Pioneer sx 434 grainy sound ?

D

dadix

Member
Hello .I bought an receiver sx 434 a few days ago but it seems to me that it has a grainy sound. Is this sound Pioneer's sound or is something not working well?
 
dadix said:
Hello .I bought an receiver sx 434 a few days ago but it seems to me that it has a grainy sound. Is this sound Pioneer's sound or is something not working well?
Click to expand...

Problem not the sound you should expect.

Does it have the same sound for AM , FM or anything hooked to it like a turntable?
 
It's 40+ years old and untouched, can't say I'm surprised. If it biases and visually looks fine, that's probably how it sounds.
It has known noisy transistors in it.
 
I've had my 434 from new. Never sounded "Grainy". It did start sounding tired and less articulate about 7 years ago. A transistor replacement of trouble prones in the whole thing, plus capacitors (electrolytics) brought it back to it's normal self. I use it with a pair of Minimus 7's in my RV trailer (it beats the factory installed JVC BPC every which way but loose!) now. There are a few 434 rebuild threads on here, and if I'm not mistaken a recap/transistor parts list thread. It's 45 years old, it's tired, and more than likely needs an overhaul. If you have the opportunity to compare it with a SX-535 or 636 do so. They sound basically the same, just with more wattage. Check the FUSES in the back (inside the rectangular plastic housing) 1st. 250V 3A AGC fuses (fast blow!) These can be gotten at Home Depot or Lowes.

Service Manual and Schematic HERE. If it's a US (Single Voltage)model it should have a sticker on the back panel with "KCU" on the Back. Get the correct schematic to match. https://www.hifiengine.com/manual_library/pioneer/sx-434.shtml

Parts list here.
Transistors part list only. http://audiokarma.org/forums/index.php?threads/pioneer-sx-434-noise-on-both-channels.811021
Full parts list by Avionic(EDIT: Actually TWO.DOGS) from 2016. http://audiokarma.org/forums/index.php?threads/pioneer-sx-434-cap-list-map.736342/#post-9981580

I honestly would bump the voltage of the Main Filter caps to 35V as the originals are 25V and the working voltage when new was 24V, and bound to be a little more now with higher voltages. 647-UHE1V332MHD6 is 3300uf 35V in Nichicon with 10000 hour rating, and a little cheaper than the closest comparable Panasonic.
 
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I realy like the sound of this and now I am looking for an 737 . Is it sound of 737 different than 434 ? More open or cleaner, warmer or better stereo separation or sound stage?
 
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The 737 is more detailed if you want to call it that. Better Tuner, mpx, amps, more options for accessory gear. Think of the 434 as a 6cyl 66' Chevy II, and the 737 as a 66 4bbl small block V-8 Malibu with AC. The 1010 as a 66 or 67 Impala SS with the Big Block 427.

Basically the whole series sounds similar across the board, with more controls, power and headroom in each succesive model. Features per dollar,(bang for the buck) the 737 is the sweet spot for the x3x series.
 
I have a Pioneer SX-434 and it makes a thumping noise in the speakers..its like thumping your foot, happens continuously no matter what selection I'm on..what would cause this?
 
Let's rule out the obvious Easy stuff 1st
Do you have LOUDNESS ON OR OFF?
How high up do you have the BASS control? VOLUME LEVEL?
Has it had ANY work done to it?
What source (Aux, Phono FM,AM) does it, one or ALL?
If you have a PHONO how close is it to your speakers?

Sounds like it's motorboating (a form of oscillation.) This can be repaired, but may take more $$ than you're prepared to spend. Ideally, It needs to be looked at by someone with an O'scope to determine where the oscillation is. But it's possible to get very close with a DVM.

How handy are you with a volt meter, and a schematic????
 
thanks for your response Larry, Loudness happens either way..bass med level..volume 0 and still here it in the speakers, usually play it no higher than 2 or 3..checked all sources does it in all, except phono, no TT at present. I've replaced many caps on the AF amp board AWK-034 and all but 1 one on P/S and none on tuner....very handy w/DVM and schematic.
 
If you have another receiver, you can use it as a signal tracer. Take a spare (cheap) RCA cable. Solder a .01uf 600v film cap on the end of the center lug of the cable. Insulate up from the exposed ground lugs on the cable to the body of the cap. The free lead on the other end of the cap is your probe.

Plug into the AUX jacks on the OTHER receiver. Turn on the 434 and check both sides of each cap, resistor, transistor for the oscillations. I'd start at the POWER SUPPLY as from what I surmise, both channels are involved. Components having oscillations on both sides are not the problem. any component with oscillation on the downstream side without oscillation on the UPStream (transformer sid of the power supply) is the problem. Finish up the power supply rebuild the 1 remaining cap, replace the transistors on the P.S.(most are undersized and heat stressed) and check all resistors (lift one leg out of circuit).


FULL POWER SUPPLY PARTS LIST. Part #'s are MOUSER. Prices as of 06JUN2019
SX-434 Power Supply Board



AWR-062: C7: 330uF 50v CEA: 647-UHE1H331MPD 330uF 50v $0.67ea

AWR-062: C8: 100uF 50v CEA: 647-UPW1H101MPD 100uF 50v $0.34ea

AWR-062: C9: 100uF 25v CEA: 647-UPW1V101MPD 100uF 35v $0.29ea

AWR-062: C10: 100uF 35v CEA: 647-UPW1H101MPD 100uF 50v $0.34ea

AWR-062: C11: 100uF 16v CEA: 647-UPW1V101MPD 100uF 35v $0.29ea

AWR-062: C12: 220uF 16v CEA: 647-UPW1E221MPD 220uF 25v $0.44ea

AWR-062: Q1: 2sc1384 : 512-KSC1845FTA $0.29ea

AWR-062: Q2 2sc945 :512-KSD1616ALTA $0.41ea

AWR-062: Q3 2sd313 : 512-KSC2690AYSTU $0.42ea

AWR-062 D6 WZ-140 : 512-1N5244B $0.13ea

$3.62 ttl parts. Do the $4.99 shipping and you're under $10.00 after taxes.
 
THANKS LARRY, HAVE ORDERED THE COMPONENTS FROM MOUSER, WILL ADVISE WHEN I FINISH...WOULD YOU REPLACE THE CAPS ON THE TUNER BOARD?..I'M THINKING OF DOING IT AS WELL..
 
understand...the tuner is fading in and out and takes a few seconds to come up when powered on...the aux starts right up!
 
Avionic; My mistake. I saw the avatar of the Eagle and it was Automatic. Sorry about that.

Larry
 
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