Echostar sr8700 power supply schematic

Llew

Llew

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The HTS legend is at the upper left corner. I have searched the net for Houston Tracking Systems without a any result. I have only found articles related to the power supplies on this forum.
I have several voltage readings from my SR8700 that I took when I was fault finding the RX (many years ago now). Only paper lists, no PC files to upload unfortunately. I still have the set somewhere at the back of the shed, but it hasn't been switched on for 10 years, if longer. I would probably need to warm it up using my variac to reform the main cap!
If you need voltages found on some of the components, I can post them. They don't relate to the components shown on the LT8700 schematic, so without looking at the SR8750 powerboard, I don't know what they are - no schematic unfortunately.
 
Channel Hopper

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The HTS legend is at the upper left corner. I have searched the net for Houston Tracking Systems without a any result. I have only found articles related to the power supplies on this forum.
HTS was the name of the company before they changed to Echostar Corporation. This would ave been md to late 80s so I doubt there is anything left on the internet with relation to Hughes when it comes to PCB manufacture.

You might find the model number of the PCB gives some results
 
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harm lok

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The more I think about this, the more I am inclined to guess that the fault is somewhere around the group of components I mentioned in post #12 - and specifically the CR8 (which is reverse-biased for 1/2 of of the drive cycle to SM1) because, if that has gone s/c then the high voltage DC rail will be pulled down by the voltage divider formed by R18 and Q2, and the circuit won't be able to "flip-flop" to provide the HV drive square-wave to SM1.
Today i have done some inspection of the power supply pcb. Altough the part numbers are different, as everyone expected, there many similarities in the design .
I have found two defective parts. The rectifier is now measuring 250 ohms en both directions and resistor measured 10 ohms. At first sight i saw brown black black so 10ohms and red for 2% but under the magnifier it is red black black with a golden ring so 2 ohms 5%. The legend on the rectifier is SRP100K and GI 401.
I think i can replace it with a standard 200V 1 A type but i would like to hear your opinions. C17DEDAB-83D9-49A2-A56F-C46770B62AC8.jpegF14EF7D4-27C0-4F0C-83F0-6FEA8AEC1E19.jpeg
 
jeallen01

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Quick search turned up the spec sheet for the SRP100K here and it's a 560V RMS rated, and 800V PIV, diode - so a 200V rated &/or PIV device is not suitable (as I suspected that it would not be)!
PS: 1N4005/ 4006/ 4007 /4008 diodes would probably work - see the spec
PPS: If you haven't already done so, I would also check all the other components in the group that I mentioned in post #12
 
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H

harm lok

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Quick search turned up the spec sheet for the SRP100K here and it's a 560V RMS rated, and 800V PIV, diode - so a 200V rated &/or PIV device is not suitable (as I suspected that it would not be)!
PS: 1N4005/ 4006/ 4007 /4008 diodes would probably work - see the spec
PPS: If you haven't already done so, I would also check all the other components in the group that I mentioned in post #12
[/QUOTE
It is a good suggestion to check the other components you mentioned. I wil check and i try to find the related components. It wil be good to check this before connecting the power supply back to the net. Thanks a lot for tips, i wil keep in touch.
 
Terryl

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Red, Black, Black, = 2 ohm

Red, brown, black, = 20 ohms
 
jeallen01

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Ref the CR6 failure in post #23 - difficult to clearly read the schematic but CR8 looks to be the same type of diode and so could have suffered the same failure
 
Channel Hopper

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A

a33

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Red, Black, Black, = 2 ohm

Red, brown, black, = 20 ohms
Is it time for some homework again for you guys?

I still come to 20 ohms for red-black-black, as I did without looking it up.
(But I'm just a lay-man...)

Greetz,
A33

Edited: Typo!
 
jeallen01

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I'm partially colour-blind and could never correctly read resistor colour-code bands - so I'm not getting into that "discussion" :-rofl2
 
Channel Hopper

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I'm partially colour-blind and could never correctly read resistor colour-code bands - so I'm not getting into that "discussion" :-rofl2
I'm nursing a partial hangover, so ditto.
 
jeallen01

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So, CR6 partially broke down (probably age + an over-voltage mains spike) and went partial short-circuit, and the resulting high current caused the resistor to overheat and then to partially internally breakdown, thus lowering the resistance?

