One of the Classic releases from Atlas were the GP35's that were closely based on the mechanism made for them by Kato several years earlier. The Atlas Classic GP30 also uses the same mechanism as the one shown here. At first glance this would seem like a straight forward replace the frame type of installation but as I discovered there are a few extra tricks that are worth covering.
If you look at the frames for the Kato made model and the Classic models made in China, they seem identical in every way. They both even have the same part numbers on them and copyright Atlas 1992.
A quick way to check is to test fit a bushing from a Kato made model. If it fits easily then it's a frame for a Kato made model. If it's a tight fit or won't fit then the frame is for the Classic version.
I was quite confused about this until John from Aztec set me straight. The Aztec part number for the milled frame for a Kato made model is TM3001 and for the Classic model it is TM3016.
Because the outside of the Kato made and Classic frames seems identical, I wondered if the shells are interchangeable. After swapping around several shells and frames I was able to confirm that yes, they are interchangeable. So now on to the decoder installation.
On some of them there is a small component added to the solder side of the board. This was added to suppress the flickering of the LED when the engine was running in the reverse direction in DC operation and will not be needed after the decoder is installed so it should be removed on both boards.
The LED needs to be removed, a small tubing place on this lead of the LED, then the LED re-installed. The Kato 77A LED board already has tubing on it's LED so I took some from those to use here.
This photo shows the component side which normally does not have any circuit traces.
For the wire lengths I followed the Aztec instructions except that I added the blue wire and cut it to the same length as the yellow wire.
Black & Red = 1-3/4", White = 1-7/8", Orange = 1"
Yellow & Blue = 7/8", Orange = 1", Gray = 1-5/8"
A scrap of .020 thick plastic was cut to fit on the frame, then the decoder was secured with some Kapton tape. The Kapton tape is trimmed to fit around the bumps on the sides of the frame that hold the shell in position.