Advice Needed V-box woes

[dafydd]

My vbox (actually labelled Gbox) packed up with a puff of smoke! Opening it up the screws were so tight that the plastic case split in various places. I discovered that a disc capacitor across the output of the 36V rectifiers had gone short circuit. The transformer primary appeared open circuit. With nothing to lose I stripped the tape from the transformer only to find a fuse which was O/C. Shorted this out, replaced the capacitor and the rectifier diodes (which measured OK but looked cooked). One of the spring clips for the motor connection had disintegrated, so the wire was soldered in place. Superglue on the case, and it now works!

And this is where I need advice!

I have another box, marked PR1000, which is immaculate, but occasionally when moving will not stop and drives all the way to the limit. I have opened it up and checked the board for dry joints or broken tracks - everything appears OK. Without knowing the firmware and an oscilloscope I don't know how to fault-find it.

 

[Channel Hopper]

Sound like one of the relay contacts is staying closed when it shouldn't.

 

[dafydd]

Many thanks for the quick reply.
Because it is extremely intermittent fault-finding is difficult. Are the relays easily available? If so it may be easier to replace both relays.
The fact that it has only occurred when moving west would confirm your diagnosis.

 

[Channel Hopper]

Try tapping the lids to clean the contacts, sometimes the tops can be prised off to inspect the condition.

 

[jeallen01]

My vbox (actually labelled Gbox) packed up with a puff of smoke! Opening it up the screws were so tight that the plastic case split in various places. I discovered that a disc capacitor across the output of the 36V rectifiers had gone short circuit. The transformer primary appeared open circuit. With nothing to lose I stripped the tape from the transformer only to find a fuse which was O/C. Shorted this out, replaced the capacitor and the rectifier diodes (which measured OK but looked cooked). One of the spring clips for the motor connection had disintegrated, so the wire was soldered in place. Superglue on the case, and it now works!

Very good faulting finding & fixing, but as you have removed the fuse protection on the transformer, I would wire a low value (500mA max slow-blo "T") fuse in series with that winding to protect both the GBox and the receiver.

 

[dafydd]

The problem is not the relays! I wired the box up to the 8" jack (which I was about to throw away!), did a reset, set limits and four positions. I spent about an hour driving it back and forwards with no problems. But when I removed the power and reconnected it had forgotten it's settings. The only other things I have checked are the voltage outputs from the regulators - 5V and 12V - which are correct. It would appear that an EEPROM has died or is dying. I am not going to spend time on it as I have the working (if tatty) Gbox. So if anyone wants it for repair, it is theirs for the asking.
Thanks again for the help and advice.

 

[PaulR]

If anyone is interested in the controller, dafydd is located in Flintshire, North Wales.

Hmm, not that far away from me...

 

[dafydd]

If anyone is interested in the controller, dafydd is located in Flintshire, North Wales.

Hmm, not that far away from me...

If you would like to have this vbox, let me know fairly soon - I need to have a clear-out and I would prefer that it did not go to the scrap.

 

[PaulR]

Lol, thanks very much but I daresn't!

 

[dafydd]

I have had second thoughts! If there is a circuit diagram for the PR1000, I may try some additional fault finding before consigning it to the scrap.
I found cct's for V-box2 on the site (version 1 corresponds to my Gbox) but not PR1000.
The most obvious difference is that the PR1000 does not have a Xtal oscillator on the PCB - perhaps it runs asynchronous.

 

[Channel Hopper]

Just Sharing This - Dead Primesat PR1000 V Box Fix : )

Good evening gentlemen : ) The Primesat PR1000 V Box that drives the jack on my C band dish failed. No display or green LED. The fault turned out to be O/C print to the regulator transistor that supplies the electronics on the board. There are two supplies, one for the electronics the other...

www.satellites.co.uk

 

[dafydd]

@Channel Hopper,
Thanks for the reply. The photographs in the post that you referenced look to be the same as my PR1000, but the circuit diagram shows the 3.58MHz crystal which does not exist in the PR1000. Also, looking at the photograph, there is a capacitor C21. On the circuit diagram the highest numbered capacitor is C20.

 

[Channel Hopper]

I did take this V box apart a couple of years ago for members to inspect the circuitry. I don't know where it ended up.

There is a difference in the position memory between manual and the cover graphics.

I could have another look next week.

 

[Channel Hopper]

What chip (if not HT48R50) is on your PCB ?

https://docs.rs-online.com/652f/0900766b8002aab5.pdf

Take a picture above and below.

 

[dafydd]

The chip line-up on the board is different to the Vbox 2 diagram.
The processor is an HT48R066 which has an internal oscillator, so no crystal on the board.
The serial EEPROM is a 24C028.
The quad comparator and the bipolar transistor array also have different part numbers but I expect they are probably interchangeable.
Hopefully, tomorrow afternoon or evening I will be able to download the datasheets for these chips.

 

[dafydd]

Photographs of the PCB, top and bottom.
The numbers on the chips are very difficult to read. The EEPROM may be 24C02B (B not 8).

 

[Channel Hopper]

Photographs of the PCB, top and bottom.
The numbers on the chips are very difficult to read. The EEPROM may be 24C02B (B not 8).
View attachment 145587View attachment 145588

Here is the top PCB imagery for the Technomate box mentioned yesterday.

A similar population of parts but it has an external crystal.

 

[dafydd]

Thanks for the photographs.
I will have to find the time to do a detailed comparison - a circuit diagram and an oscilloscope would make things much easier!
Judging from the symptoms, either the EEPROM is not saving the settings or it is failing to load at power-up.

 

[dreambox1959]

on first model (with oscillator ou µP) it was an NMC EEPROM 9306 9346 9316 (SPI) on last model and yours it was 24C02 (I2C)
you can change it by a 2402 2404 2408 2416 not bigger !!!

 

[dafydd]

I ordered a couple of 24C02 this morning - quite difficult to find in DIP now everything has gone to surface mount.
This afternoon I dug into an old spares box and discovered that I have five 24LC16B. These may be an equivalent for this application. Examining the PCB, I found that A!, A2 and A3 are connected to ground. In the 24LC16B these three pins are not connected internally. When the chips arrive I shall get out the soldering iron and will fit a socket so that, if replacing the EEPROM fixes the fault, I can do a comparison. If equivalent there will be chips available for anyone who needs a replacement.