Panasonic AG-1980 maintenance items?

[i86time]

Hello all,
Sorry that this is one of the many posts requesting info on this subject, but it appears the site only wants replies to older posts from those in the original conversation.

After 5+ years of sitting in a box in the garage since last use, I powered up my AG-1980P and it definitely needs repair and service. Thanks to @MrPete, @jaffa225man, @ aramkolt and others, I was able to create a cap list and am waiting for my Digikey order to arrive.

While I have the machine completely disassembled I figured I go through the maintenance chart. I don't have any experience with VCRs, so I am wondering what really needs doing, as I'd rather not go down a rabbit hole of trying to completely overhaul everything (unless necessary) or doing anything that requires the special tools/jigs which I do not have.

Based on posts here, I verified the loading motor coupler is undamaged, but I ordered a replacement anyway as it was covered in grease which has since decomposed to oil, so who knows if it has weakened the plastic. I also gave the mode switch a nice DeOxit bath. My pinch roller rubber is soft and unglazed. My capstan rotor does have a bit of brake glazing, but there is still a lot of felt left on the brake.

So going through the maintenance items on pg 1-25 of the service manual:

For cleaning, is hexane (generic AR S-721H) good for the metal & rubber parts and isopropyl for plastic parts? For grease, I'm planning to use molykote EM-30L for all surfaces.

The chart says to clean the supply and take-up reels and oil them. Where does the oil go? On the metal post under the reel itself? Can I just put a drop or two on the top and have it drip down or do I need to remove the reels?

For the capstan rotor, as long as it spins freely, should I just clean the visible portion in the housing and not bother with disassembling to oil it? If I do just pull the rotor out, I don't need to perform the adjustments mentioned on pg 2-3 of the K-Mech manual as I'm not removing the housing or stator, correct?

I see that only the main cam gear and the inclined base units are listed to be greased. Yet I see grease on many other gears, the main lever, plastic guide/guide pins, etc. Should I clean off all the old grease on those and re-grease? Or as long as there is still grease which has not hardened, just leave it? Also, some gears have grease and others do not. Should all gears have some grease on them or just the ones that currently have grease?

Any work that the chart is missing or pitfalls to look out for?

Thank you

[Gary34]

Quote:

I don't have any experience with VCRs

That’s a really tough VCR to work on. I have heard LS say that VCR gives repairmen nightmares. https://www.digitalfaq.com/forum/vcr...ag-5710-a.html If you botch that repair then I don’t think Deter will touch it.

[aramkolt]

I've now refurbished about 20 of them, some for other members here, I do have a marketplace listing for the service and I also have units available for sale that have already been fully refurbished.

A regular repair shop is typically trying to do minimal repair to get it working and these always will have certain capacitors that need replacement and they'd probably have to commit a tech to work on it for one or more full shifts just to do that - all to test it at the end and "hope" it works. That's assuming they've worked on one before and generally know what to exchange and have all of the parts on hand. They could get lucky and the mechanism might be without issues and that would save them a lot of time, but that's not really going to give years of maintenance-free-use - A repair shop's job is to get it working for the moment.

I missed the part about Hexane being recommended for rubber cleaning agent n the manual, but that's what I've been using anyway - American Recorder S-721H. I do use EM-30L for any grease that needs to be replaced. I use 91-99% isopropyl alcohol for anything that is not rubber. I do completely pull the capstan shaft to clean and re-lubricate it and for that I use synthetic oil like superlube. The capstan is a little tricky to get those seals back in place without getting oil on the actual shaft that the tape contacts, but I don't have that problem now that I've done so many. You can always redo it and pull again and re-oil until you are sure that oil didn't get on the main shaft. Much of the deck refurb is removing everything and re-greasing, but if you mess up the mechanism timing, that can potentially frustrate you for hours or days like my first couple did haha.

Otherwise it is the usual tape path cleaning, mode switch cleaning with deoxit 100% solution, loading motor coupler replacement, as well as pinch roller change if any evidence of cracking/glazing as far as the mechanism goes (plus old grease removal and replacement and capstan cleaning/relubing as mentioned above)

[Gary34]

New people taking apart there 1980s and trying to repair them is a bad idea. That should be sent off.

