What's inside those Power "Bricks?"

[$2 Bill]

Now an "upgrade" to the 1300 & 1400, the Tech2 Loco-motion 1500...
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Inside
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No schematic this time.
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D1-4 is same as others with Yellow wires as AC input. D5 is first step of the Pulse injection to feed the small Transistors and other parts inject the pulses and Brake function. While Does have Switches for Momentum and Brake, It doesn't use them the same as the Tech2 Loco-motion 2500. Has the same 3 pin Speed POT type used in other models. C2 is part of the Brake Function.

The 470uF C1 smooths a lot of DC Ripple but even with simple Resistor to load the unit will pull down volts fast enough to easily see it at 100% speed. Resulting in the Traces below "float" above 0 volts anytime other then 0 speed. Note that the Pulses are shorter duration now so the meter reads closer to "raw" DC volts.

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[$2 Bill]

Today is the MRC Tech2 Loco-motion 2500... While was Partly shown in another thread... https://www.therailwire.net/forum/index.php?topic=33091.0 but uses external pic links and are currently dead.
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Inside
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Partial schematic this time.
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D1-4 is same job as others but D5 now Isolates the speed control from Fixed DC out. Note the Diode DFB is a "Flyback" diode to protect the small Transistors and other parts from the train motor(s). Switches for Momentum and Brake are shown but skipped the rest of Momentum and PCM because I'm not making a replacement. Has the same 3 pin Speed POT type used in other models. C2 is part of the Brake Function and when Pushed, the Speed Volts dropped slow to 0v thru the 15k resistor and 1N4001 diode.

The Large Ceramic resistor connected to Q1 is 0.33ohm 10% 5w. Think is to limit power thru Q1 for the "weird" PCM setup.

The 470uF C1 smooths a lot of DC Ripple but even with simple Resistor to load the unit will pull down volts fast enough to easily see it at or near 100% speed. But unlike 1500 it use PCM resulting in the Traces below volts at 0 or 15 at different Duty Cycles. Note that there is No  Pulses like others and Meter shows % of Duty Cycles. But meter is near useless at either end of speed knob likely because PCM Frequency is only 60 or 120Hz. (Is same setting on the O-scope for these traces as all others.) It Does Not use 555 timer or other "Chips" for better higher frequency PCM.

Speed set @:
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I believe large Ripple is just because of the 470uF cap. They could use lower volt cap to get high uF in the same space but didn't bother here or in other models. 

[peteski]

Good informational write up.
T think It would  be even nicer of the scope trace photos were less blurry.

I also want to mention that PCM means Pulse Code Modulation. I suspect you meant PWM (Pulse Width Modulation). Except the fact that both use pulsing DC, there is quite a difference of what each represents.

[$2 Bill]

Yes I meant PWM but spell check etc didn't flag it and just forgot to fix that late at night. It takes a lot of time to generate data, pic's, etc then post each "Brick" and often need 1 or more Edits to fix problems just to post.

Blurry traces are the "Best" pics I have. If you're using a phone or smaller tablet to read, try again with big(bigger) screen on a Desktop or Laptop. The Posted Pic Size was used for screens ~ 19" standard or ~ 22-24 wide standard monitors without forcing to scroll sideways. Final format is PNG to prevent more JPG lose. Smaller screens claim has same pixel amount as them but is not the same thing even using zoom to look at a section of a pic.  (Raw pic's are about 4320x3240 pix 2.92MB Each.)

Hard enough to take them and to keep meter back light On to see both at same time to take a pic using Samsung WB150F often taking multiple shots. Even then many shots don't have a full trace depending on how camera "sync" and other timing of a shot. Couldn't find a Tripod that reach high made more issues but might not fix the Blurry traces because take a pic of 3 light sources and "Smart" cameras get confuse which one to set exposure etc. (3 sources? The Trace, Light for Red Reticle and Backlight in the Meter. ) That's ignoring the plastic over the tube that put red markings make a trace blooming problem too. I trier to clean that but 50+ year old plastic has damage no matter what you do and "bad" cleaning or polishing can easily make that far worse.

