Another Pioneer SX-1010 with blown fuses

TMaster

Transistors for teeth? They do have roots...
I picked up a very clean inside, and nothing burnt SX-1010 for a pretty good price to restore. The main fuse had a 30A in there, and the idiot fuse was blown. Thanks to Pioneer for putting the backup fuse in there! Anyways, after replacing those the DBT is showing super bright. I am in process of checking everything and I am testing the output transistors currently (left in circuit). Should I be taking all the output and driver transistors out of circuit to test? I have been getting voltage going through on every transistor with the diode function tests for (emitter to collector/ collector to emitter when it's supposed to be OL). Otherwise the other tests everything has tested good from what I have checked so far. I still need to check the smaller transistors. None have shorted continuity between the pins like I have found in the past on other receivers with blown transistors. I'm trying to save having to remove everything if it's still good! LOL.

PS. I am aware of all the 1010 threads and have gone though some already, especially the 30 page one. Any pointers would be appreciated :) thanks!
 
Pull the outputs one at a time and do a 6 way test on each. Mark each one as to position and part #. More than likely one or more are shorted. 6 way testing for BJT's here........ http://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/. Do this on the drivers, and replace the 2sc1451's and all ofthe 2SA725 and 726 transistors. These are the 3 transistor models that are the TOP 3 on the TOP TEN list of flaky, bad, junk transistors in PIONEERS. There are others down the line but these 3 cause the most problems. If Zebulon1 or MATTSD get on bothhave very good parts lists for the 1010. About $120.00 for all of the needed caps and transistors, Diodes, and resistors for the 1010. Start with the Power supply and ensure the voltages are all good.
 
I had a similar experience with my second 1010, got it with an oversize main fuse, but it wouldn't pull any power, internal fuse blown.

Testing revealed a complimentary pair of outputs shorted.

I replaced all output transistors as I couldn't get the new ones to match gain with old ones, seemed like a good idea anyway, then rebuilt both amp boards, put it on the DBT and it passed (and made music). I then proceeded to rebuild the entire receiver properly, it deserved it and was well worth the effort.

I believe that this list is still current: https://audiokarma.org/forums/index.php?threads/sx-1010-rebuild-bom-help.748841/ output transistors I believe are MJ21194G and MJ21193G
 
...I replaced all output transistors as I couldn't get the new ones to match gain with old ones, seemed like a good idea anyway, then rebuilt both amp boards, put it on the DBT and it passed (and made music). I then proceeded to rebuild the entire receiver properly, it deserved it and was well worth the effort.

Good man. I have a stack of units which have all been repaired to a functional/safe condition, but only a few which have been fully restored. The remaining 25 or so should be a good project for my retirement.
 
Ok thanks guys, I will pull them all. Sigh, Pioneer's wire twistyness... The output transistors are pricey now over $5 each.

So with the DBT hooked up, there is no power at all, like no lights or anything.

I will report back when i get more assessed. I have a SX-3800 and a Z8900DB I'm working on also. This Hobby is pretty addictive. :D
 

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I take it back, the lights are on just very very dim. Also the relay kicked on, at least I think it was a relay sound!
 
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I'm back, I pulled all the 8 output transistors and they all tested good with the 6 diode tests! Very Surprised and pleased. Now I just need to make sure the mica pads are ok to re-use. So, I'm guessing the short is most likely on one of the amp boards, or power supply. Must be a component failure.
 
Confusing post above. It passed the DBT test with the outputs in-circuit? If so, likely you don't need to replace all outputs, it does make it a bit more difficult to determine why the fuse was blown.

Yours is an early SX-1010, but it looks like it didn't spend a ton of hours on as the PS board is not crispy. The big red resistors need to be moved up off of the PS board (actually down).
 

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Wow. That's one of the coolest looking supply boards under a 1010 that has ever been posted here. It looks almost like new, with just a slight indication of heat over the resistors. With a few modifications as SatPoint has suggested, it's a keeper. The upgrade mods are all pretty well-documented.

As for the main fuse failure (and the "moron" safety fuse), that will require a bit of diagnosis. You may want to verify the main rectifier bridge and its filter caps are intact, then lift all the fuses on the PS board and see if the transformer voltages are correct.
 
I suppose its not good to power up without the DBT and the output transistors not in to check the PS voltages. The DBT always sucks voltage away from the PS. I was going to get a parts order going today, but now that you tell me this thing has low hours on it, maybe I don't need to rebuild these boards completely?
 
