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

[sp10mk11]

It certainly sounds like the speaker relay has been bypassed because of problems it does happen, I have come across amps where the output is intermittent etc due to the contacts on the relay, so good luck with that.
I wait for the next instalment.

I have a Keith Monks record cleaning machine and it is the best tool I ever bought, I often used to get second hand records and they were often covered in that damp mould, clean them up on the machine and they are like new.

Gary

[stevehertz]

Ah, Gary, that was what I wondering, if the KM machine would remove mould? Seems like it does. I can get my collection (130 records) KM'd for £150 - does that sound reasonable? Just over a pound a record and new inner bags too?

[sp10mk11]

I would go for that sounds a bargain when I think how much is involved in cleaning them
Gary

[Edward Huggins]

£150 seems a lot compared to soft water, a dash of isopropyl alcohol, a lint free cloth and a bit of elbow grease! Edward

[paulsherwin]

Back on topic please.

[Edward Huggins]

Very sorry, I know I was headed in that direction...
Just trying to save the OP a few shillings! Edward

[stevehertz]

Found the phono input poor fidelity/distortion problem. Basically a hard chunk of foreign material (general debris) that was stuck to the stylus. I had of course, prior to playing records cleaned the stylus with Audio-Technica AT607 Stylus Cleaning Formula, in fact I had done that a few times. However today, wearing my strongest close up glasses and using a magnifying glass I could see that the stylus had a blob shape rather than a sharp point. I used another stylus brush with more 'beef' than the one with the AT607 to remove the offending material. The result? miles better, it's only the general condition of my records that is at fault now, but picking out my best ones amongst them, the fidelity is excellent. So, I'm still considering whether to get the whole lot KM'd. I probably will.

[sp10mk11]

I am so pleased to hear about the problem being solved and that you are enjoying the sounds you are getting.
All the best
Gary

[stevehertz]

I've just got it back on the bench to remove those links that someone had soldered across the output relay contacts. In doing so, I'm changing a few scorched resistors that I noticed the last time I was working on it. The resistors read ok, but for the sake of a few pennies it makes sense to drop some new ones in. R911 & R912 are 560 ohms 2W, and R913 is 33 ohms, but it's nigh on impossible to read its wattage from the cct diagram. It's relatively small, so I cant see it being higher than say 3W, at the very most 5W, so I've ordered some of each from Cricklewood, including the 560 ohm ones. I'm also changing C913 100uF 50V that gets toasted nicely sitting as it does next to these resistors, I'm fitting a 105 degrees one (was 85).

So, in a few days time when the new parts are fitted I'll switch it back on again and hopefully the switch on thump will have gone.

[Goldie99]

Hi Steve - I don't quite understand R911 & R912 - the cct diagram shows them as 560R, 1/2 W, non-flammable, but the indicated voltages suggest they're dissipating closer to 1W - so 2W sounds like a good replacement if they'll fit. I assume the manual values (1/2W) are wrong.

R913 is indeed harder to read, but looks like 33R 1W, non-flammable on my screen.

R914 - the bigger 5W item in the photo is 'labelled' on the cct diagram, but its position is not actually shown. I assume it's in series with R913 ? otherwise 33R 1W wouldn't last long...

Rgds
Alan

[stevehertz]

Thanks Alan. I think those resistors are under-rated anyway. Whenever and wherever resistors are getting hot I much prefer to have an over-rated one in place.

[stevehertz]

Resistors and caps arrived today, great service from Cricklewood as I only ordered them yesterday! Those parts now fitted - see photo. I have raised the new resistors off the PCB as far as I dare and paid attention to spacing etc so as to minimise the effects of the heat they are dissipating. But mostly this latest bit of work was about removing those links from across the relay outputs. Ok, the moment of truth, switched on, no more thump!! just a gentle click of the relay after a few seconds and then it comes to life.

Out of interest, this is a very deep set (front to back) physically and what with those inline step up transformers from the phono leads, that further compounds the problem of how much room is needed at the back of the receiver, pushing it even further forwards on its shelf. To counter this, saving at least a couple of centimetres, I have ordered some right angled phono plug adaptors.

I am taking my complete record collection to be KM'd on Friday, and I'm going to source and deploy a suitable dehumidifier in that corner of the room to help prevent micro mould formations on them in future.

[sp10mk11]

Excellent News! Steve no thumps he he , and nice tidy work on those resistors.
I never understood why some manufacturers would put power supply boards upside down in some equipment, when you think how large gear was in the 70s there was always plenty of room, I was going to off board some regulator transistors on a Pioneer tuner amp I had as these ran hot, though well heatsinked there was plenty of heat there gently cooking everything else.

Anyway
Great news oh and you will enjoy your records so much more once they have been cleaned up on a record cleaning machine.

Gary

[stevehertz]

Thanks Gary, and once again thanks to everyone else who has taken an interest in and contributed to this thread.

One further thing, having been caught out with that 'bonded on' debris on my stylus, I've ordered a 40x magnifying glass to keep (literally) an eye on it in future. Seriously, I 'thought' my stylus was in pristine condition, but how wrong I was when I actually got up close and personal with it, it was filthy, yet I'd been (softly) brushing it with a stylus cleaner brush and solution thinking that it was doing the job. There's lots of info on the net about cleaning styli with crud built up, and remember, it's a diamond, so you're unlikely to harm it using a tool/blade of some sort to get the hard stuff off. How you can damage it is by being too brutal and damaging the cantilever or support. A juxtaposition..

[sp10mk11]

I think you will find Steve that once your records are clean, the amount of "crud" that builds up on your stylus is virtually nil, have not had to clean my stylus for years so to speak.
Though I still give it a go on the AT vibrating stylus cleaner occasionally
Gary

[stevehertz]

Hmm. How effective are those vibrating stylus cleaners? I didn't know they existed until you (Gary) just mentioned it and I've had a look. Not sure if the AT one is still made but found a Flux Hifi one, made in Germany. Is it like an ultra sonic cleaner effect?

[Edward Huggins]

Not had to clean your stylus "for years"? That's weird. Edward

[sp10mk11]

"Weird" ? not at all matey, all my records are clean, because I clean them on a Keith Monks cleaning machine when I get them there is no crap on them to build up on the stylus, maybe a bit of fluff occasionally but that's it
Gary

[stevehertz]

I've noticed that on FM the signal strength meter seems to pretty much always indicate a reading of 4.5 (out of 5). This, seemingly no matter how weak or how strong - within reason - the signal is. For example, BBC R2 I receive good and strong and the signal strength meter reads 4.5. On another station, although the stereo lamp lights up, it's very noisy and not really capable of resolving stereo (you have to switch to mono to clean the sound up) still shows a meter reading of 4.5, and it's like that all along the band; any channel that pops up reads 4.5 signal strength! I'm thinking that the signal strength meter/circuit may need calibrating or setting up somehow? It's not multipath issues as the receiver has a button to switch the meter to read MP, and it's fine, there's nothing there to speak of.

[sp10mk11]

It could be that you live in a strong signal area and the tuning can is not fully shielded so you are picking up a signal in the tuner aswell as through the aerial, but do not hold me to that as I am not an expert on tuners in that respect. I live down here in Cornwall and use an external aerial (only a 300 ohm circular one stuck on the side of the house), I also have a Sony ST-5950SD tuner which I always got 4.5 on the signal strength meter apart from a few pirate stations.
See what it picks up without an aerial connected
Gary