Many other "Brick Pics" posted are lighted different for each pic then heavily edited beyond the Text shown to show whatever detail(s) to cover.

The Schematics are Kicad but some parts are "missing" to revers the design so had to use Generic symbols or make Custom symbols like 4 pin Speed POT for 1400. I rarely use Kicad and related programs but is the "only way" to publish them in some kind of sense to most readers and doesn't eat more hours.

As of this, I currently have 2 "Bricks" left to Post.

[peteski]

The scope's plastic screen overlay is not the problem. The scope trace blurriness is definitely due to the camera's relatively long exposure while handheld.  You can see clearly multiple scans of the electron beam on the screen.  Still useful info though.

As for the PCM thing, you can easily go back to that post and edit it. The "modify" post link is in the upper right corner of the post.

[brill27mcb]

It would also be good to add the power pack make and model info on the schematics.  - Rich K.

[$2 Bill]

The scope's plastic screen overlay is not the problem. The scope trace blurriness is definitely due to the camera's relatively long exposure while handheld.  You can see clearly multiple scans of the electron beam on the screen.  Still useful info though.

As for the PCM thing, you can easily go back to that post and edit it. The "modify" post link is in the upper right corner of the post.

The Pic's are good enough to show the data to most readers. This isn't a Lab or Shop to make pictures for research or business use.

The overlay still cause blooming just watching the screen because cameras want max scope output and dim other lights and blocking the window behind me or even that washes out the screen. Some Pics are "better" then others because could avoid extra light, brace ageist a wall but still have "long" exposure.

You're already have a very slow trace @ 5 milli sec / cm or 50 ms total just to show 3 wave forms because of 60Hz power. Traces shown are "short" horizontally only because need adjustment inside and didn't bother to fix. Then add "Long" exposure (many ~ 1/3 sec or less) is needed by the "Smart" cameras to see all data. Any "Faster" and most times the camera gets part of a Trace.

I don't have a o-scope hood to get best trace pics and even if did can't see the meter without making/mod'ing a hood to fit it. That's ignoring the cameras often try to "think" I want Night, Fireworks, and other sub-modes that I had to stop before taking or exposure times are Seconds to Minutes.

I did try other cameras and camera modes other then "Smart" mode but was "bad" too in various ways and ate even more time.

I'm not getting paid to post the info in this tread. This is hobble together whatever equipment and as little time possible as already eats several days in total to generate these posts. Example: I could buy a new Digital O-scope but the amount need one other then this isn't worth even when under $100. I'm surprise the 545 still works as haven't been On in over a Decade and stored in a shed. As is the 545 is now unavailable because too cold to turn On without thermal problems with cold weather.

So if the 545 was dead, you won't have even "bad" pictures above showing PWM output of 2500 or any others.

I know how to edit post as edited others before and yes could fix PCM to PWM... or never now.

[$2 Bill]

It would also be good to add the power pack make and model info on the schematics.  - Rich K.

Is not marked because:
Some are very generic that covers many power packs. E2A-- Even 1300 and other Pulse units are fairly Generic with minor changes to the pulse injection setup and used by Other Makers not just MRC.
Others are to make problems posting them outside of this context etc.

Also some have "errors" or missing data for several reasons so should not be use to make or fix related models. Example: You likely can't get glass breakers now even when have the number and replacing with "Polyfuse" etc can cause legal problems if/when the "bricks" fail later and cause a fire.

And before anyone asks... All images in this thread are "Attachments" to prevent easy site rips by others including Bots if we assume the Forum Software and Admin(s) have really block guest viewing them. Google and other Bots rips sites for Decades and only got worse now to "train" their AI scams. I have uploaded them to RW to prevent External Img Links to die in weeks to years later.

Or Many push or use PCBway et al then wonder why many things quickly get "cloned" and sold by AliEx and others in China. They often will make X things with all Logos and other Marks from the original marker without paying for the Rights.

