Sony STR-6800 receiver - stiff tuning, dial lamps and...

[Goldie99]

Hi Steve - I had a look around the 'net - for what it's worth, maybe the following will help (?):

http://www.usaudiomart.com/details/9.../images/98091/ - the first photo suggests that the whole base panel can be removed. If I'm right, the area you need is under the central board, the one with the relay on it.



The next photo, from a site in Germany, suggests that you might be able to 'pivot' that central board up, with minimal if any desoldering, to get access to the area you need ? If you speak / read German, that photo is actually from a forum thread discussing the same illumination issues you've been having - http://old-fidelity.de/thread-2715-page-3.html



Hope it helps & good luck,
Alan

[stevehertz]

Alan, many thanks indeed. Actually, removing the securing screws for the relay board did not immediately help because there's a sheet of steel behind - a screen I guess. However, after pulling cable runs out of their holders and releasing certain plugs and undoing screws, the steel panel complete with two boards could be eased up on to its side - see photos. Great! It's evening and I've had a cursory look around the problem area, elsewhere too, but I can see nothing so far, all the joints look good. I'll have a better look in due course and if necessary I'll just change all the possible culprits around the area of the fault.

[sp10mk11]

if you remove the plug in connectors on the power amp ic blocks you can then turn the board to the left to give yourself even more room, it is amazing looking at these pictures so much of it is still in my mind
Gary

[Goldie99]

Excellent Steve - at least now you can get at everything, and hopefully have a better look around the likely Q210 area.

[stevehertz]

Got It! Amazingly, it was the same fault as Gary found in his receiver years ago, an open circuit resistor! R257 330k was the culprit. Given the low stress position of this resistor in the circuit, it is highly unlikely that it failed due to over current or over voltage. But there are hundreds of resistors in this receiver, yet out of all of those, the one that failed is the same value and in the same position as a known previous failure! It suggests to me that 40 years ago Sony bought a batch of 'iffy' 330K resistors, and now they're coming home to roost. I also changed the RH channel version of this resistor, R258 as a precautionary measure.

Ok, I still have to re-package everything that's been opened, snipped, unscrewed or skewed and then I'm going to check out my green dial lamp illumination, whether or not to apply more green paint or not. I'm going to see if the angle of the LEDs against the edge of the glass makes a difference brightness wise, and that will to some extent dictate my next move on this issue. Fingers crossed nothing else decides to go belly up meanwhile!

[Radio Wrangler]

Before you put the lump back together. Spend an hour or two scouring the circuit diagram for any other 330k resistors. Head 'em off at the pass!

David

[stevehertz]

Out of interest, as I mentioned earlier the Dolby FM lamp has been removed and the two feed wires connected together. Is this ok or is something going to be stressed feeding into a short? I'm not bothered about the redundant Dolby circuitry, just the way that the lamp wires have been shorted.

[Goldie99]

Good to see it's sorted Steve - and that your measured voltages were indeed pointing straight to the problem. It's satisfying when it 'comes together' like that

[sp10mk11]

Hello Steve I am glad this saga is over, I would never short wires to a lamp that is not used, a strange thing to do I would disconnect them and insulate them.

It will be good when you have this back together and can try it out

Gary

[stevehertz]

Thanks Gary, I've parted the Dolby lamp wires and heatshrunk them side by side, cut, with one longer than the other. I can only guess that shorting them must have been over-running a power supply somewhere?

Thanks to everyone who has provided input, help and encouragement. I genuinely wouldn't have been able to do it without your help, much appreciated. Here's a couple of photos of the receiver not quite fully back together. I put another coat of transparent green paint on to the dial glass ends and the green scale is fine now. Actually, the colour hue in the photo is not correct, it makes it look quite bluey-green. It is a tad bluey-green compared to the meters, but that's a small price to pay for using the LEDs with their cold blue light, the 'warmer' incandescents being unavailable, and of course the LEDs run cold, so no more scorching around them.

Again, the photos are without flash, hence the lack of sharpness.

