| Author |
 Topic  |
|
|
Restoration14
USA
7 Posts |
 Posted - 07/03/2014 : 20:20:12
|
I have a 1932 MG J2 that has a generator with a third brush. The CutOut is missing. I have a copy of the diode conversion instructions from the Practical Guide to the Restoration of the J Type by G. Howell. He indicates that the diode should be wired through a CutOut, which I don't have. His schematic shows something in parallel with the diode, but it is not clear what that something is. It is possible that, even with the contact points disabled on the CutOut, the diode conversion still requires a portion of the CutOut to remain in the circuit. Does anyone know what is needed to convert to a diode without the CutOut?
Nick Graham
Nick Graham |
|
|
LewPalmer
USA
3243 Posts |
Posted - 07/03/2014 : 22:52:21
|
Nick,
You need something to regulate the voltage from the generator, but if you don't have the cutout, you could use the DVR3 regulator. Instructions are also in Nick's book or somewhere in the archives of this forum. Of course, if you don't have a cutout, what will you use for the wiring junction box and fuses? If you want to, you could also use a cutout from a later car. It won't be absolutely authentic, but a cutout from a P-type or TA will also work.
Lew Palmer
PA1169, PB0560 |
 |
|
|
i.thomson
United Kingdom
408 Posts |
Posted - 08/03/2014 : 10:35:49
|
Nick, Your biggest problem, if you have not physically got a cutout box, as opposed to having one which has the cutout contacts inoperative, is finding somewhere to connect the wiring to which looks "period". Basically the Diode just performs the job which the defunct contacts would have done of preventing the battery driving the generator when the generator voltage drops below that of the battery on tickover or when the engine is stopped. I have an early (3 part) copy of Graham's book in front of me and on page 65 it shows two resistors in the circuit (the zigzag things) with no values on them. One of these is in series with the diode (or contacts) and the other is in parallel with the original contacts so that the A and D+ contacts of the cutout box are joined by different resistances when the contacts are open and closed. Interestingly Graham shows the new diode as completely shorting out both of the resistors when it is conducting suggesting that the larger of the two resistors in not necessary. these resistances will be housed behind the cutout box out of sight when it is mounted and will consist of two coils of resistance wire though there will be modern equivalents available. They will be of high wattage but low resistance. I am not sure what they do in a 3 brush generator circuit though but in a later regulator circuit they supply the small current needed to the field coils to ensure the generator stays "alive". I assume that they perform a similar function on a 3 brush unit. Perhaps someone more familiar with these devices would chip in with the values and function of these resistors.
Regards
Ian Thomson |
|
|
|
Nick Feakes
USA
3374 Posts |
Posted - 15/03/2014 : 12:20:45
|
Nick
Apologies for the delay, I had meant to reply to your question sooner. The diode takes the place of the cut-out so you don't need the actual device but you will want the case so for the fusebox part and so that it looks correct. I will send you a copy of my electrics book which may help.
Nick |
|
|
| |
Topic |
|
|
|
Forum Locked
Topic Locked
