briank
analog for the people!
Thankyou thankyou thankyou! I'll fiddle with it next I'm in the studio and report back-
briank
analog for the people!
I'm back to it...but I'm pretty dense about oscopes...does this look right for the Phase Locked Loop Board gain and scope settings? (10x probe)
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evm1024
New member
Odd looking trace....
Looking at your scope - Verticle mode should be set to "channel 1" not "both". In both the 2 channels can be added together (as set here), displayed one then the other (alternate) or a little bit of one displayed then a little of the other (chop) done quickly. Alt works well for fast horizontal times, chop for slower times.
Channel 1 is set for 10 volts per division which gives about 5 volts of signal (half a division) which is consistent with TTL logic levels.
Looks like the inner and outer rings of the horizontal time per division knobs are not locked together. They should be locked together unless you are using split timing modes.An advanced thing to do.... for special cases.
You have 2 "on" pulse widths. THis is odd to me. I would expect each pulse to be of equal width.
Not much else comes to mind at this time.
Looking at your scope - Verticle mode should be set to "channel 1" not "both". In both the 2 channels can be added together (as set here), displayed one then the other (alternate) or a little bit of one displayed then a little of the other (chop) done quickly. Alt works well for fast horizontal times, chop for slower times.
Channel 1 is set for 10 volts per division which gives about 5 volts of signal (half a division) which is consistent with TTL logic levels.
Looks like the inner and outer rings of the horizontal time per division knobs are not locked together. They should be locked together unless you are using split timing modes.An advanced thing to do.... for special cases.
You have 2 "on" pulse widths. THis is odd to me. I would expect each pulse to be of equal width.
Not much else comes to mind at this time.
briank
analog for the people!
Thanks...I got the same thing whether on Ch1 or both (odd), and didn't get anything that looked "right" no matter how I twiddled
and didn't see where the knobs locked together, guess that's a "gotcha"...I was advised above not to set to chop or alt so that's why that got set the way it did...in over my head with this oscope stuff 
will try again-
evm1024
New member
HEre is an example
OK you got me going.... Here is a photo of TP3 that I just took om my JH-110A
You should be able to see the settings on the 465 scope.
As you can see the vert section is set to Ch1, DC coupling at 5 volts a division with a 10X probe. The waveform shows about a 5 volt rise.
The horizontal section is 10 uS a division one positive going edge to the next is about 52 uS giving a cycle time of 19.2 KHz (the VCO frequency is on the counters and is indeed 19.2 KHz)
Each cycle takes up about 5 horizontal divisions. The positive pulse takes up 1.5 divisions. So 1.5/5=0.3 giving us our 30% duty cycle.
You will notice that the upper portion of the trace and the lower appear to overlap. The photo actually captures a number of cycles (about 160 actually because the shutter was at 1/60th of a second) and the actual duty cycle varies as the PLL keeps the speed in sync. Some are more than 30% and some are less.
Regards, Ethan
OK you got me going.... Here is a photo of TP3 that I just took om my JH-110A
You should be able to see the settings on the 465 scope.
As you can see the vert section is set to Ch1, DC coupling at 5 volts a division with a 10X probe. The waveform shows about a 5 volt rise.
The horizontal section is 10 uS a division one positive going edge to the next is about 52 uS giving a cycle time of 19.2 KHz (the VCO frequency is on the counters and is indeed 19.2 KHz)
Each cycle takes up about 5 horizontal divisions. The positive pulse takes up 1.5 divisions. So 1.5/5=0.3 giving us our 30% duty cycle.
You will notice that the upper portion of the trace and the lower appear to overlap. The photo actually captures a number of cycles (about 160 actually because the shutter was at 1/60th of a second) and the actual duty cycle varies as the PLL keeps the speed in sync. Some are more than 30% and some are less.
Regards, Ethan
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evm1024
New member
Follow up.
Cut te follow up out and pasted in the prior message cause the page break moved the follow up away from the photo....
Cut te follow up out and pasted in the prior message cause the page break moved the follow up away from the photo....
briank
analog for the people!