[sp10mk11]

aww I am getting all "want one again" such lovely bit of kit.
I had the STR-5800 aswell and it sounded nothing like the 6800, it was thin and gutless sounding whereas the 6800 is very crisp and focused by comparison
I am so pleased this has worked out, and yes the display looks good well done
Gary
Ps
I realise you are a valve guy so it will be nteresting to see what you think of it sonically

[stevehertz]

Gary, interesting that you say how the 6800 sounded different to the 5800 because I have a copy of Hi-Fi Choice's 1978 (?) lab tests on receivers. For those who do not know, Hi-Fi Choice was not a hi-fi mag back then, they (Angus McKenzie and co) did extensive listening and lab tests on different hi-fi components and put each batch into a small, A5 paperback book every couple of years as new models came out - I wish they did them now, there'd be some surprises comparing new stuff with old! Anyway, I digress, in that copy they review the Sony STR-2800, 3800 and 5800 and none of them get a firm recommendation although they were not deemed 'bad' receivers. I have heard others rave about the 6800 too - just do a search on the internet. There's also a 7800 but I'm not sure if it was available in Europe, or at least, someone on the net said that. Maybe Sony just took more time to set up their flagship models because often, with a tuner or a receiver, its ultimate performance is as much dependent on how it has been aligned as it is its paper spec. Though doubtless as you go up through the models, it wasn't just the power output they upgraded, the tuner sections too would have been more sophisticated.

While working on it, I have only been using mine on the dining room table with a 'freebie' fm ribbon aerial pinned to the wall and some cheap modern Panasonic speakers that someone gave me. So when I take it into my lounge later today and plug in a good fm aerial feed, I will be able to comment better on its RF performance. Certainly, its AM performance is the best I have heard, bar none. Indeed the reports on the 5800 said that its AM performance was above average. There is also something very 'pleasing' about its sound that I can't quite put my finger on. Although in many ways I am a valve man (guitar amps, vintage radios), in hi-fi terms I gave up with valves in the early 80s when I got fed up with intermittent faults and noises, largely attributable to valves and their bases. And also the lack of inputs etc - although I did overcome that with an input switching device. Nonethless, in hi-fi I prefer trannies because, basically, they are more accurate. I'm also a fan of the valve hi-fi sound though; I'm not starting a debate, just for my own reasons I now choose to use SS hi-fi equipment. The 6800 sounds very smooth and just 'nice' somehow (un-fatiguing?), I realise that is perhaps a weak word to describe a hi-fi component, but why not? Anyway, I'll report back later wrt how the 6800 sounds with a good aerial and good speakers.

[stevehertz]

A couple of photos with the receiver all back together.

[sp10mk11]

Like you Steve I have the "bibles" ako Hi-fi choice review books wonderful things.
When i think of some of the gear I have ehard over the years to describe some thing as "nice" is a great compliment about it.
Just out of interest it also has a very good phono stage
Hope you enjoy it
Gary

[stevehertz]

And finally, in place in my hi-fi system. It sounds nice with my Leak 2075 speakers. I have fed it with CD, but not phono yet although I have just purchased some Ortofon T5 SUTs for use with my MC10 Super cartridge. BTW, I had to purchase three extra long Spur shelving brackets and uprights, this thing weighs 17.6kg, that's 39lb in old money.

[Radio Wrangler]

Spiffing!

David

[sp10mk11]

That is a great set up there Steve oh yes get the Garrard set up running through it, I keep looking at the STR.
Just enjoy it steve and let us know
All the best
Gary

Ps in the early part of this thread I mentioned not washing the dial glass as the letters can come off, this happened to mine around the selectors, being the obsessive person I am I spent a lot of time making up the words and printing them on black paper that I could put behind the glass and it worked.

here is a jpeg of it

[stevehertz]

Gary, good advice. It was around 1978, and working on a radio set I began cleaning the back of a glass dial - with vigour. I can't remember what set it was, a nonedescript 50s table model I recall, and of course, the legends were just water slide transfers and the inevitable, they just rubbed off. That was a hard lesson, a nice condition set ruined, but etched in my neural network since that day: "Don't attack dial legends with vigour and chemicals!" So ever since then whenever I have had to clean up a dial I've always trod extremely carefully, and this set was no exception! So yes, good advice indeed..

[stevehertz]

I'm a bit nonplussed about the phono sound. The 6800 has got a pretty normal (as far as I can see) MM input stage (50k) and I'm using an Ortofon MC10 Super (MC) with a pair of the little Ortofon mono T5 step up transformers. I'm thinking that combination should be fine, but I'm having to reduce the treble setting considerably, and increase the bass a fair amount on the amp to get what I would call a flat response. Not just that but it doesn't sound too brilliant either. I've tried both sets of phono inputs. The tonal imbalance suggests to me that there's an impedance mis-match going on resulting in a treble-heavy/bass light nett frequency response, but I've looked at the specs of all three culprits and - maybe I'm missing something - it should be ok?

[Radio Wrangler]

Try using a known-good MC preamp/equaliser into one of the flat inputs on the Sony. That will narrow things down a bit. I wouldn't just assume it was loading impedance. Theories can be very misleading without a firm foundation in repeatable reality. Look up 'N-rays' for a bit of a laugh.

David