Hi guys,
I have an old Denon PRA-6000 preamp adn Im struggling to find a denon rep in NZ and order a service manual and parts.
however I have identified the dead lamps on the glass front panel as 24V wheat lamps with bare wires.
I have found 6,12 and 18 V wheat lamps on the net but not 24V?
Anyone have any idea on this and any of my other Denon parts dilemmas?
thankyou in advance.
arthur
I have an old Denon PRA-6000 preamp adn Im struggling to find a denon rep in NZ and order a service manual and parts.
however I have identified the dead lamps on the glass front panel as 24V wheat lamps with bare wires.
I have found 6,12 and 18 V wheat lamps on the net but not 24V?
Anyone have any idea on this and any of my other Denon parts dilemmas?
thankyou in advance.
arthur
Two 12V lamps in series?
Or a pair of nose-to-nose 11V zeners will get rid of 11.7V (assuming 24V AC supply, 24V DC just use a 12V zener or a 7812).
Checking a couple of UK catalogues all I see is a 28V wire-ended.
Or a pair of nose-to-nose 11V zeners will get rid of 11.7V (assuming 24V AC supply, 24V DC just use a 12V zener or a 7812).
Checking a couple of UK catalogues all I see is a 28V wire-ended.
grain o' wheat lamps...eBay worked for me
I had a similar dilemma, I needed the 12-15v equivalent, ultimately eBay was my friend. The model train enthusiasts seem to use the lower voltage versions and perhaps have the higher voltage as well...OTOH the 12v zener in series may be the easiest way to go...
If your 24v is ac, whats the average voltage you get from a simple rectifier in series with the bulb? 12v? this may be simplest of all...
Stuart
I had a similar dilemma, I needed the 12-15v equivalent, ultimately eBay was my friend. The model train enthusiasts seem to use the lower voltage versions and perhaps have the higher voltage as well...OTOH the 12v zener in series may be the easiest way to go...
If your 24v is ac, whats the average voltage you get from a simple rectifier in series with the bulb? 12v? this may be simplest of all...
Stuart
thanks for your replies. I should take a photo, but a board with contracts has a cutout where a plastic bulb holder slots in and twists, The bare wires make contact with the pcb copper track and you get light🙂
Adding a zener or 12v reg would not work very well here due to space and there is no soldering that can be done here.
So I really need bare wired 24V wheat lamps.
Adding a zener or 12v reg would not work very well here due to space and there is no soldering that can be done here.
So I really need bare wired 24V wheat lamps.
thanks for all your posts guys, but still not found the right one.
Sounds inc, I have looked at this one, but it has leads, I really need a bare wire, or it wont fit in the holder.
Sounds inc, I have looked at this one, but it has leads, I really need a bare wire, or it wont fit in the holder.
i would replace em all with
white LED and a resistor. use the "natural white" ones. you might need to rough the plastic if you can not find "diffuse" leds, seems more and more the waterclear are more commonly made.
for the resistor. just google "led resistor calculator" there are a few 🙂
If it HAS to be authentic you might want to look on some model railway or maybe dolls house forums. they might use something like that
white LED and a resistor. use the "natural white" ones. you might need to rough the plastic if you can not find "diffuse" leds, seems more and more the waterclear are more commonly made.
for the resistor. just google "led resistor calculator" there are a few 🙂
If it HAS to be authentic you might want to look on some model railway or maybe dolls house forums. they might use something like that
Luke said:
Hmmm, sounds to me like it was worth a try to take one of them down to the local car repair. Ask if you can have a look at his drawer with dashboard lamps 😉
Couldn't hurt trying.
Good hunting
Neutron,
ive seen that site, I would like to keep it original and not hard wire stuff so still prefer to find the wheat lamps.
Xeaglekeeper,
I looked at that site, but they dont have bare wire leads, so wont fit in the holders.
ess44,
took your advice and rang around, but none to be found.
I cant believe I cant get in touch with any one from Denon regarding parts for this and a service manual, its insane. the NZ agents listed on the website has a disconnected phone line, no email. Very unprofessional of Denon. I cant contact anyone from Denon International cos they dont have email, also Denon UK ignored my mail. I dont think I will buy this brand again.
ive seen that site, I would like to keep it original and not hard wire stuff so still prefer to find the wheat lamps.
