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Old 18th August 2009, 12:14 AM   #21
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I took the left channel board out, connected the test lead to ground and to the metal tab on the FET and I still get continuity.

Doesn't happen on right channel board.
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Old 18th August 2009, 12:21 AM   #22
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Quote:
Originally posted by vdi_nenna
I took the left channel board out, connected the test lead to ground and to the metal tab on the FET and I still get continuity.

Doesn't happen on right channel board.

This doesn't sound good if the ground(s) is lifted.
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Old 18th August 2009, 12:26 AM   #23
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I think you should get continuity when running between speaker terminals. Ohm setting mine sits around 30 ohms, at least when powered off.

You may have to undo the speaker post to see if its touching the chassis.
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Old 18th August 2009, 01:08 AM   #24
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Quote:
You may have to undo the speaker post to see if its touching the chassis.
I did test with the speaker terminal off the chassis.
There was still continuity.

I took the circuit completely out of the case.
Between the ground trace and metal tab on the FETs, I get continuity. That doesn't sound right either.

I can't see any shorts on the board at all. Everything looks good.

I thinking about a board rebuild...
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Old 18th August 2009, 03:04 AM   #25
cviller is offline cviller  Denmark
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Quote:
Originally posted by vdi_nenna


I did test with the speaker terminal off the chassis.
There was still continuity.

I took the circuit completely out of the case.
Between the ground trace and metal tab on the FETs, I get continuity. That doesn't sound right either.

I can't see any shorts on the board at all. Everything looks good.

I thinking about a board rebuild...
If you're able to take some well exposed hires photos of the stuffed boards, backside and connections, we might be able to spot something you have overlooked....
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Old 18th August 2009, 06:49 AM   #26
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I'll try to take some hi rez photos of the board.

I ordered parts this morning (1:30am). Can't sleep, keep running this over and over in my head.

Ordered more ZTX, Pots and FETs. I have a bunch of 2sk and 2sj JFets left. Ordered some 14 AWG wire too. Stuff I had from DH Labs was nice but too stiff and it was 12 gauge.

thx,

V~
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Old 18th August 2009, 08:36 AM   #27
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I know your pain

You will need braided desolder wire to clean the board
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Old 18th August 2009, 10:29 AM   #28
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Quote:
Originally posted by vdi_nenna


I did test with the speaker terminal off the chassis.
There was still continuity.

I took the circuit completely out of the case.
Between the ground trace and metal tab on the FETs, I get continuity. That doesn't sound right either.

I can't see any shorts on the board at all. Everything looks good.

I thinking about a board rebuild...

Okay, I did some test this AM on mine. I have one of my F5's all connected with euro-blocks, so pulling things in and out is a sinch.

OUT to ground will normally give you continuity that is a good thing. Maybe not so for the other channel.

The Metal on FET is connected or part of drain, which is normally OUT, so hitting continuity on GND plane beeps as it forms a circuit and this is normal. Same as the situation above.
The N and P drains form Out+

I dont think the Jfets being hot is a good thing. I know if you blow on them, the DC offset will jump around a bit, but not to the extent your seeing.

Wish ya the best of luck.
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Old 18th August 2009, 01:06 PM   #29
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Quote:
You will need braided desolder wire to clean the board
Got it! Also have a desoldering sucker. Depress the plunger, heat up the joint and hit the release button. Bye-bye solder.

Quote:
OUT to ground will normally give you continuity that is a good thing.
Having trouble picturing "OUT to ground".
You mean if I put a Ohm meter on - and + speaker terminals, I'll get continuity?

So it was the right channel that might have bad FETs. There was no continuity to GND.

Quote:
don't think Jfets being hot is a good thing. I know if you blow on them, the DC offset will jump around a bit
I noticed it was bouncing up and down alot. I thought after an hour it would settle, but never did. It would vary about a few tenths of a volt across R11 and 12.
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