Welcome Guest! To enable all features please Login or Register.

Notification

Icon
Error

Login


2 Pages12>
Options
View
Go to last post Go to first unread
usmat  
#1 Posted : Tuesday, June 21, 2011 9:43:41 AM(UTC)
usmat

Rank: Advanced Member

Groups: Member
Joined: 5/4/2011(UTC)
Posts: 34
Location: Southbury, CT, USA

The symptoms (black label board):
1 - All LEDs light up
2 - VREF = 3.8V
3 - Cannot adjust past 13.8V. but can adjust to -15V
4 - Shunt current = 5 ma (0.005V across shunt TP)for both polarities
5 - CCS current = 0V for both polarities
6 - QP1, QP2, QN1 & QN2 are cold. Looks like they are not on.

Any quick tips before I load pictures?

SMathews
Brian Donegan  
#2 Posted : Tuesday, June 21, 2011 9:45:57 AM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
Double-check the transistor location. Then take a break and check them again :).
usmat  
#3 Posted : Tuesday, June 21, 2011 9:57:21 AM(UTC)
usmat

Rank: Advanced Member

Groups: Member
Joined: 5/4/2011(UTC)
Posts: 34
Location: Southbury, CT, USA

Thanks Brian. I may have to load pictures. I checked all the transistors using a scope and they looked okay. I will look again. Any intermediate node voltages other than Vref that I can check?

SMathews
Brian Donegan  
#4 Posted : Tuesday, June 21, 2011 10:03:56 AM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
Working at the office at the moment, so don't have any good info in front of me...
usmat  
#5 Posted : Tuesday, June 21, 2011 10:08:43 AM(UTC)
usmat

Rank: Advanced Member

Groups: Member
Joined: 5/4/2011(UTC)
Posts: 34
Location: Southbury, CT, USA

Same here, Lunch break. I will load pictures when I get back home.

SMathews
usmat  
#6 Posted : Wednesday, June 22, 2011 5:09:18 AM(UTC)
usmat

Rank: Advanced Member

Groups: Member
Joined: 5/4/2011(UTC)
Posts: 34
Location: Southbury, CT, USA

I believe I have to post before attaching pictures. Here goes.
usmat attached the following image(s):
DSC_1430.jpg (74kb) downloaded 347 time(s).
DSC_1431.jpg (68kb) downloaded 345 time(s).
DSC_1432.jpg (58kb) downloaded 345 time(s).
DSC_1433.jpg (58kb) downloaded 343 time(s).
DSC_1434.jpg (53kb) downloaded 342 time(s).
DSC_1435.jpg (50kb) downloaded 341 time(s).
DSC_1436.jpg (52kb) downloaded 348 time(s).
DSC_1437.jpg (61kb) downloaded 341 time(s).

You cannot view/download attachments. Try to login or register.
suffolk tony  
#7 Posted : Wednesday, June 22, 2011 7:36:01 AM(UTC)
suffolk tony

Rank: Member

Groups: Member
Joined: 9/14/2010(UTC)
Posts: 84
Location: uk

I had an almost identical problem the other day and it turned out to be one of the pins on a variable resistor wasn't soldered. Guess my eyes just skipped over it and it's a very small pin and pad.
Brian Donegan  
#8 Posted : Wednesday, June 22, 2011 8:18:49 AM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
You do have some cold joints there. Try adding some flux and reheating.
usmat  
#9 Posted : Wednesday, June 22, 2011 9:08:20 AM(UTC)
usmat

Rank: Advanced Member

Groups: Member
Joined: 5/4/2011(UTC)
Posts: 34
Location: Southbury, CT, USA

Thanks Tony, Brian, I will resolder.

SMathews
usmat  
#10 Posted : Wednesday, June 22, 2011 10:34:08 AM(UTC)
usmat

Rank: Advanced Member

Groups: Member
Joined: 5/4/2011(UTC)
Posts: 34
Location: Southbury, CT, USA

I re-touched almost every solder point.

No go.

I then adjusted VR1 & VR2 (blacked out board) and then, voila current.

Was able to adjust for +/- 14.5V and 350 amps on both rails. QP2 and QN2 got hot, quite fast and stayed hot to touch. QN1 and QN2 got hot slowly, but not as hot as QP2 and QN2. Is that normal? I have no load.

Thanks again Tony, Brian, appreciate it.

