amp repair help

kerwen · 25th July 2006, 01:13 PM

Hi all,

This is my first post. My humble amp is from videologic, model sirocco 2.1. Though it's just a budget monitor for PC, it's has served me well over the years and i hope to repair it.

Recently, the right channel volume is getting softer & softer until there's no more sound. Initially, after power-cycle the amp, the sound will be back and slowly fade till no sound. I swapped to left channel and the problem follows, so it's confirmed the amp right channel giving problem. I tried opening up the amp and look for any capacitor leakage but to no avail. I tried to moved slightly some of the inductors & capacitors and suddenly there's sound from both channels. However, the problem comes back after about 5 hrs of usage.

Now, the only working channel is beginning to show some signs, e.g sound will start to sound harsh on & off. I tried to email videologic for the amp circuit diagram since its been eol but they rejected the request. So now, i need some experienced gurus here to give me any advice.

link

richie00boy · 25th July 2006, 01:36 PM

Dry joint or failed component.

I would just move one component at time and see which one makes the sound come back.

Netlist · 25th July 2006, 01:36 PM

Quote:

Originally posted by kerwen
I tried to moved slightly some of the inductors & capacitors and suddenly there's sound from both channels.

Welcome kerwen,
Get your soldering iron and rework the board(s).
Keep us posted.

/Hugo

kerwen · 25th July 2006, 02:55 PM

there is about 6 inductors just before the 2 speaker o/ps &
6 electrolyte big cap after the torrodoil transformer. Any idea what these component purposes are?

I may take some time to find the root cause, busy with work. I will update whenever i can. Thanks.

classd4sure · 25th July 2006, 03:28 PM

Usually the solder joints are bad to start with, over time they get even worse. So like they recommended already, grab your iron and rework them. Doesn't take much at all. Do all the joints with external connections/jacks etc, do all the ones for bigger components, like the power supply caps you mentioned after the transformer, do all the ones that seem to have a hairline crack upon close inspection (magnification and a good light help). Even if it works again for the time being it's not a good idea to leave it like that. The output inductors just add a bit of HF filtering, six seems like alot though, would be interesting to know their configuration.

kerwen · 26th July 2006, 01:32 PM

here's some pic of the amp cct
the 6 caps are 25V 4700uF

anatech · 26th July 2006, 01:37 PM

Hi kerwen,
It looks like a standard chip type amp. Those output inductors are for each channel (one per). Very standard.

As Hugo correctly suggested, go over the solder joints. Use a little solder flux and apply any extra solder spareingly. Do not create solder bridges. The parts mounted to the heatsink are most prone to have cracked connections. You may not even be able to see them.

-Chris

kerwen · 26th July 2006, 02:01 PM

hi Chris,

Thanks for the advice, i will resolder those joints and see if that solve the problem. For this amp, they design each channel there's 4 sets of wire, 2 goes to the tweeter & 2 goes to the midrange. Lets say if i want to connect to some other bookshelves, can i connect the 2 high together & vice versa for the 2 low? Will it improve the sonic characteristics if i change the 6 caps to those audio grade caps? Thanks for attending to my questions.

Cheers
Kevin

anatech · 26th July 2006, 02:08 PM

Hi Kevin,
This is a budget amplifier in a closed system. Don't run any speakers in parallel. You can try running completely different speakers, but with the same resistance or higher as the originals.

You may be able to improve the sound by bypassing some caps with film types. Particular brands do not seem to offer huge differences as long as they are the same type of part. Don't go nuts. Depending on the op amp types, you may be able to make some improvement there. Maybe.

-Chris

kerwen · 29th July 2006, 08:09 AM

updates:

I have resolder most of the joints especially those caps, inductors, parts under the heatsink, all the pots, inputs & outputs. Bad news is the problem on the right channel still remains, there was only sound for about 5 mins before disappearing again. Came back on intermittently but most of the time it's off. Any more ideas?