Ethan, that's huge. I appreciate the assistance very much--thanks! I'll dig back into this deck tomorrow-
C
cjmnash
New member
hey briank-
nice looking deck. i read through the posts--- one thing that caught my eye was the turntable shims. if your spindles wobble it's not a shim thing, the shims are only for turntable height in relation to the tape path, not meant to correct wobble. you may have bent posts....which would suck.
i restore MCI JH110s and do a lot of work with people on their decks via skype. i can walk you through getting it pulling tape correctly, audio alignments, etc, etc, etc. basically top to bottom.
i'm also originally from northern wisconsin and plan to be up there for the christmas holiday, perhaps we could work something out while i'm in the area. i have spare transport and audio cards of everything related to your deck, and work on JH110s everyday. check out my site at www.nobraineraudio.com (and my studio at www.welcometo1979.com )
hit me up at cym@mindspring.com and we'll go from there.
rock out.
chris mara
nashville, tn
nice looking deck. i read through the posts--- one thing that caught my eye was the turntable shims. if your spindles wobble it's not a shim thing, the shims are only for turntable height in relation to the tape path, not meant to correct wobble. you may have bent posts....which would suck.
i restore MCI JH110s and do a lot of work with people on their decks via skype. i can walk you through getting it pulling tape correctly, audio alignments, etc, etc, etc. basically top to bottom.
i'm also originally from northern wisconsin and plan to be up there for the christmas holiday, perhaps we could work something out while i'm in the area. i have spare transport and audio cards of everything related to your deck, and work on JH110s everyday. check out my site at www.nobraineraudio.com (and my studio at www.welcometo1979.com )
hit me up at cym@mindspring.com and we'll go from there.
rock out.
chris mara
nashville, tn
briank
analog for the people!
Small world Chris, I just shared a Welcome to 1979 video on my Facebook page this afternoon 
The good news is I confirmed it was the reels that were wobbly, not bent shafts from what I can tell. Regarding the shims, the tt heights were a little off too. Combined with the funky reels it was scrapesville.
Now the PLL gain and capstan tach, they're a real mess!
The good news is I confirmed it was the reels that were wobbly, not bent shafts from what I can tell. Regarding the shims, the tt heights were a little off too. Combined with the funky reels it was scrapesville.
Now the PLL gain and capstan tach, they're a real mess!
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C
cjmnash
New member
ha! small world indeed.
glad you got the reel thing figured out- new empty reels are a lot less expensive than new motors (and a lot more common of an issue)
regarding the phase lock loop board...it's rare that the duty cycle is way out of whack, usually the tensions are off and it looks like a capstan issue. we should schedule a skype thing and i can walk you through the transport top to bottom. it's an easy and affordable way to get you using the machine instead of fixing the machine.
hit me up, we'll make it happen.
-chris
cym@mindspring.com
glad you got the reel thing figured out- new empty reels are a lot less expensive than new motors (and a lot more common of an issue)
regarding the phase lock loop board...it's rare that the duty cycle is way out of whack, usually the tensions are off and it looks like a capstan issue. we should schedule a skype thing and i can walk you through the transport top to bottom. it's an easy and affordable way to get you using the machine instead of fixing the machine.
hit me up, we'll make it happen.
-chris
cym@mindspring.com
briank
analog for the people!
E sent.
After re-seating some molexes and ICs the machine was having a much better hair day today. I can pretty much sum up my problem as follows: the tension on the right side of the transport is way low. Adjusting the Right Tension pot (R41 if I recall correctly) does nothing--it's unresponsive, and is not resolved by simply re-seating boards.
Anyone have any ideas on how to restore tension to the right reel??
I suspect if I can sort that issue out, the rest of the setup shouldn't be a biggie.
After re-seating some molexes and ICs the machine was having a much better hair day today. I can pretty much sum up my problem as follows: the tension on the right side of the transport is way low. Adjusting the Right Tension pot (R41 if I recall correctly) does nothing--it's unresponsive, and is not resolved by simply re-seating boards.
