Mercury Magnetics Tone Clone PTs

[KingCameron]

Fellow Tweedies,
I have undertaken the construction of three 5E3s for me and my buddies. I am here to tell you this has been an interesting experiment which has come down to one major issue..

The "Tone Clone" Mercury Magnetics transformers don't work, without modifying the B+. They are 380-0-380 and way to hot to generate cool tone. I have experimented with three different configurations to solidify this fact.

I have wired one amp completely stock. It is cathode biased, with only some minor changes to the caps in the pre-amp. It will feed 415V, with a 350V stage and a 200V stage, respective to the drops in the power supply. I had to reduce some plate resistance levels on the 12AX7 to bring it up to the perfect range. THE AMP STILL HAS TOO MUCH DISTORTION at all volume levels.

I wired two other amps with a fixed-adjustable bias, like the 6G3. I have designed this so one amp will run 6L6s and one will run 6V6s. Actually the amps are wired similar, but the fixed-adjustable bias allows me to control which tube set I want to run.

On the 6L6 amp, I did not modify the voltages going to the pre-amp tubes, because I found them to be close....just a little hot. However, the 6L6s seem to draw more from the tranformer, but I am still seeing a 400V, 360V, 250V drop in the power supply. This is when tuned to a -38V bias voltage. This amp sounds very similar to the cathode-biased 6V6 amp, just bigger and fuller. It still has too much distortion!

The 6V6 fixed-adjustable amp sounds the same as the above amps. I tune this amp into a -26V grid voltage and get similar power drops across the power supply. (~415V, ~360V, ~230V)
This amp still does not generate the warm silky tones I have seen with other Tweed builds.

SOOOO!
Can someone tell me what the best method for modifying the B+ is?
I know I need to drop voltage off of the secondaries by using Zeners on the center tap....
The question is: I need to drop about 30V-40V. What Zeners do you recommend?
I have been on Mouser and see several options. Please let me know.

Thanks,
Kingcameron

[Chris / CMW amps]

There seem some more problems, double-check the wiring/etc.

Are you using a NOS 5Y3? The modern Sovtek 5Y3s are not real 5Y3s, way less voltage-drop (so a higher B+) and less sag (but that can be a plus when really dimed).

[KingCameron]

Tubular Attempts

Thanks Chris.
However, I have tried many...many...many, did I say many different tube combinations to rectify my rectifier problem..

The best tube I found was a French-made RT 5Y3 with a gm of ~600. This is about 200 mOhm less than other NOS 5Y3s I attempted. This more restrictive 5Y3 was only able to drop the B+ by about 10-15V.

I need to drop about 30-40V. The rectifier alone, can't help me here.

[Chris / CMW amps]

Allright...

try putting some zenerdiodes between the HT-centre-tap and ground, let's say 3 to 4 ones, 9V/5W each. Afaik some examples/diagrams can be found on this forum.

[KingCameron]

Original question

Thanks Chris
Now back to my original question. I am wondering what Zeners to use.
I see that Weber offers a Zener solution, and I see that Mouser sells 14,600 different kind of Zeners. I also see that AES and Marsh and Mojo all seem to offer 1W Zeners. It seems you are also suggesting some 1W 9V Zeners. What is the advantage here?

I am curious to learn from this panel what has been tried and what is the best known method for dropping 30-40V using Zeners. Bruce? LoudThud? are you guys out there?

[hasserl]

Check this threqd on the topic: http://music-electronics-forum.com/s...ht=zener+diode

You do not want to use 1W zeners, they will get way to hot. 5W at minimum, depending on the voltage. Do some calculations to determine the wattage dissipated, but beware that they tend to get very hot and some heat sincing is advised.

[TD_Madden]

That's what Bruce at Mission used to include in his Tweedy kits before he started using "voltage corrected" PTs.

My first kit included a 15v, 5 watt zener.

[bnwitt]

I can't imagine why MM would make their tweed deluxe HT so high. Everyone elses is around 325-0-325 I think I'd call them up and complain. What are your filament supply voltage and your rectifier heater voltage reading?

[KingCameron]

MM High Voltage

Yup. I plan to call MM and encourage them to not call these transformers "Tone Clone" because they certainly are not.