[i86time]

I probably should have added that I've been collecting and repairing classic video arcade games (power supplies, PCBs, monitors) for over a decade. Doing a cap kit is no issue, though the SMDs on the AUDIO2 sub board are a bit more crowded than I'm used to, but I'll take those slow. I know these are a different beast, but the general idea behind repairing them seems similar to me.

My main concern is with the K mechanism and it's maintenance. I know enough not to mess with anything before I get a decent handle on it. I read up on the gear timing in the service manual and watched some vids by Video99.co.uk and for maintenance saw the private vid from Quasipal, but still had some questions I wanted verification on before diving in. It seems like the manual skips steps on maintenance (for example completely removing the capstan rotor/shaft from the housing to lube it properly), which a seasoned tech would probably know but would not be obvious to a lay person. It may not something beyond their capability, but if they skipped a step or weren't aware of a method, it could do more damage than good, or at least increase repair time.

[Gary34]

I’m just saying in general people should really think about it before they make the decision to disassemble a 1980. That’s not a good thing to encourage new people to do. The temptation is there because they can be bought cheap in I maintained order but then people can get into way more than they realize off the bat by trying to refurb it themselves.

[lordsmurf]

Quote:

Originally Posted by Gary34

I’m just saying in general people should really think about it before they make the decision to disassemble a 1980. That’s not a good thing to encourage new people to do. The temptation is there because they can be bought cheap in I maintained order but then people can get into way more than they realize off the bat by trying to refurb it themselves.

So many good decks have been ruined since the pandemic. All those bored people at home, putting on their "big boy pants" pretending to be VCR techs. It's why we are where we are now. At least eBay used to be a mixed of junk and overpriced not-quite junk. Now t's just overpriced junk, many times not even good for scrap. If you know what to look for, you can see how many of them are botched repair attempts, and get passed around there. (There's always an anecdote about "I bought one that was fine", but those are exceptions, not norms -- and even "fine" is often arguable.)

I don't see that with participants thus far in this thread. But in general, far too much Dunning-Kruger.

The whole video capture community has suffered from this fact.

It's why I avoid certain models, why Deter rejects decks, etc. Too much has become unsalvageable. @aramkolt, don't give yourself burn-out. Your success rate bounces between 50/50 and 75/25, by your own admission. That means you're pissing away 25-50% of your video hardware time, and that does eventually grate on you. Been there, done that. Hence the rejections, for my own sanity.

[i86time]

No problem, I understand where you're coming from and agree- I see it on the arcade forums as well. I'm not saying I'm not going to make any mistakes, I just wanted to get as much info as possible to reduce the probability of doing so.

[Gary34]

I think sometimes people know just enough to get in trouble. If you know you don’t know you hire it out but people who do it themselves are the ones that think they know. Idk anyone personally though so maybe they know what they are doing. I’m just saying I’ve seen botched repairs in other places besides here.

I’ve heard about botched repairs in places besides this forum but I’ve noticed people don’t really post about botched repairs or if they buy gear and get screwed on this forum. You usually hear about the times it works out but not the times it doesn’t. It reminds me of casino slot machines. How they ring when they are winning so everyone is like ow there paying out but they don’t have a buzzer for when they are losing.

Anyways good luck with the repair. I hope it goes well.

[lordsmurf]

Quote:

Originally Posted by i86time

No problem, I understand where you're coming from and agree- I see it on the arcade forums as well. I'm not saying I'm not going to make any mistakes, I just wanted to get as much info as possible to reduce the probability of doing so.

Yep, you seem to have some % of sense and related experience.

That's not typical.

Very often, you'll see the "well, I installed a modchip once" type "qualifications". The amusing part is when the same person claimed to have followed (monkey see, monkey do -- literally?) a Youtube video. We had some real WTF? posts in recent years, utter deck destructions.

Quote:

Originally Posted by Gary34

I think sometimes people know just enough to get in trouble.

When younger (and a cheapskate), I started fires at least twice, trying to fix something that I should have never attempted. Oops. I didn't know what I didn't know. Lesson learned. But it wasn't something with scarce supply, or valuable, like S-VHS VCRs with TBCs, I knew better.