[$2 Bill]

In a "Newer," believe available to 2010 and maybe later, Cheap unit sold as N & HO Transformer... I give you a Life Like unit but the Model is irreverent as Many others including Bachmann sell/sold the same thing with minor cosmetic changes. I used the Life Like unit because can take it apart without breaking anything beyond a glue joint for the back. (I did grind off the Rivets for Bachmann 6605 to see the same design.)
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Why? Is Very Cheap as shown later and party done so users can't change direction without stopping that can wreck the Train Engine.

Inside there's not much but does have a GTE Glass Breaker ("Under" the transformer here) and Full Wave Silicone Diode Set.
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So many are looking at it and wonder how the 1 knob sets speed and direction... After pulling the screw for the knob we see the "Magic" of the circuit board that doesn't parts but diodes and the breaker.
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Now you wonder "WTF is this?"
Look again at first pic inside showing so many Transformer taps... Each Tap goes to Two pads on the Speed ring for each direction.
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(Top screws AC out, Bottom screws DC Train out.)

AND IF you notice the Knob Contact to hit those pads is too wide... They knew and expect them to short out some transformer winding to stop power to the train for each step. Yes, Shorted Winding will Heat the Transformer and More Reason to Unplug or Turn Off Main Power when this type of Brick is not actively run.

To make this model, they put the parts on the bottom, set both to Off to align the knob then simple stack layer together.
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Most if not all Small Plastic "Brick" shaped packs with 1 Knob like Bachmann 6605, 6607 and many other N/HO units are same on the inside.
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[peteski]

The Pic's are good enough to show the data to most readers. This isn't a Lab or Shop to make pictures for research or business use.

Well, when I spend my time running tests, compiling the info, taking photos and posting them here, I try to make the info as professional and clear as I can. As for the info not being for research - maybe so, but I expect that members of the forum find it useful and educational, and even use it for reference. I treat them as a serious audience. That's just me. I suppose we are all have different standards to go by. 

[brill27mcb]

That is one *cheap* "transformer"! What a design...  - Rich K.

[$2 Bill]

That is one *cheap* "transformer"! What a design...  - Rich K.

Yup, These "1 knob bricks" are super cheap even when you adjust prices for the years of old ones where made. Plus remember many units in this tread and other models are made in China, Hong Kong, etc that make them even cheaper and still cut corners to make this and still have UL etc Safety Marks too.

[$2 Bill]

Last 4 now... Bachmann Number 46605A and Related power packs still sold in many train sets with E-Z Track (tm).
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Rather busy Inside...
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It use Transistors to control the Speed but not same setup to other units like most MRC Tech2 and later.
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Why 2 transistors?
The Transistors are NPN & PNP pair (TIP122 & TIP127 100V 5A) with the Base and Emitter tried together...  One transistors Turns On for each direction. The Switch sends Plus or Negative power to the Base and NPN or PNP "ignores" the "wrong" current on the Base.
There are 2 more SMD Transistors plus 3 2.7 Ω resistors = 0.9 Ω seems to monitor current draw. They might be to kill power if can't see a load or DC out is shorted.
The Return path from the tracks is directly to the AC plug and Wall Wart. This Brick has 2 Thermal and 1 Polyfuse but the Polyfuse only protects the AC outs. The breakers protect both sides.

Seems way more complicated then need to be. I don't think is cheap to make as it's basically 2 dimmers that the Direction switch activates one at a time.

Schematic
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Mine is "Dead" because see +/- 13VDC as Direction changes but speed is "pegged" at max power on a meter. So no traces and no time to see why right now. Was likely "dead" when bought because didn't match part # or color of the unit on the box but only got it to tear it down anyway. If find another cheap unit later will update.

Warning: If the E-Z Track Wiring "Harness" is damage or missing and think just make a new one then note the output socket also carries Full AC from the Transformer for the Tip of the Plug. The Ring and Sleeve are use for the Train.

As shown it use a "Wall Wart" transformer with it's own Polyfuse.
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This Transformer that eats power when plugged in same as so many other PSU setups and not just ones on this thread. Is why some Power Co's calls them Vampire power units because over the home, worse over a business, eat a lot of power even when "Turn Off."
 
