Rank: Member
Groups: Member
Joined: 6/4/2012(UTC)
Posts: 50
Thanks: 7 times
|
Hi Everyone So i building a new hd bp and the negative rail was giving wacky readings on the voltage out. Readings were in the low mv. So i went back to basics and reflowed everything on that rail. This all ended with the same result I checked the pots and they do change value. Next i printed out the bom and compared it to what i soldered. Most of it had the same value however r12 and r8 were way off. R12 for example was .99k and r9 was 220r. Curiously r12 had the same value as vr2. Turning VR2 again changed the value of r12. There was some value change in r8 i think but my main focus right now is r12 in relation to vr2. I do not know yet if the positive side is working properly but i compared my observation to positive side and it does not behave the same way. I am tempted to first replace vr2 but i would like to know if anyone has more info before i start desoldering. Edited by user Thursday, September 8, 2016 8:57:20 AM(UTC)
| Reason: Not specified
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/4/2012(UTC)
Posts: 50
Thanks: 7 times
|
The other thing I noticed was that qn and qp were note coupled. Didn't know this as I was using the manual on the hd bp product page, which doesn't mention this. I will do this as well.
Also the vref was way off on the negative rail, again I will provide that but it definitly wasnt 2.5v
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/4/2012(UTC)
Posts: 50
Thanks: 7 times
|
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/17/2008(UTC) Posts: 921  Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
|
The component values you're are measuring, is that in-circuit measurements or components not mounted ?
380mv vref is not good. That we have to bring up to 2.5v.
"noticed was that qn and qp were note coupled."
what is note coupled ?
Pictures please, they really helps debugging.
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/4/2012(UTC)
Posts: 50
Thanks: 7 times
|
Thats a spelling mistake "note coupled" = "Not Thermo-coupled" The measurements taken were while the resistor on the board. Edited by user Monday, September 5, 2016 1:50:47 AM(UTC)
| Reason: Not specified
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/4/2012(UTC)
Posts: 50
Thanks: 7 times
|
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/4/2012(UTC)
Posts: 50
Thanks: 7 times
|
Please delete Edited by user Monday, September 5, 2016 11:37:54 AM(UTC)
| Reason: Not specified
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/17/2008(UTC) Posts: 921 Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
|
At first (brief) glance pictures looks good.
Please check placement of the power transistors. QN1-2, QP1-2. Just to make sure.
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/17/2008(UTC) Posts: 921 Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
|
Regarding the resistor values. Don't rely on measuring in-circuit. The surrounding components are affecting the readings.
Regarding R8 - that's an error in the BOM. It's supposed to be 220R, and yours are 220R (looking at the colour code).
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/4/2012(UTC)
Posts: 50
Thanks: 7 times
|
Thanks for the help avr.
They are in the right positions, I'm wondering if I should reflow again.
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/17/2008(UTC) Posts: 921 Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
|
No, I think your soldering looks great. Can you measure the voltage referenced to GND in the orange spots.  cut.jpg (69kb) downloaded 31 time(s).Edited by user Thursday, September 8, 2016 4:31:56 PM(UTC)
| Reason: Not specified
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/4/2012(UTC)
Posts: 50
Thanks: 7 times
|
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/4/2012(UTC)
Posts: 50
Thanks: 7 times
|
Sorry I took so long
I have v1 and 2 but I'm not sure where to measure for v3. Would you mind pointing it out to me please.
Vref - and gnd = .370mv
Tp-vin and gnd = 20.6v
I should also mention qp1 was extremely hot while measuring, far far to hot to touch... I think i could start to smell it aswell.
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/17/2008(UTC) Posts: 921 Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
|
Im not talking about Vref point. I'm talking of the point on the schematics (marked by v1). It's the second voltage reference on the PCB. The voltages I like to see is here. cut.jpg (41kb) downloaded 22 time(s).You have to bare with me. I don't have the final production PCB here. I'm on a beta board, slightly different from the final board. I have to use the the outline graphics from TPA website, to "guess" the positions of the voltages of interest. But wait, qp1 should not be that warm. Please look for solder bridges. If possible, use a magnifying glass. Solder bridges can be hard to see.
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/4/2012(UTC)
Posts: 50
Thanks: 7 times
|
V1 = -18.16v V3 = -19.6v I couldn't see any bridges, I also cleaned it again and the result is the same Edited by user Wednesday, September 28, 2016 11:55:22 AM(UTC)
| Reason: Not specified
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/4/2012(UTC)
Posts: 50
Thanks: 7 times
|
Any ideas, should I start replacing parts such as qp1
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/17/2008(UTC) Posts: 921 Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
|
Is VR1B working ?
(measure resistance across - with no power applied to the Placid)
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/4/2012(UTC)
Posts: 50
Thanks: 7 times
|
I can see a resistance of .500k and it changes when trimming
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/17/2008(UTC) Posts: 921 Thanks: 1 times
Was thanked: 70 time(s) in 69 post(s)
|
Sorry, I don't have time for doing proper support.
Lets call Russ.
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 6/4/2012(UTC)
Posts: 50
Thanks: 7 times
|
Thanks for the help anyway avr300. Was really appreciated
|
|
|
|
|
|
Forum Jump
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.
