Hmmm... you have to stick with what is fitted I think, particularly as the amp has been working OK (It was, wasn't it ? and on 240 volts). I'll look again at these later and try and reason it out... shuffling the pdf on a laptop at the mo.
The switching transistors will have a very high voltage high frequency waveform on the collectors that can be quite "searching" in finding any insulation problems.
The switching transistors will have a very high voltage high frequency waveform on the collectors that can be quite "searching" in finding any insulation problems.
It's clearly marked as being 56K for the UK/E model on all diagrams, with R609 being 100K as you mention. But on my board both are 100K. I'm not going to worry about it any further - I'm sure the resistor as fitted is correct comparing it with the pictures from other UK/multi-voltage units.
Well it did work OK until it blew several transistors on the last user
I'll try and get a replacement - will sleep better knowing it's all working safely. I know you can buy Sil-Pad in certain sizes they just seem to be difficult to get hold of in this country for some reason. I may just have to be patient and import a piece from the States.
- J
Anything here (don't look at the prices)
Semiconductors | Sockets and Heatsinks | Thermally Conductive Insulators
I'll look in later
Semiconductors | Sockets and Heatsinks | Thermally Conductive Insulators
I'll look in later
Thanks I'll have a looksy!
This is the company I sent off an email to yesterday:
Plastic Shims and Gaskets Ltd, Plastic gaskets, plastic shims, plastic spacers, polymex, plastic washers
This is the company I sent off an email to yesterday:
Plastic Shims and Gaskets Ltd, Plastic gaskets, plastic shims, plastic spacers, polymex, plastic washers
This looks promising from that link you posted above:
RS | Semiconductors | Sockets and Heatsinks | Thermally Conductive Insulators | Thermally Conductive Insulators (Heatsinks)
Cheers Mooly!
RS | Semiconductors | Sockets and Heatsinks | Thermally Conductive Insulators | Thermally Conductive Insulators (Heatsinks)
Cheers Mooly!
Maybe a bit late now but Rapid (Rapid | Distributors of electronic components, electrical products and educational supplies) sell silpad material in sheets. You could probably use TO-3P size insulators too.
Thanks for that link Jaycee
I'll probably go with the link I posted in post 87 - works up to 150C which should (I hope!) be fine here, plus it's adhesive on one side which will make it easier to position for this application. My Dad also has an account with RS which makes it easier.
The original insulation pad is pretty thin - what I'd call an average insulating pad thickness approx. 0.15mm or so, and that RS stuff looks to be about the same. If anyone can't see why this wouldn't work I'll go ahead and order a sheet.
- J
I'll probably go with the link I posted in post 87 - works up to 150C which should (I hope!) be fine here, plus it's adhesive on one side which will make it easier to position for this application. My Dad also has an account with RS which makes it easier.
The original insulation pad is pretty thin - what I'd call an average insulating pad thickness approx. 0.15mm or so, and that RS stuff looks to be about the same. If anyone can't see why this wouldn't work I'll go ahead and order a sheet.
- J
Careful, the RS datasheet doesn't state this is insulating, just that it has High thermal conductivity, weather this is an omission as the other materials say insulating...?
You could use a Kapton film and heatsink compound.
rgds
jms
You could use a Kapton film and heatsink compound.
rgds
jms
Ah well spotted - yes it doesn't mention it. Thanks!
I think this one looks more suitable:
http://uk.rs-online.com/web/search/...od=searchProducts&searchTerm=707-4819&x=0&y=0
Yeah I keep having intermittent problems with RS PDFs too - very odd! Managed to open the multi-PDF set for the insulating pads OK though (using Firefox on a Mac).
Cool I'll order that one then - it's 0.25 thickness and the original was approx. 0.35 (using a micrometer) but I don't think that'll make much - if any - difference here.
Thanks everyone
- John
Cool I'll order that one then - it's 0.25 thickness and the original was approx. 0.35 (using a micrometer) but I don't think that'll make much - if any - difference here.
Thanks everyone
- John
Well fingers crossed I'm all set then as far as ordering parts is concerned. Will test the remainder of those resistors over the weekend, and if OK will start soldering it all together, at least as much as I can do until that insulating sheet and the aluminum for the clamp arrives.
R607 is still bugging me as I can't believe Sony would list it incorrectly 3 times in the service manual (for the UK/E model). I wonder if this 100K (when it should be 56K according to the manual, or 100K for US/Canada) would be the reason why many of these SMPS from this model seem to fail quite regularly (along with old & dried out 85C rated caps)...
