Migrating to 220V

[pbiagi]

Hello,
Living in Europe, my 5E3 was built a couple years ago, using a 110 V power transformer.
Since it's kind of a hassle using a step-down transformer, I recently got a 220V power transformer and plan to swap them.
Dumb question but thought I'd put it out there (since I almost forgot..) -
By doing this I'll need to also swap the fuse with a 1 amp.?!?
Is there anything else I need to think about?
thanks in advance, Paul

[loudthud]

Not all transformers are created equal. Your B+ could change enough to make a noticable difference. Your amp may need to be re-biased or the B+ reduced.

Does your amp have a "Ground Switch" which typically connects a capacitor from the chassis to either side of the power line? If so, the capacitor should be removed.

There could be an issue with how the heater supply is wired. Do either the exsisting transformer or it's replacement have a center tap (typically green with yellow stripe)? Does the amp have an artificial center tap (typically a pair of 100 ohm resistors)? Is the "center tap" grounded or connected the the 6V6 cathodes?

[fyl]

Is there anything else I need to think about?

Euro-style PT's show a lower source R (primary to secondary ratios are halved). This isn't usually a problem with well designed/built amps, but can be a failure factor if valve current and output voltages were highish to begin with.

Check the source R on the B+, measure actual unloaded voltages and do a sim using Duncan's PSUD. Add series R between the PT and valve, trim capacitance, raise the 6V6's cathode R if needed.

[Bruce / Mission Amps]

Hello,
Living in Europe, my 5E3 was built a couple years ago, using a 110 V power transformer.
Since it's kind of a hassle using a step-down transformer, I recently got a 220V power transformer and plan to swap them.
Dumb question but thought I'd put it out there (since I almost forgot..) -
By doing this I'll need to also swap the fuse with a 1 amp.?!?
Is there anything else I need to think about?
thanks in advance, Paul

Who's PT is it? I frequently have to ship my 5E3 kits to Europe with a couple 5 watt 10v and 15v zener diodes because the line voltages there have risen to 235vac to 250vac, they are not 220-240vac.
To keep the vintage or classic tone, don't simple try to change the bias curve of the power tubes to accommodate the higher line voltages and subsequent higher B+, just reduce the B+ instead.

[pbiagi]

Thanks guys for the excellent feedback - I love this forum!
... and I love the tone of this amp! Bad tone is NOT where I want to go.

Does your amp have a "Ground Switch" which typically connects a capacitor from the chassis to either side of the power line?

No I never installed that cap, and put a standby switch there.

There could be an issue with how the heater supply is wired. Do either the existing transformer or it's replacement have a center tap (typically green with yellow stripe)?

Both PTs have the center tap.

Does the amp have an artificial center tap (typically a pair of 100 ohm resistors)?

On the 6.3VAC heater supply, I have installed the 100 ohm resistors connected to the cathode on one of the 6V6's. That was done to help reduce hum... which it did somewhat, but later I've brought the hum way down (by rewiring the inputs..), so I'm not sure the dual 100 ohm resistors on the 6V6 are necessary any more.

Is the "center tap" grounded or connected the the 6V6 cathodes?

The existing center tap is grounded to one of the PT lugs (together with the filter caps).

fyl - your advice looks great but I'm afraid I'm too much of a neophyte to get it all. In Duncan's PSUD app, I got as far as getting my rectifiers, transformer (I think??) and B+ voltage (??), but this will take me more time to figure out. Looks great though.

Who's PT is it?

The existing is Thordarson Messner - is that any good?
The new is Heyboer HTS-9409EX.

The story -
I've done several upgrades to the 5e3 amp ... and was going to replace the OT w/ a Heyboer. I only know the model no. of the existing - NSC041318.
Separately, I had a PT heat issue with an Eico hifi amp ... decided to swap the PT w a 220V PT. Had good advice to do this...
.. and so was thinking of doing the same for the 5E3, just to avoid lugging around the step-down tranny... But if I have to sacrifice tone, I'd rather bring the step-down tranny..

Currently if I use my "good" step-down tranny to provide 117VAC,
existing B+ is 370V.

Here around Paris wall socket voltage measures around 236V, give or take a few volts.
Seems if the 240V PT wire is used, B+ should be OK..??

a couple 5 watt 10v and 15v zener diodes

Bruce, what would be the purpose? How would the work?
I saw new Fenders use them, but I thought they were for protecting parts.?

