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2245 p800 problems

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Donnyhifive

New Member
Aloha AK,

I was 96% done with a full recap of my 2245 with no problems. Phono board, preamp, and both power boards all done with no shorts on DBT, audio in both channels. I adjusted the idle current and DC offset on both boards just fine. I got to the main power p800 board, recapped it, good on the DBT, set the DC voltage to 35V hooked up to j802/j803. I looked to be all done with p800 until I made the terrible mistake of taking off the clip leads before powering down. I saw smoke at r804 and immediately shut off the unit. I looked up the specs for r804 and found a 10 ohm 1/2 watt resistor locally that I believe is ceramic. The unit powers up with lights, no smoke, good on the DBT. I now have no audio in either channel and can’t get a voltage reading at j802/j803 anymore. It’s reading 50-60mV and does not change much when turning r809. DC offset is still good in both channels and relay is clicking. Main fuse in back is in tact, jumpers are in. Please help! I’m still very new at all of this so forgive me if I need clarification at any point. I’m pretty stuck so any help/advice is appreciated. Thank you!
 
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Aloha Donny,

parts list says 10 ohm 1/2 watt
schematic says 100 ohm for R804
remove and measure
replace the unhappy R804
use 10 or 100 ohm as determined above (carbon or metal film 1/2 watt)
Pull and test H805 and H806

good luck
Larry
 
Thanks Larry! Nice catch. I replaced r804 with a 100 ohm resistor and pulled h805, h806 which were both fried. I finally got the parts in and replaced both and now I’m getting something at j802/j803 but only 3-6ish volts when I turn r809, relay still clicks. What gives?! I saw that on an updated schematic the r804 part still says 10ohms.. if it is indeed supposed to be 10 could that one wimpy resistor throw off the voltage like that? I’m stuck again and pretty furious lol. Any other ideas are appreciated! Thanks.
 
I’m not sure if h807 is good. In all of the manuals I can’t find the specs for it so wouldn’t know what to test. I found in the forums talking about a 2270’s h807 being a “7.1V 500mW zener diode” the writer said “1N5236B should be close enough.” Is this the same for my scenario?
 
Yes, this is a 7.1V (500mW) Zener diode. Since your transistors went defective it is possible that your Zener is defective as well. When a Zener diode is defective, it is usually shorted (not open like a fuse). Measure the actual voltage on the Zener diode. You will not have 7.1V because you only have 3~6V at J802/J803. If you don't measure the same voltage at the Zener than the voltage at J802 (J803 is the ground), your Zener is bad. I think you will see almost 0V at your Zener. If your Zener is shorted, it is normal that you only have 3~6V at J802.
 
ecluser said:
Yes, this is a 7.1V (500mW) Zener diode. Since your transistors went defective it is possible that your Zener is defective as well. When a Zener diode is defective, it is usually shorted (not open like a fuse). Measure the actual voltage on the Zener diode. You will not have 7.1V because you only have 3~6V at J802/J803. If you don't measure the same voltage at the Zener than the voltage at J802 (J803 is the ground), your Zener is bad. I think you will see almost 0V at your Zener. If your Zener is shorted, it is normal that you only have 3~6V at J802.
Click to expand...

thank you! H807 was indeed shorted. Replaced it with the part I listed and changed out r804 to 10 ohm. Was able to adjust to 35v and she’s jammin Lee Morgan this very moment! Hooooray
 
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