Originally Posted by i86time (Post 100519)

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

Originally Posted by aramkolt (Post 104453)

I've not seen any other refurbishers (other than me) do routine full recaps to the power supplies on these.

Originally Posted by radiokom (Post 104466)

Call me paranoid

Originally Posted by lordsmurf (Post 104467)

https://youtu.be/0qanF-91aJo?t=5 :rockon:

Originally Posted by aramkolt (Post 104453)

The bad/marginal ESR and capacitance readings can be a bit tricky on the original through-hole panasonic caps because many of these AG1980's have sat for decades and it is pretty likely that the ESR and capacitance could improve some with actually using the machine as they sort of "re-form." Given that they are also the mini-caps, ESR tended to be a bit higher when they were new as well (due to less surface area inside). I'm not sure if the "new" versions of those use different electrolyte or other materials nowadays, but I would presume so. ESR meters do tend to point to marginal results for most mini versions of caps, but it's a bit hard to say when we don't exactly know what the ESR was like when it was new. I did some extensive recapping to a Betamax machine this week and all of the 10uf 16V 4x7mm caps read 10uf, but all 20 of those pulled had an ESR of 6, which is at least twice what you'd expect these days, but given that they were all so consistent, it does make me wonder what that series had for an ESR to begin with. Hard to say. Most of the 4x7mm were general purpose caps and didn't really need low ESR. The AG1980 would have had plenty of room to use full size capacitors (5x11mm) for just about everything, but they chose to use the smaller ones, probably somewhat due to cost savings, but also because there probably wasn't a significant performance difference in using larger caps which would have had lower ESR also.

SMTs are definitely all auto-replace on the TBC, the other SMTs aren't really used for playback.

I will say I am a bit surprised that many of the power supply caps were reading marginal for you - generally those tend to actually test ok, but I do replace them anyway since ESR and capacitance aren't the only properties that keep electrical noise low in a power supply. Could be you had a higher hours unit too though maybe. I've not seen any other refurbishers (other than me) do routine full recaps to the power supplies on these.

I'd be curious to see your spreadsheet if you don't mind posting!