My soldering sucks.

SMathews
usmat  
#11 Posted : Wednesday, June 22, 2011 10:36:53 AM(UTC)
usmat

Rank: Advanced Member

Groups: Member
Joined: 5/4/2011(UTC)
Posts: 34
Location: Southbury, CT, USA

350 amps!!!! ..... 0.350 amps

SMathews
Brian Donegan  
#12 Posted : Wednesday, June 22, 2011 11:33:12 AM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
Yes, the heat is completely normal. You are always dumping current, regardless of the load, thus the heat.
suffolk tony  
#13 Posted : Wednesday, June 22, 2011 1:43:57 PM(UTC)
suffolk tony

Rank: Member

Groups: Member
Joined: 9/14/2010(UTC)
Posts: 84
Location: uk

So glad you got it sorted!
usmat  
#14 Posted : Friday, June 24, 2011 2:32:21 AM(UTC)
usmat

Rank: Advanced Member

Groups: Member
Joined: 5/4/2011(UTC)
Posts: 34
Location: Southbury, CT, USA

Looks like I'm back to no current, after connecting the legato 3. I have a light bulb on the hot power line, that lit up after I connected the Legato, so that would mean a short some-where.
Disconnecting the Legato, I can adjust the Placed for voltage and not current. The current stays at 50 ma. Turning the pot does not change the current.
I guess I can used fixed resistors. I am aiming for 15V, 350 ma.

SMathews
usmat  
#15 Posted : Friday, June 24, 2011 8:15:43 AM(UTC)
usmat

Rank: Advanced Member

Groups: Member
Joined: 5/4/2011(UTC)
Posts: 34
Location: Southbury, CT, USA


From the manual for 15V I need to set :
Rf = 1K, that is R18 and R17 in the black label boards
Rg = 750 ohms, htat is R15 and R16

VR2 needs to be found out.

Can someone suggest a fixed resistor value for VR2 to get 350 ma and 15V? I'm trying to avoid getting another VR2 pot.
Thanks

SMathews
usmat  
#16 Posted : Tuesday, June 28, 2011 10:56:32 AM(UTC)
usmat

Rank: Advanced Member

Groups: Member
Joined: 5/4/2011(UTC)
Posts: 34
Location: Southbury, CT, USA

Update :
My trimmer pots seem to be okay. Here's whats happened so far

1) Previously working placid was attached to legato 3.1, which I presume had a short.
2) Disconnected Legato and in my haste connected the secondaries of transformers to the Placid for the -ve side in opposite.
3) Re-connected correctly.
4) Symptoms below

Symptoms :
1) All LEDs light up
2) Current stays a 50ma, and cannot be changed by adjusting VR2/VR1 (blacked out board). Shunt at 50 ma too.
3) But the current can be adjusted using VR3/VR4 to max 150 ma.
4) Light bulb connected to the supply hot lead is glowing very slightly and hence the secondary voltage does not go above 12 to 13 Volts.
5) Vref is okay - 3.8V
6) QP2 and QN2 are very slightly warm.

Any ideas?

SMathews
Brian Donegan  
#17 Posted : Tuesday, June 28, 2011 11:12:10 AM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
Quote:
connected the secondaries of transformers to the Placid for the -ve side in opposite.


Can you explain what you mean by this?
usmat  
#18 Posted : Tuesday, June 28, 2011 11:31:59 AM(UTC)
usmat

Rank: Advanced Member

Groups: Member
Joined: 5/4/2011(UTC)
Posts: 34
Location: Southbury, CT, USA

The 4 secondary transformer wires black, red, orange & yellow. I mistakenly connected yellow to SA2A and orange to SA2B. I had black on SA1A and red on SA1B.

SMathews
Brian Donegan  
#19 Posted : Tuesday, June 28, 2011 11:52:25 AM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
Ok, that's what I thought you meant. It should have not effect whatsoever on the Placid.
usmat  
#20 Posted : Tuesday, June 28, 2011 12:00:20 PM(UTC)
usmat

Rank: Advanced Member

Groups: Member
Joined: 5/4/2011(UTC)
Posts: 34
Location: Southbury, CT, USA

Brian, thanks. If you have any voltages I can check, that would be great.

SMathews
Rss Feed  Atom Feed
Users browsing this topic
GuestUser (9)
2 Pages12>
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.