That's about it 
Hopefully it should all work... although I'm still thinking on the best way to test all this.
You need those 2.2 ohms replacing as it won't self start without them of course.
My two concerns are running the PSU with no load, as some SMPS don't like that.
The other is using the bulb (as now) to finally power it up as again, many SMPS like the full voltage applied immediately. Sometimes they can fail to start otherwise... or worse.
I'll think on that one.
Next step though is fit the four switching transistors and replace the 2.2 ohms.
Hopefully it should all work... although I'm still thinking on the best way to test all this.
You need those 2.2 ohms replacing as it won't self start without them of course.
My two concerns are running the PSU with no load, as some SMPS don't like that.
The other is using the bulb (as now) to finally power it up as again, many SMPS like the full voltage applied immediately. Sometimes they can fail to start otherwise... or worse.
I'll think on that one.
Next step though is fit the four switching transistors and replace the 2.2 ohms.
You can obviously run the amp from your other PSU to listen to it, that's no problem.
For testing the SMPS (on it's own as now) the bulb is the right way to go up to the point we are at now. It's what we do next that's the question.
When it's all working and rebuilt the 2.2 ohms provide a measure of current limiting (soft start) each time the amp is powered up. Would it survive without them (relay shorted), probably... I shouldn't say that though.
It's a strange circuit in that department, typical I suppose of the era.
I'll think on it... want to calculate a couple of things for interest on it regarding the 2.2 ohms.
For testing the SMPS (on it's own as now) the bulb is the right way to go up to the point we are at now. It's what we do next that's the question.
When it's all working and rebuilt the 2.2 ohms provide a measure of current limiting (soft start) each time the amp is powered up. Would it survive without them (relay shorted), probably... I shouldn't say that though.
It's a strange circuit in that department, typical I suppose of the era.
I'll think on it... want to calculate a couple of things for interest on it regarding the 2.2 ohms.
Right well after all this work (not to mention yours and Jaycee's) I'll definitely err on the side of caution then and wait for those 2R2s. Just wish Maplin stocked them as they're nearby... then again Craplin never seem to stock anything I want when I want it.
Going to take my time soldering in those transistors now - am insulating the legs with teflon tube to avoid any risk of shorting to adjacent traces - I think this was part of the problem with the replacement transistors fitted by the last guy - he'd forgotten the insulation on the legs. I'll have to fit a jumper lead from one transistors leg to the PCB as well as one of the traces has completely lifted. Again shoudn't be a problem so long as I insulate the jumper where I can.
Oh yes I'm having to use those metal inserts afterall. The transistor legs fowl the PCB otherwise it's slightly too deep without the inserts. As I'm using thermal silpad now I'll only apply heatsink compound to the junction between transistor & metal inserts. On the metal insert side that faces the silpad I won't use any.
Last edited:
Sounds like your doing a good job with it.
Double check everything, the insulation sheet on those devices is critical... it has to be good and the devices have to be "flat" so that they press evenly onto the pads without cutting into it.
I would set the preset to a mid point initially, maybe even a little toward the end that gives the lowest output voltage but not right at the end as presets can jump a little as the wiper passes from resistive track to the "end" connection.
That's about it then for now I think
Double check everything, the insulation sheet on those devices is critical... it has to be good and the devices have to be "flat" so that they press evenly onto the pads without cutting into it.
I would set the preset to a mid point initially, maybe even a little toward the end that gives the lowest output voltage but not right at the end as presets can jump a little as the wiper passes from resistive track to the "end" connection.
That's about it then for now I think
Yes I prefer to keep things as they were originally designed at least in this case. However I'll give that part some further thought - anything that improves on the safety has to be a worth investigation!
Thanks Jaycee
****!!!!!
Great - in trying to be clever and bending the leg of one of the BUT11As close to the casing so I can solder that onto the nearby trace the leg has snapped off.... Flipping furious with myself!!!
I'll have to order a single BUT11A now and the minimum order for delivery is £20 via Farnall......... God I'm fuming here.. what an idiot!
Chances are a single BUT11A will be from a different batch too......... should I just order another full set to make sure they're all matched??
- J
Great - in trying to be clever and bending the leg of one of the BUT11As close to the casing so I can solder that onto the nearby trace the leg has snapped off.... Flipping furious with myself!!!
