• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Another Pionner sx 1250 repair

was having a hard time getting the Strap desoldered but i got it... it toook two days of patience but i got it without damaging the traces... found a replacement on Ebay for $17.00 but im on hold until it gets here. the rectifier checked at ~450 on the DMM for both diode posts
 
Pretty hefty price for a dual diode, there were other cost effect solutions such as using 1/2 of a bridge diode or dual diodes in a TO-220 and adding a small heatsink. The dual diode approach could have made a much higher performance rectifier using fast recovery diodes, which product much less switching noise.
 
It is but it will continue in an original configuration. No modification required. An easy replacement. No fuss no Muss. I can't think of any more phases.
That's worth the extra cost.
 
i thought about replacing the whole board for 60 then i don't have to solder anything BUT that defeats the purpose of doing REAL reapair work
 
The eBay seller has the listing for two pieces. He also sells the inverse S5151's. I wonder if he would, or why doesn't sell the Rectifier as a pair?
It might be to late to see if he would sell a set instead or two of the same diode.
 
Im gonna ask that Question... im having some Paypal issues at the moment... i was wondering the same thing why not sell as a pair,,,
 
Ok... Update... I got paypal Straightened out and got the part ordered... i ordered 2 S5151R Diodes for $17.50 will be here on or before Apr. 3. Will be back then to continue the repairs...
 
Put it back together leaving the amps disconnected.
Power up on the DBT and measure the voltages at the terminals on the large caps.
The only issue might be the AC voltage from the transformer but I think you checked that.
I should work but be on your toes.
 
@zebulon1 After re installing the diode, i powered up on DBT and 1 cap still gets Hot... the new cap in the same position as the one that blew...

here are the voltage readings
with unit standing on its rear
looking at caps terminals
Top Left - +47.3VDC
Bottom Left - +43.6VDC
Top Right (Hot Cap) - -40.4VDC
Bottom Right - +43.5

Also tested voltages on board 106
Pin 1 - -39.2
Pin2 - +39.2
Pin3 - GND
Pin 4 - +0.4
Pin 5 - +0.4
Pin 6 - +49.0
Pin 7 - +13.0
Pin 8 - +13.1
Pin 9 - +4.6
Pin 10 - +23
Pin 11 - 50.2
Pin 12 - GND
Pin 13 - -50.9
Pin 14 - -23.2
Pin 15 - -52.7
 
Joe,
This predicament is some fault of mine.
The diode you replaced is located on the Stabilizer board (AWR-106) correct?
I didn't want to get the 1250 I ave here out but this deal made it happen.
That circuit is a simple one. It powers the outputs. That's all it does.
Well the one thing I couldn't remember is how the wiring is connected.
The point I'm trying to get to:
There must be an output shorted on that right side.
Did you look at the right amp board for any visual clues? A damaged driver stage could of caused the failed output.
The four outputs should be checked.
Sorry for the runaround.
Were on the right track.
 
yes the cap that is getting hot is connected directly to an output transistor, would that be the one... the amp boards look fine visually... are my voltages checking correctly now? i noticed some pretty sizeable differences in the before and after readings
 
@zebulon1 would it be wise to just replace all output Transistors... and have the part Numbers changed from what is in the manual is 2sd555-r and 2sb600-r is that correct
 
I wanted to mention to check the wiring harness around the heatsink when removing the outputs.
The replacement outputs are the On-Semi which are supper nice but you should consider replacing the left side to match the channels.
MJ21196/95's
 
You must log in or register to reply here.
Back
Top Bottom