It would seem that something is definately amiss and if I were you would not attempt a repair yourself - even if you could find out the problem. Besides, the camera is of an age that it would benefit from a little care and attention. I suggest you send it to a specialist for repair and overhall.
I see from your profile you are in England. There are a few good repair shops in the UK such as -
BLACK ON WHITE
The Photographic Repair Shop
105 Coldharbour Road
Westbury Park
Bristol
BS6 7SD
Tel: 0117 942 0434
Fax: 0117 907 1135
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Sendean Cameras
22/23 St Cross Street
Hatton Garden
Clerkenwell
London EC1N 8UH
tel: 0844 357 1414*
email:
mail@sendeancameras.com
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Harrow Technical
Pentax House
South Hill Avenue
South Harrow
Middlesex, HA2 0DU
Tel: 020 8938 4660
Fax: 020 8938 4605
E-mail:
info@harrowtechnical.co.uk
I've had good service and can recommend this last address.
PS. All three addresses have websites if you do a search