Thanks for your alls advice.

[pbiagi]

There could be an issue with how the heater supply is wired. Do either the existing transformer or it's replacement have a center tap (typically green with yellow stripe)? Does the amp have an artificial center tap (typically a pair of 100 ohm resistors)? Is the "center tap" grounded or connected the the 6V6 cathodes?

Loudthud, I may not have been entirely correct with my last response -
The existing PT has a red with yellow stripe wire to ground, which I thought was the center tap. (It's been a few months since I've had the chassis open, but I'm pretty sure about that).

The new Heyboer replacement PT has several striped wires:
- red w/ yellow stripe
- green w/ yellow stripe
- blue w/ red stripe
- black w/ red stripe


On the existing PT I think I have the high voltage center tap to ground.. and have an artificial center tap for the 6.3VAC wiring. Is that right?

Try to access the Heyboer site (http://heyboertransformers.com/) from my home, I get 'Error 403: Forbidden'.

With the new PT - would I be putting both the red/yellow-striped, and green/yellow-striped wires to ground?
Maybe do away with the dual 100-ohm resistors?

Thanks, Paul

[loudthud]

My concern was that if an artificial CT is hooked to the output tube cathodes and you ground the CT on the replacement transformer, that will disturb the bias on the tubes and cause them to red-plate and probably smoke the resistors. You need to know what any extra wires do. Don't just assume they should be grounded.

[fyl]

The new Heyboer replacement PT has several striped wires:
- red w/ yellow stripe
- green w/ yellow stripe
- blue w/ red stripe
- black w/ red stripe

Have you got a spec sheet and a wiring diagram? Heyboer uses BLU/RED for bias taps in most models. Maybe you've got a BF Deluxe Reverb Export PT, not a tweed Deluxe Export PT (don't worry, it fits and gives the right voltages - the tweed version is too hot IMO - with the benefit of more lams and higher possible current).

Check the attached pdf's, they are the wiring diagrams for Mojo's Heyboer-sourced DLX PT's. Yours could very well be a 761.

[pbiagi]

Have you got a spec sheet and a wiring diagram? Heyboer uses BLU/RED for bias taps in most models. Maybe you've got a BF Deluxe Reverb Export PT, not a tweed Deluxe Export PT (don't worry, it fits and gives the right voltages - the tweed version is too hot IMO - with the benefit of more lams and higher possible current).

Check the attached pdf's, they are the wiring diagrams for Mojo's Heyboer-sourced DLX PT's. Yours could very well be a 761.

The Heyboer 1025130EX seems closer to the 761 with the following differences:
- there is a green/yellow CT wire
- only has the black and black/red wires - no other primary wiring choices (which is fine)
It does have the blue/red wire like in the 761 diagram, which I assume I'll tape off.

Heyboer sent this info:
Primary Black
Secondary:
370 - 0 - 50 - 370 Volts
Red - Red/Yellow - Red/Blue - Red
5 Volts Yellows
6.3 Volts CT Green - Green/Yellow - Green

Am I correct - the red/yellow and green/yellow Center Taps should be bound together and grounded to a lug.?

Also per loudthug, I'll remove the artificial (2-100ohm resistors to cathode) CT.

Thanks again, Paul

[fyl]

Heyboer sent this info:

OK. The pic below summarizes it. Is it correct?

Isolate and tuck away the bias tap BLU/RED or RED/BLU - jacket color first, stripe color second, don't invert them or you could have some nasty suprises with complex PT's.

Am I correct - the red/yellow and green/yellow Center Taps should be bound together and grounded to a lug.?

RED/YEL should be connected to your dirty ground with C1, C2 and other "noisy" stuff. Other connections depend on the grounding style you've choosen.

Also per loudthug, I'll remove the artificial (2-100ohm resistors to cathode) CT.

Either connect GRN/YEL to the top of the 6V6's cathode RC (typically 250R/22µ) in order to somehow raise your heaters *or* keep the 100R balancing resistors, which usually give better results than a straight grounded CT.

Rewire as per std layo, change the fuse on the primary - with a 240V pri you should use 1A slo blo, half the value of the 2A 120V fuse.

