No power on 4300

deedawson

deedawson

New Member
Hey all, I am in high hopes of restoring a 4300 quad. I received this unit free but not working. It appears to be in great shape cosmetically. I plan on replacing capacitors one board at a time starting with the power supply. However, before I get involved in doing anything with this unit I need to restore power first. I replaced the main fuse and power supply fuse as well. Still no power, not blowing fuses either. Power at switchable outlet as well as constant. Power on the switchable outlet powers on with power button pressed. I am a novice here so still learning. I feel like my first step should be testing the transformer input power as well as output. Should the schematic show with wires are which for testing purposes? Would any of you guys suggest a different path? suggestions are appreciated. Thank you in advance!
 
Just to be sure, is it possible it is powering up but the lights aren't getting power? Have you hooked up speakers yet?
 
Thanks for the response, I actually pulled an old speaker out last night to confirm that but didn't get to check it yet. Will check this afternoon. However, shouldnt I hear the relay click after initial start?
 
If it's operating properly you should hear the relay. But it isn't uncommon for there to be a problem in the unit that causes it to go into protection. It's a shot in the dark, but since the switched outlet works, power is getting to the unit via the power switch. Hopefully it's something simpler than a blown transformer. Others here are better equipped to help you with in depth trouble shooting. I'm just trying to eliminate the simple stuff.
Steve
 
Well, no luck. I tried connecting a speaker to the receiver to see if it was just the lights out. No relay click. No lights. No sound.
 
Find the phase converter board (PM01), it's on the bottom by the transformer. DMM across JM03 (+) and JM04 (-), should be 35V, R806 on the power supply board adjusts it.

If nothing there, check for voltage at J804 and J806 on the power supply (neg lead to chassis ground). Schematic doesn't say what voltage should be there, but there should be something since those are the feeds to the rectifiers right off the transformer.

I assume you have the service data for the 4300 - http://akdatabase.com/AKview/displayimage.php?album=1&pos=144
 
Thanks for the advice, I'll check these tomorrow and report back. Thanks for the link for the service manual.
 
I had questioned the power switch myself however when the power button is depressed the switchable outlet on the rear has power. Unless there are multiple contacts in the switch?

I just checked JM03 and JM04 on the phase convertor and read 0.00. Same as for the J806 and J804 on the power supply....

Sound like the transformer? I'm going to look a little further.
 
deedawson said:
I had questioned the power switch myself however when the power button is depressed the switchable outlet on the rear has power. Unless there are multiple contacts in the switch?

I just checked JM03 and JM04 on the phase convertor and read 0.00. Same as for the J806 and J804 on the power supply....

Sound like the transformer? I'm going to look a little further.
Click to expand...
Good call on checking the switch, sounds like it's ok.... Your mains fuse is good checking with multimeter too?
Edit: I just reread..... You replaced the fuses... Hopefully not the transformer!
 
I know this is a bit preemptive but I found a 4300 transformer in good working order today for $25. Last resort. Just in case....
 
I think you're going to be needing that transformer. Voltage on the switched outlet seems like a valid test of the switch to me.
 
Well, I should be receiving the transformer this weekend. Not sure if I'll have time to get it in this weekend or not. Very glad I found the transformer when I did. Either way, I'll update this post when i get it together for anyone who is interested. Thanks for the help. Much appreciated
 
If you have to pull the transformer, take about a million pictures of how everything goes. Labels, notes, whatever.

I'd be tempted to put in a new power switch and snubber cap before the transformer surgery. They are trouble spots anyway, so look at it as part of your restoration. Maybe we're missing something and you'll get lucky.
 
Ok, I have a replacement transformer and should have time later tonight to swap it out. Do you guys have any pointers? I am asking because there are ten wires associated with the transformer. There are 2 orange, 2yellow, 2 green, 1 black, 1 white, 1 red, 1 blue. Obviously the wires that have only 1 of the color are self explanatory. My question is with the colors that have 2. Does it matter which wire from the transformer is soldered to the power supply? There isn't any identification on any of the wires coming out of the transformer.
 
Here are a couple pictures of the overhead view of the transformer and the view of the wires from the transformer to the power supply.
 

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