Panasonic AG-1980 capacitor repair? - Page 3

Just_a_hobby · #41 03-04-2014, 05:23 PM

Argalby, Thanks for the update I too finished the video board on my 1980 and I'm very surprised how good the picture looks. I only had one cap I did not have to install while I had the board out a .22 electrolytic. I was able to do the job with a pointy soldering iron and a large halogen light with powerful magnifying glass. Some caps are very small and requires a steady hand and lots of patience and or scotch. I did mine in cap size groups and when I felt like working on it. I have noticed on some tapes I get a little color shifting and think it is somewhere other than the video board because I have had two boards in this machine with same result. Anyone have an idea what / where the caps may be other than the Y/C board to cause color shifting?

Argalby · #42 03-04-2014, 05:39 PM

I toast your accomplishment! It's very rewarding when it's done and you see the nice picture isn't it? You're right a steady hand helps a lot! I pulled all the aluminum caps on the Y/c board, and later, I tested the ESR and all were sky high! Not sure if these were made back when there were bad batches of electrolytic caps being imported or what.

As far as your color shifting problem, not sure where that would be. If it's just on some tapes I'd suspect the tape, or the original recorder that made the tape. If other tapes play well I'd say the AG-1980 is doing well. However, try running the video output thru composite (BNC) Instead of S-video and see how it is. If it's minor, maybe you can correct it during the dub process with a proc amp. There's many, many min-pots on those boards, you can't adjust them without having the right equipment and hours of time. I freak out when my hot air gun gets near them!

I've got over 4 different VCR's here for dubbing, and an (8x8 switcher so I can quickly switch between them) The AG-1980 gets used for dubs 90% of the time...my favorite "stranded-on-a-desert-island" VCR

(In that case I guess I might need a gas generator too!)

dpalomaki · #43 03-04-2014, 07:54 PM

Encouraging reports!

Before I go and break something, is there a trick to getting the daughter cards off the main board, or is it just remove screws where present and carefully pry them and hope the connectors free up?

It looks like a real bowl of spaghetti inside the case.

Just_a_hobby · #44 03-04-2014, 08:45 PM

Dpalomaki,

Remove visible screws on the main board and the screws in the back around connectors it all comes out together. There are two screws securing the video card to the main board that go through main board and into the video card. After all screws are out you can manage to get enough clearance without removing any more wires/connectors just use care and go slow pulling the main board assembly out of the vcr case. The video card just pops out of the main board connectors with a little force. Good luck and let us know how it goes.

Argalby · #45 03-04-2014, 08:48 PM

There's small "ears" inside the white plastic connectors that hold the connections to the main board. Use a very small screwdriver to pry apart the connector while you carefully pull the board out. Unfortunately the white plastic connecters are very old, and may crack while you do this.

videonut · #46 03-05-2014, 10:03 AM

Yes the plastic can break but what I noticed is that you may get some other connections loose and once you put it together you start having some other problems.....If so, take all the boards out and re-solder the connections on the main board and on the individual smaller boards. All of fleebays need rework regardless of who says what, period. You can get some that are ok but not as good as a rebuilt one. I did two units for myself and changing all caps is expensive, labor intensive and some parts are almost impossible to find (including mouser etc.). I would not pay more than $50 on any unit at any time, because all units need a lot of TLC. I did not see a rebuilt one yet so unless you do it yourself... Do not fall for like new, or looks new or very good condition etc. Look at the year of production, look at the pinch roller (that can be changed too...), look at the display, at the capstan and at the plastic discoloration (inside the unit of course) among other things. There are some caps that go first and you can check those readings and that can also give you an idea of how much it was used. I did not encounter problems with the heads. The units do not go out of alignment unless someone worked on them or a part is faulty. And yes those codes coming up are usually a electronic part problem, not alignment.... I encountered that 05 or 06 or 04 problem when rewinding the tape and reaching the end and was not an alignment problem.
Once rebuilt you will love it. The plastics are very good qualitative, the boards are very good also and you can not strip them unless you do not know what you are doing. I would try to change all electrolytic caps on all boards.

dpalomaki · #47 03-05-2014, 11:11 AM

All electrolytics?
That is what, 235 give or take?

videonut · #48 03-05-2014, 12:54 PM

Yes, all. Not the tantalum, just the aluminium polar and bi-polar. I think is more than that, the audio cards are loaded. On the power source the ceramics also, but they tend to be still ok.

dpalomaki · #49 03-07-2014, 05:14 AM

On the service manual parts list there are about 222 electrolytic caps, 44 of which have surface mount part numbers (ECEV..., a discontinued part number per current Panasonic component literature.)

Many parts, not just caps, include the letters "CH" between the part description and value; e.g., "E. Capacitor CH 16V 47U." and not all SMDs have the CH. What does the "CH" signify?

