The Pulse led by as many as eight goals during the opening quarter - the Tactix committed their first turnover after only seven seconds - as the home side found their stride.
But despite maintaining their lead for much of the second quarter, the Pulse switched off after halftime as the Tactix made their way back in to the contest.
The Pulse produced uncharacteristic errors, while their shooting slumped as Tactix defenders Zoe Walker and Demelza Fellowes put the pressure on.
The Tactix claimed the third frame 15-10 as the accurate shooting of Malawi international Mwai Kumwenda (30/31) helped the visitors get back in to the contest; they evened the scores at 38-38 at one point but couldn't take the lead.
Worryingly for the Pulse, they've made a habit of coughing up leads in recent years and as they went to the final 10 minutes with a 46-43 advantage, the contest could have gone either way.
With van Dyk on the bench, the Pulse relied on the experience of Jodi Brown in the shooting circle and she responded with 18/22.
Tactix skipper Anna Thompson, playing her 100th game in the competition, tried to rally her troops but they were unable to overturn the deficit.
It was hardly a vintage performance by the Pulse but complacency may have got the better of them during the middle stages as they were unable to build on the healthy lead they had established.
Given it was only their third victory of the campaign they were in no position to be picky and they will turn their attention to Sunday as the Steel await.
Pulse 51 (Ameliaranne Wells 33/40, Jodi Brown 18/22) Tactix 48 (Mwai Kumwenda 30/31, Bailey Mes 16/23, Gemma Hazeldine 2/3) 1Q: 17-10, halftime: 32-26, 3Q: 42-41
