Forums :: NEW! Web Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Dec Tue 06, 2022 3:03 am


All times are UTC





Post New Topic Post Reply  [ 4 posts ] 
Author Message
 Post subject: Any Pioneer experts? SX-1080 FM issues
PostPosted: May Thu 19, 2022 12:02 pm 
Member
User avatar

Joined: Jun Wed 08, 2011 1:33 am
Posts: 13481
Location: Ohio 45424
Working on this rec. for somebody. Uses the awful PA 1001 1002 3001 chips. At first the audio was garbled, no meter, no mute. Replaced bad PA3001 IF/Det. with the Hitachi equivalent. Restored meter, mute, and clean 550 mV sine to the 1001 MPX chip with 30 KHz deviation. Output of the L and R of the 1001 is down in the noise. With an OTA stereo signal, there are huge 3.7V 38 KHz tilted square waves on the L R outputs of the chip. Of course that goes thru a LPF to the audio amp chip. There is recovered stereo sound from the tuner but the audio level is a great deal lower than AM. Even with 1 mV RF from the test gen. But the tuner is super sensetive in the RF stages. I am thinking the MPX chip may be bad too with such tiny recovered audio. But the audio chip has it's own issues. An apparent 2 MHz oscillation that appears at the output at about 50mV Peak at all times except when the inputs were disconnected. Anyone have a Pioneer that they would consider taking a few measurements on with this chip set? BTW I do not have MPX in my RF gen, just FM selectable dev.

_________________
Reddy Kilowatt says; You smell smoke? Sorry about that!


Top
 Profile  
 
 Post subject: Re: Any Pioneer experts? SX-1080 FM issues
PostPosted: Jun Sat 11, 2022 5:42 am 
Member
User avatar

Joined: Jan Thu 01, 1970 12:00 am
Posts: 2935
Location: Olympia WA USA
Location: Olympia WA
Typically that problem was caused by bad coupling or 'lytic caps. Been 40 yrs or so since I worked on one of those.

_________________
FrankB
WB7ELC
(Yes, that is actually me in the avatar photo)


Top
 Profile  
 
 Post subject: Re: Any Pioneer experts? SX-1080 FM issues
PostPosted: Jun Sat 11, 2022 11:31 am 
Member
User avatar

Joined: Nov Wed 30, 2016 6:35 pm
Posts: 13037
Location: Sunbury, Ohio 43074
Location: Sunbury, Ohio 43074
I'd replace the caps, which btw I don't necessarily suspect. But they are a lot easier to get than the chips, which is most likely the problem. They are notorious, and getting extremely hard to find. You may get lucky and a few caps will fix it. I'm not betting on that ;-)

_________________
Preserving the hist. of electronics, one boat anchor at a time! :)
https://www.bbtvtestequipment.com


Top
 Profile  
 
 Post subject: Re: Any Pioneer experts? SX-1080 FM issues
PostPosted: Jun Tue 14, 2022 12:51 am 
Member
User avatar

Joined: Jun Wed 08, 2011 1:33 am
Posts: 13481
Location: Ohio 45424
Did extensive cap testing in the problem areas. I sent it back to the owner telling him to take it to one of the pro shops in the region that have or should have MPX generators for one thing.

_________________
Reddy Kilowatt says; You smell smoke? Sorry about that!


Top
 Profile  
 
Post New Topic Post Reply  [ 4 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 2 guests



Search for:
Jump to:  




































Privacy Policy :: Powered by phpBB