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Seho 1135C Wave Solder can't generate sufficient delta wave height

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Seho 1135C Wave Solder can't generate sufficient delta wave height | 26 September, 2013

We picked up this old (circa late 80s) Seho 1135 machine last year for next to nothing. It needed a bit of TLC to bring it back to working order but it's 99% working now. The only problem left is that we cannot get sufficient height from the delta wave. The manual recommends a distance of 6mm between the nozzle lip and the PCB and then adjusting the pump speed so that there is 20-30mm of solder contact. We are struggling to get any solder contact at all, even with the motor at full speed.

I have checked the following: - Solder temperature sits stably at 250°C (63/37 solder). - Pump motor swapped with a new motor to prove it's not the issue. - Pump motor is being supplied with full voltage. - Pump impeller is in good condition. - All bearings are new and the impeller spins freely. - Solder pot is filled to approximately 12mm from the top with pumps off (10mm is recommended but I can't imagine 2mm making that much difference?). - The mesh that smooths the solder flow in the nozzle is not blocked.

It's as if the solder pump just cannot provide enough volume through the delta nozzle, which is quite a large area. As an experiment we cut a piece of stainless steel tubing and wedged it into the delta nozzle so that the nozzle area was reduced. This did help a little and we are getting some contact, but it's hardly a permanent solution and is still not a perfect result.

One other thing we tried was to run the wave motor from a higher voltage (they're rated to 40V but by design the machine only runs them at a maximum of 24V). All this did was destroy the laminar flow property of the wave and created violent upwellings in the centre of the wave, without increasing the wave height where it contacts the PCB.

I'm at the limits of my knowledge now so I was hoping that perhaps somebody might be able to point me in the right direction. Any help would be really appreciated.



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