Guide to used-computer bargains

Sales of used computers are picking up. But the rising turnover, industry analysts say, can make pricing of the ''previously owned'' units erratic. Now, however, for solid comparison and standardization, there's an automotive-type bluebook put out for $15 a copy by the Computer Classified company, Reno, Nev.

The used-computer guide rates over 150 current model computers as to features - like adaptability, power, size, performance, etc. In addition, it gives a fair market value for each listing. The publication, Computer Classified Bluebook, is issued quarterly and carries no advertising. And its publishers say the dollar-value ratings shown are based on opinion research coupled with data on up-to-date retail selling information.