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-   -   Think I would need to recap this Sunfire bi-wired amp ? (https://www.badcaps.net/forum/showthread.php?t=99858)

Uranium-235 10-13-2021 06:53 PM

Think I would need to recap this Sunfire bi-wired amp ?
 
6 Attachment(s)
Sunfire bi-wired amp. Not sure if it's the 300w version or 600w version

stored in a cool place. Not turned on for like, 30 years

I'm worried about the big two after the rectifier. But if anything else catches your eye please speak up

dried out, obviously not bloated

stj 10-14-2021 02:11 AM

Re: Think I would need to recap this?
 
you could charge the caps with some AA batteries just to reduce the chances of them being de-polarised
or even better if you have a bench supply with a computer interface.

CapLeaker 10-14-2021 02:11 PM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
i'd reform these big caps with a bench power supply and put them back in service.

Uranium-235 10-14-2021 07:12 PM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
I have no bench PSU.

Are these just likely high ripple power caps?

CapLeaker 10-15-2021 07:31 AM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
Then just do what stj said with the battery trick. Better than nothing. Or using a variable transformer and bring the voltage up slowly.

kaboom 10-16-2021 12:03 PM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
Dim bulb it.

Make sure no the speaker outputs are unloaded, since some amps "slam" to one rail under extended/severe undervoltage, such as when dim-bulbing.

A Variac by itself doesn't current limit.

Oh, make sure it's an incandescent bulb, LED or CFL won't work!

momaka 10-16-2021 05:07 PM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
Quote:

Originally Posted by kaboom (Post 1077925)
Dim bulb it.

Concur x2.

A standard 40W incandescent bulb on 120V AC will present at about 360 Ohms impedance to the input caps (at full short-circuit)... which should work quite nicely to reform them without you having to take them out of the amp and doing so manually.

Dim bulb wiring (I'm sure mostly everyone here knows how... but just in case):
https://www.badcaps.net/forum/showpo...4&postcount=70

And yeah... no loading or testing the amp with speakers on the dim bulb. Just let it sit connected and powered up for 20-30 minutes. Maybe more, if you like (1 hour should be more than enough.) If all looks normal, you can power the amp after that directly from the wall... and if that goes OK, plug in speakers too. Or if you want to take it extra safe, just in case: use 100-300 Watt halogen (long bulb) or 100-500W heating element in place of the incandescent bulb. This will still limit power going to the amp, but should allow enough to test the amp with speakers at lower volume.

Quote:

Originally Posted by kaboom (Post 1077925)
Oh, make sure it's an incandescent bulb, LED or CFL won't work!

Well, LED *might* actually work, if it's of the dim-able type and you get like... 10 of them (?) wired in parallel to each other to get the equivalent power consumption of a 40W incandescent. :group:
Still I don't know if that's too bright of an idea, :thinking: if you know what I mean. ;) :jester:

redwire 10-16-2021 09:59 PM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
I blew up a Peavy power amp on a dim bulb tester, it was playing quietly and turning it up a little bit, the amp latched up bulb full lit and it killed some transistors. The power supply can collapse and do damage.
I find a dim bulb or light bulb tester is not great for reforming, you need reduced voltage and at light load the bulb goes out and voltage is high on the caps so what was the point.

This amp, looks like better quality parts. I would use a variac at 50-75% voltage.

Uranium-235 10-16-2021 11:43 PM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
Quote:

Originally Posted by redwire (Post 1078013)
I blew up a Peavy power amp on a dim bulb tester, it was playing quietly and turning it up a little bit, the amp latched up bulb full lit and it killed some transistors. The power supply can collapse and do damage.
I find a dim bulb or light bulb tester is not great for reforming, you need reduced voltage and at light load the bulb goes out and voltage is high on the caps so what was the point.

This amp, looks like better quality parts. I would use a variac at 50-75% voltage.

You sound like someone who knows a lot of the inside of these types of amps

if I wanted to replace those two main caps, where would I find them. I don't know the voltage or uf. I'm guessing the ripple is incredibly high, coming right off (or into?) those bridges.

I'm much more familiar with switching PSU's, i've seen others like these before. That bigass heavy (round) transformer. It's linear I bet. Never dealt with them.

momaka 10-17-2021 01:09 PM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
Quote:

Originally Posted by redwire (Post 1078013)
I blew up a Peavy power amp on a dim bulb tester, it was playing quietly and turning it up a little bit, the amp latched up bulb full lit and it killed some transistors. The power supply can collapse and do damage.

