Hey there, A few weeks ago I finally got my hands on a PR-7820 from October 1979. The batterie leaked and because the unit was stored on its back [god knows why] I had to fully disassemble it to neutralize the corrosion and repaint two of the metal covers. After I put everything back together, I had the same problem as you. The Focus lens was moving up to eight times, bevor the tracking kicked in. Only when I skipped through the disc manually there was "something" on the screen. So I would say it's ok to remove the laser assembly from the Spindle assembly [the three allen screws] because the holders beneath are shaped spherically and align the two parts. After screwing around with the controls beneath the right cover I got the focus to lock on at the first try and a steady picture on the screen. I still have to manually adjust the spindle speed when different parts of the disk are being read. But I am glad, that it still works, after I disassembled it to the bare chassis. Im now onto the re-capping part and I noticed that on the focus board [at least on mine] there is a Cap soldered in backwards of what the pint says [it's the one at 20:27]. Did you also encounter this or is this just a mistake on my board that the factory made? And the biggest question of all... Did you get your player to work by now?
Thanks for the heads up! No I've been overwhelmed with other work that I got as far as speccing out a full capacitor kit from the 7820's service manual and visually checking every board but I did not if that one capacitor was in backwards. Be warned though I did find a number of bipolar capacitors. I have a second donor player how that I want to do a teardown since it's unlikely to ever work again. Just need to find the time to setup the set for this....or should it be a stream?
Thanks for the fast response! Yeah I did notice the BiPolar caps and bought them separately. I’m going to recap the boards this weekend. I also wanted to make a backup of the two EPROMs on the computer card. A video could be edited easily (more information in less time) When you stream the disassembly though there is the change of some back and forth communication. Only tip I can give u in advance is to put some WD40 onto the 3 Ellen-Bolts and let them soak. They were really stuck on my unit. (I almost rounded the heads) Do you have laser safe glasses or did you just „avoid“ the beam? Best regards :D
@@raphaelschneider7852 My vision is already swiftly failing, even without lasers being involved. No that's jsut me being reckless with safety squints. Please be more careful than me.
I have the model three version of this. I am having the same issue as well. It’s frustrating not being able to track any of the documentation down to get it to work. It tries to play a disc, spins for a few minutes, then rejects back. I’ve had no luck with getting any sort of signal on screen either.
Check in the description for links to the service manual and optical adjustment instructions. Be warned though that some of the adjustments require special discs and jigs that are no longer available.
I happen to have one of these, its so heavy and I don't know what to do with it. I heard that because they're so heavy and costly to ship, theres very few people selling them. Its just a shame to throw it out
From what I've heard a working player is solid gold to Space Ace/Dragons Lair restorers as their players have totally clapped-out tubes. If you are into kiosk disks with data dumps these are the only players that support the format. If you are into "the first" (the lines are very vague and unconfirmed here) laser videodisc player it will play almost every disc ever made and this is the beginning of the technology. Honestly because of their rarity and historical significance I would (and will) spend the time to perform a full recap, even if many capacitors "seemed" to be okay. Japanese capacitors, especially from the 70's, were notorious for their poor quality. As for their weight yeah compared to the Magnavision 8000 they were built like a tank because the pricetag was never for the consumer market and cost was never an issue and yes it makes them impossible to ship unless you REALLY want one. It took me over 15 years to find another one that was within a day's driving distance.
two main things to consider here with your awesome museum piece, one is laser output power, you can measure this with a hand held laser power meter (get a sanwa, they are cheap) to check if output is correct, and the diode that should receive the signal from the disc, you can measure this with an oscilloscope right over the photo diode, it should be a high frequency signal. if there is no signal, or its not clean enough you'll need a new photo diode, if there is a relatively clean signal there you have to follow it up the chain, and check why the auto-focus electronics don't lock in to it. also, be sure to check all power supply voltages to make sure they are in good condition, and stable, it can be that the 5V supply is 4.3 for instance.
Problem is it's not easy to read the RF output of the photodiode when it's going in and out of focus. All I can get from a scope is "it saw something", which we could audibly tell because when I forgot to open the gate it wasn't so....aggressive...when trying to scan through the focus range. Power supply test points all seemed to be in tolerance but again, with no easy way to access and remove the PSU without risking the alignment there's not a lot I can do about it. :/
@@CelGenStudios are there any focus gain and tracking gain trimmers on the board? you can check their original settings, and play with it to see if you can get a better result. also check that the lens movement is perpundicular to the disc, it should not be tilted at all, just move straight up and down. also sometimes you can adjust the laser gain up a bit to generate more light, and thus more contrast, this might help as well.
@@arjenchristianhelder1027 There are adjustments, but until we can verify it's not a component problem rather than a tuning readjustment it's extremely advisable not to touch any of them because if it's not an adjustment issue we've now just messed with the factory calibration and have no way to set it back again. The only variable is if the pot is dirty, which I'll have to check.
@@CelGenStudios what can happen is that the value of capacitors shifts over time and also the laser output will shift over time you can mark down the original settings of the pots, also by measuring them in-circuit or noting down the voltages on them so you can set them back when you want.