Anyone have any ideas on how to restore tension to the right reel??
I suspect if I can sort that issue out, the rest of the setup shouldn't be a biggie.
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M
Muckelroy
Member
Not sure if this has been mentioned or not..... Just my possibly redundant 2-cents.
Any dried caps? I didn't see any mention in this thread of the caps being checked out. (Incase you haven't seen dried caps, they may have a slight bulge on top, being slightly convex instead of flat or concave... An extreme case in this photo: http://mark-lawton.com/wp-content/uploads/2010/06/Faulty-And-Blown-Capacitors.jpg )
You only need to worry about the electrolytic capacitors. Ceramic and Tantalum caps are usually just fine and don't need any attention for many many decades. Dried caps can let excess voltage pass through them, causing all kinds of wonky issues, in this case, maybe a tension voltage logic issue.)
How are your offset nulls?
Again, my apologies if this is redundant. I'm just coming from my brief first-hand experience w/ one of these machines.
Any dried caps? I didn't see any mention in this thread of the caps being checked out. (Incase you haven't seen dried caps, they may have a slight bulge on top, being slightly convex instead of flat or concave... An extreme case in this photo: http://mark-lawton.com/wp-content/uploads/2010/06/Faulty-And-Blown-Capacitors.jpg )
You only need to worry about the electrolytic capacitors. Ceramic and Tantalum caps are usually just fine and don't need any attention for many many decades. Dried caps can let excess voltage pass through them, causing all kinds of wonky issues, in this case, maybe a tension voltage logic issue.)
How are your offset nulls?
Again, my apologies if this is redundant. I'm just coming from my brief first-hand experience w/ one of these machines.
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briank
analog for the people!
Offset nulls - I check and tweak every time I power the machine up; they're not usually too far out, if at all.
A bad cap is possible...I'll check for them. Certainly haven't run into any bulging caps in my rummaging so far, though.
A bad cap is possible...I'll check for them. Certainly haven't run into any bulging caps in my rummaging so far, though.
briank
analog for the people!
Let's hear it for making things worse by "fixing" them! I went into troubleshoot the low right reel tension issue yesterday...first thing I did was pull the analog torque board and give the Molexes a cleaning to make sure it wasn't just a bad surface connection before I went crazy tracing...when I re-seated the board, it started doing this:
[video=youtube;https://www.youtube.com/watch?v=hTj10uNNFPk]video[/video]
https://www.youtube.com/watch?v=hTj10uNNFPk
...and yes, it's seated properly as far as I can tell--no missed pins. I also checked as many caps as I could see on the motherboard--no bulging, anyway. I've also tried re-seating/swapping ICs but to no avail. Urrrr...
Here are photos of the analog torque and phase locked loop boards, if anything "wrong" jumps out at anyone...sorry about the photo quality...
[video=youtube;https://www.youtube.com/watch?v=hTj10uNNFPk]video[/video]
https://www.youtube.com/watch?v=hTj10uNNFPk
...and yes, it's seated properly as far as I can tell--no missed pins. I also checked as many caps as I could see on the motherboard--no bulging, anyway. I've also tried re-seating/swapping ICs but to no avail. Urrrr...
Here are photos of the analog torque and phase locked loop boards, if anything "wrong" jumps out at anyone...sorry about the photo quality...
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evm1024
New member
No Red Sockets thats good
When You say you took the IC out and reseated them 2 thoughts come to mind.
1) I'm sure that you are sure that you put them back in the original socket in the original orientation But you might want to check just to go through the paces
2) it is possible when putting an IC into a socket to have one of the pins miss the connector and curl up under the IC body and thus not make connection with the socket. THis is a visual inspection thing.
Hope that this helps and that you find 1 curled pin that solves the problem.
Regards, Ethan
When You say you took the IC out and reseated them 2 thoughts come to mind.
