Thanks Ian ... I appreciate both your help and sentiment.
Incandescent bulbs are no problem in this neck of the woods - it's the modern energy saving types that haven't been invented yet apparently !! I'm going to try that tonight and I'll post what happens.
As for fuses - umm what fuses 🙁 The designer didn't use anything but a monster mains fuse - period. His idea I believe was start with a 1KW transformer and monster reservoir caps so that the PSU is big enough to weld with ... then add the simplest 'purest' zero-protection nothing-in-the-signal-path amp boards possible. It did work and the sound of the Audire is very very good ..... that is ..... until.
Bye for the moment from until-land 🙂 Mike.
Oh and incidentally - the amp was factory fitted with a two wire mains cable - it has no earth either.
Incandescent bulbs are no problem in this neck of the woods - it's the modern energy saving types that haven't been invented yet apparently !! I'm going to try that tonight and I'll post what happens.
As for fuses - umm what fuses 🙁 The designer didn't use anything but a monster mains fuse - period. His idea I believe was start with a 1KW transformer and monster reservoir caps so that the PSU is big enough to weld with ... then add the simplest 'purest' zero-protection nothing-in-the-signal-path amp boards possible. It did work and the sound of the Audire is very very good ..... that is ..... until.
Bye for the moment from until-land 🙂 Mike.
Oh and incidentally - the amp was factory fitted with a two wire mains cable - it has no earth either.
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Hmm..a minefield and i guess it's labelled "double insulated - dont open etc?" or does it predate that standard? Anyways, the lightbulb won't compromise any safety if it is wired externally into the active line from the outlet. I don't recommend it, but I use a modified twin socket adaptor wired to accept a tablelamp plugged into the first and the amplifier plugs into the second socket. It's very convenient but potentially dangerous if others should attempt to use it normally.
I guess from it's age, fuses weren't necessary in your case - until the inevitable did happen. You can still disconnect the DC rail power leads from the boards and temporarily solder resistors between but as you are probably going for the bulb, why worry.
I guess from it's age, fuses weren't necessary in your case - until the inevitable did happen. You can still disconnect the DC rail power leads from the boards and temporarily solder resistors between but as you are probably going for the bulb, why worry.
Bulb showed no problems, adjusted bias to 10mV (it's very sensitive to temperature though) and checked again at 1 minute intervals for 5 minutes (OK) then every 5 minutes for 30 minutes - bias still reads 10 to 12mV on both boards.
Connected CD and 'disposable' old 8 Ohm Chinese spkrs, started out volume low and l got undistorted sound from both channels. Let it play for 5 minutes and checked bias - okay. Played a further ten minutes at increased but still low volume level - checked bias - okay. Started to play music at a higher volume level and after about 3 minutes ONE of the right channel OP transistors was HOT - all others were still near stone cold. Bias was still okay. The resistor marked HOT on the pic was too hot to touch (>50C). Nothing else is overheating and nothing shows a bad reading. I've switched the amp off and I'm posting here for help again before I do anything stupid.
Please tell me where I'm going wrong? What is it that I don't understand here?
BTW Ian, the amp pre-dates me .... well almost. And Coffs harbor is one beeeeauuutiful place !!!
Best to all, Mike.
Connected CD and 'disposable' old 8 Ohm Chinese spkrs, started out volume low and l got undistorted sound from both channels. Let it play for 5 minutes and checked bias - okay. Played a further ten minutes at increased but still low volume level - checked bias - okay. Started to play music at a higher volume level and after about 3 minutes ONE of the right channel OP transistors was HOT - all others were still near stone cold. Bias was still okay. The resistor marked HOT on the pic was too hot to touch (>50C). Nothing else is overheating and nothing shows a bad reading. I've switched the amp off and I'm posting here for help again before I do anything stupid.
Please tell me where I'm going wrong? What is it that I don't understand here?
BTW Ian, the amp pre-dates me .... well almost. And Coffs harbor is one beeeeauuutiful place !!!
Best to all, Mike.
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go back to the safest test set up.
No input. No load. short input, power up with bulb tester.
Measure voltage across that hot resistor. Shut down. Compare that voltage to what is expected on the schematic.
No input. No load. short input, power up with bulb tester.
Measure voltage across that hot resistor. Shut down. Compare that voltage to what is expected on the schematic.
Hi Seebert
I'm sure the local tourist authority will love your comment about this area. It is wonderful this time of year when the migratory tropical birds flock in to the old- growth forests and show their colours and amazing calls. It's like a tropical rainforest seaward of the Great Dividing Range but at 4,000 feet tops, it's nowhere as grand as the Rockies.