[aramkolt]

None of the refurbishing services recap the SMTs on the Audio II board to my knowledge. I've recapped them before just to see if there was any change with audio output and I can't say that there was. True, those caps always test bad these days. They manual says you select it using the mono switch for an "Audio II broadcast recording" when stereo broadcast sound is poor. hence this board seems to only have to do with broadcast recording and I wouldn't recommend touching it at all. Could even be that the machine operates normally without the AudioII board installed at all, haven't personally tried it.

There's also an "audio II" LED on the front panel that I've never seen light up during playback, so I again think this board has nothing to do with playback.

Here's a couple of screenshots from the manual:

Screenshot 2024-12-15 at 4.29.30 PM.jpg

You must be logged in to view this content; either login or register for the forum. The attached screen shots, before/after images, photos and graphics are created/posted for the benefit of site members. And you are invited to join our digital media community.

[i86time]

Quote:

Originally Posted by aramkolt

None of the refurbishing services recap the SMTs on the Audio II board to my knowledge. I've recapped them before just to see if there was any change with audio output and I can't say that there was. True, those caps always test bad these days. They manual says you select it using the mono switch for an "Audio II broadcast recording" when stereo broadcast sound is poor. hence this board seems to only have to do with broadcast recording and I wouldn't recommend touching it at all. Could even be that the machine operates normally without the AudioII board installed at all, haven't personally tried it.

Looking at the schematic, the I/O line outputs come directly out of that FM Audio sub board (represented as 40 pin IC4504 labeled as VEP04353B on the AUDIO2 diagram sheet, but which is in fact the sub board), so it must do some sort of processing.

Quote:

There's also an "audio II" LED on the front panel that I've never seen light up during playback, so I again think this board has nothing to do with playback.

I believe Audio II (not to be confused with the AUDIO2 CBA), is akin to secondary audio, an optional audio track to be selected by the end user. Common examples of this are dubbed Spanish audio tracks for typically English language programs. If one was available and selected by the user when passed through or recorded by the AG-1980, I assume the LED would light then.

[aramkolt]

Yeah, I guess I don't doubt that audio does pass through the audio II card for routing purposes, I just don't know if it goes through that daughter board with the SMT caps for normal playback. The AG1980 is sort of unique in that it outputs the mono audio at the same time as stereo audio, so it is possible to record the mono/linear audio at the same time as the stereo HiFi which I'd say all but professional VTRs can do and not even most of those I think allow that either, it's more choose one or the other generally. Could be that Audio II is for the mono output which may have Dolby noise reduction maybe? Dolby NR doesn't apply to HiFi Audio as far as I know. I suppose looking up that McLeod chip that sits on top of that SMT capacitor daughter board will probably give a better idea of what that section of the board does anyway. I do maintain that no refurbishing services touch those SMT caps, probably because they are hard to get at, there are quite a few of them, and likely do not affect normal audio playback. I've recapped them on 3 machines just to see if I could tell a difference in sound, but I was unable to.

[i86time]

Long post incoming....

The cap replacement was a success and the video is much improved. As I removed each cap, I tested it with an EDS-88A ESR meter and if it tested marginal or bad, I then tested it for capacitance with a BK-886 LCZR meter @ 1kHz. The ESR meter chart is fairly unforgiving @ high ranges (above 220uF), so for values at and above, if it was at the top block of the "bad" range, I considered it marginal.

I replaced nearly every capacitor in the machine, other than those on the TV tuner/demodulator PCB as it no longer has any use for me (or anyone in the USA that I know of). I didn't replace the 100,000uF supercap. I pulled it and tried to test it, but was getting odd results. I think they generally take decades to go bad and believe it's only used as battery backup for channel list/recordings, neither of which I use.

I can share the spreadsheet here if there is interest, but it seems to generally mirror whats been reported here.

Merely 3 caps (1.3%) still tested as good for ESR. All of these were thru holes, as I found that every single SMD I tested had a noticeably greater ESR than a thru hole of the same capacitance (even for the new replacement SMDs), guess that's the nature of those components.

