Just watching this first part again Peter. Just thought it worth mentioning that I bought a 'parts only' NAD 6040 where the meters were suspect? As it was dirt cheap I bought the deck. And yes indeed the meters had developed a fault. Both L/R were stuck at different levels. On investigation I found that one was 'open circuit', but both suffered from meter needle loading-spring buckling! Seems to be very common on these NAD decks. Furthers tests suggested too that both D'Arsonval meter 'pivots' (on the axel, can't think what they are called?) had some corrosion on them, thus restricting their ability to move. I asked myself - why the corrosion? Answer- surely moisture had slowly, but surely worked its way into the enclosure, and of course multiply that by 40 years, and I had the answer. So just a little pointer out there for anyone thinking about rescuing a deck - check the photos for the condition and resting points of the meters. ;o)
Thanks Eric, your comments are always succinct and illuminating. To that very point, I always look at the needle deflection on fine resolution indicators when I bid on them. The sellers aren't always aware of the item and many times, the needle is actually out of the scale's view. That's a no-bid indicator in my book. Were you able to bring the meters back to life?
@@asbcustom Peter, I tried to repair the buckling by micro-soldering - it seemed to work, but the (foolish) perfectionist in me wanted a 'better' soldered joint, and of course the second time round melted the spring. So that was that! I ended up looking for some NOS or Chinese made VU meters that would fit the deck and 'bingo' I found some. Of course not everything is perfect, but it's infinity better than nothing. Below my comment I'll put in a link, you can then look at it and delete. No probs.
@@JamesE707 After working with me for a short time, a very wise friend lovingly told me once that the enemy of excellence is perfection. Making it better gets me trouble all the despite knowing I should stop. I'm not seeing any link?
Hi Peter, Watching this has reminded me that - it is often useful and interesting to compare (using a full track reference) wow and flutter at *both* ends of the tape. Not really relating to your machine in particular, I invite anyone to do this on any old machine - dual or single capstan. Also - compare the 'cold start' tape speed with that every 5 mins into the tape for about 30 minutes. Also, observe wow/flutter changes. You know, I've gone through a lot of various investigations, perpetually revising my thoughts on pin-pointing surprising (and concealed) sources of wow and flutter! I see in forums that sometimes folk quote '0.03%' like it's an average ... ha ha ... yeah, whatever! In reality, repairing or restoring an old machine to down about 0.10% wrms or less is an achievement, even for dual capstan machines. It's sometimes the luck of the draw as to the state of the deck we buy! Good pinch rollers and good belts can be hard to find, maybe (although expensive) it's worth risking buying 1/2 a dozen of the same, and taking the best of the bunch? Just me mumbling on as usual .... Hope you're keeping well Peter! Eric.
Nice to hear from you Eric. Testing at the three points on the tape the way you describe is both a good idea, and the stated procedure in the Tascam manual. Maybe you’ve seen me do this in previous videos. I haven’t ever done your 5 minute intervals but I do always test after an hour or more as I did on this one. Regarding your 1.0 wrms number being an achievement, maybe, but I have a mk3 here right now that I won’t deliver because it starts out in spec., then after 10-15 minutes, elevates to .08-1.0% and stays there. I’m convinced it’s a motor coil issue, they measure around 12% higher resistance than what I normally see, and I believe they warm up, and go even higher. I’ve been acquiring the needed equipment to wind my own axial motor coils and am almost ready to begin. Buying a quantity of belts and using the best one is exactly what I do, yes. There is no other choice really except for the very few Teac factory belts I can still purchase. They are still as consistent as ever. I would like to pick your engineering brain sometime if you’re up for it. I’m having an issue on a highly modified mk2 and my own brain isn’t up to the task, or maybe I’ve just stared at it so long that it’s vapor locked. I’ll be making a video of it soon, just need to get daily work caught up first. Please mumble on at your pleasure ...