If your amp blew on the dim bulb, it might have already had issues to begin with.
Yes, transistors can still get killed even with the series incandescent bulb, particularly if the amp has large bulk caps that store a lot of energy. But this can also happen with a variac as well, so it's a moot point. The only difference is that a series bulb limits how much current can go in the amp, so at least you won't blow fuses or rectifiers in the process... so damage is generally limited to only the energy stored in the bulk caps.

That said, I've never had an amp with a linear (line transformer) misbehave on a series incandescent bulb. Cranked a few until the bulb was partly lit and no problems... though they had +/- rails derived from the main HV rail, so even with a low line input, the +/- rails for the pre-amp stage still had the correct voltages.

Only thing to watch out for is if the bulb is dropping too much voltage (too small a bulb usually - can happen on amps with really large transformers that generally eat 8-15 Watts by themselves) and possibly causing issues with the biasing on the output stage or offset/DC voltage in the pre-amp supplies. So for smaller amps, 40W bulb is usually OK. But for the bigger stuff, you might have to go to 60W or 100W.

Quote:

Originally Posted by redwire (Post 1078013)
I find a dim bulb or light bulb tester is not great for reforming, you need reduced voltage and at light load the bulb goes out and voltage is high on the caps so what was the point.

The point is current limiting. When caps reform, they can draw excess current as the oxide layer literally reforms... and this excess current draw by the caps can possibly damage other components in front of them in the circuit or the caps can damage themselves - especially large caps that have been sitting with the power off for a long time. A variac will not limit the current, and that's the main reason why it's not recommended for reforming caps. Sure, if the voltage is low enough from the variac, the current drawn by the caps could be small. But you may happen to hit a voltage point to where the caps haven't been reformed yet or they're just too old and just won't reform to that voltage. In such case, they can still draw excess current and damage something else.

That said, you could also run a combo of variac + series dim bulb. That would actually give the best of both worlds: controlled slow voltage rise and limited current. Of course, care still needs to be taken to make sure any secondary +/- voltage rails for the pre-amp stage aren't offset too much from each other, or that can cause an offset DC on the outputs as well. So that also really depends on the design of the amp.

Quote:

Originally Posted by Uranium-235 (Post 1078021)
if I wanted to replace those two main caps, where would I find them. I don't know the voltage or uf. I'm guessing the ripple is incredibly high, coming right off (or into?) those bridges.

Probably Digikey or other similar parts places. They're just going to be really expensive... but that should be expected given their size.

They're pretty standard caps, actually, since they are filtering 50/60 Hz line current (well, 100-120 Hz technically, since the rectifier doubles the frequency.) So no need for anything special here. They're just going to be very large... and with that, of course, also comes high ripple current handling. Typical cap values for an amp like that might be something like 80-100V for the voltage rating and 10000 uF (10 mF!) or higher capacitance.

Quote:

Originally Posted by Uranium-235 (Post 1078021)
I'm much more familiar with switching PSU's, i've seen others like these before. That bigass heavy (round) transformer. It's linear I bet. Never dealt with them.

:nod: Linear, it is... and toroidal type, given its circular shape. Good stuff.

CapLeaker 10-17-2021 04:53 PM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
the dim bulb tester has its place, but here in this case I wouldn't. That's only my opinion...

sam_sam_sam 10-17-2021 06:04 PM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
Quote:

Originally Posted by CapLeaker (Post 1078154)
the dim bulb tester has its place, but here in this case I wouldn't. That's only my opinion...

Do you have a better solution for something like this because I have ran into this before I guess I gotten lucky that nothing let out the factory smoke

I have a stereo system that had in storage at least 5 years I just plug it in the wall at very low volume and hoped for the best and everything went well for at least an hour then I turned up the volume and ran it for another hour and then used as normal

Uranium-235 10-17-2021 11:14 PM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
1 Attachment(s)
Quote:

Originally Posted by momaka (Post 1078133)
If your amp blew on the dim bulb, it might have already had issues to begin with.
Yes, transistors can still get killed even with the series incandescent bulb, particularly if the amp has large bulk caps that store a lot of energy. But this can also happen with a variac as well, so it's a moot point. The only difference is that a series bulb limits how much current can go in the amp, so at least you won't blow fuses or rectifiers in the process... so damage is generally limited to only the energy stored in the bulk caps.

