Help with my "new" Pioneer SX 1250!!!!!!!!!!!!!!! - diyAudio
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Old 3rd October 2005, 05:19 PM   #1
next61 is offline next61  United States
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Question Help with my "new" Pioneer SX 1250!!!!!!!!!!!!!!!

Hello everyone, I'm new to this forum and I have a big request.... a 65lb request I should say:
I inherited this awesome receiver from my neighbor that had it into his garage and still plays. Knowing that is about 30 yrs old should I change the beer can caps? What mods I can do on this monster? I was thinking about a small fan (this thing heats up the wall behind it); are there any of you that can give me some detailed info? The caps are 22000mF/80v.... my Radio Shack does not have them ;-) Should I go with 80v or more?
I tried to find a thread about sx-1250 but not too much info though.... can anybody help me?
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Old 3rd October 2005, 06:30 PM   #2
anatech is offline anatech  Canada
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Hi,
Firstly, Radio Shack is unlikely to have anything of interest to you. They do not stock good parts. They work in a pinch if they have what you need.

The smaller caps are more of a concern and it sounds like your bias current is high, or it's oscillating. The large filter caps can wait unless they are defective, they have to be tested.

What equipment ('scope, meter ... ) do you have and how much experience do you have?

-Chris
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Old 3rd October 2005, 06:35 PM   #3
next61 is offline next61  United States
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I have a chepo BK 2704 multimeter and 20 yrs ago I was doing bench testing of circuit boards in Eastern Europe.... totaly different field of work here!
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Old 3rd October 2005, 06:59 PM   #4
anatech is offline anatech  Canada
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I was hoping you had an oscilloscope. Extremely handy when working on amplifiers.

If you look at the rectified DC across the main caps, you see a ripple waveform. If there are good size spikes on the leading edge - or worse, the caps are bad.

At the amplifier outputs you may see an RF waveform. Oscillation. We need those answers from you.

-Chris
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Old 3rd October 2005, 07:46 PM   #5
hongrn is offline hongrn  United States
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I was recently given a SX-1250 also. I took the whole thing apart mainly for parts, and found out that 2 of the large 4 main caps were leaking at the bottom. The volume knob has a good Alps pot. The transformer is gigantic.

Hong
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Old 3rd October 2005, 08:06 PM   #6
next61 is offline next61  United States
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I'm in Fullerton (close to Placentia)....... No, I don't have a scope; I wish I had a TTronix 465B, my favorite. In any case, do you guys have any advice for upgrades or at least what parts should I replace if I want to upgrade this monster (I might put my hands on a scope this weekend). Man, I love that silver face!
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Old 3rd October 2005, 08:10 PM   #7
anatech is offline anatech  Canada
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Wait until you have some answers. Let's find out what the problems are before you begin.

I normally find the regulator board electrolytics are bad, as well as some times some of the transistors. Coupling caps throughout the unit are suspect (electrolytic). This stuff will return the unit to maybe a little better than new. The new parts are a bit better.

-Chris
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Old 3rd October 2005, 08:25 PM   #8
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Default Next61, never fear when Charlie is here!

Here is the link to download your Power Supply, Protection Circuit and Power Amplifier...the PDF size is 1.1Megabytes.

Having problem, ask me and i will gladly upload it to your adress, just inform your adress in your thread....this one!

My adress is:

nanabrother@yahoo.com

The link to download the PDF abouth SX1250 is this one:

http://schforfree.seedhost.com/archi...er_Section.pdf

When you click in this link...have some patience, as 1.1 Megabytes use to delay a little to appear something...but will appear, i am sure...link was checked.

In advance, your amplifier is very nice and work with 70 volts positive and 70 volts negative for power amplifier.

There are also a series stabilized electronic power supply to provide 65 positive and 65 negative, to power amplifier input circuit, also plus 25 and negative 25 to protection circuit, also 13.5 and 5.4 for auxiliary circuits and panel lamps.

This amplifier, if works in class AB..... will produce more than 300 watts over 4 ohms.....maybe 400 watts!...what a beast!

You may need or not to replace your electrolitic condensers.... first connect your amplifier iddle, without sound, in series with a 100 watts lamps.... to reduce the voltage to amplifier...and let electrolitic condenser he happy, receiving dancing electrons for some time....observe if your condensers are warm or if have leakage..... if not..hehe.... let it working with full voltage...the correct voltage for it...iddle and for 1 hour.... than measure if you have around plus and negative 70 volts...with 10 percent maximum error...if oK...go ahead to burn all speaker you have in your home...ahahahah!

Hi Anatech.... good to see you active here!

Be happy, the 1250 owner,...as your speakers will be not!

regards,

Carlos
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Old 3rd October 2005, 09:02 PM   #9
next61 is offline next61  United States
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Thank you Carlos, I'm downloading as I write this message..... The image that you attached is it for the amp? My mail addres is: next61@yahoo.com
Again, thank you!
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Old 3rd October 2005, 10:04 PM   #10
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Default Everything you need...just call me.

If i had possibility to help..i will do it.

regards,

Carlos
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