@@asbcustom Regarding that rising w/f on that MK3, does the deck have back tension? (A) if not, then w/f may get worse as the supply reel empties out - less mass, therefore less inertia, therefore less perpetual (micro) drag. Having said that not all decks without back tension do this - they must have near perfect tape-to-head wrap. (B) does have back tension in the form of a spring loaded friction pad - I had a rising w/f issue on a Sony TC-206SD where the pad had sufficient cr*p on it for it to 'judder' the supply reel as it emptied out. That was (in contrast to (A)) another source of wow/flutter. Solved the problem completely with new pad.
I don't think the small difference in resistance will make any difference to be honest Peter. As cassette deck motors warm up, their armature resistances naturally increase. The motor controller circuit compensates somewhat for this by placing a complimentary 'mirror' resistance in the Wheatstone-like bridge circuit. This carefully positioned complimentary resistor also heats up at the same rate (similar coefficient of resistance) as the internal armature resistance - keeping the bridge circuit 'balanced'. Also, when any internal armature resistance changes, the bridge circuit feeds back the change in motor terminal voltage to the controller - which then compensates by inc or dec the applied voltage to the motor. There are so many potential sources of wow/flutter that it drives me up the wall! It is theoretically possible that 'dirty' brush to commutator contact may 'wobble' the speed, and so we may hear this in the music, but I'm not so sure if wow/flutter meters will pick up this slow change? In fact, experience shows that it doesn't always.
@@JamesE707 This brings up a good point. Everything is in spec. including the back tension, but, I only measured it early on. What I should do is let it get to its flutter issue, then check the back tension again. This is why it's good to bounce ideas off others, we get fixated on one thing and can't see what might be obvious to someone else.
@@JamesE707 That's a very valuable rundown, thank you. This motor is direct drive, no brushes, and a bit tricky to measure those coils in place, but I can find a way. I could even solder extension leads if I need to. The transport received the full Monty overhaul like every other one I do, and I have done quite a few of these with good success, I would bet the farm that it’s not a mechanical issue.
I love a Lincoln Continental. A MK V, or a MK VI, with those long clean lines and razor blade sharp edges... Just lovely.
Those were the days!
Just watching this first part again Peter.
Just thought it worth mentioning that I bought a 'parts only' NAD 6040 where the meters were suspect? As it was dirt cheap I bought the deck. And yes indeed the meters had developed a fault. Both L/R were stuck at different levels. On investigation I found that one was 'open circuit', but both suffered from meter needle loading-spring buckling! Seems to be very common on these NAD decks. Furthers tests suggested too that both D'Arsonval meter 'pivots' (on the axel, can't think what they are called?) had some corrosion on them, thus restricting their ability to move. I asked myself - why the corrosion? Answer- surely moisture had slowly, but surely worked its way into the enclosure, and of course multiply that by 40 years, and I had the answer.
So just a little pointer out there for anyone thinking about rescuing a deck - check the photos for the condition and resting points of the meters. ;o)
Thanks Eric, your comments are always succinct and illuminating. To that very point, I always look at the needle deflection on fine resolution indicators when I bid on them. The sellers aren't always aware of the item and many times, the needle is actually out of the scale's view. That's a no-bid indicator in my book.
Were you able to bring the meters back to life?
@@asbcustom Peter, I tried to repair the buckling by micro-soldering - it seemed to work, but the (foolish) perfectionist in me wanted a 'better' soldered joint, and of course the second time round melted the spring. So that was that! I ended up looking for some NOS or Chinese made VU meters that would fit the deck and 'bingo' I found some. Of course not everything is perfect, but it's infinity better than nothing. Below my comment I'll put in a link, you can then look at it and delete. No probs.
cassettedeckman.blogspot.com
@@JamesE707 After working with me for a short time, a very wise friend lovingly told me once that the enemy of excellence is perfection. Making it better gets me trouble all the despite knowing I should stop. I'm not seeing any link?
Hi Peter,
Watching this has reminded me that - it is often useful and interesting to compare (using a full track reference) wow and flutter at *both* ends of the tape.