The majority (121, 51.9%) tested as marginal for ESR but were still within 20% of their rated capacitance. I tested some of the new caps as they were installed, and they tended to rate a bit closer to the rated capacitance, and the thru hole caps were generally much lower in ESR. I'm not sure if that's because the original caps originally had a higher ESR, if they degraded over time or a bit of both.

107 caps (45.9%) tested bad for ESR (including 12 that had gone open), and 80 (34.3%) of those bad were also below 80% of their rated capacitance, which means they were definitely not working as intended.

2 SMD caps were damaged on removal and could not be tested. They were on the Y/C board and were probably bad (see below).

I only saw 1 cap that looked like it had vented, but when removed it tested marginal for ESR, within 20% of capacitance and looked OK, so perhaps it was just rosin from solder. All other caps were visually OK.

Every board had at least 1 cap that tested bad for ESR, but the board with the highest percentage of bad caps was the Y/C board (both analog and digital). Except for a single 1uF cap, ALL other SMDs on that board were bad in both ESR and capacitance.

The next greatest was the FM Audio board (the AUDIO2 sub board with all the SMD caps). Most of those caps just tested bad for ESR but still had acceptable capacitance. This may be due to the inherent ESR of SMD caps mentioned above.

After those were the Timer, Main, power supply & Head Amp.

One group that doesn't seem to get mentioned (other than a post I saw from aramkolt) are the caps on the head cylinder PCB. There are 3 BP caps and a 4th polar cap on it. All 4 of those tested bad for ESR and 2 of the BP caps also tested <80% of their rated cap value. When compared to the new caps, the original BP caps had 2-3x the ESR as their replacement. I would say these also should be replaced.

I haven't matched up caps with their purpose in-circuit (and may never fully do so), so I have no idea what practical effect all these marginal and bad may have had. It is clear that the SMDs on the Y/C board MUST be replaced, but that's been known for years. So it's really up to owner's whether they want to go all out and replace everything. At the very least, test caps in other sections.

I haven't yet mustered the courage to tear into the K-mechanism to do a thorough clean and lube to finish up the long overdue maintenance. I'll probably be asking more questions shortly.

Also, I have an lingering issue with the power button that I will be posting about later.

-- merged --

Hello,
Attached is an updated cap list and BOM for the AG-1980 (excluding the TV tuner/demodulator PCB), building on the hard work and efforts of MrPete and other posters, with information on current substitutes as necessary. As with the previous list, I have stuck with using Panasonic branded caps for replacement. The original series is noted in col K and the current series in col N; most are KA/KS which are still available. However, Panasonic has ceased manufacturing of many caps 1uF and lower, so those are no longer available (NA, highlighted). I prefer Nichicon caps as substitutes, so those are the part numbers provided. If you choose your own parts, be sure to check the notes/size constraints (cap length) to make sure they will fit.

Also attached is a hand drawn (i.e not exact or to scale) cap map to help with finding their physical locations on the boards. This map has only been validated with my boards; the p/n and rev are noted in the linked spreadsheet. Be sure to open your deck and verify your boards before purchasing anything.

Finally, I have linked a current (Jan 2025) Digikey parts list for the entire re-cap BOM. As of now, all items are well stocked and ready to ship. I will likely NOT be updating this list over time. The very last line item has a 0 quantity and is for the 100,000 uF supercap. This will likely NOT need replacing, however if you need/so choose, open the item page from the link in the list and add QTY 1 to your cart. Most of the items had a price break @ QTY 6 making it cheaper to order 10, so you will have some extras for certain line items.

If you only want/need to re-cap specific boards, you will have to enumerate part counts yourself and adjust the cart accordingly.

https://www.digikey.com/en/mylists/list/53PDMGOLDF

Current full list cost is $58.22 plus tax/shipping

[aramkolt]

Interesting information for sure. I have some theories why you got results showing like 98% bad caps which I've never found to be the case. I suppose it is possible that it was at some point stored in like an attic in Arizona and exposed to very high ambient temperatures for a decade, and I suppose that could do it, but this isn't the norm for that many to test bad in my experience.

