Pioneer SX-1080 soft power-on and tuning problems

[Kaerukame]

Hi everyone!

I have two questions about my Pioneer SX-1080.

I finally broke down and bought a Pioneer SX-1080. Though I knew it needed extensive repairs, I didn't care and had the unit entirely rebuilt a year ago. He replaced all caps and many other parts that are known to fail over time. The rebuild was done by an experienced hobbiest who has rebuilt many previous units.

Question #1. Hard start-up thud.
However, since my rebuild, the unit does not seem to go through a soft power-up process. Before the rebuild, after turning the switch on, the unit remained silent for nearly a full half-second before the relay would audibly click on and bring the unit to full power. However, after the rebuild, the unit powers up quickly resulting in a "thud" in the speakers.

I took it back to the hobbiest tech who did the original work and he switched out the relays to see if the problem lay there. He was unable to find anything. I took the SX-1080 to an experienced tech at a professional shop who went through the entire unit carefully. He noted that the hobbiest tech had done meticulous work on the unit and found no mistakes. Everything seems to be working to spec. He was unable to find the reason for the hard startup. Any ideas on what might be causing this?

Question #2. Poor FM reception
Recently, my SX1080 has had trouble tuning in FM stations that are normally quite weak. Other radios, including digitally tuned shortwave radios also have trouble picking up the stations. Is there a chance there's something wrong with the SX-1080 tuner? Do I need an external antenna in addition to the build-in chunky antenna on the SX-1080?

Thanks for suggestions and advice

 

[markthefixer]

The professional shop should have clued you in to the time delay expected.
The first relay clicks immediately, it's called a soft start, moderating the power inrush when the unit is turned on. Otherwise some pretty big fuses pop.
the SECOND relay should take several seconds before it engages, lately some have not liked the unusually long time period of their x80 gear.
3-6 seconds are ok, these complaints were closer to ten seconds
The hobbiest should know that fast relay pull-in is a no-no, and that the delay time is the function of control circuits - and a transistor
thus his swapping out a relay exposes a blind spot of his..He's got some learning to do.



do you have a downloaded service manual? get one, it will clue you in on radio antennas at least.

the "build in chunky antenna" only receives AM radio. Yes, the FM terminals in the back need to be connected to some sort of antenna.
In some strong signal areas a few feet of wire will do,
next step up is a twinlead "T" antenna.
after that, the sky's the limit... almost literally.

If you want, we can direct you in the taking of several close in photographs
that may help diagnose the protect problem that is allowing the thud through.

 

[rcs16]

Is The issue that the speaker relay engages immediately at power on so there is not the seconds (3-6~) of delay as it would normally be?
If so someone has to look at the protection ckt, does it get the proper voltages? Sounds like the techs that you go to do not fully understand how the circuits function.
If there is the proper delay in engaging the speaker relay and you still get a turn on tump, see if it is both channels, also measure the dcv at the amp outputs to check dc offsets.

 

[Kaerukame]

Thanks everyone for your messages. Work became too busy and I was unable to reply.
Yes my techs were unable to diagnose the problem and now the received will not power up at all.
I will download the service manual now. Hopefully it will offer clear advice on how the power protection circuit.
I will contact my techs again. Hopefully they can fix this properly.