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Help! I can't find low leakage caps for tone board - Nichicon UKL equivalent

smead

smead

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Hi all - I'm in a bind here with my Marantz 2265B. It has a bad short / pop when the tone circuit is engaged via the tone mode switch. I learned that the most likely cause is bad/leaky caps in the tone circuit. So I planned to replace the 16 low leakage caps on the tone board, and while in there replace the 2SC1345 transistors.

But after hours spent on digikey and mouser, I just cannot find the low leakage electrolytics in stock. I can use films for the 1uf caps in the signal path, but there are a dozen or so 3.3-100 uf low leakage caps that would in the past have been replaced with Nichicon UKL. But I cannot find them in the sizes I need.

I read Rubycon TWL can also be used but no luck finding those either. I also read some are using bipolar Nichicon UES, but even those I'm not finding in all needed sizes, and am concerned about what others have said about replacing non polar with bi polar.

I have the tone board pulled and am ready to go, but cannot find suitable low leakage replacements!?

Can anyone point me to where I can find a good replacement for those caps, like Nichicon UKL equivalents?

Thank you
 
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dlucy

Thread 'Low leakage electrolytic capacitors'

Low leakage electrolytic capacitors are favored by many for use in the audio signal path since they have the least effect on the signal. The Nichicon KL or UKL series has been favored most as it has the lowest leakage stats (from their datasheet), but these have been discontinued and are now hard to source.

A list I compiled years ago from the Nichicon electrolytic capacitor data sheets may help you as you look for the next-best electrolytic cap in terms of leakage:

Comparing Nichicon 200 uF caps:

SeriesPackagePNuFVHoursSeries...
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Thanks for the suggestions for Rubycon TWL, but as I said I'm not finding them in the capacitance and voltage needed for the 2265 tone board. They are not in stock at either mouser or digikey .

I read through the next best replacement thread in terms of leakage , but the concern there is replacing an original low leakage cap that may still be good with an inferior replacement, and degrading the sound.

That's my dilemma..
 
Do you have a power supply and DVM? Leakage is easy to measure, and my guess is any quality cap today will have plenty low leakage. This isn't some mysterious and magic thing. Many common commercial grade caps have extremely low leakage even though not sold as low leakage caps. I don't know if low ESR caps tend to be high or low leakage, but it wouldn't be surprising if there's a trade-off there. Small caps are so cheap you can certainly buy several types and compare measurements. As soon as you get into "inferior" and "degrading the sound" things go off into the weeds and nothing can really be proven. I will say that film replacements are technically better, but you might not like the sound and certainly don't use polyester (Mylar).
 
ConradH said:
Do you have a power supply and DVM? Leakage is easy to measure, and my guess is any quality cap today will have plenty low leakage. This isn't some mysterious and magic thing. Many common commercial grade caps have extremely low leakage even though not sold as low leakage caps. I don't know if low ESR caps tend to be high or low leakage, but it wouldn't be surprising if there's a trade-off there. Small caps are so cheap you can certainly buy several types and compare measurements. As soon as you get into "inferior" and "degrading the sound" things go off into the weeds and nothing can really be proven. I will say that film replacements are technically better, but you might not like the sound and certainly don't use polyester (Mylar).
Click to expand...
Yes I do, it only measures capacitance, but yes I can do leakage tests looking for increased resistance as I pull them. And if a leaky cap is at fault, it's going to be major because when I engaged the tone circuit, I got a spike of DC through my test speakers that was high enough to blow them both.

I'll recheck for next best UKL replacements and see what I can find.

Thanks!
 
I strongly agree with every point in the post above by @ConradH.

Testing every cap you pull is very informative and something I do on every piece of equipment that I work on. Capacitance and DF readings are very informative even before you look for leakage. Having several very high-quality LCR meters as well as testers for other characteristics makes that easy, but even if you have less elaborate/costly test gear, you can get excellent comparative data and establish baselines.

What are the brands/types of caps you are replacing? If you can find the original datasheets, you may find that their specifications are pretty easily met with contemporary high-quality caps.

The big DC spike you observed is very unfortunate and could point to one or more bad/leaky transistors causing high DC offset. I'm not informed on this circuit, but I've had similar DC spikes caused by bad transistors in tone and line circuits before, when in fact none of the coupling caps were bad.
 
It does have 6 2SC1345s in there that I also planned to replace. I can test each as I pull them.

Not sure off hand of the cap brands, they are the orange ones found on these Marantz preamp circuits.
 
I've just downloaded the service manual and see that several matched diff pair packages are used in this part of the circuit. I would check those for proper DC voltages before pulling parts and replacing caps and the 1345s without zeroing in on the source of the DC.