I have the Pioneer version from a Dragons Lair. It is in the back of storage so not sure of the exact model number. It was sensitive to the disk quality. If the Dragons Lair cabinet cooling fan fails it melts the label glue on the disk. It was very difficult to clean it and get it to play again. I sent it in several times for realignment back in the early 80's. Last time it had trouble recognizing a good disk I tried on my own and gave up. Back then I had no manuals along with not enough knowledge to fix it back in the mid to late 80's. Hope you can. I will download the manuals and try to get motivated for another attempt someday. Thanks for posting them.
I'll find one that needs work and do my usual thing of recklessly tearing into it & trusting my decades of experience with fixing old stuff and send ya the tips and tricks i learn along the way & the whole workbench video if ya like.
yeah, you can't really post that decades of experience as a youtube reply, but i feel you there, that's usually what it takes, take plenty of pictures, and get the calipers out to measure and just slowly step by step tear it down.
Has the focus lens been cleaned? (obvious things to check) I wonder also if the mirrors as well been cleaned. As far as caps are concerned, whenever I check capacitors I always remove them from circuit (or at least disconnect one lead before testing). This gives you the most accurate value on ESR and Farad amount. Replace as needed and use either Panasonic or Nichicon branded caps, as they are the best overall. You might pay a little more, but the reliability can't be beat. You might be able to adjust the focus board using an oscilloscope, but I'm not sure the best way to do that. Too bad there's no dead test board, so you can display error codes in Hex to narrow down problems. Oh, does the disk play fine in other laserdisc players? Just curious.
The mirrors are front coated, so they are very easy to scratch but I've handled that type before in my Nikon film scanners. It's a delicate job but yes, they are all clean. Recapping for me is not a new ordeal and my supplier is normally Nichicon, Panasonic and Rubycon but this thing OH MAN, it uses a considerable number of bipolar capacitors. I absolutely hate those things. The service manual does cover a few manual controls and test points but without jigs it can be hard to get to some of them. Yes the disc is known good. It's the Chevrolet product disc seen elsewhere on the channel.
Hey there,
A few weeks ago I finally got my hands on a PR-7820 from October 1979.
The batterie leaked and because the unit was stored on its back [god knows why] I had to fully disassemble it to neutralize the corrosion and repaint two of the metal covers.
After I put everything back together, I had the same problem as you. The Focus lens was moving up to eight times, bevor the tracking kicked in.
Only when I skipped through the disc manually there was "something" on the screen.
So I would say it's ok to remove the laser assembly from the Spindle assembly [the three allen screws] because the holders beneath are shaped spherically and align the two parts.
After screwing around with the controls beneath the right cover I got the focus to lock on at the first try and a steady picture on the screen. I still have to manually adjust the spindle speed when different parts of the disk are being read.
But I am glad, that it still works, after I disassembled it to the bare chassis.
Im now onto the re-capping part and I noticed that on the focus board [at least on mine] there is a Cap soldered in backwards of what the pint says [it's the one at 20:27]. Did you also encounter this or is this just a mistake on my board that the factory made?
And the biggest question of all...
Did you get your player to work by now?
Thanks for the heads up!
No I've been overwhelmed with other work that I got as far as speccing out a full capacitor kit from the 7820's service manual and visually checking every board but I did not if that one capacitor was in backwards. Be warned though I did find a number of bipolar capacitors.
I have a second donor player how that I want to do a teardown since it's unlikely to ever work again. Just need to find the time to setup the set for this....or should it be a stream?
Thanks for the fast response!
Yeah I did notice the BiPolar caps and bought them separately. I’m going to recap the boards this weekend.
I also wanted to make a backup of the two EPROMs on the computer card.
A video could be edited easily (more information in less time)
When you stream the disassembly though there is the change of some back and forth communication.
Only tip I can give u in advance is to put some WD40 onto the 3 Ellen-Bolts and let them soak.
They were really stuck on my unit. (I almost rounded the heads)
Do you have laser safe glasses or did you just „avoid“ the beam?
Best regards :D
@@raphaelschneider7852 My vision is already swiftly failing, even without lasers being involved. No that's jsut me being reckless with safety squints. Please be more careful than me.
I have the model three version of this. I am having the same issue as well. It’s frustrating not being able to track any of the documentation down to get it to work. It tries to play a disc, spins for a few minutes, then rejects back. I’ve had no luck with getting any sort of signal on screen either.
Check in the description for links to the service manual and optical adjustment instructions. Be warned though that some of the adjustments require special discs and jigs that are no longer available.
I have trouble focusing most of the time.... 😁
Booooooo! >:U
Excelente 👌
I happen to have one of these, its so heavy and I don't know what to do with it. I heard that because they're so heavy and costly to ship, theres very few people selling them. Its just a shame to throw it out
From what I've heard a working player is solid gold to Space Ace/Dragons Lair restorers as their players have totally clapped-out tubes. If you are into kiosk disks with data dumps these are the only players that support the format. If you are into "the first" (the lines are very vague and unconfirmed here) laser videodisc player it will play almost every disc ever made and this is the beginning of the technology. Honestly because of their rarity and historical significance I would (and will) spend the time to perform a full recap, even if many capacitors "seemed" to be okay. Japanese capacitors, especially from the 70's, were notorious for their poor quality.
