Thanks for the tips, I'll keep those in mind.
I might do the move of the power supply off board as well when I work on it.
We got a cool sounding SS phono stage, but since I have no volume on either it or my SET Tube amp, I am now also working on a Tube Preamp where a volume pot should magically appear and solve that problem.
I might do the move of the power supply off board as well when I work on it.
We got a cool sounding SS phono stage, but since I have no volume on either it or my SET Tube amp, I am now also working on a Tube Preamp where a volume pot should magically appear and solve that problem.
The last thing I repaired or better cleaned and maintained, is the stove's steam extractor also known as the hood. It needed a better air coupling which was previously amateurish. It also needed removal of the extractor and a good cleanup and oiling. In the process I took the opportunity to modify the extractor in such a was as to make the removal of the electric motors easier. There is still another modification which can make this job easier, which is, to modify the two bulb reflectors in such a way to make more space so that the motors are easily removed, cleaned and oiled.
Needless to state, after using some good old Singer lubricating oil, the brand used for sewing machines, the motors function much much better.
Needless to state, after using some good old Singer lubricating oil, the brand used for sewing machines, the motors function much much better.
This weekend, my washing machine, brand name Brandt, could not start, the only function were flashing LEDs on the front panel. A friend of mine, who is also a relative, repaired it for me. It was a switch which is operated when the machine's circular front door is closed. The switch's contacts were dirty with corrosion due to the arching caused by switching. This relative, patiently opened the switch, took out the contacts and cleaned them using very fine sandpaper. Then he put the contacts back and asked me to test the switch while he operated the switch using his fingers. When the switch started to make good contact, he reassembled the switch and installed it back where it was.
Needless to state, the washing machine started and completed the loaded wash without issues.
I have another repair waiting in the pipeline, but it seems this cannot be done, as it is something which cannot be replaced. It is a refrigerator with damaged door rubber which is causing the inside to smell badly.
Needless to state, the washing machine started and completed the loaded wash without issues.
I have another repair waiting in the pipeline, but it seems this cannot be done, as it is something which cannot be replaced. It is a refrigerator with damaged door rubber which is causing the inside to smell badly.
I also repaired a laptop's DC lead. This had the wrong male plug. So, I cut off the cable to remove the incompatible male plug and connected the original one from the original bad power supply. The original one had only to wires to feed the DC, while the new one had three, two thick wires and another thinner wire. When I made sure what the wires were for, I connected everything with the exception of the third thin wire. However, the laptop could not start. Testing for the DC voltage I found 15V but the power supply was in stand by supplying no power. Testing further, I found the third wire is used to start the power supply from stand by mode. Connecting a 10 kilo Ohm resistor from the white wire to ground, the negative terminal, everthing worked including laptop.
Some Dell laptop PC's have a third wire used to identify if the correct charger is being used. These have a chip in the PSU that performs the ID function. If the PSU fails the test (like a generic equivalent that isn't) then the laptop performance is reigned in and it generates an error message somewhere.
In my case, the laptop cannot verify anything as it has only two contacts in its female socket which is used for DC power. The third wire is from the power supply which is generic. The laptop is also by another brand. In fact, it is an Acer Aspire laptop with a large screen.
Mooly, don't be bothered.
Mooly, don't be bothered.
Repaired one of our Audio Precision System Ones.
Busy upgrading another to read lower THD numbers. Replacing all old electrolytics at the same time and changing lots of ICs which will help on the THD + Noise readings.
Modified the final discrete drive amps for the generator's output transformer.
Once this proof of concept is done I shall do the same to our other 4 APs.
Steve Mantz
Zed Audio Corp.
Los Angeles
Busy upgrading another to read lower THD numbers. Replacing all old electrolytics at the same time and changing lots of ICs which will help on the THD + Noise readings.
Modified the final discrete drive amps for the generator's output transformer.
Once this proof of concept is done I shall do the same to our other 4 APs.
Steve Mantz
Zed Audio Corp.
Los Angeles
A tip for LEd users / those planning to do a solar conversion:
Here food stall owners buy old batteries, and charge them with solar panels, or at home. There is even a guy who rents charged batteries, swaps discharged ones for charged ones.
Batteries used are mostly that are normal voltage, but will not crank...those are good enough for lighting, as the engine starters draw a lot of current.
Another side effect is that those are less trash.
As the battery is a very big part of the cost, for a hobby / not essential project you can use this type of battery, and save a lot of money.
There was a post on an off grid forum, a poster got huge - filing cabinet size - batteries from a submarine, sold as surplus by the US Navy.
Here food stall owners buy old batteries, and charge them with solar panels, or at home. There is even a guy who rents charged batteries, swaps discharged ones for charged ones.
Batteries used are mostly that are normal voltage, but will not crank...those are good enough for lighting, as the engine starters draw a lot of current.
Another side effect is that those are less trash.
As the battery is a very big part of the cost, for a hobby / not essential project you can use this type of battery, and save a lot of money.
There was a post on an off grid forum, a poster got huge - filing cabinet size - batteries from a submarine, sold as surplus by the US Navy.
I repaired two preamps... One I made to use a 12V SMPS that had a "dial-a-volt" voltage adjustment - set to 12.6V, this gave enough extra voltage for an LDO.
However, that SMPS failed after three years in 70°C. The replacement is potted but no adjustment. 12V. Now the LDO is on the HV side of the boost converter. It's still noisy but it's not la fin du monde.
Another preamp had a similar buzz on the phono input. Some sleuth work proved this to be a bad ground connection at the turntable.
Now to sort another preamp that I designed poorly - the transformer is magnetically coupling to the filter caps creating hum.
I removed the power from the power, and shunted in 12V from a car battery - no hum.
I used a larger transformer but sitting on the desk 6 inches from the caps - no hum.
I moved said coil over the caps - induced hum.
Always learning
I also think the problem lies in the undersized coil - the larger transformer makes less hum while being closer to the caps... (25VCT 120VA (makes 24W of heat in the regulators) vs 22VCT 252VA - I use full wave)
However, that SMPS failed after three years in 70°C. The replacement is potted but no adjustment. 12V. Now the LDO is on the HV side of the boost converter. It's still noisy but it's not la fin du monde.
Another preamp had a similar buzz on the phono input. Some sleuth work proved this to be a bad ground connection at the turntable.
Now to sort another preamp that I designed poorly - the transformer is magnetically coupling to the filter caps creating hum.
I removed the power from the power, and shunted in 12V from a car battery - no hum.
I used a larger transformer but sitting on the desk 6 inches from the caps - no hum.
I moved said coil over the caps - induced hum.
Always learning
I also think the problem lies in the undersized coil - the larger transformer makes less hum while being closer to the caps... (25VCT 120VA (makes 24W of heat in the regulators) vs 22VCT 252VA - I use full wave)
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