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Where to buy good filtering caps


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Hi folks, been a while since I've posted here- too many other things going on!

My Redgum sonofagum has started cutting out on high volume or transients- a quick look under the hood makes me suspect at least 2 of the 4 power filtering caps have failed and started leaking.

I want to replace them- they're 10000uF 50V, 30mmx50mm.

Anyone out there have a good source for longlife caps with leadout wires that will suit? I can get Nichicons from RS-online, but the life is only 1000hrs, which is only 1 album a day for 3 years! I'd ideally like something reasonably priced- these are on my 2nd system, so not really worth spending big buck on.

Any help greatly appreciated!

Cheers,

Steve 🙂

PS is it worth replacing the other 2 smaller caps on the board at the same time? They seem to be fine, but....

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Personally I'd look at AN Standard Electrolyic's, 30mm x 46mm, they are a snap in type. Most caps of such value will be snap in lugs or terminal types.

https://www.hificollective.co.uk/catalog/10000uf-63v-audio-note-standard-electrolytic.html

Not indicated as long life per-say.

 

If some show signs of leakage I would guess you are replacing them all.

Edited by muon*
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These are 5000hrs 105c

https://au.mouser.com/ProductDetail/Nichicon/LGY1H103MELB50?qs=4lWw5qRttGL2LqOe1JrH%2Fw%3D%3D

 

Remembering the lower the temps then the stated temps, life time is much greater. The stated life is at max temp so unless It's a class A amp with poor ventilation it will not be as short as stated life, even then it will likely be much longer that stated life..

Edited by muon*
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Without know what you looked at,  you’ll find that 1000hrs are at max rated temperature.  Most are rated at 80-85C for 1000hrs.   So at 20-30C, it’s way longer than 1000hrs.   There are others that are rated at 105C bit but they’re not common.  
Stick to Nichicon, Panasonic etc,  order only through reputable suppliers like RS, E14 and DigiKey,   I wouldn’t bother with anything else.   Main goal here is size,  realestate is the bottle neck,  stick to the same capacity,  higher voltage the better and ensure it has low ESR ratings as this is what makes it work. 

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Thanks for all the feedback folks!

Ray, I did try to contact Redgum, but no reply as yet. They've been helpful in the past.

 

Ian, the Nichicons look like a steal, will just have to check lug compatibility before I order them. Mouser and E14 are definitely my first ports of call for parts like this. I might do the other caps (not power caps) on that board whilst I'm at it- can't hurt, and only a couple of dollars extra.

 

Cheers,

Steve 🙂

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I'd go for the snap in caps over the leaded type. Certainly the Nichicon LKG series is popular, the Type III being better but expensive. I use United Chemi-Con SMH or KMH series, these have slightly lower esr when compared to LKG Type 1&2.

 

As mentioned earlier, the rated lifetime (1000, 2000,,,hours) is at rated voltage, temp and ripple. As soon as you ease up on any of these then the lifetime extends ... A modern replacement will last at least as long as the original. No harm in increasing the voltage rating to 63V or 80V (if they fit), it's a rating for dielectric breakdown (with margin), they will be more expensive.

 

Certainly you should confirm main caps need replacement. Play something that draws a lot of "speaker" current, eg, heavy in bass. I like Zoe Keating, Into The trees, Track 6, Hello Night(?) ok, the intro whistling is tedious but the sustain cello draw is a nice test. If your base is flabby then yeah, replace the mains.

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Thanks for all the feedback once again.

The only reason why I suggested leaded caps was uncertainty regarding whther other types would be readily compatible with the board. Guess I'll have to pull it out and do some further investigation before purchase anything. Being able to use snap-in and/or solder lug types would certainly open up my options a lot!

 

Cheers,

Steve 🙂

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So I've ordered 63v 3000hr Rubycon's for the 4 power filtering caps, and a couple of Nichicon "audio grade" caps for the other 2 on the board. Hopefully they'll arrive soon, and a) get the amp working again, and b) sound better! Can't be worse, in any case!

