Startomatic wiring advice

[ajaffa1]

Hi Tony, it comes as no surprise that WORK is a four letter word! Your ambition of building an SOM  can wait until the next power outage.

Take good care,

Bob

[BruceM]

Bob, I respectfully disagree. While there is a path, the field coil resistance will limit the current.  There will only be few amps current through the field windings, and that's all the bridge rectifier must handle.

[apbedford]

Hi Bob

I finally made a bit of time to inspect the control panel. It turns out that the D1 relay, which starts the whole sequence, was U/S - it looks as if it has been overheated in the past.

I thought that I would rewind it, but just wanted to check with you whether you happened to know the specs. My original had 100 ohms stamped on it, and I estimate that I removed about 245 meters of enamelled wire, trying to measure it as I went.

Anyway, to make the numbers work, I'd need to use 245 m of 0.224 mm wire (31 gauge) - giving about 100 ohms, but I'm pretty sure that what was on there originally is finer than this - I make it somewhere between 0.18 mm and 0.20 mm (33/32 gauge). 245 m of this would give me between 135 and 160 ohms.

Any comments? I'm sure that you guys have had to do a few rewinds like this!

All best
Tony

[apbedford]

On second thoughts, maybe the original was 0.224 after all, which would make sense. Difficult to tell even with calipers and feeler gauges.

[ajaffa1]

Hi Tony, the best way to work out how much wire you require is to weigh how much wire you have removed. Identifying the wire gauge can be tricky due to the thickness of the insulating varnish, try burning it off with a cigarette lighter. Once you have identified the gauge wind the coil until you have 5% more copper than you took off. Now measure the resistance and remove wire until you get to your target of 100 ohms. I found it difficult to find suitable cloth insulation tape to cover the coil. I found that micropore surgical tape was a good substitute and once varnished looks identical to the original.

If the coil was burned out it is almost certainly because the old selenium rectifier failed sending 240/110 volts AC through it.

Bob

[apbedford]

Hi Bob, thank you, I was wondering how to adjust the winding - excellent method.

I’ve ordered the wire, so will see how I get on. Any tips like that much appreciated!

All best
Tony

[apbedford]

Hi Bob

I've rewound the coil to 100 ohms as per original: just wanted to make sure what the rating for the load resistor DR would need to be to drop the initial voltage in the detection circuit from 24 to 12, as my coil is definitely from a 12V setup: you had originally said 5W, 6.8K ohms, which I have, but unfortunately being hopeless at electrics myself, I would have thought that it should be a far lower resistance. Presumably any load resistance has to be included in the calculation, so: coil resistance, plus load resistance, plus load resistor DR. I wondered if you would mind just explaining how it works!

All best
Tony

[apbedford]

Sorry, meant Detection Circuit resistance, DR

AB T

[Davprin]

Hello Tony, I wonder how you went with the rebuild. I have and LD1 Startomatic with no control box. I have just received information on differences between the 12v and 24v control boxes.

The Ballast resistor BR is only used in the 24v versions to drop the voltage to the heating element in the reset switch only, nothing else.

Choke CH Has different part numbers for the 12v and 24v systems so obviously some difference there. There are also different part numbers between the 230v and 115v generators.

The line contractor LC also has different part numbers between the two versions. Coil winding have different part numbers and even the contact sets are different numbers, possibly heavier contacts for the 12 v version.

The DR unit you mentioned is not a resistance, it is a rectifier.

I would be interested to know the number of complete turns on choke CH in your control box. I have checked a 24v version and it has 42 turns of approximately 12swg wire. Also, if you can, could you measure the toroidal ring that the winding in on, please. I am looking for the outer and inner diameters (not including the wire) and also the thickness of the ring.

I am going to try to fabricate a facsimile of a control box and want to wind a similar looking choke but it will not be used for current detection, just there for looks.

Dave

[apbedford]

Hi Dave

Well, I wouldn’t exactly say that it was rebuilt, but I have more or less got it working as I intended! The principle issues were rewinding the D1 relay, replacing some capacitors, resistors and diodes, adding BR, and trying to work out how to wire the Startomatic panel into a control box which is designed for button start, which took quite a while.

I will try to check out your queries, but it might take a day or two. However, I’m slightly puzzled by differences in CH for 12V vs 24V because I understood that it provides a back EMF from the generated mains voltage, so should be the same. Certainly, mine was from a 12V system, and is working ok on 24V. Also, the circuit diagram suggests that the only difference between 12 and 24V in the Startomatic panel is the BR resistor. I have also provided for a variable resistor on the D1 relay, but I’m not certain that it was necessary.

All best
Tony

[Davprin]

All ok, Tony.  I am also puzzled by the different choke part numbers as the detection relay that the back emf supplies power to is the same in both boxes. 100 ohm coil is mentioned in the parts list for both. The only other thing that I can think of, is that because the full output current from your generator would be around 18 amps and the output of the 12v units is only about 6 amps, maybe the 12v choke is winding is of a smaller diameter wire. The wire I measured on a 24v choke was 0.105” diameter which equates to about 12swg gauge, I think. It would be interesting to see what your wire gauge is, if possible.

If you could pm me an email address, I’ll send a PDF ( about 3mb ) of the info I have dated 1959.

Cheers
Dave

[apbedford]

Hi Dave

The toroid appears to be 4" external diameter, 2" internal diameter. Mine seems to have round about 50 turns: certainly more than 42. I haven't checked the wire gauge yet. I have uploaded various pics of Startomatic panels, if that's of any assistance. Mine is s-l1600(2) before the modifications, and was definitely 12V. Not sure about the others.

I'd be interested in any documents you have, I will pm you

AB T