1) I'm sure that you are sure that you put them back in the original socket in the original orientation But you might want to check just to go through the paces
2) it is possible when putting an IC into a socket to have one of the pins miss the connector and curl up under the IC body and thus not make connection with the socket. THis is a visual inspection thing.
Hope that this helps and that you find 1 curled pin that solves the problem.
Regards, Ethan
M
Muckelroy
Member
Start with the power supply rails and work your way up, seeing where the voltage may be off. Good luck, sorry I can't be of much more help.
briank
analog for the people!
So...sit-rep on the JH-110C 8-track...The right reel tension was slack and eventually the problem degenerated to where the right reel simply won't "idle" or play at all...but it'll fast-forward...and I just can't work the issue out.
I've been all over the analog torque and motor driver boards, made sure all ICs were oriented properly...subbed some 741 ICs and will do more (as I have spares) and a few spare lytics associated with idle/tension...all 741 and TL081 ICs on the torque board are passing the right voltage etc...measured every cap/resistor/diode etc I had the capability to on those boards...checked and cleaned all the molexes I could get to without taking the machine apart (and re-soldered some although it looks like someone already did at some point)...and just can't find anything amiss, though granted I'm a novice at this kind of thing, something isn't adding up. Offsets show correct +/- and right motor tach has measurable voltage when the reel is turned by hand...there's continuity all over the place on this machine...transport buttons all light up and do (or at least try to do) what they should aside of course from the problem of the right reel not moving when play is hit or a card is put in the tape sensor slot at idle.
One area I still have a question mark on is IC24 and 25 on the analog torque board...these are soldered in ICs and Mouser didn't sell 'em when I checked so no swapping/subbing there...given their association with right idle/play...should I be looking more carefully at these? Speaking of the ICs, does it seem possible that there's maybe one bad pin socket under one of the socketed ICs somewhere on the motor/AT boards? (I didn't test every single pin on every single IC, not sure how to do that...only checked the 741 and TL081 pins shown as passing correct vDC on the schematics (4 and 7 IIRC). There are also some transistors still to check, though the 2N3055s in the chimney are fine.
Any other advice to point me in the right direction would be hugely appreciated...I just can't afford to pay a tech right now, it's not in the cards and I'm dying to sort this niggle out...any advice would be huge, I'm frustrated!
I've been all over the analog torque and motor driver boards, made sure all ICs were oriented properly...subbed some 741 ICs and will do more (as I have spares) and a few spare lytics associated with idle/tension...all 741 and TL081 ICs on the torque board are passing the right voltage etc...measured every cap/resistor/diode etc I had the capability to on those boards...checked and cleaned all the molexes I could get to without taking the machine apart (and re-soldered some although it looks like someone already did at some point)...and just can't find anything amiss, though granted I'm a novice at this kind of thing, something isn't adding up. Offsets show correct +/- and right motor tach has measurable voltage when the reel is turned by hand...there's continuity all over the place on this machine...transport buttons all light up and do (or at least try to do) what they should aside of course from the problem of the right reel not moving when play is hit or a card is put in the tape sensor slot at idle.
One area I still have a question mark on is IC24 and 25 on the analog torque board...these are soldered in ICs and Mouser didn't sell 'em when I checked so no swapping/subbing there...given their association with right idle/play...should I be looking more carefully at these? Speaking of the ICs, does it seem possible that there's maybe one bad pin socket under one of the socketed ICs somewhere on the motor/AT boards? (I didn't test every single pin on every single IC, not sure how to do that...only checked the 741 and TL081 pins shown as passing correct vDC on the schematics (4 and 7 IIRC). There are also some transistors still to check, though the 2N3055s in the chimney are fine.
Any other advice to point me in the right direction would be hugely appreciated...I just can't afford to pay a tech right now, it's not in the cards and I'm dying to sort this niggle out...any advice would be huge, I'm frustrated!
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briank
analog for the people!
Today was more encouraging...I restored the right reel idle by changing IC 11 (a 741CN) for a fresh one...now it will turn with a card in the sensor and will take up slack when tape is loaded...and it'll fast forward as before, but still won't move in play (left reel will, so tape spills off the right side). Did lots more checking on/between AT and motor driver boards and crossed many more parts off my list...learned an awful lot in the process too...