Thanks

25th July 2006, 01:13 PM	#1
kerwen diyAudio Member Join Date: Jul 2006	amp repair help Hi all, This is my first post. My humble amp is from videologic, model sirocco 2.1. Though it's just a budget monitor for PC, it's has served me well over the years and i hope to repair it. Recently, the right channel volume is getting softer & softer until there's no more sound. Initially, after power-cycle the amp, the sound will be back and slowly fade till no sound. I swapped to left channel and the problem follows, so it's confirmed the amp right channel giving problem. I tried opening up the amp and look for any capacitor leakage but to no avail. I tried to moved slightly some of the inductors & capacitors and suddenly there's sound from both channels. However, the problem comes back after about 5 hrs of usage. Now, the only working channel is beginning to show some signs, e.g sound will start to sound harsh on & off. I tried to email videologic for the amp circuit diagram since its been eol but they rejected the request. So now, i need some experienced gurus here to give me any advice. link

25th July 2006, 01:36 PM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Dry joint or failed component. I would just move one component at time and see which one makes the sound come back. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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25th July 2006, 02:55 PM	#4
kerwen diyAudio Member Join Date: Jul 2006	there is about 6 inductors just before the 2 speaker o/ps & 6 electrolyte big cap after the torrodoil transformer. Any idea what these component purposes are? I may take some time to find the root cause, busy with work. I will update whenever i can. Thanks.

25th July 2006, 03:28 PM	#5
classd4sure Account Disabled Join Date: Feb 2004	Usually the solder joints are bad to start with, over time they get even worse. So like they recommended already, grab your iron and rework them. Doesn't take much at all. Do all the joints with external connections/jacks etc, do all the ones for bigger components, like the power supply caps you mentioned after the transformer, do all the ones that seem to have a hairline crack upon close inspection (magnification and a good light help). Even if it works again for the time being it's not a good idea to leave it like that. The output inductors just add a bit of HF filtering, six seems like alot though, would be interesting to know their configuration.

26th July 2006, 01:32 PM	#6
kerwen diyAudio Member Join Date: Jul 2006	here's some pic of the amp cct the 6 caps are 25V 4700uF

26th July 2006, 01:37 PM	#7
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi kerwen, It looks like a standard chip type amp. Those output inductors are for each channel (one per). Very standard. As Hugo correctly suggested, go over the solder joints. Use a little solder flux and apply any extra solder spareingly. Do not create solder bridges. The parts mounted to the heatsink are most prone to have cracked connections. You may not even be able to see them. -Chris

26th July 2006, 02:01 PM	#8
kerwen diyAudio Member Join Date: Jul 2006	hi Chris, Thanks for the advice, i will resolder those joints and see if that solve the problem. For this amp, they design each channel there's 4 sets of wire, 2 goes to the tweeter & 2 goes to the midrange. Lets say if i want to connect to some other bookshelves, can i connect the 2 high together & vice versa for the 2 low? Will it improve the sonic characteristics if i change the 6 caps to those audio grade caps? Thanks for attending to my questions. Cheers Kevin

26th July 2006, 02:08 PM	#9
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	Hi Kevin, This is a budget amplifier in a closed system. Don't run any speakers in parallel. You can try running completely different speakers, but with the same resistance or higher as the originals. You may be able to improve the sound by bypassing some caps with film types. Particular brands do not seem to offer huge differences as long as they are the same type of part. Don't go nuts. Depending on the op amp types, you may be able to make some improvement there. Maybe. -Chris

29th July 2006, 08:09 AM	#10
kerwen diyAudio Member Join Date: Jul 2006	updates: I have resolder most of the joints especially those caps, inductors, parts under the heatsink, all the pots, inputs & outputs. Bad news is the problem on the right channel still remains, there was only sound for about 5 mins before disappearing again. Came back on intermittently but most of the time it's off. Any more ideas? Thanks

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