Pioneer SA-9500 II restoration-the final frontier-Take TWO

[Ricktptman]

Okay, I initially set out trying to pull a single compromised (multiple switches brutalized-but otherwise functionally PERFECT) one of these back from the "parts unit" abyss and tried to sub out unobtanium switches. Some worked acceptably well, some didn't. I rehabilitated one of the three with a "stump" on the shaft to usability, but the other one is still way too stiff. I found a 50Hz stepped tone control that subs out with some spacer mods. Now, I just picked up a parts unit with ALL of the switches I need, but with one (balance) pot that's missing 1/2 of the split shaft. But IT has this "hum" ground potential issue with ONLY the phono board. I renewed contacts, tightened the boards (the phono input jacks were loose and not securely reattached) and cleaned the grounds on the phono board contacts. It's better than it was, but the problem remains. The biggest symptom is when you change the cartridge loading K ohms pot on the bottom control. The top one has very soft clicks when switched from one setting to the next. But the bottom one trips the relay when switching to and from the 100K ohm position. There are "pops" on all four settings. At first, I suspected the PS caps (not my first "go-to" on any occasion), but because this unit wasn't packed well and while FedEx did a decent job of not destroying it, I did find a fuse knocked loose, which means the trip wasn't feather bed gentle. Any advice is appreciated. TIA...

 

[Ricktptman]

I know I can just transplant the three switches from sample 2 to sample 1 and call it a day. I could just keep sample 2 (technically, it's sample 3, I already have a restored 9500 II with which I drive headphones in my main system) as a parts carcass, but that's how I wound up with the first parts carcass. I could just sell sample three, but as sure as I do, I'll need something from it about a week after it sells for one of the (at that point) other TWO restored models. I'm trying to cut my backup parts unit inventory down to a reasonable size. I'm down to less than a half dozen units (a few are RTR's, a CD player and the rest are various processors), maybe this is as good as good is going to get.

 

[Ricktptman]

For the first time in my restoration experience, I saw a capacitor "fail short". Can anybody tell me how likely it is that it took a bunch of neighboring "chiclets" out with it? I thought I'd shorted something but I checked everything (all of the three switches mentioned in earlier) and everything was 100%. The Cap was a 35VDC 47uF. Any suggestions are appreciated. I've ordered a couple of replacements...

 

[markthefixer]

For the first time in my restoration experience, I saw a capacitor "fail short". Can anybody tell me how likely it is that it took a bunch of neighboring "chiclets" out with it? I thought I'd shorted something but I checked everything (all of the three switches mentioned in earlier) and everything was 100%. The Cap was a 35VDC 47uF. Any suggestions are appreciated. I've ordered a couple of replacements...

Please specify WHICH cap POSITION (Cxx?) that was, on board number (ZZZ-999?) for us to have any help in determining the "chicklet's" fate.

well, there's only five of them in the unit:


sa-9500ii 47uf 35v
aws-109 is "switch assembly" which has voltage regulators on it.
aws-109 c29 47uf 35v cea +30v fixed regulator base stabilizer
aws-109 c30 47uf 35v cea -30v fixed regulator base stabilizer

These two would just substantially reduce or shut down that power supply voltage

awf-024 is "equalizer amplifier"
awf-024 C31 47uf 35v cea -30v rail bypass
awf-024 C32 47uf 35v cea +30v rail bypass

These two could hurt the +/- 30v regulator transistors back on the aws-109 board


awf-024 C35 47uf 35v cea +30v additional filtering

this last one would just turn off the phono preamps amplification

 

[Ricktptman]

