WEM Mk4 Copicat - low volume output

[Bushbaby]

Thanks Trevor and Arnie.
I bought some new tape loops and operated just one with the spliced tape section on the outside (assuming this is correct).
It was sold to me as fully working BUT I had assumed from the start that it would have potential issues being so old.
As I said in my initial post, the echo and effects side of thing does appear to be working but the output to the amp is very low indeed, 1 was just trying it out on a small Marshall Lead 12 combo and almost had the volume control at 10 with the gain up too to hear anything . I didn't think for one moment that it could be the heads that could be causing the issue. I feel a wee bit stuck where to go next but I assume that trying some new heads will be a start.

Best Regards