Pioneer SX-1250 AWR-106 part C7 Orientation?

Noonan

Noonan

Member
Hello All,
I have started the process of removing old caps from my sx-1250 stabilizer board (AWR-106) and found that capacitor C7 was placed in polar reverse compared to both the board printing and the schematic (image below). Sorry, I wish I could figure out how to put a simple circle around components so they are easier to see on pictures. I've looked at a ton of photos of other folks boards and no one has that cap in the orientation I found. While there are a TON of issues with someone butchering this board before me, this cap appears to be original. Anyone seen this before? Is it possible this revision of the board (AWR-106A IXK) had a different layout?
I should mention that I have never had the unit working. I do know that resistors R3 & R4 on the power supply board (AWR-107) are blown so perhaps this cap was placed incorrectly and caused the resistor failures?
If anyone has heard of C7 being reversed from schematic I'd love to hear from you.
Many thanks.

SX1250_Stabilizer_before.JPG
 
Yes it is backwards, see one of my reference pics attached.

121.jpg
 
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Check where the C11 plus is at, it's the same trace. Bass assward it looks.

C7 smooths the VR1 voltage adjust pot action.

That is a 106a board, I have a 106a board I just looked at, that I rebuilt long ago. It is correctly rebuilt - I will have to look closer to be sure about the markings.
 
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Thx MTF. I will certainly look closely at that trace to make sure the orientation of the replacement is correct.
 
C11 looks fine on your picture, C7 is installed incorrectly. Factory does make mistakes once in awhile.
 
Thx tsd71. I'm guessing a factory error is what happened our perhaps the 'tech' that was here before me took it out and put it back incorrectly.
I've attached a pic (not very good) of the back side of the board as I found it (and a close up) and another part way through cleaning it up. As you can see, terrible solder joints and many destroyed solder pads which i have started repairing
 

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The before is a classic example of too hot of an iron - like a wood burning iron. It oxidizes (burns!!) the pad and solder then lifts the pad. The oxidation makes it impossible to get solder adhesion. You can do the same thing soldering copper plumbing, after which you have to start over - no amount of flux will penetrate the oxidation.

hint - besides using a soldering tip cleaner (brass wool, steel wool) I keep an open container of flux that I use as a tip cleaner, dipping the tip in just before going to the pad. THAT is what allows me to get the heat into the joint, solder it and get off the joint so very quickly - IF you have to hold the iron to the joint more than a second for the joint to heat up to molten state and allow more solder to be fed in and melted, back off and check your tip.
 
lots o very bad solders, that board bakes so if your iron is too hot those pads come up easily, I use hook up wire to fix those issues when there is no pad at all.
 
I've now gone through and cleaned the whole board up. I have chosen to scrape back a little of the green trace covering and create new 'solder pads'. I'll let you know how it works out. Thx for all the advise.
 
So, I found something that I hadn't seen before. After finishing the restore of the power supply, stabilizer and protection boards (as per mattsd's amazing list), I still couldn't get the protection relay to fire (I have disconnected the power amp boards completely). I've measure all the correct voltages, etc and was really scratching my head. The only item I hadn't replaced (Mouser was out of stock) was the protection relay itself. I took it off the board for a good inspection and below is what I found. Someone had glued a piece of felt inside the relay to lock it in the 'ON' position! What kind of animal does such a thing?! The previous owner assured me that no work had ever been done on the unit except for lamps being replaced. I haven't found an unmolested board yet! Going to keep going through it with a fine tooth comb.

IMG_9422.JPG IMG_9421.JPG
 
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Hi rcs16, I am that guy! With your help, I've been enjoying my Spec 4 & Spec 1 since finishing the restore last year. Both sound great and I don't see parting with them anytime soon but this SX-1250 fell in my lap and I'm enjoying working on it.
Sadly (luckily?), I'm a mac guy so I'll just have to sit down and figure it out on Photoshop or something similar. Thx.
 
Sorry, I can't help you with MacOS. You are fortunate to have some of Pioneers finest machines, enjoy. I like to hear your listening comparisons of the spec stuff vs the 1250 once you are up and running.
Cheers
Rick
 
Just an update as promised, I put in the new relay and bingo! 4 seconds after applying power the protection relay kicks in! I've restored the left channel power amp and now moving on to the right. Hopefully that will get that done this weekend. If all goes well, I'll start in on the equalizer, flat amp, etc.
 
Are you using a dim bulb tester when you power up each time? I use a 100 watt bulb.Especially when you are replacing parts its kinda necessary
 
Yes, I absolutely use a DBT when trying a reworked board the first time. Has saved me a few times! Thx.
 
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