Answering some questions from
@slimecity here as some info may be of interest to others.
I think your 2kW transformer is a great idea.... 1kW would be fine (perhaps even 500 or 600W), but 2kW leaves no doubt that the power supply is unaffected by the step-down unit.
1. Yes there was a few errors in the service manual and a few differences between it and what i found in my amp. I definitely didn't catch all of them, but here is what I noted:
- R611/R612 (phono): 280kOhm in amp (390 kOhm in schematic). Either value is okay ( see my thread for graphs and effect on RIAA)
- C725/C726 (preamp): manual says 47 uF, 6.3 V but 47 uF, 10 V found in amp
- C823, C824 (main): 500 pF ceramic (measure voltage and update here), not listed in manual
- C813/C814 (main): 100 pF, 50 V ceramic not listed in manual
- R841 (driver): 3.3k Ohm in parts list. 2.7k Ohm installed and service schematic. Not a big deal.
- R861 (driver): 3.3 (!) Ohm in parts list. 2.7k Ohm installed and on service schematic. A big deal.
- Note there is a service bulletin on the bias resistors R851/R853 and some nearby caps. Not mandatory unless "the trouble is found" with TR811-TR814
Also note
- R005/R006 (protect.): 220 Ohm 5W resistors on protector block PCB hit a temperature of over 100 C.
There was definitely some other differences but that should be the main ones. Sorry I didn't note everything. I think you can order based on SM, and then you may have to make a small second order later. This will still be faster than measuring/reading all resistors.
Note that this is for the AU-777A. I haven't actually compared the AU-777D manual closely, although many have said only the power transformer is different.
2. If I recall correctly, the little yellow film caps are nichicon brand. Sorry, I don't remember which series. I just used them because the WIMA were too big. I'm happy with the film cap replacements! Even if not sonically better (they definitely aren't worse IMO), they will last longer than electrolytics. Basically you will find that polypro are large and you may need to go to polyester for larger values, but I personally don't really think polypro is so superior. That said, for some of those smaller values I might try harder next time to replace with C0G ceramics; this is what I did for the smallest values (the little blue caps you can see in my build) but in later rebuilds I tried a lot harder with this.
3. Yes, I used the 1845 for the C458s and a couple of others in this amp. I would not do this now since the 1845 has too small current handling specs; it is not a problem in many applications but unless a tech calculates the current being used, KSC1815 should be used and recommended as the sub. I've later used 1815 a lot and it sounds great too.
A FEW OTHER COMMENTS:
This was perhaps my 2nd or 3rd rebuild when I was getting into this hobby. I would do several things differently now, so I wouldn't take this thread as a bible.
Also, a lot of the magic is in choosing which signal path film caps to leave alone and which to upgrade (and you need to be able to read schematics, at least to the point of recognizing signal paths and feedback, to decide what to do. Sorry I didn't list them as I went along in the thread but if you have questions as you go along please do ask. (even worse, I've seen several threads lately with 'upgrades' where electrolytics where changes to film caps of same (ok), or lesser (not ok) value). Majority of the small signal path caps should go up on capacitance but not all.
Also, many caps are effectively in signal path even if they don't look like they are (for example, a cap that shunts high frequency to ground, might look tangential to signal path, but of course does effect the signal). They fact that so few people recognize all caps in signal path is a good argument for just recommending replacing all electrolytics with film caps to make things simple.
Same goes for resistors and signal path recognition. You could replace just specific resistors and save yourself some trouble, and just stick to audio path. I enjoy the idea of knowing all of my resistors are within 1%
. I think it was worth it too. My 777A is definitely up there with some amps in my collection that it probably shouldn't be and perhaps this is one of the reasons (?).
Something I get asked in PM is what did I use for the TO66 transistors mounted on the chassis near the driver boards. Those are the only two original transistors and I didn't replace them, partly because subs are not ideal. There are some modern options in TO-66 package, but I would be tempted to use a more modern package for better specs, and that just wouldn't look quite right. Anyway those TO-66 rarely fail in the AU-777 series.
And again, looking at my photos, I can definitely see a quite a few little things I would do differently, from power supply to signal path to transistors, now that I have more knowledge and experience so just use this thread as a rough guide. Also, I wrote a few incorrect things in my statements... I was very new to the hobby at that stage.
Looking forward to seeing your amp... I've yet to see another one with films caps and ceramics done AND all resistors.
Okay, back to listening to music.... now, to use my AU-777A. or the Sony TA-N902 I just finished fixing.