Pass F5 Help Needed

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vdi_nenna

vdi_nenna

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You may have to undo the speaker post to see if its touching the chassis.
Click to expand...

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...
 
cviller

cviller

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Joined 2005
vdi_nenna said:


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...
Click to expand...

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....
 
vdi_nenna

vdi_nenna

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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~
 
Tea-Bag

Tea-Bag

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vdi_nenna said:


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...
Click to expand...


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.
 
vdi_nenna

vdi_nenna

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You will need braided desolder wire to clean the board
Click to expand...
Got it! Also have a desoldering sucker. Depress the plunger, heat up the joint and hit the release button. Bye-bye solder.

OUT to ground will normally give you continuity that is a good thing.
Click to expand...
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.

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
Click to expand...

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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