Cap killer JVC (AV-xx890/xx895 series)

[Wizard]

This that utilizes the STR-F6266 main switching regulator with most complicated circuits added. What set this apart is that is more common issue especially with guide plus module installed. The ones based on same chassis without this (just row of holes where socket is for guide plus module have much LESS problems.

Either in standby or run uses 2 feedbacks for regulation, one for 13V standby feedback or 135V run mode (using a SE135 IC). Well, Here the problem that is vexing me for years:

The 13V output 1,000uF 25V or 35V capacitor kept dying, average time is about 1-3 years between cap replacements) always swells it's top or sometimes blew it's top. The diode runs hot and that aftermentioned cap runs rather warm, in fact much worse when in standby. Other 3 outputs are cool as they should be, 135V for B+, 62V for tuner, and isolated audio supply.

WHY?

There are another chassis that uses same design except power supply uses different STR IC (fat retangular with off center mounting hole with more pins) for power supply did NOT have this cap busting issues.

Cheers, Wizard

[starfury1]

Re: Cap killer JVC (AV-xx890/xx895 series)

well no idea on what your talking about (thats me.... not you)

You seem to have a fair knowledge of these units and I suspect Electronics too

So guess you know what I have posted below and are looking for some other explanation. but I'll post it anyway

What caps are used Brand series? and what sort of load is being draw.

The "cap running rather warm" is why it dies I would imagine (heat, drying it out)

This could be due to excessive heat around it but by the sounds of it the caps heating up more then it should.
Which is probably either down to bad cap selection for the circuit or the circuit its self may have some aspect to it that causing this...I don't know

I have no idea on the circuit but being a switcher
good quality Low ESR caps are usually the requirement for reliable operation
(there can be some exceptions to the rule here)

ESR is basically representative of what a cap would be if it was a resistor in the circuit.

There is another important factor that must be considered too and that the ripple rating of the Cap.


but thats about all I could guess at

Others may know these units and have a correct or more accurate answer as to why,
but thats my guess based on what you say ...caps are just not up to the job with the extras there...
(or possibly something to do with circuit design)


HTH

Cheers

[starfury1]

Re: Cap killer JVC (AV-xx890/xx895 series)

oh and what is the brand series of caps that don't pop in the other unit?
Do the units draw around the same load current?

since you mention 2 different IC's this could be really a design thing

[Wizard]

Re: Cap killer JVC (AV-xx890/xx895 series)

I agree on the design thing. I did try all kinds of capacitors even switcher output cap, still pop them. Even spent lot of time looking for the cause. I think the STRF-6626 or the transformer too massive that it is switching too low frequency for high current draw outputs (13V is what supplies lot of items and for two standby power mode (normal mode for keeping guide plus module alive or deep standby hence the complicated circuits.)

I remind you that chassis is reused 3 times with different SMPS ICs and slight different chassis configurations. The STRF-6626 was the worst.

Cheers. Wizard

[willawake]

Re: Cap killer JVC (AV-xx890/xx895 series)

excessive ripple
excessive voltage transients
excessive heat

3 years though is a typical failure time for bad caps. did you use any jap caps there?

[starfury1]

Re: Cap killer JVC (AV-xx890/xx895 series)

"transits" yeah thanks Willa

Well there are better educated brains on this forum then me when it comes to this stuff

Here a pdf link on the STRF-6626

I am guessing maybe what they used is not optimal for circuit
and yeah 2~3 year as willa said is what normally a crap cap will do

again what type of caps were originals and what types did you try?.

I dont know for sure and like I said No idea on circuit but you may need to increase a bit for that IC
This of course really depends on design and I am not an engineer with this stuff.

cheers

[Wizard]

Re: Cap killer JVC (AV-xx890/xx895 series)

All kinds of makes of capacitors even ultra low ESR even from a busted warranty parts (still smelling like new). Pffft in under 1 to 3 years. the 3 years is not right, those TVs with even crappiest SMPS and junk caps lasts longer than that BUT in JVC which is a nice brand of TV back then. 3 years. No Way. that's not normal.

Cheers, Wizard

[Wizard]

Re: Cap killer JVC (AV-xx890/xx895 series)

UGh, 10 minute edit limit.

Believe me, I know which is GOOD and correct caps to use, not general purpose in a switcher. Our supplier sends us CapXon. Ick. but it serves us ok for lot other uses that is not so stressed. I have seen lot of these survive long.

On another hand, it is TOUGH to source good stuff that why I asked Wolf for caps so I can fix my PSU and few boards for my uses which directed me here.
For our shop, we'd love to buy LOTS of good caps in qty of 100-200 for .20-.45 cents, global sells capXon around .35-45 cents ea. Often on backorder for months!

Ordering stuff is a headache for our shop with border stuff from USA so we didn't do anything much about that. (Our is in Canadian).

Cheers, Wizard

[Wizard]

Re: Cap killer JVC (AV-xx890/xx895 series)

Update, just in, a unresponsive AV-32980 woke up with 4 capacitors.

The main offenders are 470uF 35V on the low voltage for STRF-6266 and 1,000uF 35V (bulged). Replaced 100uF 35V in vertical IC just for safety since a high ESR cap will pop the vertical IC eventually. As a trial, replaced main filter cap 470uF 200V for 560uF one.

The 3 smaller caps are Rubycons YK series. Can anyone tell me what this YK is?

Cheers, Wizard

[japlytic]

Re: Cap killer JVC (AV-xx890/xx895 series)

YK Series:
These are general purpose units.

[Wizard]

Re: Cap killer JVC (AV-xx890/xx895 series)

Oh really? I'm been replacing these 1000uF with low ESR...could that be a problem?

Oh, cannot use capxon or it will come back in short time on that 1000uF spot even it is rated 105C. This is right on the SMPS output for 13V supply.

Cheers, Wizard

[gonzo0815]

Re: Cap killer JVC (AV-xx890/xx895 series)

Replacing GP capacitors with low esr is usually not a problem, it may even improve things.
If capacitors are dying that fast, there are a few common problems which can cause this:

rectifier diode to slow, to high leakage or simply defect. Replace by an better diode (faster, higher A rating, better heat transfer, lower leakage )

Voltage transients far higher then the capacitor ratings are not that uncommon. Usually an BZY06 or similar diode with the max capacitors voltage rating (or slightly above the working voltage) across the capacitor should take care of that.

Heat is an issue especially for higher wattage rails. The diode is getting very hot usually, the thick traces will conduct this easily to the capacitors.
I would try some Rubycon YXF if you can recover the higher price tag.
If they are dying too within a few years, i think there is one of the other problems in this set.

Ripple current is another issue, then i would try some Panasonic FC / FM if the YXF can`t bear it.

Most usual capacitors supplied by parts sellers have not much rated life @105°c. CapXon aren`t too bad, but most of their series is only rated at 1000h to 2000h at rated temperature. This would be conform to the survival time you stated.
An Rybycon YXF with case size 10mm or bigger does have an rated life between 6000h to 7000h. In case diameter >12,5mm even 10000h.