Panasonic AG-1980 capacitor repair?

[drzapp]

Quote:

Originally Posted by dpalomaki

Not really. That would depend on which you caps intend to replace and may also depend on whether or not your model uses the exact same boards and components as others. We know there were variations in the Y/C board over time for example, and not all caps need to be replaced. Other posts in this thread provide more information in that regard.

However, attached to this post is a spreadsheet that was based on the parts list in the back of an AG-1980 service manual. It lists the board, value, and Panasonic part number (from the 1990s). WARNING: it could well contain some transcription errors and/or omissions. It can provide a starting point for your quest. Some parts numbers have changed since then, especially the problematic SMDs, so you will need to select a substitute part that will electrically and mechanically fit the board..

Can you re-upload that file? Excel says it's corrupt and won't open. Thanks

[lordsmurf]

It's not corrupt. Use OpenOffice or LibreOffice Calc to open it.
If you have an old Excel, then it may not understand the xlsx format.

Or maybe your download was just bad, get it again.

[digicube]

Anyone has a similar list of Panasonic DS-850? Is there a one-size fits all capacitors?

[dpalomaki]

Quote:

Is there a one-size fits all capacitors?

No such thing as a one size fits all capacitor. They are specified by type/technology of construction (electrolytic, oil, ceramic, tantalum, mica, etc.) physical form factor (radial, axial surface mount, disc, etc.), max and working voltage, capacitance, tolerance, temperature range, ESR, leakage, etc. And their type is matched to the application. You will need to start with the Panasonic part number and work it out from there. Depending on its use in the circuit the exact value may be important to the circuit functioning, in other cases close may be good enough. But in general the working voltage and temperature ratings of a replacement should NOT be lower than the original.

[drzapp]

Quote:

Originally Posted by lordsmurf

It's not corrupt. Use OpenOffice or LibreOffice Calc to open it.
If you have an old Excel, then it may not understand the xlsx format.

Or maybe your download was just bad, get it again.

It was Office 365 that choked on it- Excel 2010 opened it fine though. Thanks

[drzapp]

A question about the file listed above- There are about 32 part numbers that don't match anything on Mouser or Digi-key- I'm guessing they are obsolete. I'm also hoping that someone who has done the cap replacement for the 1980 has a list of replacements for these obsolete part numbers. Or direct me to where I can check them myself- I've looked all over and can't find a list of replacement panasonic capacitors.

[dpalomaki]

Did you check Panasonic for a cross reference?
https://industrial.panasonic.com/ww/products/capacitors

If that fails, go by the capacitor rating (and check the physical size on the board)

[drzapp]

Quote:

Originally Posted by dpalomaki

Did you check Panasonic for a cross reference?
https://industrial.panasonic.com/ww/products/capacitors

If that fails, go by the capacitor rating (and check the physical size on the board)

Yep, checked there- no cross reference I can find. Searches bring up related things, but not a replacement, or even the original specs.

What I am doing now is looking through the parts list in the manual to find out the volts and farads of the unknowns, so at least I can match that. I'll post the file once I'm done, for future reference.

[drzapp]

One thing I found that may be useful is that you can tell the voltage and uF from the part number. The voltage is determined by the first letter after the "A0" or "A1". A=10v, C=16v, E=25v, H=50v, J=6.3v. The uF are determined by the last 2-3 numbers. Decimals are designated with "R". A "0" on the end means the number is multipled by 1, a "1" on the end means the preceding number is multiplied by 10. So, 0.47uF="R47", 4.7uF= "4R7", 47uF="470", 470uF="471". So an example- "ECEA1CU471" is 16v 470uF.
I have no idea what all the other characters mean, but this helped me figure out the parts with no cross-reference to current ones.

[dpalomaki]

The other letters will refer to other parameters such as type (construction, chemistry, tolerance, temperature rating, etc.).

Many of the numbers you cannot match may correspond to the bad SMD devices (I don't recall, it was nearly 5 years ago when I went through the drill) and that have been discontinued.

[drzapp]

It appears the 4th letter is the one that denotes the package- all the through hole caps have an "A" in that position, all the SMDs have a "V". there are also "C", "1", "0", "U", "F", "X" but not sure what they mean yet.

