Engl e530 filaments heater voltage help

[Disappear_85]

Hello, my Engl preamp tubes wasn't glowing and there was no voltage on the pins, so I replaced the 4 diodes (1n4007) rectifier and now its working. BUT the voltage is 7.2v instead of 6.3, is that fine? Should I leave it alone? Or should I add a resistor to drop the voltage?

Also I should mention, the preamp is for 230v power outlet, in my country last time I checked it's around 246v from the outlet.

If I should add a resistor, what value and wattage should it be?

There are no power tubes, only 2 12ax7 tubes wired pin 4-5 connected together and going to ground and pin 9 is connected to the filter cap, so pin 4 & 5 are the negative and pin 9 is the positive


Since it's a pcb board preamp, the only wat that I could add a resistor is to lift the 2 legs of the rectifier (positive side ) and solder a resistor to it and solder the other side of the resistor to the board. Is that correct? The heater circuit is transformer to rectifier to filter cap to pin 9


I'm not a tech or an electrician, but I can solder and the filter caps auto discharge when the unit is off, but I always test them to make sure.

Any help would be appreciated, and I apologize for my bad English, it's not my first language.

Thanks

P.S
The 4 diodes I took out test functioning out of circuit, that's weird huh?

[J M Fahey]

1)

in my country

And your Country is ..... ????????

2) are you measuring rectified filament voltage WITH/WITHOUT tubes plugged in? Check ONE

3) is there any fuse or connector in the path from transformer to tube sockets?

4) what is the VAC measured across transformer filament taps?

5) measure with power tubes plugged in, in fact with all tubes in place, unloaded windings tendnto give higher than expected voltages.

6) welcome to the Forum
Remember to fill location data in your Member data page, answers depend on that.

[Disappear_85]

1)
And your Country is ..... ????????

2) are you measuring rectified filament voltage WITH/WITHOUT tubes plugged in? Check ONE

3) is there any fuse or connector in the path from transformer to tube sockets?

4) what is the VAC measured across transformer filament taps?

5) measure with power tubes plugged in, in fact with all tubes in place, unloaded windings tendnto give higher than expected voltages.

6) welcome to the Forum
Remember to fill location data in your Member data page, answers depend on that.

Thanks for the response

1) I'm from kuwait ( middle east )

2) 7.2v with the tubes installed and glowing

3) There is no fuse in the heater circuit, only rectifier to a filter cap to the heater

4) If I remember correctly the voltage from the transformer was around 8, can remember exactly

5) there are no power section, it's only a preamp with total of 2 12ax7

6) thanks I will update my profile asap

[J M Fahey]

Ok, I thought it was a full power amp.
Weird, and then VAC out of transformer is also very high, my only suspicion might be power transformer is using a 220VAC rated primary and of course that will raise *everything*, please post a transformer picture to read its labels, also if it offeres different primary widing taps, some do.

If no other option, you may add a dropping resistor, say a ceramic 5W, a couple ohms (use Ohm´s Law to calculate it, for example with your current 600mA consumption 2 ohm would lower 1.2V) , but no need to butcher the PCB, just mount it on a terminal strip and cut *one* of filament wires to pass through it.

[tschrama]

try 1 Ohm or 2.2 Ohm, 3 watt

[Jon Snell]

Not sure which version you have ;
but, to run the heaters at 7.2v is not an issue. It means that the ECC83s will only last 5 years instead of 6 ... is that an issue I wonder ... no it isn't.

[Mick Bailey]

Out of interest, many thousands of Fender amps sold here in the UK run the heaters at over 7v and many have done so for over 25 years, often with the same preamp tubes. They're usually configured for 230v and our mains is 240v (mine is 248v) and even reconfiguring them for our mains they still run high. I've never though it to be a problem, though.

[Jon Snell]

Out of interest, many thousands of Fender amps sold here in the UK run the heaters at over 7v and many have done so for over 25 years, often with the same preamp tubes. They're usually configured for 230v and our mains is 240v (mine is 248v) and even reconfiguring them for our mains they still run high. I've never though it to be a problem, though.

I rewire the transformer primary to 240v.
There is an unused tapping.

[tschrama]

Your preamp tubes last only 6 years?

[Mick Bailey]

I rewire the transformer primary to 240v.
There is an unused tapping.

I also do this with every one I get in. Frustratingly, Fender refers to this as an Australian market configuration and instead lumps us in with the harmonised 230v EU voltage spec, which is also responsible for much wasted heat in electric motors here.

[Helmholtz]

I thought nominal mains voltage in the UK was 230V (-6%/+10%) since the 90s.
If so, importers must rate their products for 230V and you can't blame them.
That's no excuse for exceeding the nominal 6.3V heater voltage by more than 10%, though.

https://www.spenergynetworks.co.uk/p...e_changes.aspx

[g1]

Out of interest, many thousands of Fender amps sold here in the UK run the heaters at over 7v and many have done so for over 25 years, often with the same preamp tubes. They're usually configured for 230v and our mains is 240v (mine is 248v) and even reconfiguring them for our mains they still run high. I've never though it to be a problem, though.

Noise comparisons at proper vs high heater voltage can be interesting.

[Jon Snell]

I thought nominal mains voltage in the UK was 230V (-6%/+10%) since the 90s.
If so, importers must rate their products for 230V and you can't blame them.
That's no excuse for exceeding the nominal 6.3V heater voltage by more than 10%, though.

https://www.spenergynetworks.co.uk/p...e_changes.aspx

They goal posts were changed by the EU, not UK, We still use the same infrastructure to convert 550kV (pylon voltage) to 33kv (distribution voltage) and then to 3 phase 415 volts between phases.
One phase to ground is still 240volts and always will be.

[Helmholtz]

They goal posts were changed by the EU, not UK, We still use the same infrastructure to convert 550kV (pylon voltage) to 33kv (distribution voltage) and then to 3 phase 415 volts between phases.
One phase to ground is still 240volts and always will be.

UK utilities signed the change to harmonized 230V nominal.
I know, because I was an IEC member for 10 years.
So don't blame others.

[pdf64]

UK electricity distribution companies have had 25 years to at least make a start to get it sorted. Zero progress so far.
The lip service they pay to a 230V nominal is a brazen mendacity worthy of our great leader