Xeaglekeeper,
I looked at that site, but they dont have bare wire leads, so wont fit in the holders.
ess44,
took your advice and rang around, but none to be found.
I cant believe I cant get in touch with any one from Denon regarding parts for this and a service manual, its insane. the NZ agents listed on the website has a disconnected phone line, no email. Very unprofessional of Denon. I cant contact anyone from Denon International cos they dont have email, also Denon UK ignored my mail. I dont think I will buy this brand again.
The RMS (you want RMS not average... the average voltage of nice clean AC is in fact zero) is approximately 17 V rms, not 12 V. You can justify this to your mind by realising that if you cut out half the waveform, you will dissipate half the power. From P=V^2/R you know that power is proportional to the square of power. So for half the power, you need sqrt(1/2) the voltage. As one of my old university professors would say, "it's intuitively obvious" even though it rarely was.
well...
...so what is the heating effect of half a 24v sine wave.
The bulb of course doesn't care too much about the shape, just the heating effect it has on the filament...
I'd have to guess it would be equivalent to 12v ac, but with a weird waveform...which in this case means 1/4 power, since we have half the voltage...but then again I could be totally wrong, I haven't given it a whole lot of thought...
Stuart
...so what is the heating effect of half a 24v sine wave.
The bulb of course doesn't care too much about the shape, just the heating effect it has on the filament...
I'd have to guess it would be equivalent to 12v ac, but with a weird waveform...which in this case means 1/4 power, since we have half the voltage...but then again I could be totally wrong, I haven't given it a whole lot of thought...
Stuart
Re: well...
RMS is what tells you the "heating effect". That means that 24 VRMS AC (no matter what the shape of thewaveform) provides the same power (or heat) as 24 VDC into a resistive load. This equivalency is the very reason that RMS measurements are used.
If you want to use 12V lamps, first half-wave recitify, then add a resistor (1 or 2 Watt) in series with the bulb. You will have to experiment (starting high) to determine what value to use to give correct brightness and/or 12 V reading across the bulb.
Stuart Easson said:
RMS is what tells you the "heating effect". That means that 24 VRMS AC (no matter what the shape of thewaveform) provides the same power (or heat) as 24 VDC into a resistive load. This equivalency is the very reason that RMS measurements are used.
If you want to use 12V lamps, first half-wave recitify, then add a resistor (1 or 2 Watt) in series with the bulb. You will have to experiment (starting high) to determine what value to use to give correct brightness and/or 12 V reading across the bulb.
hmm,
So we half wave rectify the waveform, at which point do we have something that gives the heating power of 12v DC? If thats the case why a resistor? We already lose (0.6v) one diode drop, so presumably it is already a little less than we'd expect...
I guess the reason I am slightly confused by this is that all else being equal 24v ac has 4 times the heating power of 12v ac, so if you discard half the power through half wave rectification you still have twice the heating power of 12v ac, right? Hence the need for a resistor?
I think I answered my own question...
Stuart
So we half wave rectify the waveform, at which point do we have something that gives the heating power of 12v DC? If thats the case why a resistor? We already lose (0.6v) one diode drop, so presumably it is already a little less than we'd expect...
I guess the reason I am slightly confused by this is that all else being equal 24v ac has 4 times the heating power of 12v ac, so if you discard half the power through half wave rectification you still have twice the heating power of 12v ac, right? Hence the need for a resistor?
I think I answered my own question...
Stuart
sorry, quite right. Less ohms more lamps...
...did you try these guys:
http://www.kenselectronics.com/lists/lites.htm
They seem to have a modest selection that include 24v bulbs with short bare wires...small diagrams might help you judge if the fit works...
HTH
Stuart
...did you try these guys:
http://www.kenselectronics.com/lists/lites.htm
They seem to have a modest selection that include 24v bulbs with short bare wires...small diagrams might help you judge if the fit works...
HTH
Stuart
Hi Stuart,
havent tried them yet, but the page doesnt load, can you get to it still?
regards Arthur
havent tried them yet, but the page doesnt load, can you get to it still?
regards Arthur
not right now, weird...
...I am not getting 'page not found', instead I get a timeout from the server...
Sorry, it seemed to work perfectly when I tried earlier.
Stuart
...I am not getting 'page not found', instead I get a timeout from the server...
Sorry, it seemed to work perfectly when I tried earlier.
Stuart
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