Why use a "Wall Wart?"
In General:

• The marker need to reduce weight or save space taken by a Transformer or Switch PSU.
• To re-class the product for UL and other Safety Marks. The External PSU come with it's own UL Mark etc from the Contractor making them. Then the product goes thru a lighter/different testing because only has Low Volts, generally < ~ 70 - 90 Volts AC.
• To sell the same controller etc but change the wall wart to have right plug and voltage for UK EU etc. While a Switch PSU maybe Universal volts, makers often want localize plug in them and have correct Safety Certs.

[$2 Bill]

Got a "New" MRC THROTTLEPACK 501 last week...

I'm guessing it's a late 1960 to 70's unit because Made in USA, 120VAC "Safety Plug" & uses Silicon Diodes. This Example is in Very good shape & even came in the box but no papers. This unit is nice so I think will put new pop-rivets in the near future.

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Guts are interesting:
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They just soldered parts to others. Like many other old MRC metal case units has a Real Wire Wound Rheostat to set Speed & Shuts Off Train Power @ Zero Speed using the 4 terminal goes nowhere. (Main Power controls 120VAC.)

Some notice this unit has "Pulse Power" & may think works same as Tech2 etc... Nope. The "pulses" Cut Power to the Train & Fix DC too as those Terminals are for the Cab Controller box in https://www.therailwire.net/forum/index.php?topic=61264.0

FULL-PULSE POWER
For realistic scale operation slow speeds are essential. Some power packs start engines with a jerk and offer erratic control at low speeds. For smoother starts and superior slow speed operation, Model Rectifier's Throttlepack contains a pulse power switch. When you switch from full to pulse power the effective output of the Throttlepack is reduced and power is applied to the track 60 times each second. These minute pulses of energy blend into smooth, continuous motion in your train. A flick of the switch to "full" and you are operating with full normal output. Like the low gear of an automobile, pulse power gives more torque at starting and very low speed. It is not recommended for higher speed operation.

Source:  https://www.modelrectifier.com/v/vspfiles/resources/dc-ac/Throttlepack%20501.pdf Also PDF tells you the "Spare" DC Out is for the Cab Control Box. (MRC still has Many "Vintage" packs "Manuals" as PDF. )

To make it "work" the Full/Pulse switch simply "Break" the Full wave Rectifier to Reduce DC Power out. In short means you'll need more Throttle in Pulse Mode.
I think this was done so the Throttle gets a Fine Control @ lower speeds without making the Rheostat cost more to buy to make the product.

More Detail & Schematic:

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The Bottom Case is just Black painted Stamped Sheet Metal & no plastic parts to insulate the electric.

While MRC claim "These minute pulses of energy blend into smooth, continuous motion in your train." Your results may vary or not work depending on the Train.
Why? As shown there is nothing in the Pack to smooth power. Many motors don't have Flywheels & even if the do, many gears & other parts that may not work well with the pulse mode. So if a train has problems then Don't use pulse power mode.

Again If you find old units... I recommend taking apart & Checking 120VAC side @ minimum. Example: The Power Switch used here is easily damaged/rotted & possibly 1 or Both "High Volt" wires are loose & hitting the metal case. I've seen other packs from All brands stored very badly in a basement etc that very likely have problems even when looks better outside.

[$2 Bill]

A recent YT Video showing the insides of "Vintage" Hornby 900 & 902 sharing same electric design as MRC 501 & Cab Control 44... Video begins with a "Starter" controller with problems that still come with many Hornby sets. While 900 series look nice & let you nest the controller in a spot, the guts have issues from the factory.

Hornby Model Train Controller Repairs and Starter Set Controller Teardown!
JazzTech Electronics

Then have even older controllers with only 1 taken apart that works similar to 501...

While those are UK videos with 240VAC, all are basically same as relative MRC models on 12V side. Hornby "Red Dots" or H&M Half/Full switches are same as MRC Full/Pulse but do wonder just how High/Low Resistance is done on H&M units. Maybe that switch sets different wiring in/to the Transformer...