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EE50 and EE51 Fault finding hints

This MC unit should work right away, and problems should not occur. If there is hum however, finding the root cause, is better than trying random things. The combination of record player, MC Box, phono pre amplifier, and power amplifier, with all it's cables, can be complex. To find hum cause, needs some local testing, for which the EE50 and EE51 boards have some provisions. It can not give a final answer to everything, but for most cases a good hint will result from it.

Music will not play with these settings. This only for testing.

  • First, write down the regular settings you had now, for A, B, C, D, H1, L, H2, GND!
  • Keep all equipment and cables connected.
  • Important: The settings below here, must be done for both channels simultaneously.
For Test only
A, B, C, D
H1, L, H2
GND Link
Comment
1
 If hum with this test setting, the problem is more likely in the PHONO amplifier itself.
use FOUR Jumpers
None
None

This setting does two things.

First, it disconnects all transformer connections at the primary side, both signal and ground. Even when you let the cables connected as intended, on the PCB they are disconnected. Like this, absolutely no signal is passed into the transformer. Also errors from a ground loop are stopped this way.

Second, the combination B + C + D is invalid normally, because it sets the damping to zero ohms. This is only used for testing. This zero ohms value is now connected to the pre amp input, by closing jumper A. Effectively the pre amp input is now shorted.

In this condition, any remaining hum can only be generated by the pre amp itself.

A very small chance remains it is caused by a ground loop in the cables connecting pre amp to the power amplifier, but because ground is also cut off (Ground Jumper is open), this is unlikely.

Finally, try taking in and out Jumper A (while leaving A,B,C in). Taking out jumper A will remove the short. If this makes the hum come back, the hum is likely coming from the phono amp input stage itself.

2
 If inserting and removing the GND link will make hum come and go, there is probably a ground loop somewhere in the external cabling.
A, B, C
None
try In and out
 Primary transformer side is also fully disconnected here, but now the pre amp is connected, with maximum damping added. Adding and removing the Gnd Jumper, will connect or disconnect the record player ground. If this test is positive, there may be a ground loop in the record player cabling.
3
 If hum with this test setting, there may be external field radiation into the MC Transformers.
None
None
None

Though the Lundahl transformers belong to the most hum insensitive on the market, low cost mains transformers of the amplifiers can are sometimes be a source of a magnetic hum field.

What this test does: The primary windings are interrupted. So no signal can enter via the input, even if there would be a ground loop. The only way to get a hum signal out of the transformer is, when it radiates through the metal box, into the transformer core itself. Creating an output signal that way. Note, electrical fields can not enter the metal box, but magnetic fields can. Though not easy, but they will if a cheap mains transformer is near by.

You can find the hum transmitter, by holding the MC box closer to it. Try placing the MC box further away, or rotate the MC box 90 degrees. Placing it further away, should solve the problem.

4
When done:
Do not forget to restore the original settings of the jumpers :)

 

When the MC box is finished: Burn-in is probably NEEDED!

There is so much voodoo talk in the internet, even about burning in DVDs, and gold plated mains fuses. Feel free to believe this, if you are sure it doesn't harm your wallet too much.

MC transformers however always need a burn in. This is strange, no burn-in guru talks about it. So we do it here :) This is not Lundahl specific. All magnetic materials adapt to the orientation of the earth magnetic field if they are tapped on. You can try it with a large iron nail. Like 7cm length. Place it in front of you, and point it to the Earth's North Pole direction. Firmly tap on it with some a metal object. Then, hang it balanced on a thin cotton wire, and voila: you just made a nice compass. This is how easy materials can become magnetized by the earth magnetic field.

The transformers during shipment, are rattled in the truck, the package is kicked around by the post office, and perhaps you dropped a transformer a bit too hard, unaware you should treat them GENTLE. This may cause some small magnetism in the transformer, which gives a small unlinearity. Nobody can say if your transformers were dropped during shipment, or were close to magnetic fields. People ship Neodyme magnets by post, and if such a package was near the MC transformer, it will need burn in. This small magnetism inside the core will go away, just by using the transformer for some time. The remove magnetism, the naked cores are literally burned in during production, as heat above 250°C removes the magnetism very effective. So they are shipped free of magnetism, but the journey may (sometimes) add some small magnetism.

It is not possible to express the burn in time in hours, but it is in the range of a few weeks of normal use. Did you hears sometimes people say, their transformers improved sound during burn in? Well this was no voodoo, it was real, and this was the reason.