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Hello. This is my first post here and I'm very happy to have found this group. I own a GM8 that's apparently from the 90's. I've used it with autoguiding to take 5 minute exposures without problems

You should use the ATF16V8BQL, rather than the ATF16V8B, as that is the only one that drops into low power mode when it has no signal transitions on the inputs. Dave Sent: 10 October 2017 16:56 To:

The most common cause of these problems is (as I understand it) mis-connecting the motor DIN plugs. I know they are polarized but I’m told it’s still possible to mis-plug them. Dave Sent: 10

OK. I've ordered 10 of these chips, and I found a 20-pin DIP to SOIC socket on eBay to allow me to program these. Next steps... await the experiment... of giving it a try.... and talking to John...!

OK. I see the chip listed here in the Mouser catalog as: http://www.mouser.com/Search/ProductDetail.aspx?R=ATF16V8B-15SUvirtualkey55660000virtualkey556-AF16V8B15SU Atmel made these in the 20-pin SOIC

Micheal, I will call you this evening. John

Hi John, You can reach me, Michael Herman, at email: mherman346@... or by phone (I'm in California) at 408 421-1239 I suggest you call me to discuss this problem. Best, Michael On Tue, Oct 10,

Thanks David for the advice. I now see the IC's on the board now. I wonder if it would be worth swapping them to see if the problem changes to the RA instead of the DEC. In the mean time, How can I

I have fortunately not found Gemini units with this damage - yet. I cannot yet do that repair, as I have not yet developed the programming kit to make these replacements, but I will look into that.

The decoder ICs U15 and U16 are no longer obtainable from Losmandy or Aveox. However they are just AFT16V8BQL-15SU PLDs which need to be programmed. I have the jedec file to program them if you have a

Not sure what you mean? Do you need a number off the board? Did not get this from Losmandy. John

The PCB ident is under the ICs. Did you get this from Losmandy? Brendan

Thanks for all the advice guys! Did some checking today and it seems to be either the DEC encoder U15/16 or the optical encoder on the motor. The encoder is $51.00 US plus shipping. I'll start with

Not tried to read those yet, it is the soldered on quadrature decoder chips that I can make. The PIC17C42 ICs I have yet to attempt. Dave Sent: 09 October 2017 06:48 To: Losmandy_users@...

Losmandy no longer repair G1 L Dave Sent: 09 October 2017 05:27 To: Losmandy_users@... Subject: [Losmandy_users] Re: Motor stalled....... John Seen this before in DEC and RA, repaired a

Most likely problem here is either the motor shaft encoder, followed by the quadrature decoder ICs. I can fix either of these problems (I live in the UK) as I am sure can Michael Hermann (CA) and Bren

If it is the U15 or U16 chip, then David Partridge in the UK has these or can make them. I have not yet tackled that. These chips are in sockets on the main board and can easily be pulled out (say

John Seen this before in DEC and RA, repaired a DEC one not long ago (hope its not same one doubt it).. Unfortunately it's a bad DEC encoder IC. Yes there is a remote possibility its a DEC motor

Hi John, I have just repaired a mount with exactly the same symptoms you describe. In my case, it was the encoder pickup in the back of the high torque servo motor that was faulty. Luckily the optical

hmmmm... a good puzzle.... Try this: set the Gemini to "terrestrial" tracking which means it will not drive RA or DEC. If you do that, neither RA or DEC should move. If the Gemini is still driving the