My filiment taps seem to be approximately correct, I'll have to check them again. I remeber that my 6.3V tap was approximately correct. I have not checked my 5V tap.

[KingCameron]

Checking for understanding...1W vs. 5W

Are you guys saying I should not use 1W, or are you saying 5W is the only way to go?

I already ordered some 1W from AES, but I would certainly be happy to do something else..

[Bruce / Mission Amps]

Are you guys saying I should not use 1W, or are you saying 5W is the only way to go?

I already ordered some 1W from AES, but I would certainly be happy to do something else..

Email me and for the cost of postage I'll send you some 5 w zener diodes.

***********
Most of the standard Mercury Magnetics PTs are supposedly built to electrical specs of the original early to mid 50's iron.
That would mean the primary and secondary ratio is wound to be run at 110v to max of 117v.
With a mild load on my distribution panel (main circuit breaker panel), my old house in Denver would never push more then 107vac to 115vac depending on the time of day.
In my new house (built in 2005), I have 124vac at my wall outlet right now (just checked)... sometimes it is as high as 127vac but never less then 122vac anymore.
The main step down transformer from the power company is in my next door neighbors back yard and only about 75 feet from my circuit breaker panel.

All this means is that means yours and mine secondary voltages will always be much higher then what it would have been had you run an old amp on 110vac-117vac.
Since the MM trannys are "clones" I suspect you'll find the same problem.
I use a 10amp, fused Variac autotransformer on my work bench ...(connected after my 20 amp, isolation transformer), set for an output of about 120v just to be honest here.

[bnwitt]

Most of the standard Mercury Magnetics PTs are supposedly built to electrical specs of the original early to mid 50's iron.

All this means is that means yours and mine secondary voltages will always be much higher then what it would have been had you run an old amp on 110vac-117vac.

Even with the primary voltage increase over time, that still doesn't get you 380-0-380 More like 360-0-360 at the extreme end. Something else must be going on with the MM PT. Maybe they're throwing in some extra volts as compensation for the extra dollars.

[Bruce / Mission Amps]

Even with the primary voltage increase over time, that still doesn't get you 380-0-380 More like 360-0-360 at the extreme end. Something else must be going on with the MM PT. Maybe they're throwing in some extra volts as compensation for the extra dollars.

And, I forgot to ask exactly which "Clone" power transformer is being used... possibly it is not a 5E3 cloned PT.
I've measured quite a few, stock, mid to late tweed Deluxe amps at 375vdc-390vdc at the first filter cap when using fresh caps and a NOS 5Y3GT.
Some of this depends on the idle current of the power tubes of course.

[KingCameron]

MM FTDP (Tweed Deluxe "Tone Clone&quot

Bruce et al,
I used the Mercury Magnetics "FTDP" (Fender Tweed Deluxe Power) transformers. I went back to their web page and in fact it is advertised as a 380-0-380.
They also advertise a 350-0-350 "Axiom" for $15 more. I assumed that "Tone Clone" was what I was after, and thus ordered as such.

I have since written a letter to Paul Patronette and stated that my extensive experimentation and the wisdom of fellow Tweedys agree that 380 is not usable, or at least not as a "Tone Clone". We'll see what they do. they tout a 100% satisfaction gaurantee.

By the way, I ordered six "Tone Clone" transformers for this project. (3-Power, 3-Output) One of those transformers was dead-on-arrival. I contacted Paul, and they quickly replaced the dead transformer with minimal hassel. I beleive that Mercury is a stand-up operation. Their product is quality. It is just that this particular product is misrepresented as a "Tone Clone".

[KingCameron]

Mercury Magnetics

I talked to Paul Patronette at MM today and he reassured me that the MM transformers are in fact clones. He assured me that 380-0-380 is perfect for
5E3s built to the original Fender spec.

Paul did take into account that the orginal Fender Trannys were built to run on 110-117V wall power. Paul explained that people actually prefer the clones because they are the same as the original, and when run at 124V create the unique Tweed tone.

Paul was real cool, and agreed to fully exchange my transformers, if I was not satisfied. In the mean time, he agreed to send me one of their 350V PTs to compare.

I'll let you know what I find....