Updated 06.06.2013

I like this articulated old electric locomotive a lot.  Märklin 37292 was originally equipped with a c90 digital decoder.

The prototype was made in Germany, in 1925-1927.
34 of these nice locomotives were made, by Krauss and Wasseg.  As far as I know, 16 of these were allocated to the Bavarian railways, as EG5.
From 1927 DRG called them E91. They were in traffic until 1975.  For further details, see table at the bottom of this page.

Preparation for conversion:
I removed the decoder and all the electrical parts.  I also split the three parts and removed the bottom plastic part under the bogies.

The new locomotive inside:
.

Motor:
The motor is not changed. After removing the brushes, make sure that all mechanical functions, like the transmission, wheel axles and the rods, are good and that the locomotive is clean.  Make sure that the motor looks like the one in the photo, without any additional parts soldered to it.  Before inserting the brushes, make sure once more that everything rotates perfect.  If required, oil the rotating parts very carefully.  Do not use too much oil, as this may harm the operation of the locomotive.

Decoder:
The original 6090 decoder was screwed to the holder which is used for the speaker now.  I installed the new decoder in the middle section, fixed to a small home made plastic bracket (cut from an old 6090 decoder cover) and secured with some green sticky stuff from Faber Castell.  I do like things to be removable, thus now super glue, except for the plastic bracket itself to the locomotive chassis.

Decoder adjustment, with my Märklin CS1:
Max. speed:
The EG5 (or E91) had a maximum speed of 55 km/h.  The max. speed is set to 53/255.
Minimum speed is set to 1/255.

Acceleration and braking delay:
Both are currently set to 15,000 seconds.

Decoder functions:
See table further down the page.

Speaker:
Initially I installed the decoder from the 60933 set where the c90 decoder used to be.

To get a fuller sound I installed a 23 mm 100 Ohm speaker from ESU.  I made a small bracket screw to the hole for the decoder.  The speaker is screwed to the bracket and glued with some green stuff in the front end.

The bulb is for internal light, ot working very well.

The front end inside with the new speaker:

The different ends:

Most of the electric bogie locomotives from Märklin have the pick-up shoe under end 1 (front) and the motor in end 2 (rear).  37292 had the pick-up shoe under the motor, which was installed in end 1 (front).
After my rebuild the motor is in the rear end and the pick-up shoe under the front end.  I swapped the plastic parts under the bogies to fit the pick-up shoe.  I do not remember if the threaded hole for the pick-up shoe screw was there, or if I had to drill it and cut the 2mm threads by myself.

Interior light:
I am not happy with the interior light, controlled by functions f1 and f2, so I will make some changes later some time.

Parts used for the conversion:

Part no.	Qty.	Description
60933	1	mfx sound decoder set
ESU 50442	2	100 Ohm 23mm speaker with sound chamber
-	4	2-pole bulb connectors, cut from a 20-pole SIL connector
-	4	28V T1 bulbs for interior light

My setting of the decoder:

Decoder settings, 37292		Default	Mine
Analog settings:
	Enable analog mode	check	<
	Starting voltage	7,300	<
	Maximum voltage	7,200	<
Control settings:
	Swap directions	uncheck	<
	Max. speed	255	53
	Min. speed	4	1
	Acc. time	7,000	15,000
	Dec. time	3,750	15,000
	Forward trim	1,000	<
	Reverse trim	1,000	<
Motor settings:
	Motor PWM-frequency:
	Low frequency	uncheck	<
	High frequency	check	<
	Load Control:
	Reference parameter	11,300	<
	Control parameter K	60	<
	Control parameter I	120	<
	Control influence	255	<
Special options:
	Preserve direction	check	<
	Persistent acceleration	uncheck	<
	Persistent speed	check	<
	Persistent functions	check	<
Sound settings:
	Volume	255	150
	Driving Sound Rate:
	At min. speed	1,000	0,480
	At max. speed	1,240	1,000
	Random Sound:
	Min. gap	30	10
	Max. gap	50	50
	Diesel or electric locomotive
	Spacing for shift levels	?	24
	Braking Sound:
	Threshold	14	<

The 37292 function table:

37292 DRG EG5 22521
mfx sound		Light		Light		Drive sound	Shunt speed	Flute		Horn	Con- tact	Ventil- ation	Compr- essor	Press. air	Press. air	Acc/ dec.	Brake sound	Close door	Cond- uctor
funct.	dir.	front	rear	motor1	motor2			short	long
f0	forward	3
	reverse		3
f1	both			on
f2	both				on
f3	both					on
f4m	both						on
f5m	both							on
f6m	both								on
f7m	both									on
f8	both										on
f9	both											on
f10	both												on
f11m	both													on
f12m	both														on
f13	both															delay off	off
f14m	both																	on
f15m	both																		on
Stop	forward
	rerverse
Drive	forward
	reverse

   f??_m = momentary function

A screenshot from my Märklin Central Station 1:

Prototype information, from Wikipedia:

Bavarian state railways class EG 5 BDRG Class E 91 DB Class 191
Number(s):*	Bavarian EG5 22501 - 22516 DRG E 91 01–20, 81–94 DB 191 001–020, 081, 088–094
Quantity:	34
Manufacturer:	Krauss, Wasseg
Year(s) of manufacture:	1925–1927
Retired:	1975
Axle arrangement:	C'C'
Gauge:	1,435 mm
Length over buffers:	16,700 mm
Service weight:	123.7 tons
Axle load:	20.7 tons
Top speed:	55 km/h
Power output (one hour):	2,200 kW (2,822 ps)
Power output (continuous):	1,660 kW (2,258 ps)
Starting tractive effort:	294 kN
Power index:	17.8 kW/t
Driving wheel diameter:	1,250 mm
Electric system:	15 kV 16 2/3 Hz AC
Collection method:	Pantograph
Traction motors:	2 double traction motors
Transmission:	Winterthur diagonal side rod drive

* I am a bit confused about the numbering system, so maybe I'm wrong.

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