[Amps] Radio shack power meter info

[Martin Sole]

Apologies if this is a little out of line but I'm a little stuck and
since this thing measures power, which is the main topic here right, I
thought somebody here might be able to suggest a source of information.

I have a Radio Shack digital power(ish) meter, no sniggering please.
It's no lab instrument but it does come in handy on some occaisions.
Whilst I don't expect it to be very accurate it does seem to have sort
of 'gone orf'. The little book mentions test and calibration modes but
then states that a service manual is needed. RS is no help here. Anybody
have a copy of this service manual or know of an on-line source?

The meter's Cat No. is 21-527.

Many thanks and apologies for the BW.

Martin
HS0ZED