Not really relating to your machine in particular, I invite anyone to do this on any old machine - dual or single capstan. Also - compare the 'cold start' tape speed with that every 5 mins into the tape for about 30 minutes. Also, observe wow/flutter changes.
You know, I've gone through a lot of various investigations, perpetually revising my thoughts on pin-pointing surprising (and concealed) sources of wow and flutter! I see in forums that sometimes folk quote '0.03%' like it's an average ... ha ha ... yeah, whatever! In reality, repairing or restoring an old machine to down about 0.10% wrms or less is an achievement, even for dual capstan machines. It's sometimes the luck of the draw as to the state of the deck we buy!
Good pinch rollers and good belts can be hard to find, maybe (although expensive) it's worth risking buying 1/2 a dozen of the same, and taking the best of the bunch?
Just me mumbling on as usual ....
Hope you're keeping well Peter!
Eric.
Nice to hear from you Eric.
Testing at the three points on the tape the way you describe is both a good idea, and the stated procedure in the Tascam manual. Maybe you’ve seen me do this in previous videos. I haven’t ever done your 5 minute intervals but I do always test after an hour or more as I did on this one. Regarding your 1.0 wrms number being an achievement, maybe, but I have a mk3 here right now that I won’t deliver because it starts out in spec., then after 10-15 minutes, elevates to .08-1.0% and stays there. I’m convinced it’s a motor coil issue, they measure around 12% higher resistance than what I normally see, and I believe they warm up, and go even higher. I’ve been acquiring the needed equipment to wind my own axial motor coils and am almost ready to begin.
Buying a quantity of belts and using the best one is exactly what I do, yes. There is no other choice really except for the very few Teac factory belts I can still purchase. They are still as consistent as ever.
I would like to pick your engineering brain sometime if you’re up for it. I’m having an issue on a highly modified mk2 and my own brain isn’t up to the task, or maybe I’ve just stared at it so long that it’s vapor locked. I’ll be making a video of it soon, just need to get daily work caught up first.
Please mumble on at your pleasure ...
@@asbcustom Regarding that rising w/f on that MK3, does the deck have back tension? (A) if not, then w/f may get worse as the supply reel empties out - less mass, therefore less inertia, therefore less perpetual (micro) drag. Having said that not all decks without back tension do this - they must have near perfect tape-to-head wrap. (B) does have back tension in the form of a spring loaded friction pad - I had a rising w/f issue on a Sony TC-206SD where the pad had sufficient cr*p on it for it to 'judder' the supply reel as it emptied out. That was (in contrast to (A)) another source of wow/flutter. Solved the problem completely with new pad.
I don't think the small difference in resistance will make any difference to be honest Peter.
As cassette deck motors warm up, their armature resistances naturally increase. The motor controller circuit compensates somewhat for this by placing a complimentary 'mirror' resistance in the Wheatstone-like bridge circuit. This carefully positioned complimentary resistor also heats up at the same rate (similar coefficient of resistance) as the internal armature resistance - keeping the bridge circuit 'balanced'.
Also, when any internal armature resistance changes, the bridge circuit feeds back the change in motor terminal voltage to the controller - which then compensates by inc or dec the applied voltage to the motor.
There are so many potential sources of wow/flutter that it drives me up the wall! It is theoretically possible that 'dirty' brush to commutator contact may 'wobble' the speed, and so we may hear this in the music, but I'm not so sure if wow/flutter meters will pick up this slow change? In fact, experience shows that it doesn't always.
@@JamesE707 This brings up a good point. Everything is in spec. including the back tension, but, I only measured it early on. What I should do is let it get to its flutter issue, then check the back tension again. This is why it's good to bounce ideas off others, we get fixated on one thing and can't see what might be obvious to someone else.
@@JamesE707 That's a very valuable rundown, thank you.
This motor is direct drive, no brushes, and a bit tricky to measure those coils in place, but I can find a way. I could even solder extension leads if I need to. The transport received the full Monty overhaul like every other one I do, and I have done quite a few of these with good success, I would bet the farm that it’s not a mechanical issue.