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Yesterday I was balancing my 2008 Losmandy G11, Gemini-1 using servo-motor current draw to fine tune the balance. At one point I used the hand controller to move the telescope to point at the celestial pole with counterweight down. As it neared that position the mount gave a continuous tone like when a safety limit is reached. That was puzzling since it wasn't anywhere near the limit. So I switched the Gemini-1 off, thinking it just needed a reboot.

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When I turned it back on there was no response, no startup beep, no lights on Gemini electronics chassis or hand controller. Then I saw the 17-volt power had no lights. So it seemed the power supply had died. So I brought out my old Pyramid 13.8 volt power supply and hooked it up. It too had the same symptom - when Gemini-1 was switched on, the power supply lights for voltage and current went off.

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So two power supplies had same symptom - not supplying power with all lights on or connected to the Gemini-1 all lights go off. It's clear the problem lies with the Gemini-1, perhaps something like a dead short. I'll give another try today to see if a day's rest has corrected the problem. But the prognosis isn't good. Does anyone know if there is something that I can do, like a resettable circuit breaker or fuse?

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I'll be contacting Michael Herman to see if he can resurrect my old Gemini-1. If that fails, perhaps buying a used Gemini-1 or new Gemini-2 would be the path forward. My 17 year old Losmandy G11 has been a stalwart in my astronomy adventure. It now resides inside Ocean Observatory, with slide off roof.

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Presently the G11 is carrying a Celestron-8 with AT115EDT triplet refractor, like what is shown below.

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So as can be expected, I'm eager to get my old Losmandy G11/G-1 back in service.

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Best Regards,

Russ

Not much I can say except send it for repair with motors, cables and HC. ?Hard to say what the issue is atm but in general they can be repaired?

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cheers

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Brendan

Are you using the same cord when switching power supplies? Short might be in cord.

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The LittleFuse 452-454 (Fuse F1) is just to the right of the power connectors but would not short the power supply on failure.

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If your power cord has an automotive lighter plug , some have a fuse located in the metal tip but again this wouldn't cause a short.

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I really think the cord is the prime suspect as the F1 fuse would prevent a shorted board from killing the power supply

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Good Luck

Brian

Thanks Brendan & Brian. I've contacted Michael Herman for repairs. He's had my Gemini-1 a couple of times before. So he's familiar with my unit. I'm shipping the Gemini-1 and Michael's 17-volt "Power-Booster" supply. He wants to be sure that isn't part of the problem.

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As for power cords, each supply uses a different cord. The Power-Booster's cord is hardwired to that supply with a Losmandy plug on the other end. The Pyramid supply cord uses PowerPole connectors to attach the cord to that end and the Losmandy plug on the other end. Both supplies work when not attached to the Gemini-1. Each goes dead when attached. I'll measure the Gemini input jack to see if there's a dead short there. I believe the jack has 4 pins - 2 for power and 2 for ground. But Michael is the best one to fix the problem.

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Russ

Michael has repaired my Gemini-1 and it's on its way back to me. Problem was moisture got inside and accumulated in the lower end of the enclosure. This corroded the fuse holder and a capacitor. Michael recommended bringing the Gemini-1 back indoors when not being use. Also some sort of cover over its exposed surfaces will discourage dew from accumulating while in use. I'm considering drilling some holes in the bottom end of the metal enclosure to allow for any moisture that might find its way there to escape.

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Russ

sadly I’ve seen this before more than once. ?Sadly I’ve even seen ?corroded CPU sockets. ? The environment must be extremely onerous and or moisture by the buckets.?

Luckily Michael repaired it, excellent!. ?But it’s a good warning to all Gemini users not just G1s. ? G2s can get this as well?

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cheers

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Brendan

On Fri, Feb 21, 2025 at 04:10 PM, Russell Milton wrote:

Michael has repaired my Gemini-1 and it's on its way back to me. Problem was moisture got inside and accumulated in the lower end of the enclosure. This corroded the fuse holder and a capacitor. Michael recommended bringing the Gemini-1 back indoors when not being use. Also some sort of cover over its exposed surfaces will discourage dew from accumulating while in use. I'm considering drilling some holes in the bottom end of the metal enclosure to allow for any moisture that might find its way there to escape.

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Russ

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That said make your life easier, take the Gemini and other electronics inside.? At least protect them with a low-Watt heating element under the mount.??

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