Vz 3000 power but no lights

[Loveitload]

Hi . I had this machine couriered and it has had a bad drop in the process which bent metal foot , cracked plastic casing under power switch and had no power to the unit .
As I investigated, and pulled the power supply out , I noticed that the power button switch had broken off the power supply board. I replaced that and got power but only the radio was working properly but no lights or leds over the whole machine. The cassette player makes a noise but not engaging play head or moving parts properly.
I’ve checked R701 on pcb and it’s fine. Anyone help me please ?

 

[caution]

If the drop was bad enough to break a part off the power supply board, you may also have cracked solder joints.

 

[Superduper]

This is a very complicated power supply with separate supplies for the Deck/Tuner and another for the microprocessor which likely controls the lighting. It looks like there are at least 4 fuses. You would be wise to check them all, and to ensure that there is no short if there are any blown fuses. Additionally, you will need to confirm all supply rails have voltages at the power supply. It is entirely possible that the tuner and deck has power but not the microprocessor. Frankly, I don't think this is a unit that is friendly to beginner or novice repair, it is likely too complicated.

 

[Loveitload]

Thanks for the reply guys . I have fixed a lot of these before but never this problem. All the fuses are fine . All power supply rails have voltage .
many other ideas ?

 

[caution]

If the rails have voltage at the power supply, maybe you can start at the LEDs/dial illumination lamp and trace backwards from there to see where power starts to show up again. For example, check where the LED board connects to the tuner board (CNP101), where the tuner board ties to the amp board, where the amp board ties to the power supply board, etc.

 

[Superduper]

Thanks for the reply guys . I have fixed a lot of these before but never this problem. All the fuses are fine . All power supply rails have voltage .
many other ideas ?

I see a dual supply +/- 15.5V rail,
I see a +12.8V supply rail,
I see an +11.8V rail, AND
I see a +10.5V rail.

So you are saying you found all those voltages being output at the power supply? Also, you say no lights or leds throughout the whole machine. How about the tuning strength LEDs indicators or stereo leds, because you said the radio was working? BTW, as this is an AC only machine, most of the panel lights are incandescent which is not unusual for them to blow out on older equipment.

 

[Loveitload]

Actually superduper On checking the rails again , I noticed the 3 were getting 20v and 1 was getting 6v . That’s the issue there I assume . When I’ve had this problem before , I’ve swapped out the R701 fused resistor and it’s fixed the problem but this one is fine .
any other possibilities in fixing this ?

 

[Loveitload]

I see a dual supply +/- 15.5V rail,
I see a +12.8V supply rail,
I see an +11.8V rail, AND
I see a +10.5V rail.

So you are saying you found all those voltages being output at the power supply? Also, you say no lights or leds throughout the whole machine. How about the tuning strength LEDs indicators or stereo leds, because you said the radio was working? BTW, as this is an AC only machine, most of the panel lights are incandescent which is not unusual for them to blow out on older equipment.

Actually superduper On checking the rails again , I noticed the 3 were getting 20v and 1 was getting 6v . That’s the issue there I assume . When I’ve had this problem before , I’ve swapped out the R701 fused resistor and it’s fixed the problem but this one is fine .
any other possibilities in fixing this ?

 

[Loveitload]

On checking the radio again , it seems that the fm mono is only working . And Am is picking up a signal on the red LEDS .
Fm stereo is very quiet and no signal strength.
I am very confused now .
Also I wanted to confirm where I am testing the power supply output voltage and whether I am doing that correctly. D701 is where I am getting around 20v on all 4 points . Is this the Rail or is there other places to check ? See photo . All help would be appreciated.

 

[Superduper]

If you want or expect ANY type of intelligent response, you will have to provide great and very specific detail. First off, it was already mentioned that this is a very complicated circuit, not a simple one. You were advised to get a service manual from which you can work from. Right now, nothing you mentioned is of any value sufficient to warrant analysis because you did not provide SPECIFIC detail about how you are testing, where you are testing from, which rails you are testing and the resulting voltages. You are wanting folks to expend time to help you but there's no way for us to do all of the work for you. For example, you said you are getting ~20V on all 4 points. HOW? Where and how are you connecting the meter? And that rectifier is supposed to output +/- 25V. But you are only measuring the rectifier voltages, NOT the output rails, which are regulated. Also, you did not acknowledge that on at least one PS output, (and at the rectifier), you should be getting +/- voltages. If you don't know what that means, that's a problem, because that rail is a dual supply. You'll need to understand what that means, as it's not a DC positive only circuit. There will be negative voltages at play based on ground, which could be at a different potential depending upon what you are probing. Essentially, you are throwing numbers out there that are meaningless and not at all the rails. You should be measuring voltages at the output connectors CNS203 and CNS514. Instead you are measuring voltage within the PS itself. You haven't yet established that the PS isn't working properly without first checking the outputs. How do you do that? Again, start with the service manual. The schematic diagram will basically show you (at those connectors), and if you follow along, you'll be able to ascertain what voltages should be at each lead, and which are the grounds.

 

[markoneswift]

As Superduper says above, verification of your power supply voltages is crucial. I've reapired several of these units myself and I always start with verifying voltages at the CONNECTORS. From the service manual, you should be measuring what's coming out of the regulators Q704 / Q705 (for the microcomputer / turntable supply), Q701 / Q703 for the tape deck. You should see +-25v on K711 / K712 as that's the supply to the main audio amp.