Really appreciate all the help on this thread this project would be dead in the water without it
- John
R607 is still bugging me as I can't believe Sony would list it incorrectly 3 times in the service manual (for the UK/E model). I wonder if this 100K (when it should be 56K according to the manual, or 100K for US/Canada) would be the reason why many of these SMPS from this model seem to fail quite regularly (along with old & dried out 85C rated caps)...
Really appreciate all the help on this thread this project would be dead in the water without it
- John
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id say the main cause of failure of the psu's would be that those transistors were most likely pretty cutting edge (and used on the edge) in those days... but now, they're 10 a penny and much more reliable. That and the capacitors.
I wouldn't say R607 makes much difference - it's probably been increased to 100K so that the error amp runs a bit cooler. An increase in resistor value certainly wouldn't cause failure here.
I wouldn't say R607 makes much difference - it's probably been increased to 100K so that the error amp runs a bit cooler. An increase in resistor value certainly wouldn't cause failure here.
Ah right that's interesting to know - cooler running with that resistor value with the SMPS shut away in that aluminium box as it is, would make sense. The service manual is also dated 1978, and this unit was manufactured until 1981 I believe so there would have been changes that perhaps aren't documented. The aluminum box I mention is said to be there to prevent radiated muck from the SMPS affecting the audio circuit. However I would have thought it seals the heat in too to a certain extent?! Was considering leaving the top off of the SMPS box to aid with convection. Mind you Mooly says the BUT11As are cooler running so perhaps it's not of much concern.
You can see the SMPS box at the top left in this picture:
http://mariuszek.pl/sony2.jpg
- John
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This 'ere power supply...
It's very unusual in that it appears to have major differences between "intended markets. Nowadays a SMPS would work on any input voltage without change.
What I have noticed in the manual, and can't explain is this.
The 120 vac model works on just that... 120 volts and that gives around 170 volts DC as the working voltage for the PSU. The linear reg reduces that to 127 volts as per the manual. The primary winding of the chopper transformer has 38 turns. See attached image.
That's the first version.
The 120/240 model appears to employ a switchable voltage doubler at the bridge rectifier input. This in each case gives around 340 volts DC to power the PSU. Twice the voltage of the single 120 vac model. The output of the linear reg is adjusted now for 250 vdc. Puzzle... the chopper transformer is now shown as having 70 turns on the primary. All else being equal (which it isn't actually) more primary turns will give a higher output from the PSU. That doesn't happen, there is also no "direct" sensing of the output voltage as would be done nowadays... so can't quickly explain that.
As to the resistors... R607 feeds the error amp. It's shown as 56K for the PSU with 340 vdc to feed it and 100k for the one with 170vdc. That too doesn't make sense.
R606 and R609 values do seem right. The lower resistor value on the lower supply as you might expect. The value of R609 in the resistor chain with the pot directly affects the output voltage as it's the feedback network. R606 just feeds the zener reference and isn't critical as such.
It just seems odd having two distinct models... the 240vac one can work in all markets with it's doubler arrangement at the bridge. So why have another "purpose" designed one just for 120vac that uses different transformers etc... dunno
It's very unusual in that it appears to have major differences between "intended markets. Nowadays a SMPS would work on any input voltage without change.
What I have noticed in the manual, and can't explain is this.
The 120 vac model works on just that... 120 volts and that gives around 170 volts DC as the working voltage for the PSU. The linear reg reduces that to 127 volts as per the manual. The primary winding of the chopper transformer has 38 turns. See attached image.
That's the first version.
The 120/240 model appears to employ a switchable voltage doubler at the bridge rectifier input. This in each case gives around 340 volts DC to power the PSU. Twice the voltage of the single 120 vac model. The output of the linear reg is adjusted now for 250 vdc. Puzzle... the chopper transformer is now shown as having 70 turns on the primary. All else being equal (which it isn't actually) more primary turns will give a higher output from the PSU. That doesn't happen, there is also no "direct" sensing of the output voltage as would be done nowadays... so can't quickly explain that.
As to the resistors... R607 feeds the error amp. It's shown as 56K for the PSU with 340 vdc to feed it and 100k for the one with 170vdc. That too doesn't make sense.
R606 and R609 values do seem right. The lower resistor value on the lower supply as you might expect. The value of R609 in the resistor chain with the pot directly affects the output voltage as it's the feedback network. R606 just feeds the zener reference and isn't critical as such.
It just seems odd having two distinct models... the 240vac one can work in all markets with it's doubler arrangement at the bridge. So why have another "purpose" designed one just for 120vac that uses different transformers etc... dunno
