SX-1280 with no sound, no relay click.

[John Paine]

Hi,

I have an sX-1280 that I have had for many years. I had a professional audio shop go through the entire unit years ago and fix, replace, and dial-in anything that needed it. But several months ago my feral animal of a three-year-old was playing with it unbeknownst to me. It is now not playing music. When I turn the power on I do not hear the relay click that used to click. Everything lights up and the source lights illuminate as they should. The tuning and signal meters move. But there’s no sound. I have replaced the small fuses that I believe are 1 amp from the bottom of the unit. This was my issue before ( maybe a year prior ) and fixed the problem. I can read a schematic, I can solder fairly well, I have a couple solder gun’s, solder, many multi meters and feel relatively comfortable working around this equipment with some tutelage from others. Can anybody tell me where I should start?

Thank you in advance for any help that anyone gives me,
John

 

[Guest125]

Start with familiarizing yourself with the Service Manual. Next check voltages on the protection board pins listed in the manual, and report back any that do not come close to the specified voltages listed for each numbered pin. (page 79)

http://www.kallhovde.com/pioneer/sx-1280smhires.pdf

 

[John Paine]

Start with familiarizing yourself with the Service Manual. Next check voltages on the protection board pins listed in the manual, and report back any that do not come close to the specified voltages listed for each numbered pin. (page 79)

http://www.kallhovde.com/pioneer/sx-1280smhires.pdf

Thank you. I’ll be back shortly......

 

[John Paine]

Start with familiarizing yourself with the Service Manual. Next check voltages on the protection board pins listed in the manual, and report back any that do not come close to the specified voltages listed for each numbered pin. (page 79)

http://www.kallhovde.com/pioneer/sx-1280smhires.pdf

Alright, i’m finally circling back around to this. I have the covers off and have located the power supply board and the terminals that need to be tested. I am getting numbers that are inconsistent with what they should be. Just to make sure I’m doing this right am I grounding on the chassis ground on the yellow chromate chassis that has the scematic type ground symbol on it?

 

[rcs16]

Sounds alright, most measurements are made with respect to chassis ground, make sure you get good contact.
Make a table of what assembly you are testing, what pin/terminal or device you are measuring, indicate what you measure and what they say it should be referencing the big schematic.

 

[John Paine]

Here are the numbers I’m getting with the desired number in parentheses, my readings in the right column, power switch on, negative grounded to the chassis

Pin 8 (+68) +151.5
Pin 11,12,13 (+32) +71.3
Pin 21,22,23 (-32) 0
Pin 25 (-68) 0
Pin 16,17,18 (+13) 28.4

There is a resistor on the fuse board that looks a little toasty around it perimeter. Noble 3w 1.2k ohms. Slightly brown on the board around it. Resistance measurement in place is 1.2k

 

[John Paine]

Strange. I just turned it on again and it worked. I’m going to investigate that resistor. Maybe a bad solder joint that connected when I wiggled it?

 

[Watthour]

While there, it would also be a good idea to inspct the joints in the voltage regulator transistor areas as well. Q1 and/or Q3 may also have shorts if the PS voltages are that high.

 

[John Paine]

I’ll retest the numbers I got too now that it’s working. I am 100% sure that it was not working before so I want to verify those numbers now that it’s working.