GrahamH's photos with the keyword: circuit

This is one of three amplifiers at the church I go to. I was gathering interconnection information for the whole system so I could make changes to improve reliability in Toowoomba's summer thunderstorm season when I found this had stopped working. I removed it from the equipment rack and took off the cover. There was nothing obvious except the blown fuse in the mains power socket. This photo was taken then. I replaced the cover and took it home for further investigation. At home I eventually decided that the mains power transformer, the circular object with the wires going from it, was probably faulty. I contacted the Australian agent of the manufacturer, Bosch, for circuit diagrams and technical information. They weren't very helpful but did refer me to a business which did warranty repairs for this type of product. The service manager answered some general questions but didn't/wouldn't supply any circuit information. I worked out a likely AC supply voltage but didn't anything on hand to provide it to check that the rest of the amplifier was working correctly. I ordered a replacement transformer anyway with some trepidation. A pleasant surprise was that it was priced comparably with the normal pricing for similar transformers. About a month later the transformer arrived. With the aid of some photos, a soldering iron and some other tools I replaced the transformer and was relieved when the amplifier then worked correctly. I measured a few key voltages and wrote them on the chassis in case there was any further trouble. The amplifier worked correctly when reinstalled in the rack at church. Mouse-over to see some other photos of the amplifier.

A two channel wireless mic receiver used at my church. One microphone has died, to be investigated one day... The audio levels out of the receivers have always been low. I have added a one stage one transistor amplifier to the signal just before the level control of the still-working mic's receiver. The stage gain was adjusted and set using a fixed unbypassed emitter resistor. The load resistor was selected to suit the level control value fed from the new stage. Pip 1 shows the relevant level control removed during feasibility investigation. Pip 2 shows the circuit during development and test. The BC548 transistor is held in a vice and all the components hanging off it. Power during testing came from an AT computer power supply. Pip 3 shows the circuit being transferred to a piece of insulated board for mounting in the receiver box. Pip 4 shows power for the installed amplifier being obtained from the receiver's 9V regulator. Earth and negative supply was soldered to the main circuit board adjacent to the mounting location. Pip 5 shows the amplifier board temporarily mounted with all wires connected. It works as intended and I now need to replace the mounting tape with screws and standoffs.

My wife's 3-4 years old Dell Inspiron 15R 5520 laptop failed. The power pack is shut down when it is plugged into the power socket, but otherwise works ok. I opened the laptop and found dried gunk and brown deposits and stains around a partly destroyed SMD. See note. I cleaned most the mess, as shown here, reassembled it but the fault remained. Tomorrow, Monday, I'll contact Dell Australia about parts, boards and new laptops. November 2015.

My wife's 3-4 years old Dell Inspiron 15R 5520 laptop failed. The power pack is shut down when it is plugged into the power socket, but otherwise works ok. I opened the laptop and found dried gunk and brown deposits and stains around a partly destroyed SMD. See note. I cleaned most the mess, as shown here, reassembled it but the fault remained. Tomorrow, Monday, I'll contact Dell Australia about parts, boards and new laptops. November 2015.

My wife's 3-4 years old Dell Inspiron 15R 5520 laptop failed. The power pack is shut down when it is plugged into the power socket, but otherwise works ok. I opened the laptop and found dried gunk and brown deposits and stains around a partly destroyed SMD. I cleaned most the mess, as shown here, reassembled it but the fault remained. Tomorrow, Monday, I'll contact Dell Australia about parts, boards and new laptops. November 2015.

My wife's 3-4 years old Dell Inspiron 15R 5520 laptop failed. The power pack is shut down when it is plugged into the power socket, but otherwise works ok. I opened the laptop and found dried gunk and brown deposits and stains around a partly destroyed SMD. This is the underside of the panel which supports the keypad. The circuit of the touchpad is the green circuit board. Tomorrow, Monday, I'll contact Dell Australia about parts, boards and new laptops. November 2015.

My wife's 3-4 years old Dell Inspiron 15R 5520 laptop failed. The power pack is shut down when it is plugged into the power socket, but otherwise works ok. I opened the laptop and found dried gunk and brown deposits and stains around a partly destroyed SMD. I cleaned most the mess, as shown here, reassembled it but the fault remained. Tomorrow, Monday, I'll contact Dell Australia about parts, boards and new laptops. November 2015.

My wife's 3-4 years old Dell Inspiron 15R 5520 laptop failed. The power pack is shut down when it is plugged into the power socket, but otherwise works ok. I opened the laptop and found dried gunk and brown deposits and stains around a partly destroyed SMD. I cleaned most the mess, as shown here, reassembled it but the fault remained. Tomorrow, Monday, I'll contact Dell Australia about parts, boards and new laptops. November 2015.

My wife's 3-4 years old Dell Inspiron 15R 5520 laptop failed. The power pack is shut down when it is plugged into the power socket, but otherwise works ok. I opened the laptop and found dried gunk and brown deposits and stains around a partly destroyed SMD. I cleaned most the mess, as shown here, reassembled it but the fault remained. Tomorrow, Monday, I'll contact Dell Australia about parts, boards and new laptops. November 2015.

The cover off the counter to plan modifications to run from 12v car battery etc.

The cover off the counter to plan modifications to run from 12v car battery etc.

The cover off the counter to plan modifications to run from 12v car battery etc.

The cover off the counter to plan modifications to run from 12v car battery etc.

The cover off the counter to plan modifications to run from 12v car battery etc. It surprised me that the power transformer was centre tapped to earth and each side feeding a single diode ala valve rectifier ccts of old.

The cover off the counter to plan modifications to run from 12v car battery etc. It surprised me that the power transformer was centre tapped to earth and each side feeding a single diode ala valve rectifier ccts of old.

The cover off the counter to plan modifications to run from 12v car battery etc. It surprised me that the power transformer was centre tapped to earth and each side feeding a single diode ala valve rectifier ccts of old.