E-unit buzzing fix not working 100%

That is to be expected, the coil will draw more current on DC than AC.  Here is a recent discussion on this very issue using numbers from a coil on a 145 gateman to illustrate what you are experiencing.

https://ogrforum.com/...1#157970176365067831

I have an MPC diesel with this same mod but it doesn't heat up as much as your loco.

The coils run hotter on DC. In addition to the rectifier, you need to limit the current to acceptable levels. Additionally it is possible for the DC current to magnetize the e-unit  plunger leading to degraded performance.

However, I've never had an e-unit that I needed to power with DC (and it is impossible to count how many units I have serviced). I've always been able to rebuild them and get them to operate satisfactory on AC. In my opinion, running on DC masks the symptom and doesn't address the cause (something dirty/worn/degraded out of spec) which then magnified by the AC pulses.

Here is a video showing the difference in just shaving a bit off of the top of the pawl so it seats properly. Others have reported adjusting the pawl arm achieves the same:

• https://ogrforum.com/topic/buzzing-e-unit
• https://ogrforum.com/...-rid-of-e-unit-noise

I understand the issue with the gateman is similar but it also works on a constant voltage whereas my loco's voltage varies with load. Would a current limiting resistor work? Or perhaps half-wave rectification?

@bmoran4 posted:

The coils run hotter on DC. In addition to the rectifier, you need to limit the current to acceptable levels. Additionally it is possible for the DC current to magnetize the e-unit  plunger leading to degraded performance.

However, I've never had an e-unit that I needed to power with DC (and it is impossible to count how many units I have serviced). I've always been able to rebuild them and get them to operate satisfactory on AC. In my opinion, running on DC masks the symptom and doesn't address the cause (something dirty/worn/degraded out of spec) which then magnified by the AC pulses.

Here is a video showing the difference in just shaving a bit off of the top of the pawl so it seats properly. Others have reported adjusting the pawl arm achieves the same:

Others have added some padding to the top of the plunger to soften and limit its travel. Sometimes it is easier to replace the plunger.

Other links of interest

• https://ogrforum.com/topic/buzzing-e-unit
• https://ogrforum.com/...-rid-of-e-unit-noise

Thanks for the video bmoran4, I think I'm going to take your advice...

@BCianci posted:

...Would a current limiting resistor work? Or perhaps half-wave rectification?

Filtered half-wave, maybe. I've never tried it, but it will probably buzz if unfiltered.  A current limiting resistor would have to be sizeable to dissipate 20-25 watts, like the size of a Lionel rheostat.

The best solution is to rework the pawl... Lionel has demonstrated that E-units can be made to work nearly silently... most of my quiet ones are late prewar & early postwar.