Andrew, with no schematic at all, things are not so basic and straightforward so it takes time to identify parts and problems. We can hazard guesses but it's better to take careful steps until the functions are clear.
First, recheck the output offset voltage across the output terminals. Anything under +/-40 mV will be fine and indicates that the output stage is probably OK and the input stage too as this DC level is determined there. Let's consider the overheating transistor according to this result. You've identified one dead driver, usually things work and fail in pairs here even though the low current checks look fine.
I assume the 39k resistor you nicely indicated as hot is not so in the good channel. It appears not to be part of the input, but perhaps the next or voltage amplifier stage (the 2 heatsinked transistors, top & bottom) Given that the traces and parts are conveniently both on this side, perhaps you can sketch a schematic for at least this end of the board. The resistors are colour coded for value and tolerance. so you can just as easily measure many of them and some we can read. Then we can be sure what this resistor limits.
Perhaps you can use a basic amplifier schematic like Destroyer X's DX amplifier as a guide for what to expect, but the voltage amplifier is different, with only one transistor, I think, so don't expect it to be identical, http://www.diyaudio.com/forums/solid-state/96237-destroyer-x-amplifier-dx-amp-my-amplifier.htmlI I would think the input stage will be very close though. Any of his initial posts will do as examples to print or what suits.,
The input stage, BTW, is that cluster of 3 TO92 transistors on the right. They only pass a few mA. bias current, regulated by one of these and shared. equally in the others which also connect to the top (+) rail, I think, via resistors.
I hope you have some further success with this bit.
I'm sure the local tourist authority will love your comment about this area. It is wonderful this time of year when the migratory tropical birds flock in to the old- growth forests and show their colours and amazing calls. It's like a tropical rainforest seaward of the Great Dividing Range but at 4,000 feet tops, it's nowhere as grand as the Rockies.
Andrew, with no schematic at all, things are not so basic and straightforward so it takes time to identify parts and problems. We can hazard guesses but it's better to take careful steps until the functions are clear.
First, recheck the output offset voltage across the output terminals. Anything under +/-40 mV will be fine and indicates that the output stage is probably OK and the input stage too as this DC level is determined there. Let's consider the overheating transistor according to this result. You've identified one dead driver, usually things work and fail in pairs here even though the low current checks look fine.
I assume the 39k resistor you nicely indicated as hot is not so in the good channel. It appears not to be part of the input, but perhaps the next or voltage amplifier stage (the 2 heatsinked transistors, top & bottom) Given that the traces and parts are conveniently both on this side, perhaps you can sketch a schematic for at least this end of the board. The resistors are colour coded for value and tolerance. so you can just as easily measure many of them and some we can read. Then we can be sure what this resistor limits.
Perhaps you can use a basic amplifier schematic like Destroyer X's DX amplifier as a guide for what to expect, but the voltage amplifier is different, with only one transistor, I think, so don't expect it to be identical, http://www.diyaudio.com/forums/solid-state/96237-destroyer-x-amplifier-dx-amp-my-amplifier.htmlI I would think the input stage will be very close though. Any of his initial posts will do as examples to print or what suits.,
The input stage, BTW, is that cluster of 3 TO92 transistors on the right. They only pass a few mA. bias current, regulated by one of these and shared. equally in the others which also connect to the top (+) rail, I think, via resistors.
I hope you have some further success with this bit.
Quick Q - can you describe what that hot resistor connects to, there under the little transistor where your guideline peters out. I assumed the tx but which leg and what else?
thanks &
thanks &
Hello Ian and so many thanks. A very quickie post before I draw out the circuit - as best I can. Thanks for the Destroyer info - couldn't get the link to work but did a search and found it alll okay.
I just got up and before even a cup of coffee tested out the voltage on that hot resistor ---- and it's a whopping 103 VDC on BOTH channels ??? Yet it still plays undistorted music? Needless to say I switched off immediately.
That HOT R runs down to the center (centre) leg of a TO92 (2N5961) and through a 948 Ohm R (measures 942 ohms on board 2) to the BASE of an MPSU07 the 'complementary' to that burned and replaced MPSU57 yes? Obviously something is badly wrong here. I'll sketch the circuit area as best I can as soon as I have coffee and meds.
Thanks, Mike. (Freezing his b******* off in The Rockies - not so grand !!)
I just got up and before even a cup of coffee tested out the voltage on that hot resistor ---- and it's a whopping 103 VDC on BOTH channels ??? Yet it still plays undistorted music? Needless to say I switched off immediately.
That HOT R runs down to the center (centre) leg of a TO92 (2N5961) and through a 948 Ohm R (measures 942 ohms on board 2) to the BASE of an MPSU07 the 'complementary' to that burned and replaced MPSU57 yes? Obviously something is badly wrong here. I'll sketch the circuit area as best I can as soon as I have coffee and meds.