Hopefully you get the point of my question regarding the original orange caps? I would be surprised if they originally outperformed high quality replacement caps. You should be able to use higher V rated caps in those positions, which will improve DF compared to the original 25V versions.

First - have you measured DC offset at the output jacks? What are those measurements at initial turn-on, and after stabilization? If you have a DMM that can store max readings, use that, or use a good analog meter and look at meter swing. Obviously, don't hook up the speakers, and in fact, don't connect any until you've repaired the unit. Short the inputs before switching on and measuring DC offset.
 
smead said:
Thanks for the suggestions for Rubycon TWL, but as I said I'm not finding them in the capacitance and voltage needed for the 2265 tone board. They are not in stock at either mouser or digikey .
Click to expand...

Oh. I thought you needed 3.3uF, that's why I sent you the Mouser part number 232-50TWL3R3MEFC5X11, which are in stock. I wouldn't be too worried about the 100V rating of the ones you mentioned in your original post. I doubt if you would be coming anywhere near that voltage in a preamp state. Even in preamps with high level outputs, the levels are more in the region of 20V, and even then that's only at full volume.
 
GKTAUDIO said:
I've just downloaded the service manual and see that several matched diff pair packages are used in this part of the circuit. I would check those for proper DC voltages before pulling parts and replacing caps and the 1345s without zeroing in on the source of the DC.

Hopefully you get the point of my question regarding the original orange caps? I would be surprised if they originally outperformed high quality replacement caps. You should be able to use higher V rated caps in those positions, which will improve DF compared to the original 25V versions.

First - have you measured DC offset at the output jacks? What are those measurements at initial turn-on, and after stabilization? If you have a DMM that can store max readings, use that, or use a good analog meter and look at meter swing. Obviously, don't hook up the speakers, and in fact, don't connect any until you've repaired the unit. Short the inputs before switching on and measuring DC offset.
Click to expand...
Yes when I serviced the receiver, I got the bias stable at 20mv each channel, DC equally stable at 0. I played it several hours, sounded great, amp nice and cool. Amp section seems good. All controls quiet, until...

I noticed the bass, mid and treble controls were not working, even with the tone mode switch in the tone in position. Upon closer inspection, I found the shaft missing on the back of the tone mode switch. Not pushed back, just gone. So it was stuck in the tone out position.

So I rigged up a temporary shaft to get the switch wafer to turn. Then upon switching to tone in, loud pop and both speakers blew.

Was advised over in the Marantz forum that someone likely removed that shaft, rather than finding the culprit in the tone circuit. Hack workaround.. So my plan was to replace the suspect transistors and recap.
 
Huh. That sounds likely - cheap fix that doesn't solve the problem.

You'll be busy. Lots of gubbins in there!
 
From my experience having done lots of recaps, most of the newer caps work pretty good in most circuit positions, or at least it can be said they will all "work" to a large extent or be relatively comparable to one another as it relates to their functionality and overall utility within a circuit. However, this doesn't mean they will sound the same, at all. I've found impedance, leakage or ESR aren't quite as important as people think when choosing one series of electrolytic capacitor over another for what should be the intended outcome of choosing a capacitor that will somehow sound "better" in a circuit compared to other available alternatives. I think other factors may be more relevant to how an 'lytic will actually sound would include distortion, tan delta/ dissipation factor, and ripple current at both LF and HF and whether the leads are copper clad (for instance) -but these aren't always disclosed in online search results and product comparisons while shopping. They are (somewhat) more hidden parameters that aren't usually acknowledged or considered quite as much. Everyone else's approach and experience will be somewhat different than mine (most likely). This is just my own take on things from what I've personally found to be relevant and matter in cap selection.
 
smead said:
Yes I do, it only measures capacitance, but yes I can do leakage tests looking for increased resistance as I pull them. And if a leaky cap is at fault, it's going to be major because when I engaged the tone circuit, I got a spike of DC through my test speakers that was high enough to blow them both.

I'll recheck for next best UKL replacements and see what I can find.

Thanks!
Click to expand...
I should probably describe how to measure leakage. With the cap out of circuit, put it in series with a 10 kohm resistor, any type, value not fussy so long as you know what it is. Apply the rated voltage of the cap across the pair, being careful to observe polarity. No power supply? No problem. Use 2 or 3 or whatever 9V batteries in series to get what you need. Don't test them with your tongue. Use your DVM to measure the voltage across the resistor. Leakage current equals voltage/resistance. Look at data sheets to get an idea of what it should be. Notice that it will go down with time. If the voltage is inconvenient for your DVM, change the value of the resistor.
 
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