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sx 1250 tuning knob shaft damage help

Sure. The receiver was working after replacing the resistor R4 on the power supply board. I then removed the protect circuit board and replaced every electrolytic capacitor and transistor on that board. I installed the board and the soft start relay engages but speaker relay will not engage. Do you need the exact values of each cap and transistor? If so I can provide this if it helps a diagnosis I did trace 32 v to the speaker relay, thanks
 
Why every transistor?

Hopefully you used the same value of capacitor that was in there to begin with. But what transistors did you use? Here's where you likely made a mistake...installing a PNP for an NPN (or vice-versa) or getting the lead arrangement wrong.
 
sx-1250,awm-091,C1,470,6,cea,,470,10,647-UPW1C471MPD6
sx-1250,awm-091,C2,470,6,cea,,470,10,647-UPW1C471MPD6
sx-1250,awm-091,C3,4.7,25,cea,,4.7,50,647-UPW1H4R7MDD
sx-1250,awm-091,C4,100,16,cea,,100,16,647-UPW1C101MED
sx-1250,awm-091,C5,100,50,cea,,100,50,647-UPW1H101MPD
sx-1250,awm-091,C6,100,50,cea,,100,50,647-UPW1H101MPD
sx-1250,awm-091,q1,2sc945,,diff,,,,512-KSC1845FTA
sx-1250,awm-091,q2,2sc945,,diff,,,,512-KSC1845FTA
sx-1250,awm-091,q3,2sa733,,or logic,,,,512-KSA992FBU
sx-1250,awm-091,q4,2sc945,,current dump,,,,512-KSC2383YTA
sx-1250,awm-091,q5,2sc1166,,relay drive,,,,512-KSC2690AYS
sx-1250,awm-091,q6,2sc1166,,v reg,,,,512-KSC2690AYS
sx-1250,awm-091,s1,asr-010,prot relay,,,,,653-my4-02dc24
This is from my order sheet, I checked data specs for pin layout. Certainly have made an error somewhere. Thanks
 
Need to check that the transistors were installed in the proper location, and that the pins are in the proper holes. And check that the capacitors were installed with proper polarity.

I assume you plugged the board back in when you were done...
 
I rechecked them last night both correct pin location and polarity. I will recheck and post stabilizer voltages again, I assume 32v is correct for the relay. thanks
 
Rechecked all new transistors and correct pin placement also checked polarity of each cap and correct values still will not come out of protect. How to proceed from here. Are there any protect board voltages to help diagnose the issue? thanks
 
Unplug (or remove) both power amp driver boards. Does the relay engage now? If so, there's a problem in one of the amplifier boards. If the relay still does not engage:

Pin 1 on the board should have about 65V. The voltage on the relay coil pins should be about 35V (32 is OK) when the relay is off, but if/when the relay engages, you'd read that 35V (32V) on one side of the relay coil, and about 7.5V on the other.

Pins 6 and 9 are the input for DC monitoring from the power amp channels, and each should be well under 100mV (0.100V).

Essentially, it would be handy to know the voltages of the base, emitter, and collector of Q1 to Q4. But I still think that something is installed incorrectly. Take a decent high-rez picture and upload it to Google Photos and share it (local hosting here is size limited, and so is Photobucket, so find someplace that allows a good size pic).
 
I appreciate the patience here. I have spent quite the time going over my work and components installed. I installed the protect board and had not checked bias or dc offset and decided to turn the bias pots CC just for fun and the protect speaker relay engages now. I installed the protect board and addressed the DC offset and bias per manual. There is a bias adjustment issue. I know the SM suggest 100mv, however the voltages I am able to attain Fully CC to fully CW is about 45 mv. While turning the bias pot and reaching 25mv the protect relay disengages. This is for both R and Left channels. Does this have anything to do with the R$ resistor in the PS circuit? Unsure of its current rating? Thanks Glen
 
You will not get the full Bias mV's setting on the DBT.
If the Offset (DC Balance) is zero and stable, and the Bias (Idles) are responding then:
Dial back the Bias (Idle) trimmers and go to full house power.
The Offset should be good. Check it if you want.
The Idles with the original outputs might have a hard time reaching the 100mV's per the manual. If you have new On-Semi outputs they should be set for 65mV's.
Either way; Set the Idles for 65mV's instead; That will work just fine.
 
Once you have confirmed that it is possible adjust the bias trimpot and can see that the bias changes as it should, you should dial it back to about 2 or 3mV and leave it there till you are eventually running straight from the AC line, then you can set to the value given in the manual. NEVER attempt to set the bias to factory specs when running on the DBT, as once you plug it straight into the wall the bias will skyrocket.

While doing this adjustment on the DBT, did you happen to notice that it was getting pretty bright?:p

Personally, I set the SX-1250 to the factory setting of 100mV when I eventually am ready to do so.
 
I removed the DBT and have the bias set at 50 mv and dc offset at 0. Stabilizer set at 65 v, thanks for the help here guys. I have a tuning shaft assembly coming to install and wrap tuning string around. Any ideas how to proceed?
 

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Very carefully. :p

Seriously, the service manual shows the tuner string setup, but if you were thinking ahead you'd have taped the string to the pulleys to keep in in place when you removed the original tuning shaft.
 
That would have been a great idea. However it was very obvious the tuning dial string had been off and loosely wrapped to the shaft when i acquired it, Thanks
 
I have located a new tuning dial shaft and assembly. After installing (due to blunt force to the tuning knob into receiver) I notice the tuning shaft is at at 30 degree angle. What to do? Has anyone straightened the aluminum dial? The bend is an obvious issue where the tuning shaft fastens to the dial. Has anyone ever removed the dial and repaired or is this a lost cause? Should I just find another dial. Thanks for the replys
 
Yeah, I think I'd be pulling the whole tuner dial section off to get it on a bench. If it's just the section where the shaft goes through the tuner dial face, maybe a wooden down covered with something like duct tape can be used, with a backing on the other side of the face of something like another piece of wood.

I don't envy you.
 
eBay has a (that) extruded panel with tuning calibrations for 22 bucks shipped.

Since it is an appearance item and is bent, I would go for the replacement.

You can try hammering - ON A BENCH - and keep the replacement option open. Then decide if you can live with the results. If you are going to sell it, then, it's a no-brainer, just replace it.

An alternative is to clamp the entire plate down, get steel hardware that clamps the entire mating area of the knob assembly and has a LONG rod, then BEND it back - gotta have good clamping all around.
 
I see the one for $37 shipped...

Worth it for a classic piece. I'm jump on it and then see if the old panel can be straightened and resold.
 
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