I have an SX-550 receiver and is in great shape except that it has the balance pot missing. Somebody has jumped the board with 100,000 ohm resistors and the 550 functions with that mod. Is it safe to use it with this mod? The SX-550 balance pot is ACV-126. I have access to an ACV-135 balance pot out of an SX-750. If the SX-750 pot will physically fit, is it ok to use it in the SX-550 ..read more

I have a question about this SPEC-2 power amp board I'm redoing. It has a circuit modification that is factory but I cannot find it in any of the available board layouts or schematics. Basically D8 has been relocated next to pins 9 and 10, the space where it was has a 15k ohm resistor now, the traces are also different. A .22uF cap and a 2sc1885 tranny was added and there is also a jumper set in between R42 and R44 running between the collector of the 2sc1885 tranny and the cathode of D8. It... Read more ..read more

I was looking around eBay when I came across a SA-5200 and noticed the serial number was marked "RICH". I figured it was just a owners name. Then I found another marked "RICH". Went and looked my SA-5200 and it also has RICH added to the serial number tag. Who is RICH? I think its warranty or recall work being done, anyone know? its placement isn't machine accurate ..read more

Is there a new Pioneer SX-1980 Transistor Modification out there someone has come up with or is this still the way to go? Pioneer SX-1980 Transistor Modification I received the clamps from technut (and there are also some on the way from englissa), and I just had to see what they'd look like... Cool huh? Not all of them have the logo, and once mounted I don't think you will be able to see them anyway. Still cool. I think someone is bored at work. :D... audiokarma.org ..read more

Hello. I am working on a Pioneer M-90. The unit operates ok, just needs some minor fixing. I noticed that even without input signal it gets kind of warm. I have connected a power meter on the AC plug and it draws more than 100 Watts. Is this normal ? I find it quite.... excessive. Maybe it was not built to be "green" but still... !!! BTW: There are no adjustments (bias, DC) that can be made on this unit. There is a dedicated chip for that. There is no significant DC on the output of... Read more ..read more

Hi All, Quick question (I hope…) I have a Pioneer SX 1250 That I have recently re-capped/rebuilt. Without getting too long winded I changed quite a few semiconductors also during the rebuild. Cleaned all of the switches...Came out great, everything works well but the unit has an occasional issue with protection. Here’s the issue: Every once and a while, it just quits, goes off into protection, some times there seems to be a little pop in there at the beginning of shut down. The pop I believe... Read more ..read more

I have a dead tuning meter movement and they seem to be unobtainium. However there are lots of others on Ebay. I'm guessing the movements are all about the same but the plastics/bezels are different. Anyone know of a good candidate for an organ transplant of just the movement. I see SX-636, 727 and 838 ..read more

Hi, I've been studying my SX-737, trying to learn as much as I can before tackling a restore. Just reading a bunch of threads and stuff on line really. Noticed this in an old brochure: Cool, it has dual power supplies, I wonder what that means . . . It looks like both outputs are driven off the same winding in the block diagram and they go through the same rectifier, through pins 9 and 10? I compared to the SX-636 block diagram and it's very similar (the SX-636 marketing... Read more ..read more

Hi all, I've perused many of the SX-1980 tuner threads from over the years and can't find anything similar. Nor am I an electronics specialist capable or comfortable of doing any measurements myself so I am looking to get an idea of what I'm potentially in for, if I can find an appropriate tech. After a power supply board failure, where I had the board replaced by a new Delta Electronics AWR-154 board, the tuner now has the following symptoms, whereas it was working perfectly fine before... Read more ..read more

Parts needed: (Qty. 3) #276-1363 TO220 heatsinks from Radio Shack, cost $1.69 each. http://www.radioshack.com/product/index.jsp?productId=2102856 Epoxy (I used JB Weld, slow cure). (Qty 3) 3MM metric hex nuts from the local hardware store or the junk drawer. Solder, 60-40 rosin core NON-CONDUCTIVE Heat Sink Grease (NTE 303) 91% rubbing alcohol or medical alcohol pads, like they use when you get a shot at the doctors. Optional: New transistors (Q19, Q25 =... Read more ..read more