OTHER Receiver Output Voltage Fixed at 11.6V

[cyberham]

I pulled an old receiver out of storage. The problem symptom is straight forward: on both H and V polarities, LNB output voltage from the receiver is 11.6 V. So on blind scans, I get all vertical transponders two times listed under H and V. If I can figure out how to get the output voltage to be 11.6 V on vertical and something closer to 19 V on horizontal then the receiver should work fine.

Thoughts?

 

[waylew]

Most likely a bunch of blown electrolytic capacitors in the power supply and/or possibly voltage regulators and diodes.

 

[cyberham]

Yeah...it's a little modern device powered by a 12V wall wart. So no big power supply inside. I'm cracking it open now to take a look.

New looking. Capacitors physically look good. Lots of surface mount parts. Very little I can do with this, I suspect. Nothing obvious. Photo attached.

 

[KE4EST]

Have you tried restoring to factory?

 

[cyberham]

Have you tried restoring to factory?

I did! I figured I had nothing to lose. So, of course, it has only eastern sats now. But I edited one for 103W and the same symptom still remains. What bugs me is I paid $5 for it used and picked it up locally.

 

[KE4EST]

Sounds like someone has fed voltage into it somehow. Trying to do, who know what, with it.

 

[cyberham]

Oh...that was probably me. I think when experimenting a couple of years ago, I connected the GSP microHD on this receiver's loop through. I believe I tried powering from the microHD instead of from this receiver. So I may have fed 13 or 18 V into this receiver.

Added: Thinking back...I was trying to get an elegant way to receive JBS from 99W Ku. Neither the GSP microHD nor Openbox S9 can receive the video from JBS. I thought I could use the cheap receiver as a front end tuner to receive JBS but control the LNBs and motor and receive all other sats from the microHD.

Also, the blind scan on the cheap receiver is very fast and accurate.

This is the week of playing with all old receivers I have including this cheap receiver, a Fortec Star Mercury, the Coolsat 5000, Openbox S9 and of course the cool microHD. The old receivers, especially if they support DVB-S2, are still nice to use.

 

[waylew]

Just a thought,did you check the wallwart to be sure it's putting out at least 12v?

 

[cyberham]

Just a thought,did you check the wallwart to be sure it's putting out at least 12v?

It's a good thought. I tried two different warts: 1.5A and 2.67A. The second one is what I regularly use for my microHD with success. I am using a fixed dish with no motor which might pull down the voltage. I do have a diseqc 4-port switch in line which works with all other receivers. To be thorough, I could temporarily remove the switch and connect directly to the dish LNB. I'll try measuring the wart output today just to be sure.

One further observation: I notice the "LNB Power" command on the receiver does not switch off the power to the LNB. This is odd. It is like something in the circuit is shorted so that the V voltage is permanently connected to the receiver output.

 

[cyberham]

Measured no load voltage from 1.5A wart: 12.3 VDC.

 

[waylew]

Measured no load voltage from 1.5A wart: 12.3 VDC.

I usually expect wallwarts to output higher than rated,maybe 14 or 15 for a 12v,but that one may have a voltage regulator in it.
Pretty much sounds like something in the receiver is hosed.

 

[KE4EST]

I usually expect wallwarts to output higher than rated,maybe 14 or 15 for a 12v,but that one may have a voltage regulator in it.
Pretty much sounds like something in the receiver is hosed.

All the older ones with a big chuck of iron in them were mostly like that. Now they have all went to switching supplies, so the regulation is way better. With the tradeoff of noise if you are a ham or SW listener.