SidecarJoeG I'm actually quite versed in linear power supplies, so I understand what this thing is doing. I do plan on ripping the rectifiers out of this thing, but even the transformer wiper doesn't work so hot anymore, so I may just toss it. And the old rectifiers are only 1 fin each, making them really really thin. So putting a brick rectifier isn't an option. I could get a smaller one but in the end I think I'd rather try getting something better first. If this new one turns out to be problematic (basically if the transformer is bad) I'll revisit this thing. I have an old Marn-O-Power that I put a new rectifier and new switches into and it works great now. And, I'm currently in the process of rebuilding the high voltage circuit in an ADA MP2 (tube guitar preamp). Plus I'm still finishing up the odds and ends to my new high performance Caddy 500 project in my '68 Coupe 'de Ville. So, I'm pretty busy with some unfortunately expensive hobbies. The only way I can afford them is to buy things that need work for cheap and then fix them up. Anyways, I really appreciate all the feedback! Does anyone remember that memory pack I was talking about above? I think it was called "Throttle for all Seasons". I knew a friend that had made a couple for his layout and they worked exceptionally well.
I'm actually quite versed in linear power supplies, so I understand what this thing is doing. I do plan on ripping the rectifiers out of this thing, but even the transformer wiper doesn't work so hot anymore, so I may just toss it.
And the old rectifiers are only 1 fin each, making them really really thin. So putting a brick rectifier isn't an option. I could get a smaller one but in the end I think I'd rather try getting something better first. If this new one turns out to be problematic (basically if the transformer is bad) I'll revisit this thing.
I have an old Marn-O-Power that I put a new rectifier and new switches into and it works great now.
And, I'm currently in the process of rebuilding the high voltage circuit in an ADA MP2 (tube guitar preamp). Plus I'm still finishing up the odds and ends to my new high performance Caddy 500 project in my '68 Coupe 'de Ville. So, I'm pretty busy with some unfortunately expensive hobbies. The only way I can afford them is to buy things that need work for cheap and then fix them up.
Anyways, I really appreciate all the feedback!
Does anyone remember that memory pack I was talking about above? I think it was called "Throttle for all Seasons". I knew a friend that had made a couple for his layout and they worked exceptionally well.
Well, I received my "new" power pack the other day and hooked it up this morning. It definitely does very well! I think the controls work very well. I was doubleheading one train with 2 Bowser H-9s and the other side was running one of my Mantua 2-8-2s with no issues at all whatsoever. Thanks for the advice! Im definitely an MRC fan now!
I'm not sure why you need a "brick" rectifier. The 3 amp, 50PIV Radio Shark ones I've used come in about a 3/4" square package that's perhaps a 1/4" thick, with the 4 leads attached in the package. I've seen others of similar size with a bolt hole for mounting to a heat sink. Or wire 4 3amp 50PIV diodes in a bridge configuration - these are about the size of 1/2 watt resistors.
The transformer is usually the most expensive component. Just move the wiper to the full voltage position and leave it there. Build a nice hand-held transistor throttle to attach to it. Circuits for various throttles are found at http://www.awrr.com/throttle.html and at http://home.cogeco.ca/~rpaisley4/Throttles.html.
my thoughts, your choices
Fred W
Try and find a MRC Sound and Power 7000 on EBAY ETC
Great sound for both diesel and steam including whistle/horn --adjustable to sync with train speed
And a momentum feature for realistic start up and stoping
I have 2 one for each oval
51% share holder in the ME&O ( Wife owns the other 49% )
ME&O
Hi!
Unless you are really understand the rebuild/repair of a powerpack, I would cut the cord and throw it out. There are an awful lot of good packs for sale on Ebay, and I've used several of the MRCs over the years with never a problem. Before I switched to DCC, I had two Controlmaster 20s - and they were outstanding. But, they are expensive and probably overkill for your needs.
I currently use a Controlmaster I for powering my turnouts & accessories, and have recently also used a Throttlemaster model - also with good results.
Soooo, if you can't afford a new one, check out Ebay.
Mobilman44
ENJOY !
Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central
It looks like an MRC cheering section!! I agree. I have a couple of MRC powerpacks dating from the 1960s and they still are good, although I probably would recommend you look at something newer from the Tech series.
George In Midcoast Maine, 'bout halfway up the Rockland branch
I just picked up an old MRC 700 dual control power pack. It is rated at 4 Amps, I'm assuming 2A per side. That will actually work out really well for me and since the thing is decently large I should be able to fit new rectifiers and things in there if need be. Thanks for the tips! I'll still keep my eyes open for an MRC Tech 4 350 or a 9500... then I can get rid of this other really shotty thing I use on my test bench area.
Sidecar, seems you are intent on repairing you older unit. But, I will bring up the MRC 9500 transformer. I sold mine 3 years ago so I have forgot what functions it had. But it is a power house and very dependable. I bought mine new for $95.00 and sold it for $60.00. I wishes I had kept it, the meters would have been handy on the workbench.
Cuda Ken
I hate Rust
I don't know squat about fixing them. But I have MRC TechII 2800. The one with two throttles and overload protection built in. Its over 20 years old and has never given my a moments trouble. Of course, 16 of that was spent in the attic in a cardboard box. I have run as many as 4 loco as well as a lighted city (on the AC side). Have no idea how many amps, or no other criteria. I have seen them in grab boxes at local train shows for $15.
