I recently noticed a high pitch noise coming from our cheap Asda Alba ST102 freeview STB. Its a very cheap STB which we use in our kitchen. We have noticed no other problems but the high pitch noise which has been very annoying.
I opened the casing and this noise seem to come from the 22uf 400v capacitor.
Apart from this noise the capacitor seemed OK. It measured 25uf with an esr of 1.25ohms measured out of circuit with my esr micro V4.
I ordered some new Panasonic capacitors of the same rating from RS.
Today i replaced the capacitor and totally balls this simple job. I accidentally put the capacitor in reverse polarity. I've done a few recaps and never done this before.
When switching on the unit was completely dead. When opening the unit to investigate i noticed my big mistake. I then replaced the cap with another spare altho the cap tested OK. On switching on the unit was still completely dead. I then tested the main primary fuse on the PCB. The fuse was a 2A soldered to the PCB and open circuit. I had a 2A fuse but without leads. So i soldered in a fuse holder and replaced the fuse. On switching on the fuse blew again.
I then checked the 4 rectifier diodes and noticed 2 shorted diodes. The diodes were IN4007. I didn't have any IN4007 but did have IN4001 diodes. I replaced the 2 shorted IN4007 with the IN4001. This time on switching on the STB worked and there is no high pitch noise.
I have ordered some IN4007 diodes and will replace these.
My question is will i damage the STB with the use of IN4001 diodes until my replacement IN4007 arrive.
Many thanks
I opened the casing and this noise seem to come from the 22uf 400v capacitor.
Apart from this noise the capacitor seemed OK. It measured 25uf with an esr of 1.25ohms measured out of circuit with my esr micro V4.
I ordered some new Panasonic capacitors of the same rating from RS.
Today i replaced the capacitor and totally balls this simple job. I accidentally put the capacitor in reverse polarity. I've done a few recaps and never done this before.
When switching on the unit was completely dead. When opening the unit to investigate i noticed my big mistake. I then replaced the cap with another spare altho the cap tested OK. On switching on the unit was still completely dead. I then tested the main primary fuse on the PCB. The fuse was a 2A soldered to the PCB and open circuit. I had a 2A fuse but without leads. So i soldered in a fuse holder and replaced the fuse. On switching on the fuse blew again.
I then checked the 4 rectifier diodes and noticed 2 shorted diodes. The diodes were IN4007. I didn't have any IN4007 but did have IN4001 diodes. I replaced the 2 shorted IN4007 with the IN4001. This time on switching on the STB worked and there is no high pitch noise.
I have ordered some IN4007 diodes and will replace these.
My question is will i damage the STB with the use of IN4001 diodes until my replacement IN4007 arrive.
Many thanks
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