I'll have to order a single BUT11A now and the minimum order for delivery is £20 via Farnall......... God I'm fuming here.. what an idiot!
Chances are a single BUT11A will be from a different batch too......... should I just order another full set to make sure they're all matched??
- J
Well, safety I dont think theres much in it, but reliability certainly. NTCs are what is used to soft-start limit pretty much all modern SMPS circuits. They were probably nonexistant or expensive when Sony designed theirs, but nowadays they're common and cheap too. £0.95 ex VAT for a 5 ohm 5A one on CPC!
Oops. I always use a pair of needle nose pliers to clamp the legs near the body of the transistor when i'm bending them, so that the pliers take the strain and not the legs.
It's a pity CPC don't stock them - they are Farnell but with a smaller product range and no minimum order. What they DO have is MJE13007 which also looks like it'd be suitable. (edit) or TIP50G - I think I recommended that to begin with.
Last edited:
For the heck of it have just emailed Farnell to see if it's possible to send out a single replacement from the same batch - worth a try.
Failing that I can get my Dad to order some more BUT11As from RS as he has an account and they're not quite as bad with postal charges as Farnell. I'll look into the MJE13007s too.
Sheesh that's put me in a foul mood - it was typically the 4th transistor too and the others all went in neatly. Arghhhhh!
Time to pack it all away again and grab a cider I think....
Still thinking on how best to test this.
The 2.2 ohms allow sufficient current to pass to power the whole amp initially, and will pass around 1.5 amps while being within their 5 watt rating.
If it were me I think I would fit a 100 watt bulb for F801 (in the way we are doing now) and put a single low wattage (as in around 40watt or less) across the -/+49 volt rails with nothing connected to the centre ground. That will provide a "light")) load for the PSU to run putting hopefully around 98 volts across the bulb. Let it run for a few seconds... switch off and check by feel that transistors are "cool". If that's OK then adjust for correct output voltage.
The 2.2 ohms allow sufficient current to pass to power the whole amp initially, and will pass around 1.5 amps while being within their 5 watt rating.
If it were me I think I would fit a 100 watt bulb for F801 (in the way we are doing now) and put a single low wattage (as in around 40watt or less) across the -/+49 volt rails with nothing connected to the centre ground. That will provide a "light"
)) load for the PSU to run putting hopefully around 98 volts across the bulb. Let it run for a few seconds... switch off and check by feel that transistors are "cool". If that's OK then adjust for correct output voltage.
Hey Mooly
Thanks for that - not sure if I have another bulb holder spare unfortunately. Will have a look. I may throw caution to the wind this time since everything else has checked out this far and just power it up, set the voltage and keep 'em crossed! Afterall the only extras since we last checked the PSU are those four switching transistors.
Despite spending the past day or so 'upgrading' to Vista (this time with SP2), then remembering what a heap of rubbish it is (at least on my laptop) after using it for an hour, and then having to reinstall XP from scratch again (much better!), I have also gotten around to soldering the switching transistors in, as well as fitting a new transistor clamp today. I took the precaution of electrically insulating the reverse side of the clamp with the same SilPad material I used before, apart from one corner, where the clamp is grounded by a tiny die-cast nipple to the main SMPS chassis casting. As one of the pads for the center leg of one transistor was lifted, I had to solder a wire from there to the middle leg of the adjacent transistor. Hard to see it in the middle picture, but it is there. Last check was going over it all thoroughly with the meter set to continuity to make absolutely sure nothing was shorted...
Some pics:
Thanks for that - not sure if I have another bulb holder spare unfortunately. Will have a look. I may throw caution to the wind this time since everything else has checked out this far and just power it up, set the voltage and keep 'em crossed! Afterall the only extras since we last checked the PSU are those four switching transistors.
Despite spending the past day or so 'upgrading' to Vista (this time with SP2), then remembering what a heap of rubbish it is (at least on my laptop) after using it for an hour, and then having to reinstall XP from scratch again (much better!), I have also gotten around to soldering the switching transistors in, as well as fitting a new transistor clamp today. I took the precaution of electrically insulating the reverse side of the clamp with the same SilPad material I used before, apart from one corner, where the clamp is grounded by a tiny die-cast nipple to the main SMPS chassis casting. As one of the pads for the center leg of one transistor was lifted, I had to solder a wire from there to the middle leg of the adjacent transistor. Hard to see it in the middle picture, but it is there. Last check was going over it all thoroughly with the meter set to continuity to make absolutely sure nothing was shorted...
