 Sinclair attributed the higher failure rate of the kits to customers breaking the components by inserting or soldering them the wrong way , though the company admitted that there was a persistent problem with power supplies that affected both kits and pre @-@ assembled ZX81s . The bigger problem was perhaps Sinclair 's lack after @-@ sales service , which Robin Clarke of New Scientist described as " one of the worst after @-@ sales performance records of any company ever established . " The Financial Times observed that " Clive Sinclair 's offices are filled with returned computers which can take months to be repaired . " The company 's slowness in replacing returns and delivering freshly ordered machines meant that Sinclair Research gained a poor reputation for poor customer service . 
