Commodore CBM - Extractor Tooi

Locating a Defective RAM
On earlier model PETs. the RAM failure rate was high. This prompted the
manufacturer ta recommend a procedure for owners of the first PETs ta check for
a defective RAM themselves.
We reproduce this procedure below; vou may want
ta learn this procedure if vou have an aider PET and are experiencing frequent
RAM failures.
It applies only ta PETs with compact keyboards.
If vou do not get the standard number of bytes free at power-up (Iess
than 7167 for an 8K PET or 3071 for a 4K PET) or if the RETURN key is not
working properly, the problem
is probably a defective memory device, or
RAM. The following procedure describes how ta locate a faulty RAM yourself, sa
that Vou do not have ta ship the PET ta the factory ta have this done.
Ta perform this procedure, vou
will need an "extractor tool" (see Figure
2-14) available fram electranic supply houses.
Photo
Figure 2-14. Extractor Tooi
1. Unplug and open the PET as described above.
2. Refer ta Figure 2-15 for RAM numbering conventions. If bytes free are
less than the number shawn in the first column below. then the number
of the RAM ta
be tested is in the second column below.
Bytes Free
1023
2047
3071
4095
5119
6143
7167
RAM Number
2
3
4
5
6
7
8
45