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Pioneer SX-1250

xXColdShotXx said:
the pre-amp works like a charm by itself, only acts up when the jumpers are in and only on the left channel. i have it's jumpers out and am using the pre-amp section of it with my yamaha power amp and it rocks. i can't wait to get it to where i don't have to worry about it tearing up at any time. is there any way you could post a bom re-build list of AWH-048, mark? i think i'd be better off to replace every transistor on AWM-091 instead of just 3.

are there any way to drill a real small hole in the volume pot to get deoxit in better instead of taking it off the board?
Click to expand...

it is already listed in several places, I will look for them before monday daylight, and check for obsoleted or oos parts. If you find them first and post a copy here, I will get to it a bit quicker... KingBubba's thread??

Clean the bare wire jumpers and the RCA sockets on the back panel, because that sounds suspiciously like a bad connection - problems should be tripping the protection, and problems IN the amp circuitry will continue even if the jumpers are pulled.

did you clean the amplifier card pin connectors?

what happens when you run a signal IN to the amplifier inputs from ANOTHER signal source (with a volume control :yikes: )

you can also take a pair of cables and run the left pre-out into the right amp in and the right pre-out into the left amp in and see if the symptoms change places. As well as running the left pre-out into the left amp in and the right pre-out into the right amp in to see if the bare jumpers are doing something unexpected and unusual to you..

I had some terrible commotion once with a receiver as I moved it around on the bench, some grounded metal was hitting the bare surface of those metal jumper loops. - ouch - my ears -
 
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i hooked a lil speaker up to the 1250 without pre-amp/ amp in jumpers and it's almost like before i re-built AWR-106 board, quiet on right channel, scratchy with a lil cracking on left channel, but it is constant now and i was wrong about it sounding like the volume was turned all the way up. before i re-built AWR-106 the scratchy, cracking and popping would come and go.

i cleaned everything on the back with the tubes of deoxit first and gold last, even the jumper pins, which looks a lot better now. just wish there was a way to clean the volume easier.
 
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Ok, LAST experiment.... turn off the unit, and dial the idle current adjustment for that amp channel down to zero, and see if the crackling continues. When it does, then we (you) have some work to do on the amplifier card(s).

Before ordering components, we will have to do some tests on the board to be sure there are no burned out resistors that we will have to order at the same time.

The volume control is VERY deceptive - almost certainly it is a multi-position low rotation force SWITCH, with GOLD PLATED contacts!! It will probably be constructed of ceramic plates with thick film printed resistors that were laser trimmed to the correct value, and drilling into it is exactly the wrong thing to do.

The volume control is the same on the 1050 and the 1250, and while I have a 1050 on the shelf for parts or repair, and I have worked on others, the volume controls I have worked on have never needed that level of intervention and I currently don't have the time to tear open the parts/repair unit just to check the internal details of the volume control for this warning. It's physical size alone indicates that is the case.
 
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xXColdShotXx said:
do you usually clean the volume control good from the back with the label on it peeled off some?
Click to expand...


It's sealed, and I don't remember any holes under that label. The lablel/hole thing is on a much smaller alps pot. And on THAT pot the deoxit won't get through to the other layers (either).

IF you find a hole UNDER the label use it even though gold doesn't corrode. But with a hole and the construction I remember, the sections are almost completely sealed from each other. Deoxit won't penetrate through in any useful quantities.

You seem to be obsessing on that volume control.

PROVE the volume control is at fault before risking a rare, irreplacable and expensive coponent.

I feel like you pushing me to open up that 1050 to positively check that volume control- it won't happen.
 
not trying to push you at all, just trying to find out all the info i can on that volume control though. the reason i am obsessing is the first few notches from minimum volume to about 1/4 volume is staticky and if i put pressure on the pot pushing from loudness switch side to the -20db switch the static disappears when rotating the control, turn it normally and the static is back.

was there 2 different pots used in the 1250? I'm not gonna drill into it, but may take it off the board and figure out a way to get some deoxit and faderlube in there.
 
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xXColdShotXx said:
not trying to push you at all, just trying to find out all the info i can on that volume control though. the reason i am obsessing is the first few notches from minimum volume to about 1/4 volume is staticky and if i put pressure on the pot pushing from loudness switch side to the -20db switch the static disappears when rotating the control, turn it normally and the static is back.

was there 2 different pots used in the 1250? I'm not gonna drill into it, but may take it off the board and figure out a way to get some deoxit and faderlube in there.
Click to expand...


OK, that qualifies. You need small screwdrivers for the hardware holding it together.

But first just try rotating it through the range a bunch of times.

BUT I have found staked parts ** inside these that only allow a little bit of opening - but should be enough for squirting in stuff.

Take pictures!!

(** staked parts - parts with tight clearances, where the metal is deliberately deformed to lock the parts together - might see "notches" near the sides on the end of a shaft etc... these don't want to come apart because reassembly may never work...)
 
well, got the volume lined out, unsoldered it, took apart as far as i could and sprayed dn5 in everywhere i could, put back together and it's static free, but the scratch and crack is still in left channel using it's own power amp section, as a pre-amp it is static free. my camera batteries are dead or i would've taken pics of the little project. next time i do something i'll make sure the camera is ready to go. just so you know, got my weller iron in a few days ago, iron combined with the solder sucker is the way to go. my soldering has improved. thanks a lot, mark.
 
i am just going to re-build both AWH-048 and AWM-091 and get new output transistors. should i take the output transistors out and test them before i order new ones?
 
xXColdShotXx said:
i am just going to re-build both AWH-048 and AWM-091 and get new output transistors. should i take the output transistors out and test them before i order new ones?
Click to expand...