Another addition is if the last number is "2" then it means multiply the preceding number by 100 for uF. So "ECEA0JU102" is 6.3v 1000uF

[waggs]

Quote:

Originally Posted by drzapp

One thing I found that may be useful is that you can tell the voltage and uF from the part number. The voltage is determined by the first letter after the "A0" or "A1". A=10v, C=16v, E=25v, H=50v, J=6.3v. The uF are determined by the last 2-3 numbers. Decimals are designated with "R". A "0" on the end means the number is multipled by 1, a "1" on the end means the preceding number is multiplied by 10. So, 0.47uF="R47", 4.7uF= "4R7", 47uF="470", 470uF="471". So an example- "ECEA1CU471" is 16v 470uF.
I have no idea what all the other characters mean, but this helped me figure out the parts with no cross-reference to current ones.

This post was REALLY helpful in getting me close to specs on discontinued caps. I also found this document from Panasonic that gives more details about part numbers and specifications for the capacitors.

[waggs]

...and this document that has replacement series for the discontinued capacitors in 2006

[jaffa225man]

Thanks to everyone here for giving me the particulars into which board I'd need to repair for my AG-1980 with deteriorating video! The Y/C PCB's video had deteriorated to the point where I needed the TBC on to even see output (and even then it was quite dark and supersaturated).

I am posting the corrected list for the parts I used to repair mine. It's corrected because the 6V 22UF cap has a smaller pad than the one I'd bought for it, which I decided to force onto the space anyway.

https://www.digikey.com/en/mylists/list/MS7TNYPHO4

Better longevity capacitors at higher temperatures are chosen as preferred, but for the shorter (for sandwiching) 47UF and 22UF capacitors they're still an upgrade than the originals at 1000 hours @ 105 degrees Celsius.

I wanted others to have a parts list, but of course as we've read here, the PCB revision may vary and you might have to modify to the list according to yours.

I hope everyone who still wants to attempt this repair has success like me!

[aramkolt]

Using 105c through hole caps on the YC board is probably overkill, but it probably doesn't hurt anything to do so as long as they fit. Seems the ones on the list above are up to 12.5mm in length seated whereas the original mini caps were more like 7-8 mm tall. I personally use new Panasonic versions of the originals (KA series) since the circuit may have been designed with the original capacitors' characteristics in mind, including the ESR and other properties. Physically larger caps usually have lower ESR, but again, it is hard to say if the circuit was specifically designed to factor in the original capacitors' characteristics or not.

I believe the original through-hole caps were mostly Panasonic KA series which are rated 1000 hours at 85c and at the max rated voltage.

The general rule is that for every 10 degrees celsius below the rated temp, the expected life of the capacitor doubles. If the ambient temperature around the capacitor is 35c, that is 5 doublings of the 1000 hour life, which is 32,000 hours at 35c, or 4 doublings to 16,000 hours if the ambient temperature is 45c. Odds are that the voltages running through these are also a fair bit lower than the rated max voltage. The formula estimate I've seen shows that capacitor life is multiplied by (Vrated/Vactual), meaning that if Vrated (rated voltage) is 6V, but the cap is only exposed to 3V on average (Vactual), you get an additional life multiplier of 2x just from the lower voltage exposure.

Based on this, I think it is fair to say that the average lifespan of new through-hole KA series Panasonic cap rated at 1000hours@85c will most likely last at least 20,000 hours in the sort of temperature and voltage environment that they'll be exposed to on the YC board. That sort of lifespan is likely to outlast the rest of the VCR by quite a bit.

Of note, Deter does not replace the original through hole caps on the YC/TBC board, or at least that was the case for the unit that I was able to inspect that he refurbished and sold. Same was true of the power supply caps on that unit (none were changed).

The surface mount caps originally used on these were known to fail prematurely and should always be replaced. I have no hesitation about using 105c caps for those since they are the same physical size and likely just use a more advanced/heat tolerant electrolyte. SMT caps need all the help they can get to not fail prematurely, so higher temp rating seems reasonable.

I personally change all power supply caps, all caps on the LCD and front control boards, all caps the pre-amp, and ALL caps on the TBC/YC card (both SMT and through hole). I'll also usually also change some of the caps on the main board that are located in higher heat areas as well as the three caps below the head drum. While a lot of those caps test fine, there's a lot you can't test for easily and it gives me more confidence in the reliability of the refurb to replace them all. Changing all of those gets rid of the sometimes VERY audible buzz from the power supply area which presumably can translate into some image noise depending on the severity.

There are a bunch of SMT caps that are hard to get to that are on the Audio II's daughter board (mounted upside down) that are almost always also bad, but I can't say that I've actually heard an improvement in sound playback after changing them and I wonder if those are used in mixing features controlled from the front panel? None of the "professional" refurbishers replace those to my knowledge.

