RADIO Circuit Breaker feed.

[butts260]

Is the RADIO (15A) circuit breaker fed generally from the battery side of the battery knife switch, or are some EMD models one way and on others the breaker is connected like most other breakers on the circuit breaker panel?

[Desertdweller]

Golden Arm: You'll get a kick out of this one.

I was working on a short line railroad in Mississippi. We had some wide-cab GP40s (originally CN) the railroad had acquired third-hand. This railroad used them for power on locals.

I went to pick up a local at an outlying point. There was a wide-cab GP40 (GP40W?) on the point.

It was my first time running one of those. But on making my inspection, something was apparently wrong with the radio.

The radio would not work unless the headlight was turned on. OK, but....if the headlight was on low, the radio would receive but not transmit. If the headlight was on high, the radio would both send and receive.

Les

[Desertdweller]

butts260:

From what I have seen, pulling the battery knife switch should kill the radio.

Les

[RRCOMM]

Hello from a new member.
The theory behind the location of the radio feed is interesting. Early radios in particular were very sensitive to electrical transients (spikes) on the 72 volt control bus (64 volt battery, 72 under charge). The power converter transistors were gemanium devices that were run close to thier limits in normal operation. There were many inductive devices on the 72 volt line Lots of voltage spikes ranging up to thousands of volts for extremely short duration are generated from relay coils, DC motors, power contactors etc. It was important to power the radio from as close to the battery as possible, the battery acting to absorb many of these transients like a big capacitor would. The other point was to make sure that the radio circuit breaker was connected to the battery side of the knife switch becaue the crew would often fail to open the radio circuit breaker when shutting down the Loco. If the radio was not on the battery side of the switch, when the battery knife switch was pulled all the remaining relays that were still energized would drop out at the same time. This would produce some real big spikes on the line that would have a good chance of killing the radio because the battery was not there to protect it.
(To get a little more technical, E= L* DI/DT).

I repaired thousands of Locomotive radios and blew up a few screwdrivers when connecting the feed to the live 72 volt knife switch!!

Dennis

[GOLDEN-ARM]

Golden Arm: You'll get a kick out of this one.

I was working on a short line railroad in Mississippi. We had some wide-cab GP40s (originally CN) the railroad had acquired third-hand. This railroad used them for power on locals.

I went to pick up a local at an outlying point. There was a wide-cab GP40 (GP40W?) on the point.

It was my first time running one of those. But on making my inspection, something was apparently wrong with the radio.

The radio would not work unless the headlight was turned on. OK, but....if the headlight was on low, the radio would receive but not transmit. If the headlight was on high, the radio would both send and receive.

Les

it almost sounds like a watco locomotive. i was in kansas recently, running a watco train. the eot head end box was wired to the speedo circuit. when you plugged it in, the speedo quit working. so, it was just pushed into the socket enough to hold it in place. need to see if the train's all there? push it in hard. once you knew it was, wiggle a little bit on the plug, and get the speedo back. and yes, that pile was one of the cn (un)comfort(able) cab gp-40's.

[Engineer Spike]

One other similar thing is the turbo pumps. We have some ex B&M GP40-2s. The turbo pump circuit breaker is wired to the hot side of the battery knife switch. With these units, there is no need to wait half an hour to pull the battery switch. This might save the turbo from someone who is to impatient to wait. The down side is that I have seen units where the timer got stuck, and the turbo pump light stayed on all day. If someone didn't notice, he might shut down the unit, and pull the battery switch. This could drain the battery.

[Desertdweller]

Goldenarm,

It was an ex-WATCO unit. It was on the Meridian and Bigbee. The first year this railroad was in operation under its present owner, WATCO was contracted to operate the railroad with M&B power. I think they managed to destroy four M&B units.

The next year, M&B took over operation themselves. WATCO owed them four units, so gave them four GP40W's. I have a friend who was an engineer on the Timberrock Railroad in Texas. I think he ran those same units while he was down there.

Except for a few quirky things like that, they weren't bad units to run. The wide-nose Canadian cab with multiple windshields took a little getting used to.
The windshields reminded me of a DL-109, and the engineer's and fireman's seats sat on high raised platforms. I guess with the raised short hood, the seats could not be mounted on the floor like in a regular GP40.

I would say these were the oddest locos I ever ran.

Les

[GOLDEN-ARM]

i ran on the m&b back in late 2005, just after katrina. i ran the detour trains between the kcs in meridian and csxt in montgomery. the motley assortment of junkers there, was an interesting time. run through power was sweet. 8-10 sd-40's on a 200 car train of loads was a regular deal. i also ran the timber rock, mid 2004. we had a lot of potash traffic from the southwestern railroad using run through dp power. in a strange twist of fate, i went to the swrr, after i was done on the m&b.

back on topic, some radios are wired to the bus bar that runs the breaker panel. some have a switch that's attached to the battery switch, and you have to shove the knife switch all the way in, to hit the toggle that runs the radio. i've seen them hardwired, and once you pull everything, the radio is still on. i guess it depends on how under-qualified the people were, that worked on them. if you can't figure out a circuit, why not just run a new wire from where you want to start, to where you want to end. happens a lot more than you'd believe.

even class one guys can relate to the retards that can't fix an antenna wire, so they just stick a magnetic one somewhere on the cab, and leave 50 feet of coax hanging in the cab.

[Desertdweller]

I retired off the SW almost our years ago at Deming. Handled locals Hurley-Deming-Rincon and coal trains Rincon-Deming.

On M&B I ran locals, bridge traffic between Meridian and Selma, and switched Nahola Yard. We would swap power at Nahola or Yantly between east and west bound trains so the class one power would wind up in their home yards.

The class one power was pretty good. One night I ran CSX #1.

It is a small world.

Les