New member intro and SX-737 stereo light question

M

Marley

New Member
Hi everyone,

I've been lurking here for a while now, with this being my very first post. I have been very interested in getting into vintage audio gear for some time, and I finally took the plunge. My first (and currently only) piece is an SX-737 that I picked up from a moving sale for $15.

The face had quite a bit of grime built up on it, most of the lamps were burned out, and it wasn't hooked up to any speakers for me to listen to, but I bought it anyway. Just couldn't help myself.

I brought it home, hooked it up to a set of speakers and it worked. After cleaning the face w/ a toothbrush and toothpaste (a trick I learned here), the shiny aluminum face looked great. Next I ordered some fuse lamps off the internet and viola, this thing looks SWEET! The blue lights are beautiful. Even my wife likes it (she was very skeptical w/ me putting this thing in the house). I haven't even used any deoxit on it since all off the knobs and switches work and nothing sounds scratchy (at least to my ears).

So at this point, I’m in Pioneer SX heaven. The only thing that bothers me is that the red "stereo" lamp is now out. Since I know nothing about electronic jargon, could you guys help me out? The little sleeve surrounding the stereo lamp says that its 8V .25a. Radio Shack sells a similar lamp, but its 6V .25a. Will that work? How does the lower voltage affect things? I know that I can order the exact bulb off the internet, but I'm sort of an instant gratification kind of guy.

Here's a picture of my baby. I'm not a very good photographer. Next up...speakers (preferably bookshelf sized).

Thanks for all of your help.
 

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A 6V lamp isn't gonna last long at 8V, but you knew that, right? :scratch2:
The little sleeve surrounding the stereo lamp says that its 8V .25a
Click to expand...
Either the sleeve is wrong, you're reading it wrong, or you mis-typed. That's 250mA, and a buttload of current for a stereo indicator. These are generally 4mm or 5mm diameter lamps, and rated at about 50mA of current.

Pull the bad one out, and contact AK member dwojo. He'll get you what you need.
 
Hey Marley,
Welcome to AudioKarma, and especially the Pioneer forum!

That SX-737 is a nice looking unit. I have one of those sitting on my work bench right now. It needs a few lamps as well, and a good cleaning.


Retro
 
Thanks for the warm welcome.

Echowars - No I didn't know that a 6V lamp will not last as long. Why is that?

Seriously, I know nothing about electronics, voltage, amps, etc. I'm a total idiot when it comes to this stuff. I am hoping to learn though, so that I can continue with this hobby. Amps are similar to the wattage rating of a regular household lightbulb, right? i.e. the higher the amp number, the brighter the bulb and the more juice it uses? What's the voltage rating mean?

I'm at work right now, so I'll have to wait until I get home to open the receiver up again. I could very well be wrong when I read things on the bulb the first time.
 
It appears that the lamp is 8v @ 50mA. Can't really see, that part of my schematic is "missing", but it sounds about right.
 
Yup. Just opened her up again to double check the stereo bulb. It's rated 8V and 50mA. I probably won't get the ratshack one, but would someone like to educate me on this? If the ratshack one is 6V 25mA, what would be the effect? I assume that 25mA is half as bright as 50mA. Where does the voltage come into play? I'm sorry if this is a dumb question. I should go buy a book.
 
Hi Marley,

I'm not sure what the voltage on the lamp is, often there is only 6.3v nominal on the lamp and by using a slightly higher voltage rating, the lamp will last longer.

However, if there is some 8v nominal on the lamp, then you would get away with inserting three 1N4001 diodes in series with one of the leads; the diodes will drop the voltage sufficiently to lower the operating voltage for the lamp. This would entail cutting one of the leads to the lamp and insert three diodes in series (e.g. x--|>|--|>|--|>|--x with the now two open ends of the wire connected one to each spot at "x").

A 25mA lamp will glow somewhat dimmer, but I doubt you would really need to worry about this.

Hope this makes sense...
 
Welcome to AK and the Pioneer forum
Thats is the only bulb in the receiver I would not mess with :no: I would get the correct bulb.

Ron
 
Welcome Marley
The 737 is a beautiful receiver, isn't it? I use one for my Family Rm. system (probably my main system). Sorry I can't help with the tech stuff, I know even less than you! :D
Ed
 
The best advice you have gotten is to get the lamp from dgwojo.

Every other lamp in the 737 is just switched by copper switch contacts, the stereo lamp is driven by electronic circuits in the stereo detector. They can only deliver a small amount of current without damage. Too much of a "load" by the lamp could (WILL) destroy them. Doing that in any other lamp position would just pop the fuse, instead of (probably) an integrated circuit that is no longer manufactured.

For a good, but technical explanation, spend some time learning "Ohm's Law" from one of the many excellent instructional websites that cover it.

Thumbnail sketch explanation: when more voltage than the lamp is rated for is applied, a lot more current also flows. This results in drastically more heat then the lamp can handle, resulting in it burning out VERY quickly or just going POOF!!!! The lamp filament can melt, or in extreme cases, explode.
 
I went and measured the voltage on the stereo lamp, it is 6v. However, as others here have pointed out, if you are not sure what you are doing, rather leave it to someone who has electronics experience.

That being said, a 6v 25mA lamp should work fine, but do not exceed the rated 50mA of the original lamp.

-Eric
 
Hey, welcome to AK. The SX-737 is a nice receiver!
If the stereo lamp not goes on, it is likely that the lamp is dead, but maybe you also could have a problem in the stereo decoder (misalignment or defect).
 
Thanks everyone! You are all very friendly and extremely helpful. I've let go of the idea of messing with a different rated bulb. In fact, I'm just going to enjoy my receiver's great looks and warm sound. :music: I'll probably get a proper stereo light bulb eventually, but for now its not really that important. Maybe I'll find a new receiver in the near future to tinker with, and I can make a larger lamp order then.

For now, I'll spend my energy looking for speakers. :D

Thanks Redboy for the suggestions. I'll keep an eye out for those.

By the way, Dr. Strangelove, I've cast my vote for Pioneer, but it looks like a close race...
 
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