Those values look fine to me 🙂
Was there any doubt over the diode packs being intermittent or anything like that? I can't remember, was this the amp that failed after being repaired previously.
Also remember that the offset and idle current values should really be re-checked when it is running on full mains rather than via a bulb to check all is OK on the full rail voltage. Don't get hung up on any slight variations though 😉 It is just to check it is all operating normally.
Was there any doubt over the diode packs being intermittent or anything like that? I can't remember, was this the amp that failed after being repaired previously.
Also remember that the offset and idle current values should really be re-checked when it is running on full mains rather than via a bulb to check all is OK on the full rail voltage. Don't get hung up on any slight variations though 😉 It is just to check it is all operating normally.
When i brought it only one channel was working(although i never plugged it in and tried it.) the diode was never questionable from my perspective, it just kind of went in that direction under general conversation.
R632 and C616 were burned up but after that i never realy found anything at fault apart from that transistor Q610 where the leg fell off, but it does make sense why Q610 may have been at fault now i look back.
im going to put all my stuff away, tbh , im still a bit washed up with the covid thing, but ill keep the amp out,and check things while its being used and sitting idle,voltages and temp etc.
All i have to do now is look at why the power meter lamps are not working, then maybe look at a way to fit VBE'S, on a board perhaps as there isnt any room to just plonk things on the board.
Its been a real slog this one as im sure ive ended up correcting more than one or 2 things, maybe more while trying to located the faults i was chasing.
been interesting though this one, thats what makes it fun, it wouldnt be if everything was the same all the time.
I feel like im starting to be able to look at things more now without constantly bothering people , and wasting peoples time over silly things.
I realy appreciate your time when you get involved because you take the time to not only suggest what maybe wrong, but explain why and that realy goes along way in helping me with things going forward both technicaly and practicaly ,thank you !🙂
R632 and C616 were burned up but after that i never realy found anything at fault apart from that transistor Q610 where the leg fell off, but it does make sense why Q610 may have been at fault now i look back.
im going to put all my stuff away, tbh , im still a bit washed up with the covid thing, but ill keep the amp out,and check things while its being used and sitting idle,voltages and temp etc.
All i have to do now is look at why the power meter lamps are not working, then maybe look at a way to fit VBE'S, on a board perhaps as there isnt any room to just plonk things on the board.
Its been a real slog this one as im sure ive ended up correcting more than one or 2 things, maybe more while trying to located the faults i was chasing.
been interesting though this one, thats what makes it fun, it wouldnt be if everything was the same all the time.
I feel like im starting to be able to look at things more now without constantly bothering people , and wasting peoples time over silly things.
I realy appreciate your time when you get involved because you take the time to not only suggest what maybe wrong, but explain why and that realy goes along way in helping me with things going forward both technicaly and practicaly ,thank you !🙂
Last edited:
Hi,
I know it won't be too helpful in your case, but just for info, I found the bug in my NAD310 amp. The least expected one, after I checked all semiconductors, replaced a lot of caps...
So: A broken resistor. It was a part of a voltage divider which set the voltages of the input transistor and the suceeding stages. If was just plain dead, no visible signs, no burnout. It should have had 11k ohms but had none (infinite).
But, finding the trouble was just a pain in the...
I never had a case that a resistor breaks like that and causes "ghostly" behavior of the amp. All I want to say is: look where you think it should not be 😀
I know it won't be too helpful in your case, but just for info, I found the bug in my NAD310 amp. The least expected one, after I checked all semiconductors, replaced a lot of caps...
So: A broken resistor. It was a part of a voltage divider which set the voltages of the input transistor and the suceeding stages. If was just plain dead, no visible signs, no burnout. It should have had 11k ohms but had none (infinite).
But, finding the trouble was just a pain in the...
I never had a case that a resistor breaks like that and causes "ghostly" behavior of the amp. All I want to say is: look where you think it should not be 😀
all stable at idle on for 4 hours now/idle and being used.
heatsink temp 35c, which given the ambient is pretty good.
If need be, and you have one handy, use a multi turn pot, that will give better resolution.
4K7 or 1K, whatever is suggested by Mooly.
4K7 or 1K, whatever is suggested by Mooly.
R632 burned up just suggests classic output stage failure. I know its all been around the houses to get it working 😀 Well done.
And thanks for the kind words 🙂 its been interesting and from my point of view it has been good to have someone interested enough to see it through.