Based on that scenario, I would suggest replacing as many of the components as possible in the group I mentioned earlier because they could be suffering similar degradation even if they haven't already failed.

PS: I hope that the above has not damaged the windings of transformer SM1, because that would probably be the "end of" that PSU board and thus likely the whole receiver - but whether that has actually happened or not will only become clear when the faulty (and the "may be faulty") components have been replaced and the receiver is connected to the mains supply.
 
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Llew

Llew

cerca trova...
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Messages
14,973
My Satellite Setup
Triple Dragon, Dreambox 8000, Echostar AD3000ip, TBS6522,6925,6983 PCie cards.
Gibertini 1.25m motorised dish driven by the AD3000, with either Inverto BU Quad or Norsat / XMW Ka LNBs . SMW 1.05m + 3 other dishes. Speccy: Promax HD Ranger+
My Location
The Flatlands of East Anglia
Today i have done some inspection of the power supply pcb. Altough the part numbers are different, as everyone expected, there many similarities in the design .
I have found two defective parts. The rectifier is now measuring 250 ohms en both directions and resistor measured 10 ohms. At first sight i saw brown black black so 10ohms and red for 2% but under the magnifier it is red black black with a golden ring so 2 ohms 5%. The legend on the rectifier is SRP100K and GI 401.
I think i can replace it with a standard 200V 1 A type but i would like to hear your opinions. View attachment 130273View attachment 130274
I can't locate R9 or CR6 0n my SR8700 power board. Are you using the LT8700 component numbering to identify their working position in the circuit? Whereabouts are they on the board?
 
Terryl

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OpenBox X5 on a 1 meter motorized dish.
And now a 10 foot "C" band dish.

Custom built PC
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Is it time for some homework again for you guys?

I still come to 20 ohms for red-black-black, as I did without looking it up.
(But I'm just a lay-man...)

Greetz,
A33

Edited: Typo!
Sorry..old age creeping in, the old think pot is on it's way out.

Red Black gold = 2 ohms
Red Black Black = 20 ohms

Now sometimes when the resistor is subject to high heat, the bands change color, this makes it hard to repair without the correct schematic.
 
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jeallen01

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Sorry..old age creeping in, the old think pot is on it's way out.

Red Black gold = 2 ohms
Red Black Black = 20 ohms

Now sometimes when the resistor is subject to high heat, the bands change color, this makes it hard to repair without the correct schematic.
Fitting a 20 Ohm resistor instead of a 2 Ohm one is likely to do less damage, even if the unit does still not work!:D
 
Llew

Llew

cerca trova...
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14,973
My Satellite Setup
Triple Dragon, Dreambox 8000, Echostar AD3000ip, TBS6522,6925,6983 PCie cards.
Gibertini 1.25m motorised dish driven by the AD3000, with either Inverto BU Quad or Norsat / XMW Ka LNBs . SMW 1.05m + 3 other dishes. Speccy: Promax HD Ranger+
My Location
The Flatlands of East Anglia
If ever there was a case of not singing from the same hymn sheet...
Referring to the LT8700 schematic component numbering is confusing when we don't have an SR8700 circuit. I'll take a guess that the two components are most likely CR5 and R22 coming from T2 Pin 9 (juxtaposed in the SR8700).

CR5 is definitely a s/c candidate when C8 pops -

8700 PSU Fail.JPG
 
jeallen01

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FWIW, that seems to imply that, and I guessing again, both of the diodes in the circuit area mentioned earlier should be 1N4006 or better (thus 1N4007 or 1N4008).

FWIW2: active components like semiconductors are generally more likely to fail than passive components (unless the latter are subject to severe overheating or overvoltage)
 
H

harm lok

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echostar / pace / aston
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Again thanks a lot for youre suggestions. Today i had to work for my paycheck. But tomorrow i can spent some time to look after the suggestions for the power supply repair. I wil try to indentify the circuit and replace the defect components . Off course there wil be some degradation of parts but i think it is not needed to replace parts that are not affected. If the power supply is up and switching again , i wil replace the electrolytic capacitors. About the resistor , the schematic and the rings both pointing to : 20 ohm. The rings are red black black gold . red black 20 and multiplication black = 0 gold = 5% for 2 ohms the code should be : red black gold gold . I hope i wil make some progress tomorrow.
 
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