1. The standard higher end ESR testers usually will do their testing at 100KHz rather than 1KHz or 10KHz- I'd have to drag out my DE-5000 LCR meter that can also test the lower frequencies to check if a lower test frequency typically gives lower or higher ESR values, but my guess is the ESR readings anyway are higher if 90%+ of your non-SMT caps were bad by that method. Capacitance testing I'm not sure if is much different at different test frequencies though

2. Some of it depends where you put your "bad" threshold for a specific cap. The general guidelines you'll find online are usually for full size caps and most of the ones in the AG1980 are mini ones which start off with a higher ESR. The capacitors that are replacing the old ones, even if the same model may have been charged/discharged at the factory more recently than the machines's older ones or use a newer electrolyte formulation than the ones 25 years ago.

3. Depends when the VCR in question was used last for a significant period of time - I don't know that I'd call it re-forming per se, but ESRs do improve when a capacitor is used and brought up to working temperatures for several hours and then will slowly drift back up when not used for years which is probably the case with most AG1980's that are turning up these days, in storage for years unused. Capacitor testers like they actually had in the old days would actually test them at their rated voltages and measure leakage current (out of circuit of course). Essentially it is any current that flows after the capacitor is charged up to the rated voltage which is essentially has to be current leaking from one side to another as a "perfect capacitor" once charged would not lose or accept further charge once already charged to the supply voltage. Bringing them up to their rated voltage can also show different failures under what is essentially load. Maybe it only leaks voltage if the test voltage is higher than our ESR/capacitance meter is feeding it with?

4. Standard allowed variance on capacitance for almost any capacitor even when new is plus or minus 20% (still to this day), so a 100uF capacitor that reads 80uF is technically still in spec. I'd still replace one like that generally, but it could still pass quality control at the factory that way. Generally I'd say most capacitors that I don't replace are within 10% though.

5. It's actually quite rare for power supply caps to test bad in AG1980s by ESR/capacitance testing alone (outside of the small 25V 22uf capacitor on the primary side, but if that's bad, the supply just won't start switching at all, so that's rarer yet to be bad enough not to perform its function. This also makes me think something is off with your testing. That being said, I still replace all power supply capacitors anyway since things like leakage and noise aren't going to show up on ESR or capacitance testing. Oddly, we think of noise as being an AC voltage, but capacitors are supposed to pass AC voltages uninhibited which is somewhat counterintuitive since certain capacitors are used for noise suppression and voltage stabilization, though for noise suppression, my guess is the circuit design is to allows the AC component of noise to go to ground which is what allows for the elimination part.

I could probably do a short video showing testing of something like 10 original power supply caps with caps with a value/size only found within the power supply from different AG1980's (already removed) and my guess is they'll all read within 5-10% of the rated value and have acceptable ESRs when using a 100KHz meter if that would interest anyone.

I do agree it is best practice to replace the lower drum caps and I have yet to see any refurbishing service do it other than myself - probably because there's some additional risk of damaging the drum or PCB and it also requires removing the video head drum from the mechanism.

[i86time]

For quick ESR grading I am using the EDS-88A. I looked in the manual for specs, but it didn't provide. Looking at the website, it states it tests @ over 100KHz. This unit has a matrix graphic on the front with green, yellow and red blocks. Green indicates good and red, bad; I called those that tested in the yellow area marginal in my results. Since only the top blocks indicate good for caps over 470uF (which corresponds to an ESR of under 0.10 ohms), I allowed for an extra block (less than 0.25 ohms ESR) to be considered at least marginal. The manual also clearly states SMD caps always have higher ESR than thru hole counterparts.

For capacitance/ESR values, I used a B&K 886. It can test from 100Hz to 100KHz and @ 50mV, 250mV and 1V. I just chose 1KHz and 1V as that is what it defaults to on startup. The manual states caps 10uF and larger (pretty much every electrolytic in this unit) should be tested @ 120Hz. I could find no mention in the manual about if/how frequency affects ESR measurements. I do not think it's as nice as benchtop units, but I have no reason to believe it's unreliable.

