Those things are generally super reliable. If you are in the UK, just send it to me and I will have a look at it. the most it will cost is £25 plus the cost of return (about £5)
(I normally charge a fixed service fee of £50 to fix old gear from that era, but as this is a ‘Hooter’ I’m happy to deal with it for less…. that would go for a VC3 or similar as well) 
We originally made about 200 of those ‘B1’ units and this is the first ‘failure’ I have heard of.