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- Thread Starter
- #222
Yes not perfect and not typical, the reason were the shortes signal tracks. This was a prototype for me only. In my avatar you can see a similar headphone pre (top) that I designed and that was produced in a small series and has usual placement of the connectors.
Indeed, but who cares, MAKE IT SHORT !
Hey just thinking loud:
For the sake of the shortest signal, you could put these
No, on the sides (like a RPi) but then you need a U shaped case.
But true, your Avatar's one looks more "conventional".
PS- Why "small" series ? This site and the web is waiting for you
- Thread Starter
- #224
Why "small" series ? This site and the web is waiting for you
I am enjoying it as a hobby now. Never was a fool enough to want to make a living with this
- Thread Starter
- #225
Measurements of that headphone amplifier are in another thread
https://www.audiosciencereview.com/forum/index.php?threads/pm-h2-headphone-amplifier.21014/
https://www.audiosciencereview.com/forum/index.php?threads/pm-h2-headphone-amplifier.21014/
- Thread Starter
- #227
I need 3 wires: +15V, 0V and -15V. I use the Neutrik (beside the output 6.3 mm TRS) and shielded twisted pair wire to lead the power. 0V/GND on the shield. Usually the 4-pin Neutrik, though here is the 3-pin version, just for myself.
A Kenwood KR-8010 that could use some love. Needs pots and selector switches cleaned, and probably some re-capping. Sigh...
Since I'm fixing a piece of audio equipment, I thought I'd post details here.
This is the chassis of a Bush tabletop radio (AC34) which was bought by my father in the mid-fifties. I remember it in our house as a kid. Then, later it got cast out to be used as a barn radio where it had a hard life. Birds roosted on it, spiders nested within, the veneer peeled away in the damp & it just gave up. I discovered it in a pile of junk in the early eighties, rescued it, had the veneer replaced, and fixed it up. Over the next 30 years it had periodic use (it has a shortwave band which can still be quite interesting to listen to), but I remember that it suddenly died around 10 years ago. I've been meaning to look at it since then &, now that I'm in "repair mode", its turn has come.
The ravages of time have taken their toll. But it has a common fault: the aged waxed paper capacitors have started to leak (electrically) & the output stage grid has slowly been pulled towards the anode potential of the previous stage. Presumably, the current increased and, finally the output transformer could take no more & the primary went open circuit. I've just unwound the transformer to investigate but, with 3000 turns of 0.1mm diameter wire on the primary, it's not something I care to rewind! Fortunately, I've found a modern equivalent &, after replacing all of the waxed capacitors with polypropylene types, and a few high-value resistors too, it works once more!
But we're not out of the woods yet: the radio still has a horrendous powerline hum, even using smoothed HT from my lab supply. Investigation showed that there's considerable leakage between the heater & grids in the output tube/valve. I guess that the mica insulators have accumulated a thin metal film from the excessive current flow. The tubes are all Mullard U-series types with heaters designed to be series connected. With approx. 50V AC on the heater, even a couple of Mohms leakage resistance feeds considerable hum into the audio circuit & the tube will have to be replaced.
I just had the crazy idea of zapping away the metallic deposit by putting a few kV between heater/cathode & the other pins. I'd need several Watts to vaporize this, so it would be a pretty lethal setup... It's probably fortunate that I don't have a suitable EHT supply to hand!
Maybe I'll post an update when I've replaced the UL41...
This is the chassis of a Bush tabletop radio (AC34) which was bought by my father in the mid-fifties. I remember it in our house as a kid. Then, later it got cast out to be used as a barn radio where it had a hard life. Birds roosted on it, spiders nested within, the veneer peeled away in the damp & it just gave up. I discovered it in a pile of junk in the early eighties, rescued it, had the veneer replaced, and fixed it up. Over the next 30 years it had periodic use (it has a shortwave band which can still be quite interesting to listen to), but I remember that it suddenly died around 10 years ago. I've been meaning to look at it since then &, now that I'm in "repair mode", its turn has come.
The ravages of time have taken their toll. But it has a common fault: the aged waxed paper capacitors have started to leak (electrically) & the output stage grid has slowly been pulled towards the anode potential of the previous stage. Presumably, the current increased and, finally the output transformer could take no more & the primary went open circuit. I've just unwound the transformer to investigate but, with 3000 turns of 0.1mm diameter wire on the primary, it's not something I care to rewind! Fortunately, I've found a modern equivalent &, after replacing all of the waxed capacitors with polypropylene types, and a few high-value resistors too, it works once more!
But we're not out of the woods yet: the radio still has a horrendous powerline hum, even using smoothed HT from my lab supply. Investigation showed that there's considerable leakage between the heater & grids in the output tube/valve. I guess that the mica insulators have accumulated a thin metal film from the excessive current flow. The tubes are all Mullard U-series types with heaters designed to be series connected. With approx. 50V AC on the heater, even a couple of Mohms leakage resistance feeds considerable hum into the audio circuit & the tube will have to be replaced.
I just had the crazy idea of zapping away the metallic deposit by putting a few kV between heater/cathode & the other pins. I'd need several Watts to vaporize this, so it would be a pretty lethal setup... It's probably fortunate that I don't have a suitable EHT supply to hand!
Maybe I'll post an update when I've replaced the UL41...
Remote control getting sluggish and one button not working. Genuine replacement ~ $AU80
Mine is similar to the one in this fix:
https://vk4ghz.com/panasonic-dmr-bwt720-ir6-remote-not-working/
I followed the instruction and the remote control is like new again.
I am puzzled as to what the gel-like residue on the circuit board and contact side of the silicon button pad is - see link.. Anybody know?
Mine is similar to the one in this fix:
https://vk4ghz.com/panasonic-dmr-bwt720-ir6-remote-not-working/
I followed the instruction and the remote control is like new again.
I am puzzled as to what the gel-like residue on the circuit board and contact side of the silicon button pad is - see link.. Anybody know?
restorer-john
Grand Contributor
Coca Cola, beer or whatever else you dropped it into.
When the membrane button pads cease to work again down the track (they all do), paint the upper pad with conductive paint- it lasts longer in between repairs.
Coca Cola, beer or whatever else you dropped it into.
When the membrane button pads cease to work again down the track (they all do), paint the upper pad with conductive paint- it lasts longer in between repairs.
No spills. One idea is a reaction between battery vapour and the silicon.
Further www. searching: http://www.michaelshell.org/gadgetsandfixes/keypadsiliconeoil.html
Sounds reasonable.
Sounds reasonable.
restorer-john
Grand Contributor
- Thread Starter
- #238
Looking very good!
Thanks John! It is only a prototype case/heatsink/box, so it could be better. Just taking what I have here. The case is
1) heavy (those heatsinks, transformers etc.)
2) expensive
30 kg, however I will pass the 1 hour 1/3 continuous sine power test
. And the full power BW Similar threads
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