Hi Mark,
It's C30 on the Switch Assembly Board. (AWS-109). I didn't think I'd need to be so specific, I was just curious in general terms. I've never seen one self-destruct like that before. I've found them "bad" but I've never seen one "die". Decades ago, I did see one kid (not me, but I was a kid, too) accidentally put one in backward in my electronics class and it went off like an M-80. I've had this amp as a parts donor (it works, or worked, fine, just with brutalized Speaker Selector/Mode and 50 Hz Bass controls) for at least fifteen years. I looked it over when I first got it and didn't see any suspicious-looking caps, but when I hauled this one out, it looked very er, "expectant". It didn't pop, but it hissed some magic smoke at me. I was really taken by surprise because no fuses opened. Maybe the relay opened and saved everything else. I was fixing a power switch lead which had come loose (but still cable-tied and not touching the chassis) from the power switch because of this months-long three-act opera of trying to "bring her back online" and the attendant assembly/disassembly cycles. I found a sub (I had to make it by combining parts from other sub 50Hz tone controls but the tactile nature of the seven stepped positions was annoyingly incongruent with the other three, but the resistance values were close) for the tone switch, but there's just not anything else out there that will sub for the Speaker Selector Switch and Mode Switch, at least that I could find. So against my better judgment, I bought somebody's part's donor which had the parts I needed. It's on the one-yard line. Naturally, that was the time for something new to go wrong...lol. Now I have two almost functioning (the other one has either a Phono board cap problem or a PS cap problem, the cartridge loading control pops loud enough to open the relay when switching to and from the 100K Ohm position) 9500 II's and one fully restored beauty. Not the end result I was hoping for. : - ) TIA for any help you can provide. You were a big help with my orphaned SX-980 restoration last year.

 

[Ricktptman]

Good to know. Thanks, Mark! Should I replace C29 and C30? C29, C31, and C32 "look" okay, but I know that isn't conclusive. I have ten of them on the way, so they'll be looking for a place to call "home" and the money's already spent. I'm just SO ready for this project to be done...

 

[Ricktptman]

Update Update: Well, it's blowing fuses NOW. It blew the left 800ma fuse when the replacement cap blew. The replacement (a physically smaller "Nichicon") went about 10 seconds in the circuit and blew my last 800ma immediately when I tried to get a reading on the connections after I took the breached Nichicon out. This is not good. There is an adjacent resistor that appears to be fairly beefy but it's not appearing stressed nor did it get unusually warm. The capacitor adjacent is not warm to the touch. The transistor (thus far) is apparently (?-or this pure AC? If so, how/why is THAT happening?) holding up, but now I'm unsure what to do next. The fuse blew before I could put my meter on the cap's connection points after taking it out. I'm not installing another cap until I know more. I know Mark's got his hand's full with family matters but Mark (or anyone), if you can find the time, please post back if anything suggests itself. Thanks again...

 

[Ricktptman]

Okay, when C30 went, it apparently (and more slowly) cooked/took Q11 with it. It's split clean in half. (Another thing I've never seen before...) So now it's blowing both 800ma fuses, and that's a step backward. Looking for a 2SA720Q or R. Update cubed: 2 2SA720R's ordered and on their way. I thought I hadn't plugged the amp back into AC, before the time I discovered that loose AC switch wire, but maybe I did before I saw it to check connectivity on those switch installations. I think AC had to have fried that transistor and cap. Hopefully, that's the extent of the damage. Still waiting for some helpful suggestions if anyone has any. I've only worked on three of these so far, so my experience level with this particular amp is still what I'd call "lowish". Any help appreciated, thx...

 

[Ricktptman]

Update: Replacing the 720 didn't help. Still blowing both 800mA fuses. I had my eye on the transistor and I started to see a wisp of smoke coming off the new 720 (I think it's a Q) so I pulled the plug before anything could totally fry. Something's not right. The voltages going to that transistor have to be crazy high. I can yank those controls back out of this one (the formerly better performing of the two) and stick 'em back in the one with the slightly cranky phono stage. I've almost got the relay trip problem on that one nulled out. I think some Caps are involved there. Two parts donors is one too many, but I can put 'em both back into deep storage and let somebody else take care of 'em in (if I'm lucky) twenty or thirty years...lol...

 

[markthefixer]

It could be that something has shorted OFF of the AWS-109 switch board (the location of the power supplies) causing the power supply to self destruct.
First i would check C35, 3.3uf 50v which is in a location of the -48v to be able to pull that much current if reversed or defective.

The way I would do this section is to pull Q9, Q11 and Q13, and when re-filling the positions, I would use new silicon.
Before applying power I would change D6 and D14. (all new silicon)
I would check ALL the polarities of the new capacitors, and any OLD e-caps would be replaced.
All resistors would be tested when the caps and silicon are out.

Now, OFF the board - to the -48v rails.
on the AWG-045, R65 and R66 are 1.3 k ohm 1/2 watt R's of an RC filter. IF the caps C53 and C54 (100uf 35v) were shorted the resistors R65, R66 would be burned up, MAYBE before the power supply self destructed.

on each of the AWH-052 amp boards have R6 & R7 3900 ohm 1/4 watt resistors which won't pass enough current to fry the power supply, while R11 82 ohms might. BUT it might be damaged.

