GZ34 vs 2 x triple solid state diodes (fender amps)

[Justin Thomas]

Yes, cheap amps for the time. Sure, Champs were cheap, and yet, Fender's "bottom of the barrel" amps weren't as cheap as many others. And I'll put a vintage Champ against anything made today. Cheap for then was still better than cheap for now. They were made to be repaired, not thrown away. Now everything is made to be thrown away. That's why it's a disease of society at large, not just amps.

Also, sometimes on a production line it's still cheaper to make stuff the old way indefinitely rather than update the factory - capital expense.

Justin

[Enzo]

The Champion 600 amp is on the do not repair list, but all that means is they won't pay for warranty repairs. It has nothing to do with repairability. That Champion 600 is every bit as repairable as the original Champs were. The circuit is similar, it uses the same tubes, it has power and output transformers, resistors and caps, etc. The only problem is that at $129 a pop new, people are shy about paying me an hour labor ($60) plus parts to fix it. $60 labor, replace a blown 6V6 and burnt screen resistor, $20. We are now at $80. If I had to replace a transformer, we might as well buy a new one and stick the chassis in the guy's cab.

$129 today would have been about $15 in 1957. What did Champs sell for then? I bet more than $15.

[mikepukmel]

The second part is the answer why Fender did it... the fact the amps still sounded good either way, and that diodes were ".ore reliable," is a bonus. Leo wasn't a musician, he was an engineer/inventor & a businessman. He built the best amps he could, as cheaply as he could get away with, for as much profit as possible. All other later "discoveries" and opinions of vintage Fenders being so awesome and durable is just coincidence, and a by-product of a different mindset of a different age.

As to the technical side, I'll leave that to others.

Justin

I looked at the data sheets for GZ34 and best I could guess as well (with my limited electronics knowledge at this point) is that a single tube rect could not supply enough current to keep an 80 or 100 watt amp, e.g. a Twin, alive and breathing. I started looking into tube rectifier circuits and found some tube power supplies with multiple tube rectifiers to get over this. But, ok that would cost a lot more: even bigger transformers, more tubes, sockets, wiring ... So, I double back and wondered why, if the solid state power supply worked OK for the Twin, did they not go cheap and replace all of their amps (Leo or CBS) with a similar power supply used in the Twin, except lower V high voltage windings for the smaller wattage tubes.

[Malcolm Irving]

... So, I double back and wondered why, if the solid state power supply worked OK for the Twin, did they not go cheap and replace all of their amps (Leo or CBS) with a similar power supply used in the Twin, except lower V high voltage windings for the smaller wattage tubes.

I don't know, but as a guess I wonder if the cost of re-engineering (when you have a well proven design and an efficient production line set up) might outweigh the cost saving?

[Enzo]

REmember, silicon diodes capable of the voltages and currents have not always been around. Look at the Fender Twin circuits (not Twin Reverb)

5C8 - two power tubes and a 5U4
5D8 - two tubes and a pair of 5Y3
5E8 - two tubes and a pair of 5U4
5F8 - four tubes and a number 83 rectifier
5F8A - four tubes and a GZ34
5G8 - four tubes and the six silicon diodes

So you can see from the initial design, they were struggling with power supply for that circuit, especially when the power tubes doubled.

In the 1950s and early 1960s, we had little germanium 1N34 diodes, which could never be used as power rectifiers, let alone at 400v. In things like TV sets we used selenium rectifiers. I don't recall just when good reliable rectifiers came along, but they solved Fender's problem. SMaller amps, they just kept making them the way they always did.

[mikepukmel]

REmember, silicon diodes capable of the voltages and currents have not always been around. Look at the Fender Twin circuits (not Twin Reverb)

5C8 - two power tubes and a 5U4
5D8 - two tubes and a pair of 5Y3
5E8 - two tubes and a pair of 5U4
5F8 - four tubes and a number 83 rectifier
5F8A - four tubes and a GZ34
5G8 - four tubes and the six silicon diodes

So you can see from the initial design, they were struggling with power supply for that circuit, especially when the power tubes doubled.

In the 1950s and early 1960s, we had little germanium 1N34 diodes, which could never be used as power rectifiers, let alone at 400v. In things like TV sets we used selenium rectifiers. I don't recall just when good reliable rectifiers came along, but they solved Fender's problem. SMaller amps, they just kept making them the way they always did.

Thanks, makes a lot of sense. They had a design, tubes were cheap, so leave the old ones alone, and solve problems for the newer high powered twin. And people liked the Fender sound on the existing amps, so a redesign would probably have hurt CBS.


http://www.mif.pg.gda.pl/homepages/f...s/021/8/83.pdf

Wow, mercury vapor!
Try that today in the US and you'd have 3 alphabet agencies knocking your door down for environmental terrorism.
I wonder if any of these amps are still around working with original tubes?
I read about some mercury vapor tubes, but thought it was much earlier, 1930's, 1940's.