Indeed G2 tweaks and bias adjustment

[Deleted]

May 12, 2010 20:59:02 GMT @clausdk said:

May 12, 2010 20:01:19 GMT @heliharris said:

Any ideas why my iPod has broken after connecting to the RCA on my G2, worked fine when connected to 3.5 socket on front of Amp.

Its making broken noises on both channels,( tried it on a couple of Amps) but the rest of iPod seems to function normally.

And yes i had switched over the input switch to RCA.

Any recommendations for a decent iPod repair service, would be appreciated.

Have you tried another cable ??

My best advice would be to enjoy your Cowon

I cant claus its just buggerd that up as well.

[Deleted]

Mick,

Are you saying the amp has done in both players?

Ian

[Deleted]

looks like it Ian.

[clausdk]

May 12, 2010 21:07:04 GMT @heliharris said:

May 12, 2010 20:59:02 GMT @clausdk said:

Have you tried another cable ??

My best advice would be to enjoy your Cowon

I cant claus its just buggerd that up as well.

One of the good days then. ;D

If the headphone out works, I hope it works in the dockend too..

On my G2 the 3,5 mm input makes strange noises, but it does not follow the Ipod to other amps.

But it sounds strange if a cable would break in both channels at once..

arghh I do not know anything

If only I had a spare Dock-->RCA it would be in the mail tomorrow, I do have a spare dock->3,5 mm if that could help ??

[Deleted]

Mick,

I hope it wasn't a 160 Gig Ipod.

If you would like one, I can send you a 4 Gig Nano. (G4 You can have it.

Ian

[Deleted]

The cable checks out fine on my meter Claus, its a good make a"Chord", and works fine with my other Amps, it has to be the G2, will send the Cowan back under guarantee, cant understand why it worked fine on 3.5 front socket but blown my mp3`s on RCA. HELP!!

[Deleted]

Oh dear, is it a bad thing if when you push the right channel (red) rca male socket on lead into the corresponding female one on the Amp the center pin touches the fin on the heat sink, doesn`t happen on left channel as there is clearance on the heatsink, would that have blown my mp3`s, help required please.

[Deleted]

Mick
Have the devices fitted to the heatsink been installed using insulating bushes and washers ? As an example, the metal tag on the LM317 is actually connected to V OUT.
Alex

[Deleted]

Hi Alex,

the heat sink is soldered directly to the pcb, no insulation.

Thanks.

Mick.

PS Alex, i get continuity on my meter when i touch on RCA center pin AND earth of the RCA casing with the soldered retaining pin on the heat sink, when pin is touching heat sink, only get continuity on the earth when i pull RCA plug out a bit so that its not touching heat sink.

[Deleted]

May 12, 2010 22:48:08 GMT @heliharris said:

Hi Alex,

the heat sink is soldered directly to the pcb, no insulation.

Thanks.

Mick.

Mick
Just double check that the LM317 etc. are mounted using either mica insulating washers, or perhaps the grey looking thermal rubber type bushes. (TO220 type)
If whichever device is mounted to the heatsink in question uses these insulating bushes, there should be no problem.
Alex

[Deleted]

Alex,

Its the 510 mosfets that are using these heatsinks, this is the right hand bank, the set up is duplicated on the left side of amp, where the RCA OUT connections are for use as a pre-amp.

Mick.

[Deleted]

May 12, 2010 23:09:18 GMT @heliharris said:

Alex,

Its the 510 mosfets that are using these heatsinks, this is the right hand bank, the set up is duplicated on the left side of amp, where the RCA OUT connections are for use as a pre-amp.

Mick.

Mick
The IRF510A data sheet does not show the mounting tab as having an electrical connection. Is the heatsink connected to earth ?
The iPod may not have liked a short circuit on it's output. Only guessing !
Alex

P.S. Try checking with your DMM for any voltage or connection to earth at the mounting screw of the IRF510.

[Deleted]

Yes Alex, it must be as i get continuity on my meter between earth on RCA connector and the soldered heat sink retaining point on pcb, there for a short would occur with the RCA plug centre pin touching the heat sink. That`s a bad design and looks like my £80 G2 is now going to cost me £200-300 for replacement of my ipod and Cowan mp3 players. Members BEWARE.

Mick.

[Deleted]

Hi Mick,

Sorry to read this only now.
The heatsinks carry about 10 V DC to ground when on.
The Source of the FET is connected to the casing and thus the heatsinks as NO insulation is used (nor needed in theory as the fins normally won't touch other parts.
IF the centre pin of the audio plug touches this fins it will SURELY destroy the output of a player that is connected to it.

I think you should file the fins down where it can touch.

Very bad design indeed !

[Deleted]

Hi Frans,

Thank you for your reply.

What was doing my head in, was that i just could not understand why the 3.5 socket connection was working fine, as it looked to me( even with my limited knowledge) that it is on the same circuit as the RCA connection, one worked fine the other blew my mp3`s up.

It was a shear fluke that i noticed that when RCA plug was fully "home", the centre pin was just touching the heat sink, i counld not have machined a more perfect coincidence on the plug.

