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Repairing Clarion MCD 360 Crossover

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kasey

New Member
Ok so I am reparing a clarion MCD360 Crossover. The problem is that it is not powering up at all i.e. the red power led is not illuminating when the remote terminal, the batt+ terminal and the ground terminal is connected to a reliable 12volt supply.

I obtained the service manual from online and traced the problem to the power supply stage, but I cannot seem to figure out what is the problem. Attached is the power supply stage schematic.

I am not getting any voltage out of T1 (The step up power supply transformer). On IC2, I am also not getting anything out of pins 9 and 10. I assumed the IC was bad and replaced it, but that did not solve the problem (my bad. lol) I also replaced ZD1 because I was getting voltage before it, but nothing after. But after replacing it, I got the same readings. So now I am perplexed as to what is the problem. No caps shorting, all resistors seem to be fine. What am I missing?
 

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alec_t

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What voltages do you have on input P39-C and on pin 12 of the IC?
 

alec_t

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Can you list the voltages on all of the IC pins and on P39-A ?
 

kasey

New Member
Sorry for the late response. But here are the details you asked for:

Pin Voltage
1 0.050 Volts
2 2.048 Volts
3 0.051 Volts
4 0.042 Volts
5 1.699 Volts
6 3.529 Volts
7 0.000 Volts
8 12.17 Volts
9 3.318 Volts
10 3.856 Volts
11 12.20 Volts
12 11.35 Volts
13 5.03 Volts
14 5.03 Volts
15 4.36 Volts
16 2.048 Volts
 

alec_t

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Is the oscillator section of the TL594 working correctly? (Check pins 5 and 5 with an oscilloscope).
 

kasey

New Member
Is the oscillator section of the TL594 working correctly? (Check pins 5 and 5 with an oscilloscope).
I do not have an oscilloscope. And I think you meant pins 5 and 6??

Also, I replaced that IC with a new one bought from the store when I found no voltage going into T1. Could it be that the IC I bought and replaced, is defective also?
 
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alec_t

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I think you meant pins 5 and 6?
Oops. Yes.
A pity you don't have a 'scope. A multi-meter with a frequency-measuring range would be handy instead.
It's always possible the replacement IC is faulty, but unlikely if bought from a reputable source.
 

Les Jones

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In post #9 when you say "I found no voltage going into T1." Do you mean that there was no voltage on pin 2 of T1 ? If this is the case then check for a break in the track to that pin. This is because you have about 12 volts on pins 8 and 11 which are fed from the same supply via 10 ohm resistors.

Les.
 

kasey

New Member
Oops. Yes.
A pity you don't have a 'scope. A multi-meter with a frequency-measuring range would be handy instead.
It's always possible the replacement IC is faulty, but unlikely if bought from a reputable source.
Thanks for your input Alec. I think my meter can measure frequency. What exactly should I be looking for? What is a 'good reading' when measuring the frequency on pins 5 and 6?


In post #9 when you say "I found no voltage going into T1." Do you mean that there was no voltage on pin 2 of T1 ? If this is the case then check for a break in the track to that pin. This is because you have about 12 volts on pins 8 and 11 which are fed from the same supply via 10 ohm resistors.

Les.
Thanks for your input Les. When I said no voltage going into T1, I meant that I assumed that I would get an AC voltage going into pins 1 and 3 of the transformer (T1). I know T1 is a step up transformer and only AC can be stepped up. So no AC voltage BETWEEN pins 1 and 3.
 

alec_t

Well-Known Member
Most Helpful Member
What is a 'good reading' when measuring the frequency on pins 5 and 6?
With the component values listed, the oscillation frequency should be about 97kHz according to my LTspice simulation.
 
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