To recap Pioneer SX-780

[ReynaldoGonz]

Hello, I'm new on AK and I wich you having a great day, I want to ask you about to recap this great receiver. Where I can found the whole kit to recap, relay, transistors and principal replacements?

Another Q is, I bought some caps for power source section, same uf, same Voltage, even a little bit more temperature but the new ones cap phisical size's is smaller than original, and I mean like half or smaller than original. I was thinking and didn't replace them. The new ones are Nichicon UFW Audio Grade. What do you think about the size? It is ok?

Thank you.

 

[Watthour]

Welcome Aboard!

You will probably find that many newer electrolytics are smaller than the same capacity and voltage rated parts from a few decades ago. This is not a problem until lead spacing or mounting becomes an issue. Since the 780 does not use mounting clamps, that avoids any problems other than lead spacing.

 

[ReynaldoGonz]

Ok, thank you For your answer. So what is the brand and line you recomend or popular than everybody use to recap? And where people buys? I mean favorite web site to buy electrolytic caps? Thank you again.

 

[Bob]

start with looking at the inside, note any that look bad (bulging tops, stuff leaking, corrosion of wires, etc)
then (first download the service manual from hifiengine/electrotanya/etc) and look at the schematic.

using the parts list - and using the schematic - try to find each cap on the PCB. make sure
the value on that cap, the parts list, and the schematic match. if you're experienced then note
the polarity, size, and LS (lead spacing - important if you have a replacement choice that is
physically different).

I don't personally recommend downloading someone else's list, there could mistakes (accidental
and due to version changes), and you now have a 4th list to match the PCB, schematic, and parts
list ----- ALL 4 MUST AGREE identically, and completely.

then for each electrolytic cap, mark the polarity on the pcb. that way when replaced it will be correct.

for each cap, pull the cap (unsolder), measure the cap (some testers have a capacitance meter built-in
and ebay has sellers of cheap meters), and pull replacement from bag (do not scatter on desk - you will
spend more time looking for the right one), measure it (in case its bad, its from the wrong bag, or you picked
it up wrong), then solder it in. any other method means one or dozens of wrongly replaced caps.

you can easily do substitutions - try Nichicon MUSE ES - bipolar caps - in green, for replacing low value
caps near the audio signals. note there's a 35v 1000uf limit but the VP line has more choices.

group the values together (some folks don't like this) and go for a bigger order quantity, so five 10uf/10v, plus
3 10uf/16v, plus one 10uf/25v becomes a quantity ten (one extra) 10uf/25v at qty 10 discounts. the folks
who do this including me, say, the 10v may be too close to the 12v rails, 16v an 25v caps are minimum due
to bad tolerances of the lower voltage equivalents. and my personal favorite reason is that I can get the
better larger quantity caps cheaper than buying several smaller quantities. for example, I can buy
10 nichicon Muse ES's for less than polarized versions in small quantities.

just to be complete. buy a cheap vom/dmm. a cheap tester (for caps and transistors/diodes)
and good soldering iron, a solder sucker AND desoldering braid, etc.

lastly, document this if you sell (or try to fix 20 years later and have no memory like me)
and post here on AK to help others. and do research on all the posts here on AK to get
the hidden tricks.

good luck

 

[Watthour]

Depending on your location, different suppliers have different components available and different shipping rates.

A list of commonly replaced caps is:
Tuner
Rating V Qty Location
220 16V 3 C44,C53.
1 50V 2 C38,C40
10 16V 2 C71,
3.3 50V 1
22 16V 1 C35,C67
2.2 50V 1 C27
1 50V 2 C34,C41
4.7 35V 2 C60,C28

Amplifier
Rating V Qty Location
0.22 50 2 C227,C228
0.47 50 4 C401,C402,C403,C404
2.2 50 8 C103,C104,C117,C118,C229,C230,C309,C310
4.7 25 2 C217,C218
4.7 35 7 C201,C202,C324,C325,C326,C327,unmarked position
10 16 2 C318,C405
33 16 1 C317
47 6 2 C213,C214
47 16 1 C319
47 35 2 C305,C306
47 50 1 C316
100 25 4 C301,C302,C303,C304
100 50 2 C307,C308
220 6.3 1 C406
220 16 1 C311 (See Note 2)
220 63 1 C315
470 6.3 2 C105,C106
470 63 1 C314

 

[ReynaldoGonz]

Thank you guys, awesome tips. I see that a lot of folks likes to buy electronics components on mouser.com

For FM/AM calibration is there are some tricks to replace AM/FM signal generator????

By the way, to calibrate wattmeters, you can download a function generator to your cell phone. Then you choose 1kHz sin wave and plug to aux in on Pioneer sx-780.

Have nice week

 

[Watthour]

The tuner AM and FM sections can be peaked for signal without using a signal generator, but using broadcast signals instead. It is not an alignment, and will not work very effectively if the IF and decoder circuits are way out of spec, but it can adjust for some RF section drift or weakness. When the unit has been repaired, restored, and otherwise serviced to restore normal operation, alignment of the tuner would be the last step.

Incidentally, if you can burn a CD you can download an Audio Test CD file and create your test disc. It may be more controllable than a portable phone. The ISO disc image file is here:
www.wwdsltd.com/files/AudioTestCDImage.iso

The disc directory is also available:
www.wwdsltd.com/files/AudioDiagnosticTestCDKey.xls

 

[ReynaldoGonz]

Awesome!!!!! Thank youAgain.