[pbiagi]

Thanks for the advice. It's all put together with the new PT and OT.

The 6.3VAC (green) CT is not connected to ground, and I kept the dual-100ohm resistors instead.

Verdict:
Only played for 20 min. and would always be a victim of wishful thinking the 1st day - there seems to be better balanced sound (OT?) and have more sustain (another story, below?). Sounds great!

Hooked up a meter, and initially found B+ at 350V. Wonderful... but then looked back and it was at 425V... and stayed there. (Caps must have been charging.)
So here are the stats -
Line voltage: 235 VAC
B+: 425 V
Tube 1: 39.2 mA
Tube 2: 43.2 mA

I think that's ok, but may be a little high.
Before this change, depending on the step-down transformer I used, B+ was as high as 415V, and one tube at 41.7mA.
Later I found a step-down tranny to take the supply voltage down to 117V though. With that B+ is, or was, 370V, 36.2/33.2mA.

Should I be thinking of getting 5 watt 10v Zener diode and put it on the CT to ground.?? (is that right?)
I'm not sure where to buy one - it's quite large? - and how it's suppose to work.
[Edit: I found one at Mouser, but still am not clear on the how, and if it's really needed...]
The amp sounds good, and maybe it's still in the safe zone - don't think so - and I have NOS tubes, so don't want to naively do them in either.

Thanks in advance for your advice.
Paul

[fyl]

I think that's ok, but may be a little high.

B+ is too hot by at leat 25V. A 5E3 sounds nice with 370 to 390V on the 6V6GT's plates and 250R or 270R cathode R's.

What is the voltage across the cathode R?

Should I be thinking of getting 5 watt 10v Zener diode and put it on the CT to ground.?? (is that right?)

I'd use a 10W 30V zener or three 10V in series for a drop of around 25V (the actual voltage drop is lower than zener ratings). Connected from HV CT => Z cathode(s) to ground.

You can also use a larger cathode R for the 6V6GT's, try 300R or 330R. Tone won't suffer - some people have reported good results with higher values such as 470R, but IMO the amp doesn't behave like a 5E3 anymore.

[Bruce / Mission Amps]

If you are not using a NOS 5Y3GT rectifier, you will need to.
With that Deluxe Reverb power transformer, reduce that B+ down to the 355vdc-385vdc range.

There is only two or three ways to do it easily...
Use the NOS 5Y3 will help a lot.
Use two or three 10v-15v 5 watt zener diodes in series with the red/yellow high voltage center tap to ground.
Make sure the banded ends of the zener diodes are pointing at ground.
The 3rd way is a waste, but you can use a couple 10 watt, 100-150 ohm resistors in series with the red leads to the rectifier tube socket.

FYI... I think the MOJO 761EX is made by Lenco, well, it used to be Lenco... possibly a Heyboer now.
Mag Com makes and excellent one too and the cost a little less.

[pbiagi]

Hi Bruce,

If you are not using a NOS 5Y3GT rectifier, you will need to.

Had a RCA 5Y3GT. Replaced with same RCA from the 50's. B+ went down 2 volts.. however that could have just been AC line fluctuating.
Have a couple GE 5Y3GTs in the states but it'll be a while before I get my hands on them.

With that Deluxe Reverb power transformer, reduce that B+ down to the 355vdc-385vdc range.

Actually have a Heyboer 220V PT for tweed deluxe (I presume - that's what I ordered).

Use two or three 10v-15v 5 watt zener diodes in series with the red/yellow high voltage center tap to ground.

Ordered these and installed two as suggested. Have two more.
Previously I had measured voltages without writing them down.
Today the AC line is the highest I've ever seen - 240 VAC.
At 240 VAC, B+ 411 V, plates 402 V, tube 1 37.8 mA, tube 2 41.7 mA.
From memory at 235 VAC, B+ 402, plates 392 V, heater filament 6.3 V..

Both the PT and OT were replaced with Heyboer's. (Two changes at the same time.)
The sound now has more sustain (because of higher voltages??) and a better low end (Heyboer OT??).

Should I add a 3rd zener diode to bring down voltages a bit more? What affect on the sound will these zener diodes have, if any?
Or should I try to get the GE rectifiers first?

Thanks in advance, Paul