Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > General Electronics Technical Discussion
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 11-06-2019, 10:57 AM   #1
jinu_j
Member
 
Join Date: Feb 2016
City & State: Mumbai
My Country: India
I'm a: Knowledge Seeker
Posts: 24
Default Shredder very slow to start

Hi Folks

I have a shredder, the problem is after putting the paper it takes about a minute for the motor to start and shred.

I trouble shooted a lot and figured out that the problem is the voltage at the coil end of the relay is taking time to reach 24V. It rises very gradually and as soon as it reaches 20V the motor starts.

The question is what component could be causing this ? Could caps be the problem. Please see PCB images below

Attached Images
File Type: jpg Comb.jpg (603.5 KB, 48 views)
jinu_j is offline   Reply With Quote
Old 11-06-2019, 11:06 AM   #2
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 1,923
Default Re: Shredder very slow to start

try new solder on those bad joints .
if that doesn't fix it then you may as well change all 3 electrolytic capacitors .
if that hasn't worked change relay driver transistor

Last edited by petehall347; 11-06-2019 at 11:10 AM..
petehall347 is offline   Reply With Quote
Old 11-06-2019, 11:37 AM   #3
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 4,873
Default Re: Shredder very slow to start

Also check that the gears etc. are not full of paper dust and causing things not to operate, Check the motor to make sure it is turning freely and that the bearings are not causing the fault.
R_J is offline   Reply With Quote
Old 11-06-2019, 10:08 PM   #4
jinu_j
Member
 
Join Date: Feb 2016
City & State: Mumbai
My Country: India
I'm a: Knowledge Seeker
Posts: 24
Default Re: Shredder very slow to start

Thanks. This is a new shredder and not used much so no issue with gears. I have ordered the replacement CAPS. will replace those and update once done. Thanks folks
jinu_j is offline   Reply With Quote
Old 11-06-2019, 11:01 PM   #5
eccerr0r
Solder Sloth
 
eccerr0r's Avatar
 
Join Date: Nov 2012
City & State: CO
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 4,414
Default Re: Shredder very slow to start

Other possibility is that one of the resistors went open or one of the tracks broke. Some of the tracks on the bottom looks corroded or something weird is going on with them ... could they be to blame?
eccerr0r is offline   Reply With Quote
Old 11-06-2019, 11:12 PM   #6
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 36,354
Default Re: Shredder very slow to start

I see some crappy solder joints too.
Attached Images
File Type: jpg Crappy solder joints.jpg (290.7 KB, 16 views)
__________________
Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999

Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl

Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/

TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
budm is offline   Reply With Quote
Old 11-09-2019, 06:53 AM   #7
jinu_j
Member
 
Join Date: Feb 2016
City & State: Mumbai
My Country: India
I'm a: Knowledge Seeker
Posts: 24
Default Re: Shredder very slow to start

Hi Folks

I have replaced the caps with new ones. and resoldered some of the joints showing poor solder. But still the same problem, infact replacing the capacitors seems to make it worse. Now the voltage across the coil of the relay is stuck at 10V. i believe it has to reach 24 volts for the relay to trigger. What else could be the problem ?

I looked at the transistor. All that written on it is A44 B331. Cant find the data sheet for this transistor. Is there an equivalent you are aware off.

Some voltages i have recorded
- Voltage at the receiver end of the IR recerive when path is blocked : 2.5V
- Voltage at Base of Transistor (pin 2) : 1 V
- Voltage between C and E (Pin 1 and 3) : 30V
- Voltage across coil of relay : 8v (This should be around 24) but this is gradually very gradually increasing and climbing upwards

Last edited by jinu_j; 11-09-2019 at 07:07 AM..
jinu_j is offline   Reply With Quote
Old 11-09-2019, 09:37 AM   #8
eccerr0r
Solder Sloth
 
eccerr0r's Avatar
 
Join Date: Nov 2012
City & State: CO
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 4,414
Default Re: Shredder very slow to start

I'd also make sure the paper sensor is actually working properly too...
eccerr0r is offline   Reply With Quote
Old 11-09-2019, 09:40 AM   #9
jinu_j
Member
 
Join Date: Feb 2016
City & State: Mumbai
My Country: India
I'm a: Knowledge Seeker
Posts: 24
Default Re: Shredder very slow to start

Paper sensor is working fine. Without the paper blocking the path between the sensors i see volts 0.5v and when i put the paper the voltage rises to 2.5V
jinu_j is offline   Reply With Quote
Old 11-09-2019, 10:56 AM   #10
eccerr0r
Solder Sloth
 
eccerr0r's Avatar
 
Join Date: Nov 2012
City & State: CO
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Hobbyist Tech
Posts: 4,414
Default Re: Shredder very slow to start

what's the reference point of base of transistor when you say 1V ?
eccerr0r is offline   Reply With Quote
Old 11-09-2019, 10:59 AM   #11
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 1,923
Default Re: Shredder very slow to start

transistor looks duff . try shorting emitter to collector and see if relay clicks in .
petehall347 is offline   Reply With Quote
Old 11-09-2019, 11:16 AM   #12
jinu_j
Member
 
Join Date: Feb 2016
City & State: Mumbai
My Country: India
I'm a: Knowledge Seeker
Posts: 24
Default Re: Shredder very slow to start

Quote:
Originally Posted by eccerr0r View Post
what's the reference point of base of transistor when you say 1V ?
The problem is i cant find the specs on the Transistor. It is just numbered as A44 B331.

