/////350

5V4
75////75////152ma////399

5U4
85////80////153.5ma////385.5

[Craig B]

I use a 5R4GYB in my DR clone with a Weber power transformer. It puts out 408 volts. A Sovtek 5AR4 puts out 458 volts.

I am very pleased with the performance using the 5R4GYB.