I could use some electronics help...

shaygetz · Associate Editor Joined: Feb 16, 2005 Posts: 1583

I purchased an MRC Cab Control 77 that, for all intents and purposes looks mint in box. I cannot seem to get it to work and was wondering if one of you electronics folks could look it over for me? Thanks in advance for any help.

VicB

I've looked all over the place for some info on your cab control and don't find anything on it. Is it one of the really older ones that is in a gold colored case and draws its current from a power pack?

shaygetz · Associate Editor Joined: Feb 16, 2005 Posts: 1583

Most definitely old school...

ray_m

After reading the ad, The Cab Control 77 sounds to be very similar to a throttle I built from a schematic that I found in MR. It didn't have as many brake positions as the Model 77 but used a quad op amp chip to generate the pulses. The braking circuit was done with capacitors on the input of the power transistor.
The one I built didn't handle as much current but controlled the locos that drew less than an amp really well.
The momentum feature took some getting used to. A panic switch would have been nice.

jmarksbery

Shay, I have that one I bought years ago and have never used it yet. It has the poop sheet with it, would it be any help for me to scan that and send it to you? I dont know

shaygetz · Associate Editor Joined: Feb 16, 2005 Posts: 1583

jmarksbery wrote:

Shay, I have that one I bought years ago and have never used it yet. It has the poop sheet with it, would it be any help for me to scan that and send it to you? I dont know

Thank you for the offer, Jim, I do have the sheet. It was NIB old stock I picked up at a swap meet never figuring an MRC would fail me. I'll be sending it to Ray to tinker with as I'd really like to run my old school stuff with old school power. Getting ready to pull all my decoders and sell my throttle as I'm no longer a member of the club and have no desire to put out the coin for DCC on my small pikes.

shaygetz · Associate Editor Joined: Feb 16, 2005 Posts: 1583

ray_m wrote:

After reading the ad, The Cab Control 77 sounds to be very similar to a throttle I built from a schematic that I found in MR. It didn't have as many brake positions as the Model 77 but used a quad op amp chip to generate the pulses. The braking circuit was done with capacitors on the input of the power transistor.
The one I built didn't handle as much current but controlled the locos that drew less than an amp really well.
The momentum feature took some getting used to. A panic switch would have been nice.

I probably built the same one Ray. Wink

I'm pretty handy with assembly and schematics...its diagnosis and servicing I'm none too familiar with. Embarassed

VicB

ray_m wrote:

After reading the ad, The Cab Control 77 sounds to be very similar to a throttle I built from a schematic that I found in MR. It didn't have as many brake positions as the Model 77 but used a quad op amp chip to generate the pulses. The braking circuit was done with capacitors on the input of the power transistor.
The one I built didn't handle as much current but controlled the locos that drew less than an amp really well.
The momentum feature took some getting used to. A panic switch would have been nice.

Yep that's the one I was thinking about. Considering its age I would suspect a deterioted solder joint(s) and/or a dried out capacitor(s). The op amp and/or transistor(s) should be ok unless its been subjected a severe overvoltage/current. Should be easy to track down with a multimeter.

shaygetz · Associate Editor Joined: Feb 16, 2005 Posts: 1583

VicB wrote:

Yep that's the one I was thinking about. Considering its age I would suspect a deterioted solder joint(s) and/or a dried out capacitor(s). The op amp and/or transistor(s) should be ok unless its been subjected a severe overvoltage/current. Should be easy to track down with a multimeter.

How would I do that? I'm familiar with a multimeter and know most components by sight, I just don't how to go about diagnosing problems with them. I'd be much obliged if there was a sight you could direct me to.

IronGoat

Bob... I'm probably as far off base with this info as I can get, but I thought I'd give it a shot.

This site is an N scale operation that uses an MRC Cab Control #55 with a dualpack 77ON. Bill might be able to walk you thru some diagnostic steps IF this is the same critter that you have.

Bob/IG

www.billsrailroad.net/

shaygetz · Associate Editor Joined: Feb 16, 2005 Posts: 1583

Great, thank you.

VicB

shaygetz wrote:

VicB wrote:

Yep that's the one I was thinking about. Considering its age I would suspect a deterioted solder joint(s) and/or a dried out capacitor(s). The op amp and/or transistor(s) should be ok unless its been subjected a severe overvoltage/current. Should be easy to track down with a multimeter.

How would I do that? I'm familiar with a multimeter and know most components by sight, I just don't how to go about diagnosing problems with them. I'd be much obliged if there was a sight you could direct me to.

I just Googled Basic Electronic Troubleshooting. There seems to be a number of sites that offer tutorials on the subject. Take a look at them and see if there is something that you might be comfortable with. Taking a course at your local Vo-Tech in basic electronics is fun and you will learn far more than I can explain here. Its really something you learn by hands on experience. Also Google How to Use a Multimeter. There are a number of tutorials and even videos on the subject.

shaygetz · Associate Editor Joined: Feb 16, 2005 Posts: 1583

VicB wrote:

Its really something you learn by hands on experience. Also Google How to Use a Multimeter.

Just like how I learned household electrical troubleshooting... The Chair