NJRoadfan · #50 03-07-2014, 06:34 AM

Don't know what the CH means, but 16v 47uF low ESR SMD caps are very common and easy to find. The part numbers are all discontinued because they have been superseded by a more modern (and hopefully longing lasting) series of capacitors.

http://www.panasonic.com/industrial/...ctrolytic.aspx

More about those polymer caps. They cost a bit more, but don't have any liquid electrolyte to dry up.

http://www.panasonic.com/industrial/...ts/os-con.aspx

videonut · #51 03-07-2014, 11:22 AM

In replacing caps I go with what is on the board. I noticed one 47uf cap that is listed as nonpolar and actually is polarized on the main board. After that I stopped checking the schematics, plus there are some variations in the Y/B card schematics. Change one cap at a time. Keep the same values for capacitance and do not go lower in voltage. You probably can not find the exact serial number..... Low Esr is good but sometimes lower does not mean better, but that is another story. As long as the ESR is in the average range is ok. Depends on the voltage, on the size and on the materials of course. You will ahve to check the charts for the SMD caps to see the range.The sad part is that the new caps are mostly made in a country with not optimal quality control. You can still find old stock and some are still very good, some are marginal good or bad. How do you guys explain caps made in Japan and sold from China? I have no ideea. Just my 2 cents.
Do your own research and good luck with the decisions you make.

dpalomaki · #52 03-07-2014, 12:09 PM

The badcaps.net web site has some interesting information and a lot of threads, although the focus is mainly on motherboards and other PC gear, including graphics cards.

I've read that one should try to match the original specified ESR in power supplies applications. Going too low might result in increased in-rush current and stress other components beyond the intitial design.

Non-polar may make sense in applications where the signal excursions could exceed the DC bias on the cap. Figuring out where they are means reading and understanding the schematic.

What are the preferred source for caps? Digi-Key, Mouser, Allied, Newark, ...
Preferred brands? Panasoanic, C-D, Nichion, etc.

I would be hesitant to go with E-Bay discount sources - no telling the age or origins with any degree of certainty.

I see Panasonic published a news note related to countries of origin for their electrolytics a while back.

Just_a_hobby · #53 03-07-2014, 03:25 PM

In this day and age I figure most of these caps today are made in China or similar foreign country. I bought the cheapest ones I could find on ebay for the Y/C video card and they are working great no problems at all! In the end they are probably better than the originals in this machine. I'm sure some will disagree and that's fine it works for me.

NJRoadfan · #54 03-07-2014, 04:55 PM

I source Panasonic caps from Digi-Key. No mysteries there, you get the real stuff. Fake capacitors are a problem believe it or not.

dpalomaki · #55 03-10-2014, 08:09 AM

Read some current Panasonic litrature on SMD caps. Bottom line is that heat kills. And ripple current higher than 30% of the cap's rating causes life shortening heat issues. Other life-shortening issues include over voltage, frequest charge/discharge cycles (power on/off cycles), and use of polar where non-polar are indicatd to accommodate occasional reverse voltages (as dueing power on/off transients).

Common caps have a 85C 1000 Hour rating. One step up better caps might be rated 105C 1000 hr. These are guaranteed life.

Now put them in a piece of equipment operating at, say 40C (about 104F), not uncommon inside a case, and the expecte life becomes say 20,000 hours for the lesser, and 90,000 hours for the higher rated. At 8 hours per day that amounts to around 7 and 30 years respectively.

But if the temp is more like 50C (122F, not unexp[ected in a full rack bay w/o special cooling) the life is cut in half.

I believe that the existing EVEC series caps were 85C rated. The existing AG1980s lasted 10+ years with the original caps so using similar replacement should get you another 10 years fromteh caps as a minimum. Pay a few cents more for a 105C rated cap and the caps should last a lot longer (and maybe survive soldering better as well).

dpalomaki · #56 03-11-2014, 04:32 AM

However, if going for a higher rated cap be sure to check the physical size. to be sure it fits in the available space.

videonut · #57 03-12-2014, 12:37 PM

I have been very satisfied with the flee bay capacitors overall with few exceptions. You can still find some made in Japan, Korea or even Europe and they are of very good quality, even if old stock. The rest of them are made in China. The good ones are not cheap, so its not like you pay few cents more for the good ones. No way. You have to read carefully the description and make sure you get what is in the picture. If you ask a question and you do not get an answer or the feedback is not so good, stay away from that. Some do not know what they sell and you can be very lucky too. Takes a lot of time and research to get everything you need that also matches the values and size. Now it is clear why nobody so far put a kit together... It is time consuming and not rewarding. At the end of the day you will still find someone complaining about something. It takes a lot of time, perseverance and a lot of work if you want to do it.
Good luck.

Argalby · #58 03-12-2014, 01:04 PM

Yes, I agree. It's a real chore repairing these. I've done several and you can't rush it, one blob of solder in the wrong place, or one misaligned capacitor and you're out of luck. To say nothing of the risk of bumping a nearby tiny smd cap.

While we're on the topic, I ran across what I think is an early design AG-1980. Date code on the machine has a "5" (so I guess either 1995 or 2005?) It's Y/C card is somewhat different, it has about 6 wires that come out and go to a connector under the transport mechanism. It also has some sort of metalized cardboard around the Y/C card. I haven't had this one apart, because it works well, but I'm guessing it's got the same parts inside. Any thoughts?

cruisinforgold · #59 03-12-2014, 06:21 PM

Must be early production model in 1995 given info herehttp://www.digitalfaq.com/forum/vide...sonic-pro.html

videonut · #60 03-13-2014, 09:52 AM

It' s probably a 1995 Panasonic. As long as the heads and mechanics are good it is worth repairing. I saw two variations of the Y/C card. The older ones tend to strip easier, though still very good. They say the newer one is improved. I did not notice any difference in the picture nor in the caps quality.
I am pretty sure that those repairs offered by some people on some sites consist of changing few caps in the power module and a couple caps in the board next to the display. By changing those will help a lot, but I would at least check other caps and you will be amazed how many are out of range or dead and the unit is still working. A lot has to go bad in order to notice major changes in the picture. I would also check the audio modules because I noticed a big difference in the sound once they are rebuilt.
After all is done and over you would not want to sell it.
Good luck.