(maybe try something different to a NAD next time 😀 😀 😀 or maybe you could build a small amp on the breadboard and then build it. Nothing beats hearing the sound coming from something you have made)
i did use the breadboard for this, so ill be using that alot more going forward.meant to say actualy my old fluke 110 meter read across that diode pack ok at 2.2v drop.Its by far the best of the 3 multimeters i have and its 30 years old.
some of the new meters dont have that capability and they are not of the same quality either, although i do like my keYsight U1233A,thats a great meter.🙂
some of the new meters dont have that capability and they are not of the same quality either, although i do like my keYsight U1233A,thats a great meter.🙂
The Marantz sounds different. Crosstalk... just imagining... worth checking the input sockets are soldered properly and that the solder hasn't cracked around them giving a floating ground at the inputs 🙂 Dunno... like the NAD it all begins with methodical evidence gathering.
I have four meters 😀 none of them as good as yours... well the old AVO8 is a different thing actually but my digital ones are a SOAR ME502 (museum piece)
Digital Multimeter ME-502B Equipment Soar Corporation;
and an Escort something or other (mid price digital about 30 years old).
And the AVO 🙂 Nothing tests transistors like an AVO8 and its 15 volt internal battery.
Also have a DVM that cost about 50p from a radio rally but it works although the leads are non existent (weird non standard plugs) and so I have leads soldered to bits of wire (don't laugh) from the original plugs once I chopped the tops off them.
I have a very good scope though 😉
And I keep a check on the calibration of three of them.
I have four meters 😀 none of them as good as yours... well the old AVO8 is a different thing actually but my digital ones are a SOAR ME502 (museum piece)
Digital Multimeter ME-502B Equipment Soar Corporation;
and an Escort something or other (mid price digital about 30 years old).
And the AVO 🙂 Nothing tests transistors like an AVO8 and its 15 volt internal battery.
Also have a DVM that cost about 50p from a radio rally but it works although the leads are non existent (weird non standard plugs) and so I have leads soldered to bits of wire (don't laugh) from the original plugs once I chopped the tops off them.
I have a very good scope though 😉
And I keep a check on the calibration of three of them.
i used to have an AVO 8 years ago but somehow it got thrown away when my mum died and the house was cleared.they are great meters, used by the BBC years ago i think.
Everyone has thier own favourites dont they, if i had to keep only one it would be the fluke, the new version hasnt got all of the test functions the iold one had.
calibration is essential realy, havent had mine done for a while, must get them done.
Everyone has thier own favourites dont they, if i had to keep only one it would be the fluke, the new version hasnt got all of the test functions the iold one had.
calibration is essential realy, havent had mine done for a while, must get them done.
those soar meters are realy good,they have a realy good reputation
i recon the older stuff is much better, there is alot of rubbish out there, hundreds of makes these days
I used to have company SOAR meter (a 3020 was it) that was auto ranging. That was excellent.
One thing to remember with an analogue meter (most analogues actually) is that meter lead polarity on the ohms ranges is the opposite to a DVM. For example a diode conducts when you put the red lead on the anode and the black on the cathode but for the AVO it is the other way around. Black is the lead that has the positive internal test voltage on it.
You can test a transistor for leakage and also get a good idea of functionality (current gain) with just one single reading and a slightly conductive finger 😉 Try doing that on a DVM.
Feeding time...
One thing to remember with an analogue meter (most analogues actually) is that meter lead polarity on the ohms ranges is the opposite to a DVM. For example a diode conducts when you put the red lead on the anode and the black on the cathode but for the AVO it is the other way around. Black is the lead that has the positive internal test voltage on it.
You can test a transistor for leakage and also get a good idea of functionality (current gain) with just one single reading and a slightly conductive finger 😉 Try doing that on a DVM.
Feeding time...
so the lamps in the 2 watt meters at the front-no 6vac supply from the transformer, so not sure what i can do here,maybe try and replace them with a couple of LEDS and nick 5vdc from somewhere, so its out with the meters,which are not easy to get out and have a look!
scrub that the wire was broken, but the lamps are blown lol
scrub that the wire was broken, but the lamps are blown lol
Last edited:
LED's can always be used but you are best running them off a highish DC rail (because they use so little current anyway) and connecting the LED's in series with a suitable resistor. A practical problem can be getting good and even illumination. You want diffuse wide angle LED's and sometimes a bit of plastic to spread the light can work wonders. Old plastic milk cartons, the kind of thing.
Using AC for LED's also requires a diode to protect the LED's from high reverse voltage, and you also have the problem of visible flicker at 50Hz (a bit like on old TV's). So a DC rail is best.
Using AC for LED's also requires a diode to protect the LED's from high reverse voltage, and you also have the problem of visible flicker at 50Hz (a bit like on old TV's). So a DC rail is best.
All finished now apart from the lamps and all stable on idle and centre.
realy pleased with this how its turned out and after listning to it it has realy grown on me, might even be replacing my 3240PE its that good, and its in top condition🙂
Job done with this one.