Since these are the only draws on the -48v power supply, my suspicions center at C35, either old and shorted or new and installed backwards.
REMEMBER, C35 is on the -48v dc rail, so the POSITIVE terminal is GROUNDED.


Look, I don't get in very much, and I worry that my answers are SUPPRESSING other respondents from chiming in.

guys n gals: CHIMING IN IS NOT ONLY O K , BUT IT IS NEEDED!!!!



BTW: C30 blowing needed the help of a destroyed Q13 to get enough current, EVEN if it was installed backwards...

 

[Ricktptman]

Thanks for the replies, Markthefixer. This C30 APPEARS (I know, a problematic term) okay now, at least relatively speaking. I left power on it for about a second, maybe two. The heat appears to be coming off the (replaced) 2SA270 that had previously been blown into two pieces. (As I said, that was a new one for me...)
Since I had to go back into it (taking it as apart as apart gets) I looked closely for scorch marks around the (repaired) power switch wire that had come loose along with pretty much anywhere else and there's no signs of that kind of mishap anywhere. No solder drips, or any other "chaos generators". My narrative has always been that unless there's a reason to suspect caps, not to suspect caps, but the more I poke around, the more it seems like this might be the poster child for the "pro-recapping" side of that debate. The ONE cap I've replaced is installed (polarity-wise) exactly like the old one (it was swollen but still "whole" and not hard to read, plus the polarity's marked on the board) so while I'm definitely NOT beyond making dumb mistakes (usually because I'm constantly having to put on or take off my progressive lenses) I don't think I installed anything (basically two components, the 2SA720 and C30) backward. I'm going to print off your post and go back and focus on your suspects. I appreciate it very much. Power supply problems aren't my strong suit and I know it. I'll post back, and yes, anyone else who has experience with 9500 II's, please weigh in. BTW, the replacement 720 is a Panasonic and there are no markings at all on it. The original was a Mitsubishi. I did not test it prior to install, I installed it "flat side" opposing (180 degrees, which appears to me to be how it reads on the circuit board in terms of Mitsubishi on the other side. Which is how it's oriented in the other 9500 II with the "pop" in the phono stage 100K ohm setting. Emitter on the right, yes?

 

[Ricktptman]

Update: the Panasonic, which didn't crack when power was applied was NPN. I hauled it out after I found out. An unbranded generic (ostensibly PNP) popped immediately like the original before it. So...that's weird. If I'm reading it right, Q11 is PNP, yes? I'm replacing C35 next...

 

[Ricktptman]

Update: I have one of them running and pretty much "done", using parts from the greater disabled of the two to restore the less abused, lower hours (but cranky-ier) survivor.
I think Markthefixer was pretty much dead on w/ his insight that the Power Supply ate itself. It appears to me that everything is okay on the left half of the board, but something is seriously wrong (rectification diodes?) in the right, rearward quadrant of the PS board. I'm going to start a new thread about the phono stage "instability" issue in the Pioneer forum. I appreciate Markthefixer holding up the "karma" end of the equation. Thanks, man...

 

[Ricktptman]

Here's a pic of the end result.

 

[Ricktptman]

On second thought, there's no reason to start a new thread. I just wanted to comment and seek advice from other owners. I've seen this thing about the volume control noise, relay opening when rotating it quickly or switching in Loudness or tape monitor switches posted elsewhere. Here are a couple of thoughts based on the two (Excluding the sacrificed 9500 II from Hell.) with which I have direct experience. First, if you let 'em sit and run for a time (if they've been left unused for extended periods) a lot of that instability disappears.
I've had this one on nonstop (letting it run through both phono inputs and the line-level inputs) for about three days. I shut it off yesterday late, cut it on today and it's pretty well behaved. There's still a little bit of noise on the phono side (not on "1" but some on "2") but if there's a turntable installed on either, the problem goes away. I tried shorting plugs and that solves the problem as well. The tape monitor/loudness/volume "click" and "pop" issue was pretty much eliminated by running ground wires to the grounds on both sides on the Phono jack board. I've seen twitchiness in the amps I've owned before, but this one was uniquely sensitive to it. I'm going to knock the dust (that I didn't see until I posted the pic) off of the bonnet, seal it up and call it a day.