Echostar sr8700 power supply schematic

harm lok

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In addition to the diode and the resistance, the mosfet in the same circuit was also defective. After replacing the defective components, the power supply still did not work. Unfortunately Jeallen turned out to be right, the winding of the transformer is broken. Repair is therefore no longer an option. I would have liked to use the SR8700 as a better positioner instead of my current V-box-II.


Edited by @Lazarus to cut and paste info about a potential design for Positioner with DiSEqC Decoder to a shiny new standalone Topic

 
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Captain Jack

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It may be possible to get a replacement transformer if anyone has the specs for one.

Happier news here. I replaced the two big caps in my LT8700 and it sprung to life.

20200515_164344-1612x907.jpg
 

Captain Jack

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It's broken again. The more I look at it, the more I think it's nothing to do with the PSU. Indeed, all the voltages look OK and all ICs are getting the power they need.

However, nothing is lighting up on the front panel - or occasionally I get some odd characters.

20210119_135110.jpg

If I disconnect the MAC board, I will get snow on screen from both TV and decoders SCARTs but nothing more.

I keep thinking that it may be to do with either a corrupt EPROM or some fault in CPU? It was always a bit temperamental with sometimes not turning on (or at least the display staying blank).

Any thoughts?

If anyone has a scrap LT8700 lying around - motherboard mostly - it might be handy to get this revived.
 

harm lok

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Sorry to hear captain Jack . My repair has taken a lot more time , but the my SR8700 power supply is also already up and running.
But your defect looks like there something wrong with the embedded system. Is the system up , you can measure if there is a clock signal.
Maybe there is something wrong with the Eproms , but the characters on the display looks more like there is no synchronization between the segments and the displays. When the processor halts at a random point this could be the result. A common failure in older embedded systems is the reset and also the watchdog circuit.
 

Captain Jack

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Yeah it doesn't look like it's initialising at all. Initially, the display should light all segments and LEDs up but that's not happening.

Need to check the reset line to the main ST CPU but yeah could be anything. Not really worth troubleshooting - especially without a service manual working in the blind.
 

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Sorry to hear captain Jack . My repair has taken a lot more time , but the my SR8700 power supply is also already up and running.
But your defect looks like there something wrong with the embedded system. Is the system up , you can measure if there is a clock signal.
Maybe there is something wrong with the Eproms , but the characters on the display looks more like there is no synchronization between the segments and the displays. When the processor halts at a random point this could be the result. A common failure in older embedded systems is the reset and also the watchdog circuit.
Shades of the AD3000, though the 7700 predates the dual standard boxes by quite a few years.

The last time manuals and software were issued by Echostar was over fifteen years ago, I believe the analogue only machines were left off the list, possibly because they were the last of the true HTS receiver designs.
 

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It's broken again. The more I look at it, the more I think it's nothing to do with the PSU. Indeed, all the voltages look OK and all ICs are getting the power they need.

However, nothing is lighting up on the front panel - or occasionally I get some odd characters.

View attachment 134200

If I disconnect the MAC board, I will get snow on screen from both TV and decoders SCARTs but nothing more.

I keep thinking that it may be to do with either a corrupt EPROM or some fault in CPU? It was always a bit temperamental with sometimes not turning on (or at least the display staying blank).

Any thoughts?

If anyone has a scrap LT8700 lying around - motherboard mostly - it might be handy to get this revived.
Llew mentioned in the other thread (from two decades ago :-wow ) that he had a schematic somewhere of the motherboard, is the eprom /cpu on there, or the front panel/daughter board ?
 

harm lok

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I have uploaded a schematic already. But there is no service manual captain Jack asked for. I have received a lot off support about the analog part (power supply) from members of this forum. If captain Jack wants to put more effort in the 8700 may I Maybe could assist with my knowledge of embedded systems.
 

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I have uploaded a schematic already. But there is no service manual captain Jack asked for. I have received a lot off support about the analog part (power supply) from members of this forum. If captain Jack wants to put more effort in the 8700 may I Maybe could assist with my knowledge of embedded systems.
I haven't seen that schematic, which post/thread ?
 

Llew

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I haven't seen that schematic, which post/thread ?
A little fuzzy after my Covid jab yesterday, so bear with me.
SR or LT? Here's my SR8700 motherboard schematics. Possibly posted somewhere else here, but here it is for convenience.
 

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  • ECHOSTAR SR-8700 Service Manuals.zip
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Channel Hopper

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A little fuzzy after my Covid jab yesterday, so bear with me.
SR or LT? Here's my SR8700 motherboard schematics. Possibly posted somewhere else here, but here it is for convenience.
Nobody has reported the covid jab does that.

Interesting that the schematics are marked as HTS still (within a 134 page manual), I thought the last machine designed inhouse was the SR-5500/HTS VIII.
 

Llew

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Nobody has reported the covid jab does that.

Interesting that the schematics are marked as HTS still (within a 134 page manual), I thought the last machine designed inhouse was the SR-5500/HTS VIII.
My immune system got a kick up the fundament and is over-reacting. That's my story :oops:

Would've liked to had the other 100 or so pages.
 

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My immune system got a kick up the fundament and is over-reacting. That's my story :oops:

Would've liked to had the other 100 or so pages.
So, where's the hair growth

(If it's not a personal question)
 

Llew

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Captain Jack

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Mine is LT, which is really rather different inside from the SR, sadly.
 

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Just sharing some info about a repair of a dead SR8700. First, all electrolytic caps at the secondary changed. After that, the psu looked like working, but i couldn't measure all voltages on the connector (with the cable connected to the main board). And then with moving the connector I found out, the connector is faulty too! The steel springy things corroded over time, some of them are broken or just isn't springy anymore. Cable is nov soldered into the PSU side and works fine. Note that that cable got some extension, so it's nice loose and not in tense.
 

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