Wow, this takes me back!
As I remember there were 2 types. one with multiple heads, rather like a Wem/Watkins copy cat, ad the other had one playback head on a mechanical slider. I owned the former but wanted the latter. With the moving head one, you could play and speed up/slow down the echo - great fun..
Anyway, the reason I had one was that there was quite a long loop of tape in it as compared to the affore mentioned copy cat which had a loop about a foot long. This meant that if you covered up the erase head with a bit of cardboard you could achieve sound on sound long loop effects.
I remember my tape chewing up on the H/H unit and making a new loop by splicing some 1/4 inch tape together. This worked but the sound was different. The problem is that different analogue tapes have different bias characteristics. Without knowing the specs of the original tape it would be hard to match up your new tape. You'll end up with foggy or bright echoes - but this might be good too!
So maybe you should experiment with different types of 1/4 inch tape. And remember to clean and de-gauss the heads. Little bits of oxide will get trapped in the heads and this will cause dropouts.