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Electron Engine ™
Printed Circuit Boards by Emissionlabs.

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EE50 and EE51 Fault finding hints

If you have a kit version, and the soldering was done well, the unit should right away. If there is a persisting hum problem however, the cause must be found first. The combination of record player, MC Box, phono pre amplifier, and power amplifier, with all it's cables, can be complex. To help finding the cause, the EE51 board has some special test settings. Hum can be caused before, after, or at the MC unit itself. Just Unplugging cables can lead to wrong conclusions. That is why we leave all cables in, and use the test features which the boards offer. Finally, the board is not a test tool for solving any cabling problem there is, but in most cases give valuable hints. So in case of a hum issue, take some time, and do the below tests one by one. Read what each test does, and try to understand the results. Note, by some settings of the links, the board input or output can be disconnected or shorted intentionally, so if the record player appears not working, this is normal.

Desoldering of the transformers

This was not intended by Lundahl. If there is a need to do it anyway, this is on your own risk. In that case, do not try to pull out the transformer while some pins have melted solder. This may break off the tiny wire inside the transformer, and there is no repair for this. If pulled on the cold pins, this will not easily happen. For this reason, the pins should be carefully freed from any solder, with a good desoldering tool, until each pin is loose inside the PCB. Then when cold, the transformer can be lifted out, without force.

Transformer testing

This is not needed with new transformers. For used transformers, you need to test them. Windings are never shorted, but they can be open, due to bad un soldering. However MC transformers do not allow DC current, unless it is very little. Do NOT just test the windings with a multi meter. This will magnetize the transformer core, which may cause distortion. To convince yourself, try this with a LED, on the "Ohms" setting, and you will see the LED burns (at the right polarity). For testing of MC transformers, put a 5 mega ohms resistor in series with your multi meter. Then, you will see 5 Meg for a good winding, and otherwise "open connection".

Note the following three points: Do not play a record, but keep all equipment and cables connected. Write down the regular settings you had now, for A, B, C, D, H1, L, H2, GND. Settings must be done for both channels at the same time, otherwise test results are invalid.
For Test only		A, B, C, D	H1, L, H2	GND	Comment
1	If hum with this test setting, the problem is not in the MC unit, and not in the record player, or it's cabling.	A, B, C, D	None	None	What this setting does: It disconnects all transformer connections at the primary side, both signal and ground. Like this, absolutely no signal can be passed into the transformer. Also errors from a input ground loop are stopped this way. The phono amp input is shorted to ground. Errors from a output ground loop are stopped this way. There should be no hum with this setting. I there is hum however, this is generated by the pre amp itself, or by the cabling from the pre amp to the output amplifier. This has nothing to do any more with the MC unit.
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	In and out	What this setting does: The Primary transformer windings are all disconnected. No electrical signal can get into the transformer. The pre amp however is NOT shorted now. 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	3.1) If hum with this test setting, there is an magnetic field radiation into the MC Transformers. 3.2) If NO hum with this setting, but it returns when you put in the links H1 and H2, there is a ground loop somewhere in the cabling from the record player to the MC Box-	None	None	None	What this setting does: It tells you if there is magnetic radiation into the transformer, or a ground loop at the pre-amp to MC box connection. With the settings here, it can only be those two options, since all input windings are deactivated. In case of magnetic field radiation, try placing the MC box further away from the equipment which radiates the hum, or rotate the MC box 90 degrees. This is not intended as solution, it only proves, if so, where the problem is coming from.
4	When done:	Do not forget to restore the original settings of the jumpers :)

 

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

There is so much voodoo talk in the internet, even about burning in DVDs. MC transformers however always need a burn in. This is not Lundahl specific. All magnetic materials adapt to the orientation of the earth magnetic field if they are tapped on.

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 too. This small magnetism inside the core will go away, just by using them for some time. The transformers are literally burned in during production, as heat removes the magnetism too. So they are shipped free of magnetism, but the journey may (sometimes) add some small magnetism. The burn in time is the range of a few weeks of normal use.