Some pics:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
....and this evenings problem (there had to be yet something else last minute didn't there!): the new 2R2 wirewound ceramic 'box' type resistors for the PSU board don't QUITE fit into the tight space...
ARGHHHHHHHHHHHH!!!
So going to have to order a pair of radial ones and have those upended on the board instead.
Typically when I was looking at that the mains voltage selector suddenly decided to ping off that PSU board... Just working out how it fits back together... if the worst comes to the worst I'll just fit a bypass and put a sticker on there as a reminder that it's hard-wired for 240V only.
Right... another two day wait beckons due to these damned resistors (WHY can't they leave things as a standard size instead of changing specs all the time?!).
- J
ARGHHHHHHHHHHHH!!!
So going to have to order a pair of radial ones and have those upended on the board instead.
Typically when I was looking at that the mains voltage selector suddenly decided to ping off that PSU board... Just working out how it fits back together... if the worst comes to the worst I'll just fit a bypass and put a sticker on there as a reminder that it's hard-wired for 240V only.
Right... another two day wait beckons due to these damned resistors (WHY can't they leave things as a standard size instead of changing specs all the time?!).
- J
Hi John,
I'm just looking at the pictures... looks good.
In the piccy it looks like that link runs right over the top of Q612... it is insulated fully from it isn't it? and with something that will withstand the temperature.
Vista is wonderful It's what I use on a four year old + Acer laptop.
I'm just looking at the pictures... looks good.
In the piccy it looks like that link runs right over the top of Q612... it is insulated fully from it isn't it? and with something that will withstand the temperature.
Vista is wonderful
It's what I use on a four year old + Acer laptop.
Yes it's insulated with teflon tubing - it barely shows in the pictures because of the lighting I guess. Made very sure that jumper wasn't shorting to anything else.
The voltage selector is quite simple to put back together - whew! Gives me a chance to de-oxit the connectors too so perhaps it was a good thing it went PING!
New 2R2s ordered and on their way... (drums fingers on the table-top!).
You ARE joking about Vista aren't you??! I've never used such a buggy operating system ever! In the history of.... er... ever! Even with the SP2 installed I still had trouble with the hard drive being accessed virtually endlessly, not to mention ceratain function buttons that just would not work on my laptop even using the Sony Vista drivers for them. I think as it's a celeron my 4 year old laptop was just not suited to it at the end of the day. Back to XP and running very smoothly
The voltage selector is quite simple to put back together - whew! Gives me a chance to de-oxit the connectors too so perhaps it was a good thing it went PING!
New 2R2s ordered and on their way... (drums fingers on the table-top!).
You ARE joking about Vista aren't you??!
I've never used such a buggy operating system ever! In the history of.... er... ever! Even with the SP2 installed I still had trouble with the hard drive being accessed virtually endlessly, not to mention ceratain function buttons that just would not work on my laptop even using the Sony Vista drivers for them. I think as it's a celeron my 4 year old laptop was just not suited to it at the end of the day. Back to XP and running very smoothly
Last edited:
Not joking about Vista... honest but pleased you have X.P. up and running OK.
Just to wander of the topic, but I find Vista super stable, quick and generally a joy to use. This screen shot shows the CPU and Disk activity while this DIY page was open in IE8.
Cold boot startup time is around 75 seconds for full desktop/sidebar and aero.
Shutdown time is around 15 seconds.
HDD light barely flicks every couple of seconds.
Four year old Acer Aspire 9301 2GB RAM and AMD Turion 64 mobile.
I clean installed Vista with no "bloatware"... honestly, it's ace.
but pleased you have X.P. up and running OK.Just to wander of the topic, but I find Vista super stable, quick and generally a joy to use. This screen shot shows the CPU and Disk activity while this DIY page was open in IE8.
Cold boot startup time is around 75 seconds for full desktop/sidebar and aero.
Shutdown time is around 15 seconds.
HDD light barely flicks every couple of seconds.
Four year old Acer Aspire 9301 2GB RAM and AMD Turion 64 mobile.
I clean installed Vista with no "bloatware"... honestly, it's ace.