As for their weight yeah compared to the Magnavision 8000 they were built like a tank because the pricetag was never for the consumer market and cost was never an issue and yes it makes them impossible to ship unless you REALLY want one. It took me over 15 years to find another one that was within a day's driving distance.
Excelente
Love me some Laserdisc for sure, glad to see the upload! Gonna be a good one
two main things to consider here with your awesome museum piece, one is laser output power, you can measure this with a hand held laser power meter (get a sanwa, they are cheap) to check if output is correct, and the diode that should receive the signal from the disc, you can measure this with an oscilloscope right over the photo diode, it should be a high frequency signal. if there is no signal, or its not clean enough you'll need a new photo diode, if there is a relatively clean signal there you have to follow it up the chain, and check why the auto-focus electronics don't lock in to it. also, be sure to check all power supply voltages to make sure they are in good condition, and stable, it can be that the 5V supply is 4.3 for instance.
Problem is it's not easy to read the RF output of the photodiode when it's going in and out of focus. All I can get from a scope is "it saw something", which we could audibly tell because when I forgot to open the gate it wasn't so....aggressive...when trying to scan through the focus range.
Power supply test points all seemed to be in tolerance but again, with no easy way to access and remove the PSU without risking the alignment there's not a lot I can do about it. :/
@@CelGenStudios are there any focus gain and tracking gain trimmers on the board? you can check their original settings, and play with it to see if you can get a better result. also check that the lens movement is perpundicular to the disc, it should not be tilted at all, just move straight up and down. also sometimes you can adjust the laser gain up a bit to generate more light, and thus more contrast, this might help as well.
@@arjenchristianhelder1027 There are adjustments, but until we can verify it's not a component problem rather than a tuning readjustment it's extremely advisable not to touch any of them because if it's not an adjustment issue we've now just messed with the factory calibration and have no way to set it back again.
The only variable is if the pot is dirty, which I'll have to check.
@@CelGenStudios what can happen is that the value of capacitors shifts over time and also the laser output will shift over time you can mark down the original settings of the pots, also by measuring them in-circuit or noting down the voltages on them so you can set them back when you want.
I have the Pioneer version from a Dragons Lair. It is in the back of storage so not sure of the exact model number. It was sensitive to the disk quality. If the Dragons Lair cabinet cooling fan fails it melts the label glue on the disk. It was very difficult to clean it and get it to play again. I sent it in several times for realignment back in the early 80's. Last time it had trouble recognizing a good disk I tried on my own and gave up. Back then I had no manuals along with not enough knowledge to fix it back in the mid to late 80's. Hope you can. I will download the manuals and try to get motivated for another attempt someday. Thanks for posting them.
Looks like wobble spending
I'll find one that needs work and do my usual thing of recklessly tearing into it & trusting my decades of experience with fixing old stuff and send ya the tips and tricks i learn along the way & the whole workbench video if ya like.
I await your findings!
yeah, you can't really post that decades of experience as a youtube reply, but i feel you there, that's usually what it takes, take plenty of pictures, and get the calipers out to measure and just slowly step by step tear it down.
Nope
Nope
Nope
Nope
Nope
Nope
That's a really great looking machine. I really wish you can get it working. It deserves that.
Has the focus lens been cleaned? (obvious things to check) I wonder also if the mirrors as well been cleaned. As far as caps are concerned, whenever I check capacitors I always remove them from circuit (or at least disconnect one lead before testing). This gives you the most accurate value on ESR and Farad amount. Replace as needed and use either Panasonic or Nichicon branded caps, as they are the best overall. You might pay a little more, but the reliability can't be beat. You might be able to adjust the focus board using an oscilloscope, but I'm not sure the best way to do that. Too bad there's no dead test board, so you can display error codes in Hex to narrow down problems. Oh, does the disk play fine in other laserdisc players? Just curious.
The mirrors are front coated, so they are very easy to scratch but I've handled that type before in my Nikon film scanners. It's a delicate job but yes, they are all clean. Recapping for me is not a new ordeal and my supplier is normally Nichicon, Panasonic and Rubycon but this thing OH MAN, it uses a considerable number of bipolar capacitors. I absolutely hate those things. The service manual does cover a few manual controls and test points but without jigs it can be hard to get to some of them.
Yes the disc is known good. It's the Chevrolet product disc seen elsewhere on the channel.
Is it my imagination that the disc was spinning in the wrong direction? 🤔
Remember that the disc is being played upside down relative to every other laserdisc player, so you are correct.
@@CelGenStudios Ok… I guess I missed that I was seeing the bottom angle of the player. Thanks for the explanation.
its off balance... ovs.. can you not see
Excelente 👌