SX 1010 Blowing fuses

[TigMan]

Hello all,
I recently acquired a Pioneer SX 1010, guy told me he had it stored in a shed for 10 years but it worked when he put it away. He didn't want to plug it in nor did i without cleaning her out first. I bought it, I cleaned the inside with air, and found one blown capacitor right under the hood on the protection board. Swapped it out. Fires up and I have power and all working bulbs light up, that's it. No needles swing, no static or noise, the relay is not clicking. Digging in further, I realized the fuse board in the bottom has 6 glass fuses. 2-3A, and 4-1A. The first two 1amp fuses blow as soon as I give her power. Haven't done much besides look for burnt and blown things at this point, hoping this sticks out like a shore thumb to somebody... any ideas?? Thanks!

 

[rcs16]

A few ways to approach such hard faults. Have to figure out if it a power supply issue or a load on the power supply is causing the fault. You can measure the resistance on each PS output to determine what those are. You can isolate the power supply from the loads to determine if it is a PS or a fault in the loads. You can with power off measure, use your DMM in resistance/diode modes to check the components on the PS to determine if you have faulty transistors, diodes, resistors, ecaps.
Check out this thread, great information for you
http://audiokarma.org/forums/index.php?threads/pioneer-sx1010-repair-diodes.849563/

 

[markthefixer]

Which cap on the protection board? There really aren't any exposed to powerful enough circuits to "blow" them.

It's blown status throws into doubt the seller's claims.

Plus, what do you mean by "blown" ? (it's important!!)

Those 2 fuses supply the +/- 56v regulated power supply.

Major loads can be isolated at the power supply by disconnecting R11, R12, and R21, ALL 10 ohms.

Fuses that blow can have appropriate value resistors substituted for them, to feed some energy into the circuit, to look for caps that are not charging etc....
I'm ball parking about 100 ohms in place of a 1 amp fuse, but if it's a solid short, it could burn them up.
There's not a lot in those circuits that can suck down that much current, C8 & C9...

Frankly I would pull the 3 resistors and risk 2 10 ohm resistors in the fuse positions -
BUT with a BAD short those fuse substitute 10 ohm 1/4 watt resistors would be toast.

in the same vein of thoiught, frankly R11, R12 or R21 would be toast quickly if something were shorted off the regulated rails,
so either a shorted bridge diode (D1, D2, D3, D4) or shorted C8 or C9 is my considered guess.

 

[zebulon1]

D1 thru D4:
512-1n4004

 

[TigMan]

Hey guys, thanks so much. That gives me some ideas how to start. This is all new stuff to me so I appreciate the help. I got my boards mixed up. My "blown" capacitor was in fact on board AWM039 the muting circuit board. It was cap# C2. What happened was the positive leg was disconnected. I unsoldered to discover the leg piece looks like it was kind of fried out and cap was burned opened where the leg used to be. It appears to have been that way for a long time. It looked fine from the top though. And yup, I do believe this guy knew a bit more than he told me.

 

[markthefixer]

Being new to the process, it may behoove you to just replace d1-d4 and c8, c9.

C8, C9 just on general old cap principles, d1-d4 as an inexpensive silicon upgrade.
It would still be a good idea even if nothing changes (unlikely).

 

[verate]

I should add that one channel on the receiver has had R29-R32 replaced and I will have to look again, as I'm decently sure they are not the correct value. The protection circuit has also had some substitutions to it I.E. a UO7 in place of a 2sc1384 and a a984in place of a 2sa733.

 

[TigMan]

Perfect guys, I'll make a little shopping list and see if I can get my brother in law who just chimed in there, to show me a few things with the multimeter. At the very least I'll get into swapping some parts by the weekend and get back to you. Thanks again!

 

[TigMan]

SOMETHING HAPPENED! I hope it's in the right direction, but is my highlight of the week. Okay, I switched out R11, R12, R21, C8, C9, D1, D2, D3, D4. I stabbed myself with a dental pick, learned how to read resistors, broke off one of the spiral twisted wires, soldered it back on, learned how to read diodes with the multimeter, have two capacitors that I thought were fine and were double the voltage but are too tall to clear the floor plate, but now have a stereo sitting upside down on my bench with no floorplate that turns ON WITHOUT blowing the two fuses!! Other than that the differences are: Now the lights only work on the dim setting when I hit the dimmer button, they used to work in both positions. I now have tuning needle that jumps to one position while in FM then another position while in AM, other than that it sits idle, it used to sit idle always. I get no fluctuation as I cruise the dial. I still hear no relay and no static or noise through any settings. Thanks for your time guys! My fingers are crossed.

 

[zebulon1]

I'm proud of you. I can see your smile from here.
Now:
Build a DBT (Dim Bulb Tester) and learn it's use.
Check all your power supply pins for voltages and report.
If pin 8 is over 13v's shut it down and recheck your work.
Pin 6 is the supply for the lighting.
Build the DBT first if you already haven't.

 

[Fairlane]

The power supply board on these bakes everything on it, sadly a major flaw with these beauties.

The last one I had the board for the power supply was cracked from being pushed in and one of the large caps on it had vented but looked fine while still installed on the board.

Once I ran some jumpers to remedy the broken traces I still had nothing, no click or sound but everything else worked and lit up etc. Power supply caps were the issue in my case, the one in particular.
They would be my first suspect with a 1010.

Good luck. They are a lovely receiver when working visually and sonically.

 

[TigMan]

Hey guys, I've done a few things and still nothing jumping out. Decided to go ahead and recap all electrolytic capacitors on the power supply board. Using a dim bulb tester now. Power up is the same result as my latest, of not blowing fuses but no relay coming on, my DBT does dim down and stays that way. Checking voltages on the board-a snowstorm took my power out just now- but these were the ones I got locked in first:
Pin 1= 14.1mV
Pin2= 16.8mV
Pin6= 4.47 V
Pin8= 12.56V
Pin7= 0 V
Thanks for any help, I am lost, I don't even know where to throw parts if all I did was throw parts at this thing. I did enjoy the hell out of recapping that board though. Any direction, or thing to check, or flake of hope is much appreciated, thank you guys.

 

[verate]

I'm curious to see what the voltages on pins 13,14,15 are, if they don't get your power back in the next couple days you ought to bring it up and we will check it here.