The original TopCon caps won't be missed, I'm sure...

Thanks again,

Steve

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  • 3 weeks later...

HI All,

I hope things are well in your world.

I've recapped my amp; sadly the problem persists, I'm not worried that I've replaced the caps, I figure it's an upgrade anyway. 😉

When it cuts out I can hear the relay cutting in/out, which makes me things the amp is going into protection mode- does this sound right?

Can any one offer any thoughts on what might be the cause? I simply can't afford to send it back to Redgum to have them look at it, but would love to be able to get the amp working properly again, and I'm happy to do the work myself.

Cheer and thanks in advance,

Steve 🙂

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Hi, well done on the cap replacement.

If a relay is intermittently operating, it might be worth going over the relay control part of the amp. Do you have a photo of the main board, lid off, again 🙂   If the problem is the same and the amp sounds well after your work (other than dropping the power), you are half way there to fixing it 🙂 .  

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24 minutes ago, playdough said:

Hi, well done on the cap replacement.

If a relay is intermittently operating, it might be worth going over the relay control part of the amp. Do you have a photo of the main board, lid off, again 🙂   If the problem is the same and the amp sounds well after your work (other than dropping the power), you are half way there to fixing it 🙂 .  

Thanks for the quick reply and for the kind words.

Here's 2 photos (taken from opposite angles) with the lid off- hopefully they give some insight...

🙂

IMG20231115133837.jpg

IMG20231115133901.jpg

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The speaker relay appears to be of the delay turn on (mute) variety only, as there does not appear to be any connection from the main amplifier to suggest that there is a protection circuit involved for DC, overload or thermal faults.  If the amplifier is not running excessively hot at normal listening levels or even idling without any input signal, then since as Steven has indicted that the fault only occurs when playing at loud levels, the fault could be caused by using a low wattage power transformer.  The scenario is that the voltages from the secondaries of the power transformer drop when there is a high current demand from the power amplifier and this can cause the speaker relay to turn off. This fault would correct itself when the transient signal passes. If this is indeed the case then modifications are needed to overcome this fault.

Edited by VanArn
typo
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Do you have a multimeter?

Are you comfortable taking meter readings on a live unit? Warning, lethal voltages inside.

 

Hard to say what's going on, maybe,

- excessive Vdc at speaker outs due to component breakdown under high load

- voltage at relay coil sags causing the relay to release

 

A few things to try,

- Measure dc offset for both L&R channel.

- Measure dc voltage at the relay flyback diode.

 

The steps required are,

(Warning, take extreme care with connection of probes so as not to sort anything out otherwise you can toss the amp)

- power off, unplug the unit.

- using minnigrabbers or similiar, connect the red meter probe to the leads of either left channel emitter resistor, marked in blue. These are the large white rectangular resistors in front of the power transistors. Connect black meter probe via minnigrabber to black wire from RCA board(GND), marked in white, ensure contact with solder blob.

- Set meter to 200mV scale

- power up the amp allow 1-2minutes then read the dc voltage, ideally 0mV. Less than 10mV is great, 10-20mV is ok, less than 70mV is tolerable. Also note if voltage is reasonably stable, eg, it may ramp from -10mV to +10mV.

- set meter scale to 20Vdc

- play audio, reproduce the fault while keeping an eye on the meter, take notes what happens, eg, what is the voltage immediately before the relay clicks out.

 

Power off/unplug the unit.

 

Repeat the above for the right channel, ie, connect red minnigraber to either right channel emitter resistor, marked with red cross. Repeat measurements as above.

 

Power off/unplug the unit

 

Connect red meter probe/minnigraber to banded end of relay diode, marked in yellow.

 

Set meter scale to 200Vdc

 

Power up the unit wait 1-2 minutes then read the voltage, typically about 12 or 24Vdc

Play audio/bring on the fault while monitoring the meter voltage. Wanting to see the voltage sag as the volume is would up.

