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need help palomar deluxe 35A

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140NC
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need help palomar deluxe 35A

Post by 140NC » Sunday, 16 October 2016, 20:37 PM

I have a palomar deluxe 35A and i was talking on the amp tonight and all of a sudden the amp cut off. The power supply is still on but the light on the amp will not light up when i turn it on and it doesnt do any watts when i key up? Anyone know what the problem is or can lead me in the right direction? Thanks in advance!


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Re: need help palomar deluxe 35A

Post by pabxone » Monday, 17 October 2016, 3:14 AM

Blown fuse ?
Also make sure you can measure approx 13.8 volts at the power supply output terminals

-- 17 Oct 2016 20:19 --

There is a circuit diagram for that model here :- http://www.cbtricks.com/Amp/palomar_oth ... ite500.pdf" onclick="window.open(this.href);return false;

But I suspect the diagram may not all be there?

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Re: need help palomar deluxe 35A

Post by MDYoungblood » Monday, 17 October 2016, 5:21 AM

Hello 140NC,
Welcome to the forum. The power switch is wired to the AC power so naturally it will work. Does the preamp work? Was there any smoke when it shut off? Like pabxone asked is there power to the terminals on the front? What do you have hooked to the terminals?
As a new member could you post an intro in the "Welcome to the Forum" topic, viewforum.php?f=89" onclick="window.open(this.href);return false; ,so others can say"Hi", thanks.

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140NC
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Re: need help palomar deluxe 35A

Post by 140NC » Monday, 17 October 2016, 20:18 PM

I used a voltmeter and checked the power supply terminals, only getting around 7 volts. Any ideas on what to try next? All help appreciated!! Thanks

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Re: need help palomar deluxe 35A

Post by pabxone » Tuesday, 18 October 2016, 16:12 PM

There is something going wrong in the power supply section of the amp then,

Look at page 1 of the diagram in the link I posted earlier.

Measure the Output voltage from the mains power supply transformer inside the unit.
You should see about 17 Volts AC on the low voltage side of the transformer going into the bridge rectifier AC input side.
You should be able to measure about 23 volts DC on the DC output side of the bridge rectifier.

IC 1 ( LM723 Voltage regulator IC ) You should be able to measure around 18 volts DC (Give or take a few volts) on Pin 11 and 12 of the LM723 and around 14 volts DC on Pin 10 of the LM723 , if the output on Pin 10 is a little bit off use Trimpot VR1 to adjust the voltage on pin 10 to be 13.8 volts DC

For the pin numbering of the LM723 have a look at the datasheet here :- http://www.ti.com/lit/ds/symlink/lm723.pdf" onclick="window.open(this.href);return false;

The output of IC1 goes to switch PB1 on the front panel - It's hard to tell exactly without having the unit here but it looks like it will be the smaller black power On/Off switch on the top LEFT corner of the unit - check to see you can see 13.8 volts DC on both sides of the switch when the switch is ON.

There is also a RESET switch on the front panel (where it is wired in the power supply is NOT clear from the diagram) - it's worth having a look at it to see that you have voltage on BOTH pins of the reset switch - It could be either AC or DC voltage depending on where it is wired in the power supply chain.

There is a Relay K1 that should energize and operate when the mains power switch is turned ON - If you cannot see or hear this relay operating the fault will be either the Mains transformer , The bridge rectifier or Transistor Q3 (TIP35)

It should be pretty easy to fix and shouldn't cost much in parts unless it is the mains transformer.

Be extremely careful working inside this unit with the mains power ON - There is 110 Volts AC on the supply side of the mains transformer , the mains power switch and fuse - if you have never had a 110 volt electric shock -> now is not the time to get one - IT CAN KILL YOU - Be ULTRA CAREFUL where you stick your hands , fingers and tools inside there !


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Re: need help palomar deluxe 35A

Post by 140NC » Thursday, 20 October 2016, 18:46 PM

Checked the volts coming from the transformer to the board and its only 10.30 volts. What to do next get a new transformer?

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Re: need help palomar deluxe 35A

Post by pabxone » Friday, 21 October 2016, 3:13 AM

Disconnect the 2 secondary wires coming directly off the transformer to the bridge rectifier. (The rectifier could also be 4 diodes on the board?)

Measure the voltage coming out from the 2 transformer wires when they are connected to absolutely nothing other than the multimeter.

Make sure the multimeter is on the AC volts scale - If you are measuring anything less than 15 volts AC the transformer has had it.

If you need to get a replacement transformer you will need a 35 Amp transformer with an output of 16 - 18 Volts AC.


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