'A' or 'B' circuit generator?

This is so embarrassing, I must just be getting old; I can't remember
if the generator in my '61 C-172 is an A or B circuit. Worse, I
forget which one is which. Does the 'A' supply controlled voltage
to the field and the 'B' does a controlled "ground out" of
voltage coming from the field or do I have it backwards? My system
seems to be charging, just not enough. It might be OK and I'm just
taking too many short hops with too many bells and whistles on. Can
someone refresh my memory so my checks are correct?

Jim

wrote:
This is so embarrassing, I must just be getting old; I can't remember
if the generator in my '61 C-172 is an A or B circuit. Worse, I
forget which one is which. Does the 'A' supply controlled voltage
to the field and the 'B' does a controlled "ground out" of
voltage coming from the field or do I have it backwards? My system
seems to be charging, just not enough. It might be OK and I'm just
taking too many short hops with too many bells and whistles on. Can
someone refresh my memory so my checks are correct?



Almost certainly it's a car generator and I think most car generators
are one or the other. The other one is used in heavy aircraft.

This is so embarrassing, I must just be getting old; I can't remember
if the generator in my '61 C-172 is an A or B circuit. Worse, I
forget which one is which. Does the 'A' supply controlled voltage
to the field and the 'B' does a controlled "ground out" of


A circuit field tied to voltage source inside generator and regulator
switches resistance in and out of circuit to ground to control field
current. Grounding field terminal produced full output.

B circuit field is grounded inside generator and regulator switches
resistance between field terminal and voltage source to control field
current.

Cheers:

Paul
N1431A

Tri-Pacer wrote:
This is so embarrassing, I must just be getting old; I can't remember
if the generator in my '61 C-172 is an A or B circuit. Worse, I
forget which one is which. Does the 'A' supply controlled voltage
to the field and the 'B' does a controlled "ground out" of


A circuit field tied to voltage source inside generator and regulator
switches resistance in and out of circuit to ground to control field
current. Grounding field terminal produced full output.

B circuit field is grounded inside generator and regulator switches
resistance between field terminal and voltage source to control field
current.

Cheers:

Paul
N1431A


Excellent! Now...which one does the Cessna have?

Jim

Excellent! Now...which one does the Cessna have?

Jim



Is the generator a Delco?

Post the part number & I'll look it up

Paul
N1431A

Tri-Pacer wrote:
Excellent! Now...which one does the Cessna have?

Jim



Is the generator a Delco?

Post the part number & I'll look it up

Paul
N1431A

Well Paul, The Cessna/Continental part # is listed as 534111 and
Delco-Remy as 1101890. That is for the stock 20 amp generator. Mine was
replaced with a 30 amp about 40+ years ago and I can't read the number
in the log book. However, I have every reason to believe that if it was
an "A" it would have been replaced with an "A" and B for B. Any help
would be appreciated.

Jim

It's probably an A. You could tell with a digital ohmmeter.

Bill Hale.


wrote:
This is so embarrassing, I must just be getting old; I can't remember
if the generator in my '61 C-172 is an A or B circuit. Worse, I
forget which one is which. Does the 'A' supply controlled voltage
to the field and the 'B' does a controlled "ground out" of
voltage coming from the field or do I have it backwards? My system
seems to be charging, just not enough. It might be OK and I'm just
taking too many short hops with too many bells and whistles on. Can
someone refresh my memory so my checks are correct?

Jim

..com...


Is the generator a Delco?

Post the part number & I'll look it up

Paul
N1431A

Well Paul, The Cessna/Continental part # is listed as 534111 and
Delco-Remy as 1101890. That is for the stock 20 amp generator. Mine was
replaced with a 30 amp about 40+ years ago and I can't read the number
in the log book. However, I have every reason to believe that if it was
an "A" it would have been replaced with an "A" and B for B. Any help
would be appreciated.

Jim


1101890 is an "A" type circuit.

Cheers:

Paul

1101890 is an "A" type circuit.

Cheers:

Paul

Hello,

I have a problem, related to this topic:

I have an 1101890 generator but I don't have an original regulator for it.
Because in my country (Romania) this things are very rare I intend to adapt a car regulator.
Unfortunately I don't find a regulator for "A type" generators, just for "B type".

I have two possibilities (in my mind):
1. to switch the field's coil to ground, inside generator, making it a B type
2. to modify the regulator to provide "ground" instead "voltage" on the F pin
in attachment, the regulator's schematic BEFORE and AFTER
I suppose will work.


what should I try? 1 or 2?

I know, the best variant is to buy an original regulator, and I'll do it... but until then...

Regards,
Seb