99 times out of 100 i would not have pushed it in quite as far, so up till last night no problem.

The same problem is evident on the RCA OUT connections on the other side, but the problem would be on the white(left) RCA connector, as its a mirror image.

This has really pissed me off, and i will not be buying any more Chinese Amps, they sound nice but the build quality is rubbish. All 3 Amps that i have purchased have required new on-off switches as the originals, lasted only a couple of weeks(and i am not heavy handed with my equipment). Surely a decent on-off switch is a basic requirement,s it not on any Amp, as its the most used item.

Oh well, lick my wounds, and sort out a new iPod not spending probably near a £100 for repair on a 3yr old one, even though it was in perfect unmarked condition. The COWAN, dont know which direction to go on that, probably be honest and tell them what`s happened as its only 3 weeks old.

Thanks Mick.

[Deleted]

The Source of the FET is connected to the casing and thus the heatsinks as NO insulation is used (nor needed in theory as the fins normally won't touch other parts.

Frans
Some makes show the case as connected to the drain.
A Fairchild data sheet that I downloaded earlier showed no connection
to the case. So much for compatibility between different manufacturers !
Alex

[Deleted]

It was a shear fluke that i noticed that when RCA plug was fully "home", the centre pin was just touching the heat sink

Owch, that's a nasty turn of events.
I wish I'd piped up earlier now, I didn't because I only have two makes of leads that are able to reach the fin through the socket and so thought it was more the lead plugs fault than the G2. I have been in the habit of "retreating" the offending plug a couple of mms before switch on.

Presumably you could call it a design fault, any guarantee cover from our 'freind' in China that used the forum to get sales

[Deleted]

Presumably you could call it a design fault, any guarantee cover from our 'freind' in China that used the forum to get sales

No i won`t be Chris, the ars"""ls, coudn`t be bothered to answer my emails concerning a replacement switch, even though i offered payment for a replacement. Live and learn, and i have learned a lot about our Chinese "friends", and the way they do business.

Mick.

[Deleted]

@ Alex,

You're right... it's the Drain that is connected to the casing.
This is even worse for the drain has 24Volts on it !!

The LM317's have around 8V on the heatsink.

@ Mick,

When your Miri arrives I will make a nice amp from it.

[Deleted]

Yeah, I did say that tongue-in-cheek, knowing it would be a lost cause.

I have said before that I would re-case mine, maybe I should get on with it before I forget to twiddle-the-middle.

[leo]

May 13, 2010 16:52:12 GMT @heliharris said:

Presumably you could call it a design fault, any guarantee cover from our 'freind' in China that used the forum to get sales

No i won`t be Chris, the ars"""ls, coudn`t be bothered to answer my emails concerning a replacement switch, even though i offered payment for a replacement. Live and learn, and i have learned a lot about our Chinese "friends", and the way they do business.

Mick.

Thats real bad luck Mick, what a PIA

I won't comment too much regarding stuff built in China, I can say I've had a lot of dealings with electrical stuff built over there from my last job.

Anyway, I don't know the I-pod innards , do you know if it uses coupling caps on the output or if it just uses one of those dac chips with integrated op-amp driver? I'm wondering if say things after the dac has blown, example if it uses very low voltage coupling caps or muting circuitry the high input voltage may have blown those rather than say the dac chip

[Deleted]

Hi Leo,

I am sorry to say my Electronic Knowledge is sadly lacking, apart from basic stuff, so i really don`t have a clue what the internals consist of.
I think because of the size of the components, complete board replacements are the only repairs most of the company`s that deal in repairs have to offer, the main board being around £80, i can get a new 160GB classic ipod for £157. Still awaiting a reply on my Cowen(3 weeks old) told the dealer what happened, may get a replacement as i know the guy, fingers crossed.

Mick.

[Deleted]

May 13, 2010 7:58:38 GMT @heliharris said:

Oh well, lick my wounds, and sort out a new iPod not spending probably near a £100 for repair on a 3yr old one, even though it was in perfect unmarked condition. T

Thanks Mick.

Mick, I have a 4G Nano if you want it.

[Deleted]

That`s VERY kind of you Rabbit features, bought a lump to my throat, but my lovely wife is going to buy me one next week, that really is a nice gesture which i DO APPRECIATE very much, lost for words really.

Thank you very much for the offer.

Regards Mick.

PS Didn`t know it was you Ian.
YOU ARE A TRUE GENT, but then i knew that anyway.

[MaN227]

man that REALLY sukx Heli , damn.

and I thought I was the only one getting yanked.

I sent my Miri back for refund and they claim its never made it mailed march 31 , unreal the shit luck I have had with the mail . so I'm out all my coin on that amp. as stupid me did not insure this one package. post office has NO clue where it is, claim its prob been received but they can't track outside usa lol. been here before lol . and get this the only record they can show me says it was RECEIVED at the same post office I mailed it from, unreal.... now the real kicker. the record shows it was received over 1 hour before it was even mailed out. GRRRRRRRRRRRRRRRRRRR

I will NEVER send anything of worth uninsured again.