 

The above steps are simple however if you are not confident then best to pay a tech to do this.

 

 

 

 

 

 

Redgum.jpg

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There are some brown looking parts/board at both the, blue and clear cover relays, one does input/output switching the other on the power board. 

Would be worth checking both  the relay control voltages.

@mbz

Yes the DC offset., it's a nice looking amp. Wonder what relay is intermittent ? 

 

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8 hours ago, playdough said:

 

Thanks for the quick replies again, and especially Mike for your very detailed description of next steps. VanArn, this amp has worked well for many years, and I definitely don't think the power supply is too small. I shoul dpoint out it's not cutting out at high SPL- anything above talking volume will trigger it to cut in/out. It is definitely happening on high transient peaks.

Mike, I've got a DMM, and am confident enough to take readings from the amp whilst live- my question is, do I need to have speakers connected to it whilst running the in-use test you suggest? Or is it enough to have the amp on it's own and just listen for the relay to cut in/out? I will have to get some mini grabbers however, as I only have probes for my DMM ATM.

 

 

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10 minutes ago, playdough said:

There are some brown looking parts/board at both the, blue and clear cover relays, one does input/output switching the other on the power board. 

Would be worth checking both  the relay control voltages.

@mbz

Yes the DC offset., it's a nice looking amp. Wonder what relay is intermittent ? 

 

Thanks for that Glen, they always were regarded as a pretty decent amp, especially given the relatively modest price. As to why it started misbehaving, I've got no idea! Nothing in it's physical surroundings/connections changed, but it just started out of the blue...

I knoew the clear "box" at the rear was a relay, didn't realise the blue one on the power board was as well. I don't know if the board is brown, or if it's just the angled shadows from being near a window. Is it worth reflowing the connections on the power relay to see if they've gone dry?

Cheers,

Steve 🙂

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There is a toasty looking resistors and zenre diode, close to small heat sinked regulator transistors., the photo shows enough detail to follow the brown looking. hot rail around the relay power circuits.

If the amplifier circuit plays ok, probs ok,,, just a hunch.  Nothing on the amp board looks cooked, fresh. 

Relay intermittent when pushed ? Vdrop across the relay power rail. 

 

EDIT, yea, its a nice amp, serviceable, the amp module looks sound..  Always been a fan of Redgum Power Amps.  Check the relay power supply voltages, looks like 12v.

Edited by playdough
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1 hour ago, playdough said:

If the amp has has a lot of on time 🙂 over the decades. There are some hot looking parts there, Controlpower12v.jpg.f3ed6ab98c939010d10010129012d44e.jpg

Just a hunch by looking at the boards.  

Cheers. 

Thanks Glen, I must admit I was a little suss on the resistor closest to the cap, although it kinda looked ok when I had a quick look at it this afternoon. Will test them all tomorrow and see what I come up with. Resistors are cheap and easy to replace, right? 🙂

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8 hours ago, Steven Hinchliffe said:

do I need to have speakers connected to it whilst running the in-use test

I expect so. First try without speakers connected.

Preferred method is to use a dummy load (6-16ohm 10/20W+++ resistor).

Use your B-grade speakers.

 

Since the amp is shutting down at modest sound levels then suspect the blue psu relay/control so those stressed resistors in the area are in play as is the 3 transistors.

 

Assume you don't have a schematic.

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8 hours ago, Steven Hinchliffe said:

Resistors are cheap and easy to replace, right?

Yes, if it was me, I would start with identifying those resistors and put some new ones on. Same with the tiny caps.

 

Luckily the boards look to be unpluggable for the most part, far enough to swing out of the box for some service work. 

The amp isn't broken, it's an intermittent relay operation, under stress. Those parts would likely get hot and go out  of spec.  I'll wager it's a normal occurrence. 

Schematic would be nice, shopping list.

 

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