Thanks, Mike. (Freezing his b******* off in The Rockies - not so grand !!)
Another quickie Ian (still drinking coffee and letting the meds take effect) - I looked up Coffs Harbour on the map a while ago and downloaded some pics - just fantastic!! I was in Oz with some guys in 1962 but we didn't get to know where in Oz it was - all I know is that it was bloody hot and just about all sand. Great respect for the Oz guys (and the Kiwis) - they were good guys - tough well-trained professionals with a hell of a sense of wicked humour.
I just can't grasp how the amp played so well last night with all that's (so obviously) wrong with it. Oh for a schematic !!! BTW I overlayed the track side and the compnent side in Photoshop - the rest of the time I have to work with a lamp behind the board to see what's what. Biggest problem is that you can't do anything at all with the boards in situ - and it's a monster PITA to keep taking them out and putting them back in to try them. If I extended the leads from the OP transistors and PSU it'd be easier but I'd probably make it an RF oscillator - and find just another way to fry it 🙂 BTW ... tx to me means transmitter 🙂
My best, Mike.
I just can't grasp how the amp played so well last night with all that's (so obviously) wrong with it. Oh for a schematic !!! BTW I overlayed the track side and the compnent side in Photoshop - the rest of the time I have to work with a lamp behind the board to see what's what. Biggest problem is that you can't do anything at all with the boards in situ - and it's a monster PITA to keep taking them out and putting them back in to try them. If I extended the leads from the OP transistors and PSU it'd be easier but I'd probably make it an RF oscillator - and find just another way to fry it 🙂 BTW ... tx to me means transmitter 🙂
My best, Mike.
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Hey Mike,
I repaired a Quatre DLH100 a couple of months ago and from what I have found it is the same as your Audire, Model 2? I tried to post it but it is too large. Send me a PM with your email and I'll send it directly to you. Should save some time drawing one, just check the values of the components.
Craig
I repaired a Quatre DLH100 a couple of months ago and from what I have found it is the same as your Audire, Model 2? I tried to post it but it is too large. Send me a PM with your email and I'll send it directly to you. Should save some time drawing one, just check the values of the components.
Craig
Hello Craig and THANKS a MILLION times over. PM sent. Let me know if it got to you okay ... I'm a bit 'shredded' more than usual this morning I'm afraid. Still kicking though so can't complain 🙂
Thanks again and best regards, Mike.
Thanks again and best regards, Mike.
Ah....ex military, I deduce.
Your guys still get shunted off into the central desert of the Northern Territory for war games every so often. Times don't change that much. I was not even in high school then so I can't recall the scale of things but military exercises were not public in those times and there were experimental devices, missiles and bad stuff being tested out there. Tx....yes Transistor is a pain if you can't call it Q1,2 or T1,2 etc. Sorry but as the son of a Ham Radio guy and Army signals officer, that's how I learned it too. I just didn't think audio guys would be aware.
Sorry you have that regime with medication, It is utterly debilitating for some but it may buy us some time to enjoy our audio, eh? I have asked Craig for a copy of the schematic he has and we can wait a bit and take this up faster as he probably has better technique. The 103V, I suggest, is near the full potential across the rails, so if that leads to the transistor base, it may be shorted dead. Check that offset voltage at the output too.
best wishes
Hi Seebert
llwhtt gave me the hint that this amplifier is very close to the Tigersaurus design which obviously goes way back. I looked at the SWTPC version which looked a little complex on PB2s simulation schematic. However one titled 1971 Plastic Tiger Popular Electronics October 1971 looks more familar, as does Universal Tiger.
http://www.swtpc.com/mholley/PopularElectronics/Oct1970/PE_Oct_1970_pg32.jpg
They are sure the same at the input end anyway. After that, going to the right side things are simpler as you can see but the basics are clearer. It's amazing how many popular designs were spawned by these. Brystons even! Anyway, it's just to clarify what is supposed to be going on. The real schematic we have now. 'hope the links work this time.
llwhtt gave me the hint that this amplifier is very close to the Tigersaurus design which obviously goes way back. I looked at the SWTPC version which looked a little complex on PB2s simulation schematic. However one titled 1971 Plastic Tiger Popular Electronics October 1971 looks more familar, as does Universal Tiger.
http://www.swtpc.com/mholley/PopularElectronics/Oct1970/PE_Oct_1970_pg32.jpg
They are sure the same at the input end anyway. After that, going to the right side things are simpler as you can see but the basics are clearer. It's amazing how many popular designs were spawned by these. Brystons even! Anyway, it's just to clarify what is supposed to be going on. The real schematic we have now. 'hope the links work this time.
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