Pioneer SA-7800 Repair Part 2

Repair of a Pioneer SA-7800 Part 2 of 2. In this video I show how I fix the display that I inadvertently broke while recapping the unit. I also show bias (DC offset) and display adjustments. Thanks to AudioKarma.org for help and support.

[@manicminer8813]

Thanks for these videos, I have one of these amps with metal outer case. Still works, but I am in the process of replacing the broken speaker terminals to be able to accept banana plugs

[@YT32-16branch]

I would have changed the potentiometers. Leaving these old ones in, is the best way to burn the stages up during adjustment. You were very lucky...

[@SevenFortyOne]

I was a little unsure of that step now that you mention it - thanks for the clarification!

[@Steve-bo6ht]

Absolutely beautiful amplifier I am going to on the lookout for a very similar one as a restoration project.

[@skatt757]

Great recap job! I did the same with my SA-7800 last year :) A little pointer I noticed in your video- BOTH channels should read 66mV not 66mV left and 53mV right. The manual is a little misleading but you would adjust each channel, first for 53mV, and then 66mV. Hope that didnt sound too picky but just a little pointer :) Cheers

[@tough213]

great video and repair job thank you for sharing the video and keep them coming

[@jon123423]

I knew that the caps were not responsible for that unwanted noise, usually its resistors, pre driver transistors, or driver transistors (differential) but not output transistors. Even dried joints around those components as in your case. But recapping is great move so it extends the life of your amp.

[@guillermosequeira1927]

An advice, replace those dual fets K129A with smd's SST-404.

[@SevenFortyOne]

I had a problem with my camera while working on this part of the refurbish and don't have any video. The noise I was getting was due to cracked solder joints on the two transistors in the power supply section that have heatsinks attached (I don't recall their designation). Go to the audiokarma website and do a search on SA-7800; there is a bunch of into there to help you firther troubleshoot this problem.

[@cruel77]

Hello, the video is great !! I have the Sa 8800 and the display is not as bright as it should be, could it be that I have to change the capacitors? thanks!!

[@SevenFortyOne]

I think these displays loose brightness over time. You can try new capacitors but it may not help

[@cruel77]

@@SevenFortyOne thanks!

[@SevenFortyOne]

The transistors in question can be seen around 3:45 in my part 1 video - just behind the large filter capacitors.

[@SevenFortyOne]

No, those are resistors. I'm not sure how you can hear anything coming out of them but maybe their solder joints are bad. You could try re flowing the solder that hols them to the other side of the board. One word of advice/caution though...you can get seriously hurt by the large filter caps. When doing any work on this unit you should unplug it and THEN DISCHARGE THE FILTER CAPS!!! If you don't know the proper way to do this then you may want to stop and have some who does help you.

[@mdrummond194]

Own one of these, looking to mod the “tape out” into a amplifier preout, any insight on how to do this?

[@enriqueidy8]

I think that I found the problem, on the left of the 4 large filter capacitors there's two kinda red cylinder things (capacitors?) I don't know what they're called, each one has 2 little white tubes around the solder joints (where they're attached to) and I can hear noises coming out of them the noises stop for a bit and then comes out again and so on Are those the problem?

[@jiml20]

Very Intriguing. One question about your capacitor replacement. Was that brown gunk on the bottom from a bad capacitor or was that glue placed to hold it from the manufacturer? I did see some caps with brown gunk on bottom also. I have an SX 1050 that smoked the large resistor and thermistor when I turned it on. (Bad ebayer said it worked) I also heard a loud gunshot (probably one of the big capacitors that blew up). He did a miserable job at packing so had to fix the bottom of receiver from shipping. I purchased for around $ 350.00 so will keep and try to fix or ? shipping would cost me nearly 100.00 to send it back to him. Also owns an SX 1080 ( I love those meters) and an SX 1250 (getting repair on tuner section) ebayer did not know what he was doing. Perhaps I will purchase an SX 1980 someday?

[@SevenFortyOne]

It very well could have been leaked electrolyte... Too bad about the dishonest eBayers - I've had that happen a time or two myself. Thanks for taking the time to comment and good luck with your project!

[@IDunno655]

The brown gunk on the bottom of the capacitors is most likely just glue. A lot of amplifiers back in those days used it to keep capacitors from moving around too much. Problem is, sometimes the glue becomes conductive. I'd replace them for that reason. A leaking capacitor (most of the time) would have a bulged top, what kind of looks like brown battery acid leaking out of it, or burn marks. In the case of this amplifier shown in the video. The stuff from the first video is definitely just a glue type substance.

[@vintagestereocollector4159]

I have the same model but it has no power I did replaced the transformer but still won’t work,the display board lit on but when I plug the MP3 audio cord in audio and hit play no movements in the display board like those long blue lights like those equalizer light when you play the MP3 so what it seems to be the problem there is it the relay need to be replace anyone has idea what could be the problem,Appropriate your help big time. Thank you 🙏

[@enriqueidy8]

I was wrong now I flipped the receiver and took the back part off and they're good and the sound that I hear its not coming from there but its almost impossible to know were the sound its coming from it seems that the sound its from the other side of the power supply were the screen and buttons are

[@eldonmeans111]

I'm having trouble with my 7800 pioneer stereo sound is low until you touch the Land R ,stereo nob

[@SevenFortyOne]

sounds like the controls need to be cleaned

[@enriqueidy8]

Hi I have the same noise problem but I don't know how to fix it, and u didn't showed on the video so I don't know were I need to look for or what do I need to change, so I would really appreciate if you could please upload a video of that or if you could at least send me a picture of were do I need to look for and what do I need to change...I need your help!!... Please help me! Thanks! ;)

[@enriqueidy8]

Oh ok those are the only ones that seem kinda bad I will have to take everything of and flip it then I'll see what can I find tanks!

[@enriqueidy8]

Ok thanks!! ;)

[@Audioupgrade220]

Cade o som ???

[@katla4991]

Give that case to me ille sort it out to perfection!

[@enriqueidy8]

Never mind it got burned :'( but its ok