New to the forum.. Pioneer SX-434

alsh9

New Member
Hi, sorry if this isn't being posted in the correct section of the forum...

I recently picked up a Pioneer SX-434 off eBay.

There is a bulb out to the right of the dial..

I am not very clued up on electronics... Can anyone recommend a company that could service the amp for and replace any old bulbs?

I am in the north west of England.

Or is it not a hard job to do ? (Replacing bulbs).

Ideally I would like the amp services as it will be used daily.


Thanks in advance.

Alex
 
Getting the bulbs for a 434 is fairly easy. Getting in there to replace them is a bit harder.
Get the SERVICE MANUAL HERE....http://www.hifiengine.com/manual_library/pioneer/sx-434.shtml
If you aren't registered, do so, it's free.

Open the manual to page 9. This is the "EXPLODED" Diagram.

Remove the top cover (4 screws on sides)
Pull off all the knobs.
Unbolt the two nuts on the pot shafts holding the front panel on.
Remove the two screws on the top of the front panel.
Remove the two screws on the bottom of the front panel.

Turn the TUNING KNOB Clockwise ALL THE WAY so the pointer is past 108mHz.
There is a metal strip screwed on to the top of the tuning dial face. Remove that.
I can't remember if there is a coresponding lower strip, so check for one.

CAREFULLY!! Pry the Dial face back (toward you) from the left side. There is some double sided tape holding it to the front (manufacturing use only) and it will peel away. The face will flex some but DO NOT FORCE IT. Once you are free of the tape, SLIDE the DIAL FACE to the LEFT without engaging the Tuner Dial pin.

Your lamps will be in plain sight. They are 8V .250a or .3a fuse types. I'd replace all of them, cleaning the white background as good as possible. Keep the old working lamps for spares (put them in a sandwich bag and mark them so you don't use them as fuses!!).

Assembly is reverse of teardown.
 
Ok I have managed to change the bulbs easy enough.. thanks for the help!

I have now noticed the Stereo bulb is out...What type is this and where can I get one?

Very happy with how it's looking [emoji2]
 

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It's a 6 volt 30 mA bulb. We are spoiled here in the states as Dave is the go to lamp guy. He might ship internationally. For one bulb? Its possible.
 
Put an antenna on it 1st, and 2nd tune it so the meter is CENTERED. The light if it and the HA1142 chip is working should come on.

it's a 6V 30ma wheat grain bulb with leads. This bulbs is operated from the mpx and power supply ( you have voltage on each side of the bulb. Equal voltage when off , unequal when on. The switching is done by the Multiplex Decoder.) You can disconnect the lamp, and put an ohmmeter across it to test. If you get an ohm or 3 it's good. If you get an open circuit indication, it's bad.

If the bulb is good, find a known close STRONG STATION that plays on stereo on another tuner/receiver. Then tune it in with the 434 (make sure it has at least a dipole antenna strung up on the wall as high as you can get it. ). With the bulb out of circuit you can check the voltages as you tune across the station. under ideal conditions, As you get to the center of the tuning range of each station the light will come on, and then go out as you get away from the center tune. Pin 13 on the tuner board is where you want to check the voltage change. In MONO or off station you should have 4VDC. When it switches to STEREO, the Voltage will change to 0V. And change back to 4VDC when it switches back to MONO.

If the bulb is good, then you most likely have a problem in the HA1142 chip.
 
Dave the Bulb Guy

Hi,

I bought a complete set of bulbs for the SX-636 from Dave a while back.

He has also just sent me a couple of bulbs for the SA-9800 I'm repairing and I'm in the UK.

So I think he would sell you a bulb or two for your receiver.

Great to deal with

Kind Regards

Steve


It's a 6 volt 30 mA bulb. We are spoiled here in the states as Dave is the go to lamp guy. He might ship internationally. For one bulb? Its possible.
 
I'm hoping that is just a case of the bulb needing replacing as I had strung the aerial up and tuned it to a local station ensuring the meter was centered.. and it failed to light. I will search to see if I can source a bulb locally, if not I will try Dave. Cheers fellas.
 
Another option would be to install an LED. Easy to do because the stereo lamp is on its own separate DC circuit. The voltage needs to be reduced a bit, so you can either add a resistor to one of the wires going to the lamp, or you can swap out the dropping resistor on the circuit board. The link shows how to do this - look at the four last pictures.

http://www.audiokarma.org/forums/showthread.php?t=526435

twodogs
 
Twin brother (Two Dogs) You don't by chance have an A&P?
That mod turned out sweet! Nice work. I had run across it once before and was inspired. I am in the hunt for a broken smaller Pioneer. Preferably a 626, doing the LED mod and getting a lesson on the cap coupled amp design.

Back to the Thread!!!!
 
Thanks two.dogs. not sure which route I am going to take but will update on my progress this week. Decided to spray the case of the amp black as the dark wood really didn't suit my room.. very happy with the result.
 

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