So I took a few of the power supply caps (56uF, 120uF and 1800uF) and re-measured them at all frequency and level combinations. What I found was that measured ESR declined with increasing frequency. However, it would have only changed the ESR "grade" for the 56uF; though the ESR measurement dropped by more than half with increasing frequency, it still ranged from good to marginal. But the capacitance varied greatly with test frequency. For the 120uF cap, capacitance was very similar @ 100Hz, 120Hz, 1KHz and 10KHz tests (all around 113uF), but dropped off considerably @ 100KHz (35uf). For the 1800uF cap, measurements were also steady @ 100Hz & 120Hz (all around 1740uF). But @ 1KHz dropped to ~1700uF. At 10KHz the tests provided no stable reading. I'm wondering if there was some sort of harmonic issue. Then @ 100KHz, test values ranged from 85uF to 165uF based on voltage level. For the 56uF cap, measurements were also steady to about 1KHz (57uF), then dropped to ~50uF @ 10KHz, then to 16uF @ 100KHz.

Based on these results, at least w/ the B&K tester, I would stick with testing capacitance @ 120Hz or 1KHz. With this unit, 100KHz should not be used for these "large" electrolytics, though it affects ESR readings to a much smaller degree than capacitance.

Regarding the +/- 20% variance, yes, that is why I reported out on those that tested <80% of their rated value.

The caps in the power supply that tested bad for ESR were both 220uF, both 330uF, the 1200uF and 1800uF. Both 220uF also tested <80% of their rated capacitance.

[aramkolt]

Very interesting. I'm pretty sure the meter I use shows the originals to be within 5% most of the time in terms of capacitance, but it's a Atlas ESR70+. I think most capacitor testers don't actually fully charge and discharge a cap unless it's a small one, but it is more of an extrapolation of what it thinks it could charge to based on how rapidly it absorbs voltage and starts to taper off maybe. Capacitance really should not vary based on a frequency since it's storing a DC charge. Capacitance might change some with temperature though.

I think the meters I have are the MESR-100, DE-5000 LCR meter, ESR70+ Gold, GME-236, and the BLUE K7214+ (which is the same as an MKII). The only ones that actually will show capacitance are the ESR70, DE-5000. The DE5000 is the only one that I can change the test frequency.

Is there a particular test that would be of interest to you using the above meters and identical origital pulled caps from several AG1980's?

[i86time]

Wow, you have a whole slew of testers! If you had the time, it might be interesting to see if your DE-5000 shows changes in capacitance/ESR at the various frequencies for a couple of caps.

Ultimately I'm not sure how much help this would all be though. Based on what I could find, most of the folks who still repair the AG-1980 don't replace all the caps anyway. I doubt they would go through the trouble of testing every single cap on the boards; if they're not already using and in-circuit tester, removing the cap to simply test it is half of the labor of replacing it. But maybe if it could be shown that a quick in-circuit ESR test @ xx Hz was a pretty good marker, maybe they would be more inclined?

I just replaced all caps in my deck as 1) it's a habit of working on old electronics (if there's many bad caps, all the other caps are the same age, so it's only a matter of time before those fail and I'm in there already anyway), 2) I was looking for a project during the holidays and 3) the parts cost is trivial to the value of a working unit.

[aramkolt]

Yeah, I can go overboard when it comes to wanting to try different hardware haha.

My main point is that most caps should test ok in most AG1980's, it's mainly the high heat areas and the SMT caps that will always be bad, which is why I am kind of shocked that yours tested with so many of the other ones being bad. Reason I bring up power supply caps is that they are easy to identify being that they are much bigger than all of the others and you'd think since the power supply can get warm that they'd be usually bad, but I haven't found that to be the case personally. I do replace them all anyway since the tests we do can't test for every characteristic of a capacitor in-circuit, but the tests you did I wouldn't have expected that percentage of failures which is why I was curious about the testing method. I'll grab a few of the pulled 1200 and 1800 uF power supply caps and see how they read on the DE-5000 and post about it.

[lordsmurf]

Quote:

Originally Posted by aramkolt

Yeah, I can go overboard when it comes to wanting to try different hardware haha.

Yes.