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Another inop SX-1250 (Sorry)

I forgot to tell you guys that there was this time I was removing one of the black screws that holds down the top deck PCB mounts. It fell down into the Driver heatsink area and when I went to retrieve it with my needle nose pliers…………… BAD! I don’t know why I didn’t mention that earlier; maybe because I wanted to forget about it. I did check the Drivers and they checked ok. Would this be why it runs on 31 volts and not the full 65? I am repairing the Stabilizer and going to unplug the amp board associated with the accident. This should verify my theory. I am pretty sure this is where the problem lies.

Thanks MTF for explaining the EQ board voltage flow. I did check on your advice and all checked good. I was removing the screw to repair the Stabilizer board for the first problem and may of made a second problem out of it. Anyway live and learn! :thmbsp:

I can’t get to it until tomorrow, got family in town. That hard winter in the East is bringing them out in droves. :dunno:
 
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I can’t get to it until tomorrow, got family in town. That hard winter in the East is bringing them out in droves.

Can I make reservations to come next, In my area we got 76" + snow fall with out a thaw and when it gets above 10 degrees it feels like a heat wave .I will tell old women to start packing.
 
My backyard has looked like this for months, I'm sick of it, my poor dogs are getting buried every time they need to go outside.
 

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tsd71 said:
My backyard has looked like this for months, I'm sick of it, my poor dogs are getting buried every time they need to go outside.
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My brother's samoyd mix would LOVE that and go absolutely NUTS!!
 
I bet you just figured it out on your own there. That is almost the same as my last problem with mine where I touched the wrong pin while testing and wiped out a transistor and a diode on one board. You helped me to identify where. Mine is good now. Hope yours is cranking soon. Down here where "winter" might get down to 50f at night one of these can light up a room with the dial lamps and keep it warm too.

zebulon1 said:
I forgot to tell you guys that there was this time I was removing one of the black screws that holds down the top deck PCB mounts. It fell down into the Driver heatsink area and when I went to retrieve it with my needle nose pliers…………… BAD! I don’t know why I didn’t mention that earlier; maybe because I wanted to forget about it. I did check the Drivers and they checked ok. Would this be why it runs on 31 volts and not the full 65? I am repairing the Stabilizer and going to unplug the amp board associated with the accident. This should verify my theory. I am pretty sure this is where the problem lies.

Thanks MTF for explaining the EQ board voltage flow. I did check on your advice and all checked good. I was removing the screw to repair the Stabilizer board for the first problem and may of made a second problem out of it. Anyway live and learn! :thmbsp:

I can’t get to it until tomorrow, got family in town. That hard winter in the East is bringing them out in droves. :dunno:
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Its still in a heap! I am taking a break and fixing other things trying to build my confidence back!! :D
 
I have been back working on this beast, with the EQ board regulator issue.
I scoured the board again and again………………..and again. After the one hundredth look see, I found Q6 installed incorrectly. Now, Q6 is the (-) 47 volt side. My troubles are with the (+) 47 volt side. I did check the flat amp per MTF’s advice and nothing was out of place.

Recap of the issue:
All was working great! The set had played for a week straight. One last board to complete; the EQ board. Replaced all caps and transistors with Matts list from 2013.
On power up I lost all the (+) 65 volt regulated supply. It was reading (+) 5 volts.
I pulled Q11 and Q12 on the EQ board to isolate the (+) 65 supplies and repaired the Stabilizer Board. The (+) 65 was good and rock solid. So I suspected the EQ for sure.
I replaced Q11 and Q12 on the EQ with Marks updated list from 08/2013 attached to Matts original 1250 Thread.
Powered up and the (+) 65 regulated was running at (+) 31 volts. Set was in protection (No relay).

Today, checked all the resistors associated with the EQ (+) 47 volt regulator, checked D5 (good, but replaced), checked Q11 and Q12 and they checked good. Performed a good visual inspection and found Q6 installed incorrectly. Checked all components for proper connections per the schematic and compared all components to Matts pictures posted on his inspirational Thread (That’s how I found Q6 backwards) Arf.

Would Q6 (on the EQ board) installed incorrectly cause my problem? My wee brain says no. It would cause one channel to not operate. I think. Would you guys look and see what you think?

What really stinks about this problem is that every time I try to power up after a possible fix, I end up back in the Stabilizer Board again. It’s getting expensive! I am not going to repeat this any more, I hope!! :sigh:

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With Q6 on the EQ board in bass-ackward, it may have pulled down the -65V supply. That would affect everything using that source. Both AWH-048s would be affected.
 
Thanks Watthour! I'm working on it as we speak. I would like to have her up and running today.
 
Hey! I got it fixed! It was Q6. I am back in business. Closing it up and will post pictures soon.
Thanks again, Watthour!
 
Done! :banana:

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Thanks, MTF, Larry, Watthour, rcs16, Kahoona, tsd71, Kutzlertrans, craxx6969, sawdust, CapZark, AJD1964, slow-jazz and Mattsd for the great Thread to use as referance!!!!!!!!
 
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Glorious job, man.

Currently having Mattsd restore my abused 1250, and I cannot decide if I want to keep the 6 volt bulbs a friend put in for me, new all around, or go with Mattsd's suggestion of all LED's. I REALLY like the look of those old bulbs. Anyway, very very nice job. It looks amazing.
 
onwardjames; Whatever you decide, you will like it. It is one of the greatest Receivers!
 
Looks absolutely amazing. That newly veneered case really sets it off too. I like the color of the original type bulbs in it too. I am sure that it would be possible to get the same temperature of light with a LED and enough research but it is so easy to just get a full set of originals from Dave and they will probably last forever anyway. Have fun and thanks for the help you gave me on mine.
Rob
 
I replaced all the lamps with an order from Dave and if you remember the housings for the function lamps were toasted. A guy on ebay was selling something (I cant remember what it was) but he indicated that he was beginning to part-out a 1250. So I got the whole front face and dial assembly which solved two issues. The scratched up face and the lamp housings, Sweet!

The veneering I did to the wood cover was the first attempt it that procedure. I think Larry was the member that had posted a link for the supplier. The cover is my favorite part of this set. For many years I have wanted to try veneering and this was the perfect opportunity. It wasn't that expensive or difficult and I have enough material to do ten more sets! Anyone need veneering supplies!!

Thanks, Rob!
 
zebulon1 said:
Hey! I got it fixed! It was Q6. I am back in business. Closing it up and will post pictures soon.
Thanks again, Watthour!
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Good for you, I've done the same thing, now I check my leg placements twice before moving on. Looks good and sure it sounds good too. I listen to both of mine daily.
 
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