Yes that would be good, but replacing them if all are good might be over kill. Either way, you will need replacement white goop, and be sure when replacing them to use new mica insulators and that there are no shorts to the heat sinks. Also on the sockets there are alignment bumps that fit into spots on the heat sink, and the sockets will be damaged if tightened when they are not inserted.

You will still need to measure the resistors on the boards for damage.

Do you want to work up the list and post it for checking (faster) or have me find it?
 
i will work up what i can and check the availability on mouser, and if you don't mind to find what i can't, that'll be greatly appreciated. i forgot i already downloaded kingbubba's lists. i will use what i can from them.
 
I posted this on an earlier thread, but have edited it some.

UNTIL THIS LINE HAS BEEN REMOVED, I AM NOT YET DONE EDITING THIS POST FOR CORRECT INFORMATION, THUS SOME OF THIS IS EITHER INAPPROPRIATE OR INCORRECT. Prices and availability are definitely old.

Mouser parts numbers, a mix of Fairchild (512-) and ON-Semi (863-)

differential inputs,
2sa750 to-92 ecb 50v .05a .25w 100mhz hfe:450
2x 512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea

bias / vas
2sa858/2sc1439 to-92 ecb 150v 0.5a .5w 100mhz hfe:150
old:
512-KSA1013YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17
512-KSC2383YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17
or
512-KSA1381es x to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe $0.27 ea
512-KSC3503estu to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe $0.28 ea



pre-driver
2sa899/2sc1904 to-126 ecb 150v .05a 1w 100mhz hfe:150
512-KSA1220AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.39 (R=60-120, O=100/200, Y=160/320)
512-KSC2690AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.40
or:
512-KSA1381es x to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe $0.27 ea
512-KSC3503estu to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe $0.28 ea

-------------


drivers
2sb630/2sd610 to-220 bce 200v 2a 25w 4mhz hfe:80
512-KSA940TU_Q pnp to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54


power outputs
2sb600/2sd555 to-3 200v 10a 200w 14mhz hfe:70
4x 863-MJ21194G to-3 NPN 250v 16A 250W 4mhz 8-75hfe $4.10
4x 863-MJ21193G to-3 PNP 250v 16A 250W 4mhz 8-75hfe $4.10

overcurrent detector
2sc869 to-92 npn bce 50v 30mA .2w 150mhz hfe:35
2x 512-KSC2310OTA to-92 ecb 150v .05a .8w 100mhz 40-240hfe $0.11 ea



here's the insulators and thermal grease:
ten: 534-4662 to-3 mica insulators $0.16 each (two spares)
six: 534-4672 to-220 mica insulators $0.12 each
one: 532-249 1 oz thermal compound $4.71

two VR2 500 ohms single turn bias pot 652-3386H-1-501LF $1.60 ea
two VR1 500 ohms 12 turn offset pot 652-3266P-1-501LF $2.94 ea



as for the capacitors:
two C11 0.22uf 50v 598-DSF050J224 $0.52 ea CDE Metallized Polyp
substitute: 0.22uf 100v ecq 667-ECQ-V1224JM $0.35
four C15 C16 470uF/80v 647-UPW2A471MHD @ 1.92 ea nichicon pw - power filter substitute: 647-UHE2A471MHD6
two C2 10/16 647-UPW1C100MDD @ $0.13 ea nichicon upw - offset smoothing
two C5 220/16 647-UPW1C221MPD @ $0.28 ea nichicon upw - feedback integrator

Plus I am going to look at the diodes, at $0.10 each, what the heck..
eight: 512-UF4004 $0.12 d6, d7, d10 & d11
four: 1s2471 512-1N4454 $0.03 d8, d9
two: 1s2473 512-1N4148 $0.03 D5
four: 1s1886 200v 1A, 512-UF4004 D3,D4


protection circuits...
one: Q4, 512-KSD1616GBU to-92 ecb 50v 1a 0.75w 160mhz 135-400hfe $0.10 current dump transistor
relay driver transistor and voltage regulator
two: Q5, Q6 (2sc1166 50v, .2a .6w) 512-KSC2690AOS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.38
one: C4 100uf/16v (100/35) 647-UPW1V101MPD $0.26 protection circuit timing capacitor
one: C3 4.7uf/25v (4.7/50) 647-UPW1H4R7MDD $0.14 protection circuit ac power on signal integrator
two: C5,C6 100uf/50v (100/50) 647-UPW1H101MPD $0.28 protection circuit voltage regualtor
two: C1,C2 470uf/6v (470/6) 647-UPW0J471MPD $0.23 protection audio input caps
 
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yes, that is one awh-048 board and one awm-091 board.

it has been so long that the stock checks/adjustments I did are useless, so you WILL be coming back saying "this is out of stock and what are the alternates", and I will be repeating some if not most of the work I did.
 
Internet search. Google "Pioneer SX-1250 restoration Audiokarma" and you will find the most comprehensive one available by Matt updated in 2014.
 
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