Service manual

PLL

A Ex

mpl

The PLL02A chip is used extensively for export models and in 40 channel rigs in the USA.

It is a versatile PLL with nine programming pins, however the export rigs do not take

advantage of this and normally switch in different crystals to change the frequency band.

The crystal fitted for the FCC band is normally 10.0525 MHz followed by a

doubler

circuit, although a few export models use a crystal of twice this frequency at 20.105 MHz

without the

doubler. The coding for the

Eprom is unaffected by which of these crystals is

fitted and the PLL02A has just enough range of coding to allow conversion to the "Novice"

band without the need to change the crystal. A very cheap board can be made with only an

Eprom, voltage regulator and a few resistors.

The normal "N" codes are 255 to 211, giving 26.965 to 27.405 MHz and the Novice band

would therefore require codes of 71 to 32. You can see from the table that the two

MSBs

are "1" for the FCC band but "0" for the "Novice" band. Pins 7 and 8 on the PLL02A

must, therefore, be grounded. Pin 7 is already grounded but, since the 5

.5 volt track runs

through 8 and 9, you will have to do a bit of cutting to achieve the alteration! The

Eprom

output pins must be connected to pins 15 - 10 on the PLL02A. The tracks between these

pins and the channel switch will have to be cut and six Eprom inputs connected to this

switch.

In all of the conversions mentioned so far you will have to retune quite a lot of coils in the

rig. This procedure is not for the "novice" and should be left to a qualified technician.

Suitable

10 meter conversion boards with fitting instructions are available from CB City, in

the USA, or S.J. Tonks in Britain. There should be plenty of information in this book to

allow you to make your own, however, should you so wish!

The general purpose Eprom board, described later, is suitable for this, and other,

conversions.

The location codes in the table are worked out from the channel switch codes in the

American rig. There are six inputs: see if you can understand how they were derived. As a

clue, channel 40 "N" code is normally 211 in decimal. That's 011010011 in binary, but the

three MSBs are not needed, leaving 01 0011 or 13 in HEX.