[jaffa225man]

Thanks for listing other boards that I may need to improve in the future, although for now, it's working better than when I bought it used from a university sale so I'm ecstatic!

I forgot to say that with that exception of the choice of either of the 22UF caps (for size), most of the caps I picked are of higher voltage, but work fine to replace any of those with lower voltage requirements. And as you've said, the circuit likely requires less than the maximum voltages shown on the original caps.

While considering which caps would need replacement on mine, I tested the originals all in-circuit with my ESR meter. Its manual says, as a general rule, good capacitors with >= 1UF should have less than 1/2 an Ohm ESR. For me, that turned out to be none of them (with some having infinite, and only a couple as low as 1 Ohm ESR), so I replaced all the electrolytics (through hole and SMD), selecting capacitors with negligible ESR. Coming from badcaps.net, in the heyday of dead motherboards and PSUs, I hadn't considered nonzero ESR to be a conscious favorable PCB design choice. Anyway, if the originals were higher ESR on purpose, my chosen capacitors don't seem to have negatively affected my AG-1980 at least in this first day.

[jaffa225man]

While I doubt this applies to the Y/C PCB, my ESR meter manual goes on to say, that non-switching power supply and high power audio (> 63V or general purpose) electrolytic capacitors are generally good at < 3 Ohms, and that signal level audio, low frequency bypass and coupling "Low Quality" electrolytics vary from 1 to 10 Ohms ESR.

[aramkolt]

I don't anticipate any negative effects from using lower ESR caps, They are almost always preferred, all else being equal. Low ESR is more important in high ripple current applications such as switching power supplies as the internal resistance combined with rapidly fluctuating current will cause damaging internal heat buildup.

The sort of "magic" caps (if you want to go all out spec-wise) are organic polymer. They have extremely low ESR (usually 20-30x lower than regular "low ESR" caps) and they are rated to handle much more ripple current.

Here's an example of a Nichicon SMT cap from your list that could be upgraded with organic polymer:

https://www.mouser.com/ProductDetail...1ZaPyoEw%3D%3D

22uf Regular SMT 105C - 5mm diameter
Voltage Rating: 16V
Life: 2,000 Hour
Ripple Current: 30mA
ESR: not listed (but probably at least 1 ohm)
Price on Mouser: $0.56


....Versus a Panasonic SMT organic polymer of the same diameter:

https://www.mouser.com/ProductDetail...IDxxWENw%3D%3D

22uf Organic Polymer SMT 105C - 5mm diameter
Voltage Rating: 35V (2x advantage)
Life: 10,000 Hour (5x advantage)
Ripple Current: 900ma (30x advantage)
ESR: 0.1 ohm (10x advantage)
Price on Mouser: $0.56 (same price)


Organic polymer will beat out regular electrolytic in every possible category (aside from cost), but they are almost certainly overkill for something that originally needed to have the specs of the regular ones. Since they happen to be the exact same price in this instance, I'd pick the organic polymer, but often organic polymer will be 2-5x more expensive and may not be available in the form factor needed.

[jaffa225man]

I do consider polymer capacitors to be better for longevity, but was turned off by the ESR specs I saw when researching the ones at digikey. I suppose I wasn't used to seeing milliOhms and was interpreting mOhms as MegaOhms (MOhms). Although, I'm only guessing that now by my first reaction to the mouser page you linked.

Anyway, I'll have to measure the ESR of the Rubycon and Nichicon capacitors I bought that have the ESR listed as "-", which I thought meant near 0 Ohms. Maybe sometime in my life the Y/C board will be failing again, and I'll need that as a baseline, although by then my soldering skills may be nonexistent. Hopefully they're all below half an Ohm, since my ESR meter manual will most likely be my guide again.

[aramkolt]

It is often frustrating to look at stated ESR on places like digikey and mouser as they are often simply not listed with the "-" being there. You can also receive the capacitors and the measured ESR can be quite a bit different than what is stated. I am pretty sure that different manufacturers calculate/measure ESR differently, so even when they are listed, you can't really be sure.

At the end of the day, ESR is a good screening tool to find obviously bad capacitors, but if the capacitor isn't in a high ripple current or high heat environment such as a switching power supply, I suspect as long as you used Japanese name brand capacitors in your refurb (even if they are 85c rated in areas other than the power supply and front LCD board), the capacitors should last at least 20,000 hours of use, in which time it's probably more likely that other mechanical components like the video head drum will wear out first.