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Hi There.

I have a XTi4000 that will not switch on. I purchased it on 31/05/2010 from an Ebay company which has since ceased trading. Upon contacting Sound Tech (just within the warranty period) they told me they suspect it is a grey import and would not fix it for free. How can I tell if it is from the US or UK?

ser: 8500332406

part: NXTI4000

build: 11/29/2009

Can anyone help me here? I need to get it fixed (I'm in Somerset, UK)

The Amp doesn't respond to being switched on, no leds light, etc. The internal fuse is ok.

I tested the output of the rectifier that is putting out 300v DC... Is this normal?

Please help!

Thanks in advance.

Andrew

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joust    0

Yes! And there are two others hidden amidst the filter caps (total 8). Furthermore, locate two of the same type of resistors (37.5K) near the output coils: these two would also need to be replaced, if they're the bluish version!

A.

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Thank you so much for your advice.

Are these the resistors that were/are part of the recall? Do you think this will fix the issue or could it have wiped out something else on the board?

I will go ahead and replace these ten resistors. Thanks again, I will post the result of my progress!.

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So I've de-soldered all ten of the resistors and eight of them are testing incorrect values (by quite some way). I'm now finding it quite a challenge to find a source to buy the correct replacement resistors.

If anyone can help me, I need

8x 47.8KΩ, 1 Watt, 1% resistors

2x 35.7KΩ, 1 Watt, 1% resistors

Thanks in advance

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joust    0

There are a few reasons why an XTI will not power up nomally:

- Check 20A AC fuse; Make sure when cycled on, that 170V is available at the BULK voltage TP;

- If the SMPS has not fired, make sure that there is no shorted output or Tracker module devices; Verify that the chopper drivers are OK;

- Verify all the small SMT caps in the SMPS: I have found shorted C201, C186, for example.

- Verify the kickstart cap C196;

Alain

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joust    0

You're in Great Britain? Then it may be possible that the 335V is derived from the 220V operation. Here in North America, where 120V is accessible, the BULK voltage is half that, and once the SMPS is started, a doubler circuit brings it to normal (340V) operation.

Though, I am quite surprised that the resistor replacement has not worked out.

NOTE: Reference in the SMPS is not chassis GROUND! Locate and use TP21 as your 0V [V_BULKRTN] reference.

Are the eight resistors are properly located in the SMPS section and the two other resistors in the output coil section?

Can you verify the signal at R375 in the SMPS section? (Normally, a 16V DC signal should be present.)

At the zener and R375 junction describe the signal there: Is it steady (around 1.5V)? Does it flucuate like a cap charging and discharging?

Alain

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joust    0

In an earlier post in this thread, I mentionned to verify kickstart cap C196. It's the electrolytic near the six resistors in the SMPS circuit. I'm pretty sure that it may be defective.

Note: If the cap was good, you would see a low voltage (perhaps 4 to 8V) pulsing signal at the R375 junction. Replace the cap with a 100uF/25V; I would try a 35V if available and I recommend the 105°C version (because of the heat generated by the resistors, though less problematic than the eight resistors in line of a previous version of the XTI!).

Alain

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joust    0

Hello Andrew,

Are you connected to the correct V_BULKRTN? Make sure your 'ground' or reference is hooked and located at TP21. (I believe the correct measurement should be 16V because a 16V zener is located at this junction!) Also, can you tell me what is the voltage at the junction once R375 when it is reinstalled? (It should be the same voltage as the zener diode!) Perhaps this is your issue: the zener diode is open; As such, the voltage at the base of triple regulator circuit being higher than at the collector, may cause the regulator circuit to be at cut-off!

Can you confirm that you have the 30V control voltage (+30V_CTRL) at the triple regulator circuit?

Can anybody confirm that on a 220V XTI main board, the D31 zener diode is a 16V device?

Also, can anyone confirm that on a 220V XTI main board, the V_BULK voltage 'prior' to SMPS power up completion is 170V?

Andrew, do you have a variable transformer? If so, can you adjust for 220V operation? (Unit should operate within 240VAC; At 250VAC, it may have reached HIGH LINE activity and doesn't power up!)

Alain

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FAO Alain (and anyone elso who could help!)

Firstly thanks for all of your help so far..

A little time has passed since i last posted and I have since passed the Amplifier into the hands of a professional! He is in the process of getting validated onto here but until then I will post his results and findings.

The unit was powered up. After which Q47, (IRF260N) popped. This was replaced along with it's companion diode D35, as were C196, C275 & C193.

C201, C186 & C188 all measure ok as do these resistors:

8x 47.8KΩ, 1 Watt, 1% resistors

2x 35.7KΩ, 1 Watt, 1% resistors

The 16V zener at the R375 junction is OK too.

All the IGBT devices are ok (not short)

all that happens now on power-up is the device

RT6X gets hot very quickly!

Thanks in advance for any replies.

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