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Old 02-10-2015, 10:45 PM
legenbass77 legenbass77 is offline
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Join Date: Jan 2011
Posts: 44
1966 Airline am/fm/phono with overheating filter caps

Hi all, I am having a problem with an Airline model GHJ2346A overheating the filter capacitors. The schematic I have to work with is Sams Set 892 Folder 4. I found nearly all the electrolytic capacitors had failed in some way. Either open, high esr, or the capacitance value had drifted out of tolerance. Here is the work I've done so far. I replaced the multi-section 1000/500mfd @35 volt with a 1000mfd@63v, and a 470mfd@63v. On the original can X is 500mfd, Y is common, and Z 1000mfd, and I double checked the replacements with a dmm, and esr meter, also checked polarity before soldering in place. I went through each module the same way one at a time checking each capacitor as mentioned above before soldering in place. I also powered up the unit after replacing two or three capacitors to check for improvement of operation, or for disaster. Thankfully I got improvement in performance upon each power up. After replacing all electrolytics I did a final smoke test. While the performance greatly improved, I noticed the filter cap tops swelling, were quite warm to the touch, along with a tiny bit of electrolyte boiling out the vent seam, so quickly shut it down. I can operate it for a few minutes at a time to check some voltages with higher voltage rated caps installed, but they still get very warm after 5 minutes of operation. So far I have checked voltages at the six transistors on the power supply board:
Sams voltage| Actual voltage
Q15: E 0, B -.1, C -10.5 | E -.004, B -.1, C -9.8
Q19: E 0, B -.1, C -10.5 | E -.0046, B -.00016, C -10.6
Q14: E -10.5, B -10.6, C -17| E -9.84, B -10.02, C -20
Q18: E -10.5, B -10.6, C -17| E -10.4, B -10.6, C -20
Q17: E -16, B -15.4, C-.6 | E -15, B -14.5, C -.4
Q13: E -16, B -15.4, C-.6 | E -14.70, B -13.90, C -.7
Do these voltages seem within acceptable range? Something I'm overlooking? I'm getting am, and fm reception loud, and clear throughout the dial range. Any help to steer me in the right direction to resolve the overheating capacitors is much appreciated!
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