On my culprit shortlist: IC 10 and 4 (Mouser didn't have TL081 chips so I couldn't order any to sub in, will have to swap some around instead and watch for changing symptoms)...also still IC 24 and 25 (soldered in...would it be worth my time to desolder and swap them with 15 and 16?)
Can anyone familiar with the MCI JH110s tell me if I'm barking up the right tree here?
On my culprit shortlist: IC 10 and 4 (Mouser didn't have TL081 chips so I couldn't order any to sub in, will have to swap some around instead and watch for changing symptoms)...also still IC 24 and 25 (soldered in...would it be worth my time to desolder and swap them with 15 and 16?)
Can anyone familiar with the MCI JH110s tell me if I'm barking up the right tree here?
evm1024
New member
OK I'll take a stab at it.
First off you should have a look at fig 3-13 on page 3-17, as well as reading the play servo loop info in 3.4.2. I'm sure you have but this is where I started in thinking about it.
It basically says that the reel servo torque is set by the difference in the capstan speed and the reel speed. Moving over to 8.3 on page 8-4 it points out that because the difference in speed is calculated then the capstan signal must be right and if wrong can look like a bad analog board. (Check the capstan PLL waveforms for any problem)
Then it says that if the tap spills in play you should suspect IC3 and IC7. IC7 is the one in question for the takeup side but I would leave that alone until you have eliminated oher things. These are the dividers.
You can trace the takeup tach signal through IC 10, IC 8 and IC 9. Also follow take up torque signal through IC 12 and thus to the fet switch IC 25.
The goal here is to look for anything that does not look right. The tach signal is a DC level that corrosponds to the takeup reel speed. you can rotate the takeup reel by hand and you shouuld see the level change at each place in the signal chain.
The fet switch selects which torque signal to send to the motor driver so you should be able to see the torque level before the FET switch even if the switch is off. IC 24 is the driver for the fet switch. Only one of the gates should be "on" and the others off.
You shouuld also be able to check the torque level at IC 26 and 27....
Hope this helps
--Ethan
First off you should have a look at fig 3-13 on page 3-17, as well as reading the play servo loop info in 3.4.2. I'm sure you have but this is where I started in thinking about it.
It basically says that the reel servo torque is set by the difference in the capstan speed and the reel speed. Moving over to 8.3 on page 8-4 it points out that because the difference in speed is calculated then the capstan signal must be right and if wrong can look like a bad analog board. (Check the capstan PLL waveforms for any problem)
Then it says that if the tap spills in play you should suspect IC3 and IC7. IC7 is the one in question for the takeup side but I would leave that alone until you have eliminated oher things. These are the dividers.
You can trace the takeup tach signal through IC 10, IC 8 and IC 9. Also follow take up torque signal through IC 12 and thus to the fet switch IC 25.
The goal here is to look for anything that does not look right. The tach signal is a DC level that corrosponds to the takeup reel speed. you can rotate the takeup reel by hand and you shouuld see the level change at each place in the signal chain.
The fet switch selects which torque signal to send to the motor driver so you should be able to see the torque level before the FET switch even if the switch is off. IC 24 is the driver for the fet switch. Only one of the gates should be "on" and the others off.
You shouuld also be able to check the torque level at IC 26 and 27....
Hope this helps
--Ethan
briank
analog for the people!
I did, and subbed known working chips in for all those; no change and things seem ok (well, since I replaced 10 which restored the takeup "idle."
I did swap these chips (fairly terrifying considering they're not exactly off the shelf chips lol) and no change in the symptoms.
I've looked those over but the way you put it is easier for this novice to understand...and very compelling. I'll take a closer look at the PLL. I think your manual must be slightly different than mine--page numbers don't quite match up but get me in the right area.
It helps hugely, I've got some more testing/tracing to do now...I can't thank you enough for the detailed response. Thanks, Ethan!