That said, I've never had an amp with a linear (line transformer) misbehave on a series incandescent bulb. Cranked a few until the bulb was partly lit and no problems... though they had +/- rails derived from the main HV rail, so even with a low line input, the +/- rails for the pre-amp stage still had the correct voltages.

Only thing to watch out for is if the bulb is dropping too much voltage (too small a bulb usually - can happen on amps with really large transformers that generally eat 8-15 Watts by themselves) and possibly causing issues with the biasing on the output stage or offset/DC voltage in the pre-amp supplies. So for smaller amps, 40W bulb is usually OK. But for the bigger stuff, you might have to go to 60W or 100W.


The point is current limiting. When caps reform, they can draw excess current as the oxide layer literally reforms... and this excess current draw by the caps can possibly damage other components in front of them in the circuit or the caps can damage themselves - especially large caps that have been sitting with the power off for a long time. A variac will not limit the current, and that's the main reason why it's not recommended for reforming caps. Sure, if the voltage is low enough from the variac, the current drawn by the caps could be small. But you may happen to hit a voltage point to where the caps haven't been reformed yet or they're just too old and just won't reform to that voltage. In such case, they can still draw excess current and damage something else.

That said, you could also run a combo of variac + series dim bulb. That would actually give the best of both worlds: controlled slow voltage rise and limited current. Of course, care still needs to be taken to make sure any secondary +/- voltage rails for the pre-amp stage aren't offset too much from each other, or that can cause an offset DC on the outputs as well. So that also really depends on the design of the amp.


Probably Digikey or other similar parts places. They're just going to be really expensive... but that should be expected given their size.

They're pretty standard caps, actually, since they are filtering 50/60 Hz line current (well, 100-120 Hz technically, since the rectifier doubles the frequency.) So no need for anything special here. They're just going to be very large... and with that, of course, also comes high ripple current handling. Typical cap values for an amp like that might be something like 80-100V for the voltage rating and 10000 uF (10 mF!) or higher capacitance.


:nod: Linear, it is... and toroidal type, given its circular shape. Good stuff.

Thank you for the info (someone finally did) between BC and an audio board. This guy has money. He's been collecting audio stuff for years (he also has three carver amps-yes I know same company). 0.5t, 1.5t and this smaller one (TFM-6CB). He's planning on possibly getting two of these of the sunfire works

https://cerwinvega.com/xls-215.html

Cause well...he had "specifics"

https://www.badcaps.net/forum/attach...1&d=1634533697


The whole plan here is analog vinyl (Dual CS-1257...unused). To a good pre-amp to the sunfire bi-wired to the CW speakers

The only thing in question now is the pre-amp. He has an old rotel but it doesn't looks that great, and for the time, didn't get that good ratings

Anyone know of a good Pre-amp. Has to have phono connectors of course

CapLeaker 10-18-2021 05:07 AM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
we've got 4 of these xls 215 running on a NAD C375BEE. Needless to say, it's nad's!

CapLeaker 10-18-2021 05:16 AM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
Quote:

Originally Posted by sam_sam_sam (Post 1078160)
Do you have a better solution for something like this because I have ran into this before I guess I gotten lucky that nothing let out the factory smoke

I have a stereo system that had in storage at least 5 years I just plug it in the wall at very low volume and hoped for the best and everything went well for at least an hour then I turned up the volume and ran it for another hour and then used as normal

My plan would be to reform the big caps first. Then I'd put it back together plug it into my variac and bring the voltage up very slowly. Then check bias etc. Put some music in and watch the amplifier stages. Usually (pre) drivers go within the first minutes. You'd be rocking out, all of the sudden a puff of smoke and an old transistor is gone... so run it with the lid open and stare at it. Once it survived the first 10 minutes, she'll be fine...

stj 10-18-2021 06:21 AM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
how about you isolate the amp from the psu, and then put series resistors on the caps

Uranium-235 11-14-2021 04:22 AM

Re: Think I would need to recap this Sunfire bi-wired amp ?
 
Thiiiiis guy is a dick. I've known him for over 10 years and over that time I suspected he makes excuses for cancelling and they're lies. His recently divorced wife confirmed it.

I did something I've never done with him before, gave him an itemized invoice of the parts and labor. He owes me slightly over $1500 for the computer work. Giving him a chance to pay me $300/mo

haven't heard a peep. What he owes me is about $400+ in parts his down payment didn't cover


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