I run an old MRC Golden Throttlepack on my test track and a Troller Autopulse 1 with momentum on my HOn3 layout, both with excellent results. Cant beat the old MRC throttles, but with the coreless motors in my Hon3 engines, the Troller works great so far. Mike
LHS mechanic and geniune train and antique garden tractor nut case!
There is some great ideas here. I actually have two other power packs that I have done just what has been suggested here and used a full wave rectifier to replace the originals, and also changed the power and directional switches. The problem with this particular one is that it has a wiper that rides on the actual secondary windings to set the output voltage and there is 1 bad spot, right at about the perfect operation speed. Also, the rectifier is split into 2 diodes, one on each side of the case. Problem is that the case is only slightly larger than the transformer and there isn't enough room for one of those "brick" rectifiers. I've debated just putting 2 diodes in there, but you don't get full wave and there really isn't a good way to mount anything in there. I think I'll just use it for the AC output to power scenery down the road.
Anyone else use the MDC 350? That particular unit seems interesting to me because of the memory function.
I also recall that Model Railroader had a throttle years ago that had a memory to it and then a few years after made modifications to it to make it alot better. Does anyone happen to remember what year / month those issues were? I'm pretty sure they used PWM.
As for caps, I've debated adding them. The other two trains don't really seem to have a problem, but then again, it might help keep the motors alittle cooler.
Thanks for the thoughts! It gives me some things to think about!
cacoleIf you know enough about electronics and electrical wiring, you could replace those old selenium rectifier stacks with a diode bridge and possibly salvage the power pack that you currently have. All Electronics in Van Nuys, California has diode bridge rectifiers rated at up to 35 Amps, and up to 800 PIV for $4.75 or less. You would probably also need a new electrolytic capacitor to smooth out the rectified current. All also has them in stock, but your primary consideration on which one to use would depend on how much room is left inside the power pack's cabinet. Of course, the cap could be mounted externally, too, somewhere under the layout. http://www.allelectronics.com
If you know enough about electronics and electrical wiring, you could replace those old selenium rectifier stacks with a diode bridge and possibly salvage the power pack that you currently have.
All Electronics in Van Nuys, California has diode bridge rectifiers rated at up to 35 Amps, and up to 800 PIV for $4.75 or less. You would probably also need a new electrolytic capacitor to smooth out the rectified current. All also has them in stock, but your primary consideration on which one to use would depend on how much room is left inside the power pack's cabinet. Of course, the cap could be mounted externally, too, somewhere under the layout.
http://www.allelectronics.com
As cacole states, all you need to do is replace the selenium stacks with a silicon full wave bridge that will take up about a hundreth of the space. A 3 amp full wave bridge, 50 PIV or better, will cost less than $5 even at Radio Shark markups. Selenium rectifiers do break down with age, and become a fire hazard when they do so.
The existing transformer should be just fine - just rewire the output from the selenium rectifiers to the AC leads on the full wave bridge. Your DC out to the reversing switch comes from the DC leads. If you are actually drawing 2.5 amps on a regular basis, make sure there is airflow to the full wave bridge, and if a heatsink can be mounted, mount one. Then toss the selenium.
The capacitor cacole advised is totally unnecessary. Your trains have been running just fine without filtering for all these years; there is no reason to add it now.
Once the rectifier has been replaced, you may want to look at replacing the rheostat with a transistor circuit as another upgrade. This is not necessary, just a possible upgrade for your consideration. Attached is a photo of a simple handheld transistor throttle I built for $20 using Radio Shark components.
I built it because the rectifier and rheostat on my AHM power pack gave up the ghost. I simply attached the throttle to the AC terminals of the power pack, and stayed in business. The transistor throttle will give much better control of any newer (low current) engines you buy than the old rheostat will.
Hi,
I wrote an evaluation of the power packs on my layout including the one that was linked to by the one poster in this topic.
Here is the thread: http://cs.trains.com/trccs/forums/p/168228/1850773.aspx#1850773
Hope it helps
Frank
"If you need a helping hand, you'll find one at the end of your arm."
In generalm you can't go wrong with MRC power packs. I have and old AMPACK from '59 that I still use on the layout. Granted, its for lights and switches, but it still works fine.
Tilden
You might want to check out THIS. If your old pack puts out enough amps, you can use the AC side as the power source.
Wayne
I have an old DC power pack that is on the fritz. The celenium rectifiers short out when it gets hot and end up just putting AC to the tracks, which needless to say is causing my engines to over heat. I took it out of service after it did that to a 2nd engine. Fortunately the engines are fine. But I've debated just putting new rectifiers in there, but there isn't much space to do it w/o having wires touching the case, etc, so I am debating getting or building a new one. I do plan on eventually going to DCC, but not for at least like 5 years, minimum. So who make something with at least a 12v / 2A capacity? Most of the newer ones seem to top out around 1.25... and I sometimes double head Bowser 2-8-0's, and they require some amperage... along with running some passenger trains with lights, etc, etc. Thanks.