Also, to lower inrush current you need a soft start circuit. It's absolutely necessary with toroidal transformers with power greater than 300W (this amplifier has ~400W transformer).
vwestlife Yes, probably. But I don't want to risk anything. Each time the breaker trips, it takes down the computer and my alarm clock looses the time...
As soon as I saw this amp, I immediately recognized it - it's Koda KD-269 (at least I think it's Koda or it may be Conrad). There was a very similar amp Koda KD-261 - same power amplifier I suppose, but with preamp built in. I really wanted the latter, but at that time it was too expensive for me. The output power of this amplifier is 2x110-120W / 8Ω - that may be true considering 400W max. power consumption - it's all in the manual.
Nice find. I'm afraid I don't know what you mean by this inrush current but I suppose it's used to charge those huge caps? I wonder if that was the reason it got dumped in the first place. Would it be possible to change that behaviour at all? May be a nice project...
There's a pretty good class A inrush current circuit board on eBay if you still have this amplifier... Another thing to look out for is the filter capacitors, if they have low parallel resistance, they will be passing DC current which could be the cause of your breakers tripping...
Dear Dr. It's been a blast to watch all your videos so far, please keep the excellent work up. It'd be great and kind on your behalf if you did a video on how to clean all those crusty boards. What kind of solvents should be used and what shouldn't, etc. There are 0 videos on this matter and we all can agree all those 60's, 70's and 80's receivers are quite often a mess of dirt and whatnot inside. Best regards, thanks a lot.
CofeeAuLait I have used soap and water, but that only works on boards that don't have components on them that would be damaged by water (coils, inductors, anything that could rust). Normally I use Kontakt WL, that's a rather aggressive spray cleaner. And the compressor is always a big help to get the cleaning started.
I have 550VA 2x12vac toroidal transformer and capasitor bank when power is connected will be 660 000uF and still my old filament lamp is only one that a little bit dim first but still nothing major things happening and everything is fine and working. Maybe CM&DM filter and PI filter middle with capasitors will slowing down inrush current... :)
It does look quite good.A nice clean,and it will be perfect.Oh,and something for the too fast charging. You might take into consideration this fact when getting the AC unit.Won't that trip the breaker?
costellom5 The AC unit arrived. The maximum rated current is 4,2 A, so it'll be fine unless I have another, much bigger load on at the same time (fuse is rated 16 A).
theedrstrangelove I guess you've never seen a typical German window. You can't fit a window a/c unit into there unless you modify the window. I can't do that and I can't install a split unit either because this is a rented place. The landlord won't allow any modifications to the windows and/or walls.
A simple soft start circuit would be a light bub in series with the mains input power. Use a timer circuit to wait a second or two then have the timer close a relay contact and short across the light bulb to electrically remove it from the circuit. The light bulb acts like a variable resistor that will limit the in rush current to what the maximum current the light bulb is designed to draw. As the light dims and the filament cools the resistance drops significantly after the filter caps charge up. The voltage drop across the bulb will be minimal and the relay closure will see a minimal current surge. This will limit the toroid transformers inrush current draw.
Boah ja, bei uns ist es auch sengend heiß. Hatten vorgestern mal eben so alle Temperaturrekrode der Region gebrochen und ich hatte keinen Ventilator :D Hab mir jetzt nen Cluster aus altem PC-Netzteil und alten Gehäuselüftern gebastelt. Läuft :D Zurzeit (grad draufgeguckt) hier drinnen 34°C, draußen hatten wir vorgestern 42,8°C. Puh.
Nik Paulussen Es ist unerträglich. Heute hatten wir endlich ein Gewitter mit Temperatursturz, draußen sind's 21°C, in meiner Wohnung jetzt noch 27°C, und das dauert jetzt Tage, bis der Beton wieder auskühlt. Ich hatte heute zum Glück die Möglichkeit meine große Windmaschine zu holen, die ich beim Umzug dummerweise nicht mitgenommen hatte. Und nächste Woche kommt das Klimagerät. Und wenn ich während Hitzeperioden jetzt 100€ statt 20€ jeden Monat für Strom zahle, das ist es mir wert. In dieser Hitze ist man ja zur völligen Untätigkeit verdammt.
Ich habe da nicht groß geforscht, ich habe etwas genommen, was (relativ) billig war und von den technischen Daten her reicht, um die ganze Wohnung zu kühlen. Ich hoffe, das Ding ist kein völliger Schrott...
Also, to lower inrush current you need a soft start circuit. It's absolutely necessary with toroidal transformers with power greater than 300W (this amplifier has ~400W transformer).
It'll probably be fine as long as you don't turn it on again while the capacitors are still discharging.
vwestlife Yes, probably. But I don't want to risk anything. Each time the breaker trips, it takes down the computer and my alarm clock looses the time...
DrCassette Just put in a cap on the power lead to slow the charging. it will be fine.
I like this simple and yet powerful amplifiers
As soon as I saw this amp, I immediately recognized it - it's Koda KD-269 (at least I think it's Koda or it may be Conrad). There was a very similar amp Koda KD-261 - same power amplifier I suppose, but with preamp built in. I really wanted the latter, but at that time it was too expensive for me. The output power of this amplifier is 2x110-120W / 8Ω - that may be true considering 400W max. power consumption - it's all in the manual.