On a 1010 Power supply, Low hours/ high hours, no difference, it get HOT!!!!! (Think Equatorial region in the summer with no shade HOT!) Caps dry out, period! These P.S. are notorious for running at the ragged edge of the envelope, are upside down in the bottom of the unit with damned near nowhere for the built up heat to go. Best thing you can do for it is to rebuild the whole P.S. with the recommmended uprated parts, with some extra heatsinking on the transistors, and raising resistors OFF the board for additional cooling, and 105*C rated caps. Do it Right, Do it once. The 1010 can be a PITA, but it also has some big rewards if you rebuild it right.

Don't mess with the Wirewrap on the pins. There is enough slack in the wiring (when you open the tiewraps) to move everyboard. If you absolutely need to remove a wire, remove the pin from the board. It's soldered in. https://en.wikipedia.org/wiki/Wire_wrap
 
Thanks, ok i'll rebuild the PS board. I'm going to go with all PW's, unless some need to be different? Yes I found out last night that the wires are totally movable and the transistors had sockets holding the pins. No need to unwrap! :) I will tell you it is easier to work on this than the 3800.....

Anyone have a updated parts list for the PS?
 
AWR-054-0: C8: 470uF 80v CEA: 647-UPW2A471MHD 470uF 100v
AWR-054-0: C9: 470uF 80v CEA: 647-UPW2A471MHD 470uF 100v
AWR-054-0: C10: 100uF 63v CEA: 647-UPW2A101MHD 100uF 100v
AWR-054-0: C11: 100uF 63v CEA: 647-UPW2A101MHD 100uF 100v
AWR-054-0: C12: 100uF 35v CEA: 647-UPW1H101MPD 100uF 50v
AWR-054-0: C13: 100uF 35v CEA: 647-UPW1H101MPD 100uF 50v
AWR-054-0: C14: 47uF 50v CEA: 647-UPW1J470MPD 47uF 63v
AWR-054-0: C18: 1000uF 35v CEA: 647-UPW1H102MHD 1000uF 50v
AWR-054-0: C19: 220uF 16v CEA: 647-UPW1V221MPD6 220uF 35v
AWR-054-0: C20: 2200uF 10v CEA: 647-UPW1C222MHD 2200uF 16v
AWR-054-0: C21: 2200uF 10v CEA: 647-UPW1C222MHD 2200uF 16v

R11: 10 Ohm 1/4 watt: 660-MFS1/2DCT52R10R0 10 Ohm 1/2 watt
R12: 10 Ohm 1/4 watt: 660-MFS1/2DCT52R10R0 10 Ohm 1/2 watt
R20: 3.3 Ohm 1/4 watt: 660-MF1/2DCT52R3R32F 3.32 Ohm 1/2 watt
R21: 10 Ohm 1/4 watt: 660-MFS1/2DCT52R10R0 10 Ohm 1/2 watt

Q1: 2SD313: 863-MJE15032G
Q2: 2SC869: 512-KSC2383YTA
Q3: 2SC869: 512-KSC2383YTA
Q4: 2SB507: 863-MJE15033G
Q5: 2SA628A: 512-KSA1013YBU
Q6: 2SA628A: 512-KSA1013YBU
Q7: 2SD313: 863-MJE15032G
Q8: 2SC1384: 512-KSC2690AYS

Main filter caps, 18000uF 63v, 50mm dia x 90mm high:
 
Thanks for the list, will save me hunting! I just got done probing the PS board. Everything is ship shape. All the DC pins are showing the right voltages minus a few because of the DBT. The AC pins 1 to 5 are about 49V,49V,14V,14V,4.6V. The relay is clicking on also. So I will redo the PS board later. I need to probe the amp boards now and circuit protection board.
 
ITS WORKING! I don't what happened but its running and there is sound on both channels. I probed everything on the amp board and protection board and all the voltages were correct by the outputs pins and transistor legs. I noticed during the hour with it on and on the DBT that the brightness of the bulb was getting dimmer and down to where there is not a short. After probing for an hour with nothing showing bad, the DBT brightness in the safe zone, and the panel lights were brighter too, I decided to temporarily put back all the transistors. I unplugged the DBT and had a 5A fuse in to test. It didn't blow it. I hooked up speakers and antenna and it WORKS!!! If I was a kid, I'd be jumping up and down.

I did deoxit some of the push switches last night, because they were almost frozen and not staying pushed in. Currently there is static on the balance knob and I haven't tested everything yet, or deoixt everything. We live in a world of physics so I am just trying to figure out what resolved the problem. I do plan on rebuilding the boards in there, but wow.....!!!!!
 

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Once you've verified correct voltages then check and set the idle voltage and set bias current to 25mA.

This is my board:

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ok will set the voltages soon as i rebuild it. So you guys are not replacing the small resistors according to the part list above?
 
You may have reformed an oxide layer on a dying capacitor with all the power on/power off business.
 
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