Tomas Sabalas Indeed the electronics store I referred to is Conrad. They sold this thing in the early 2000s.
Nice find. I'm afraid I don't know what you mean by this inrush current but I suppose it's used to charge those huge caps? I wonder if that was the reason it got dumped in the first place. Would it be possible to change that behaviour at all? May be a nice project...
There's a pretty good class A inrush current circuit board on eBay if you still have this amplifier... Another thing to look out for is the filter capacitors, if they have low parallel resistance, they will be passing DC current which could be the cause of your breakers tripping...
Nice find are you going to keep this or sell it on?
Dear Dr.
It's been a blast to watch all your videos so far, please keep the excellent work up.
It'd be great and kind on your behalf if you did a video on how to clean all those crusty boards. What kind of solvents should be used and what shouldn't, etc.
There are 0 videos on this matter and we all can agree all those 60's, 70's and 80's receivers are quite often a mess of dirt and whatnot inside.
Best regards, thanks a lot.
CofeeAuLait I have used soap and water, but that only works on boards that don't have components on them that would be damaged by water (coils, inductors, anything that could rust). Normally I use Kontakt WL, that's a rather aggressive spray cleaner. And the compressor is always a big help to get the cleaning started.
I have 550VA 2x12vac toroidal transformer and capasitor bank when power is connected will be 660 000uF and still my old filament lamp is only one that a little bit dim first but still nothing major things happening and everything is fine and working. Maybe CM&DM filter and PI filter middle with capasitors will slowing down inrush current... :)
It does look quite good.A nice clean,and it will be perfect.Oh,and something for the too fast charging.
You might take into consideration this fact when getting the AC unit.Won't that trip the breaker?
costellom5 The AC unit arrived. The maximum rated current is 4,2 A, so it'll be fine unless I have another, much bigger load on at the same time (fuse is rated 16 A).
Good find! What capacitance rating are those large filter caps?
adumanter I unfortunately didn't check. I'm pretty sure they are under 10.000 µF each.
Why don't you get a window a/c unit? My aunt in Frankfurt is thinking about getting one.
theedrstrangelove I guess you've never seen a typical German window. You can't fit a window a/c unit into there unless you modify the window. I can't do that and I can't install a split unit either because this is a rented place. The landlord won't allow any modifications to the windows and/or walls.
looks similar on the inside and outside to denon and onkyo amps from the 80s
I would like to know to output power of this amp, the transformer looks quite beefy.
Das OSi It is 100Wx2 at 0.05% THD or 300Wx2 at 1% THD. So quite good actually.
Joshua's Recordings Impressive. Does anyone know who produced this device?
Das OSi I think it is Koda, I do not think they sell them in the US (where I am from)
A simple soft start circuit would be a light bub in series with the mains input power. Use a timer circuit to wait a second or two then have the timer close a relay contact and short across the light bulb to electrically remove it from the circuit.
The light bulb acts like a variable resistor that will limit the in rush current to what the maximum current the light bulb is designed to draw. As the light dims and the filament cools the resistance drops significantly after the filter caps charge up. The voltage drop across the bulb will be minimal and the relay closure will see a minimal current surge. This will limit the toroid transformers inrush current draw.
Just make a inrush current limiter and you can use it
Boah ja, bei uns ist es auch sengend heiß. Hatten vorgestern mal eben so alle Temperaturrekrode der Region gebrochen und ich hatte keinen Ventilator :D Hab mir jetzt nen Cluster aus altem PC-Netzteil und alten Gehäuselüftern gebastelt. Läuft :D
Zurzeit (grad draufgeguckt) hier drinnen 34°C, draußen hatten wir vorgestern 42,8°C. Puh.
Nik Paulussen Es ist unerträglich. Heute hatten wir endlich ein Gewitter mit Temperatursturz, draußen sind's 21°C, in meiner Wohnung jetzt noch 27°C, und das dauert jetzt Tage, bis der Beton wieder auskühlt. Ich hatte heute zum Glück die Möglichkeit meine große Windmaschine zu holen, die ich beim Umzug dummerweise nicht mitgenommen hatte. Und nächste Woche kommt das Klimagerät. Und wenn ich während Hitzeperioden jetzt 100€ statt 20€ jeden Monat für Strom zahle, das ist es mir wert. In dieser Hitze ist man ja zur völligen Untätigkeit verdammt.
DrCassette Welche Anlange würdest du empfehlen ?
Ich habe da nicht groß geforscht, ich habe etwas genommen, was (relativ) billig war und von den technischen Daten her reicht, um die ganze Wohnung zu kühlen. Ich hoffe, das Ding ist kein völliger Schrott...
Looks like "KODA" brend.
Doc in my Laboratory is 38 C° during the day :-(
This is German Conrad
Yes, this amplifier was sold by Conrad.
Koda is the brand.
33c? Try 40c plus days in Australia during Summer you weakling lol ? ?
I am a European, not an Australian. We can't cope with high temperatures like you can.