I think its ground. Please see image below. The voltages measured are:

- Voltage at the receiver end of the IR receiver when path between IR Transmitter and receiver is blocked (Points C and D : 2.5V
- Voltage at Base of Transistor (pin 2) Points C and H : 1 V
- Voltage between C and E (Pin 1 and 3)Points G and I : 30V
- Voltage across coil of relay Points E and F : 8v (This should be around 24) but this is gradually very gradually increasing and climbing upwards
- Points A and B are points to the IR Tranmitter - 1V
- The transistor is at points G, H, I

Attached Images
File Type: jpg Ref POint.jpg (236.2 KB, 23 views)
jinu_j is offline   Reply With Quote
Old 11-09-2019, 11:22 AM   #13
jinu_j
Member
 
Join Date: Feb 2016
City & State: Mumbai
My Country: India
I'm a: Knowledge Seeker
Posts: 24
Default Re: Shredder very slow to start

Quote:
Originally Posted by petehall347 View Post
transistor looks duff . try shorting emitter to collector and see if relay clicks in .
Actually it did. When i shorted the Emitter and collector the Shredder started working. Thanks a lot.

So can i assume the transistor is bad and needs replacement. If so the problem is i cant find the replacement of a transistor with the name A44 B331 is there an equivalent.
jinu_j is offline   Reply With Quote
Old 11-09-2019, 11:25 AM   #14
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 4,873
Default Re: Shredder very slow to start

This could be it. Either the transistor is bad OR the base is not being turned on enough.
Attached Images
File Type: jpg product_109048_431591_0x0.jpg (28.1 KB, 3 views)
Attached Files
File Type: pdf A44-TO-92.pdf (276.4 KB, 16 views)

Last edited by R_J; 11-09-2019 at 11:43 AM..
R_J is offline   Reply With Quote
Old 11-09-2019, 11:44 AM   #15
jinu_j
Member
 
Join Date: Feb 2016
City & State: Mumbai
My Country: India
I'm a: Knowledge Seeker
Posts: 24
Default Re: Shredder very slow to start

Quote:
Originally Posted by R_J View Post
This could be it. Either the transistor is bad OR the base is not being turned on enough.
Is there anyway i can test for the second issue (base not being turned on enough) ?
jinu_j is offline   Reply With Quote
Old 11-09-2019, 11:46 AM   #16
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 4,873
Default Re: Shredder very slow to start

Check the voltage between emitter and base. It should be around 0.7 volts or a bit more, also what is the voltage across C2

Last edited by R_J; 11-09-2019 at 11:50 AM..
R_J is offline   Reply With Quote
Old 11-09-2019, 11:56 AM   #17
jinu_j
Member
 
Join Date: Feb 2016
City & State: Mumbai
My Country: India
I'm a: Knowledge Seeker
Posts: 24
Default Re: Shredder very slow to start

Quote:
Originally Posted by R_J View Post
Check the voltage between emitter and base. It should be around 0.7 volts or a bit more, also what is the voltage across C2
The voltage between the Emitter and base is 0.45V
jinu_j is offline   Reply With Quote
Old 11-09-2019, 12:07 PM   #18
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 4,873
Default Re: Shredder very slow to start

That seems too low to turn on the transistor, check the voltage across C2 (or R6) also check R7 10k, it could be open
Check that the trace that goes from R9 to D5 to R6 to ZD1 is not open, this is the ground or common point
C1+ seems to be the low voltage supply (5V?) It then goes through R5, through D6 to C2+

Last edited by R_J; 11-09-2019 at 12:19 PM..
R_J is offline   Reply With Quote
Old 11-09-2019, 12:17 PM   #19
jinu_j
Member
 
Join Date: Feb 2016
City & State: Mumbai
My Country: India
I'm a: Knowledge Seeker
Posts: 24
Default Re: Shredder very slow to start

Voltage across C2 is 1.8V. R7 is 10k and is not open. That would indicate a a problem with the diode D5? If I check the voltage between points after R7 and before D5 it about 1V, but i move it to after D5, it drops to 0.45V
jinu_j is offline   Reply With Quote
Old 11-09-2019, 12:21 PM   #20
R_J
Badcaps Veteran
 
Join Date: Jun 2012
City & State: ☻
My Country: Canada
I'm a: Professional Tech
Posts: 4,873
Default Re: Shredder very slow to start

D5 has nothing to do with the base circuit, it connects the emitter of Q1 to ground.
Check the voltage across C1. C1 negative is the ground of this circuit.
There are 2 wires next to the relay (Violet and Grey) where do they connect? The violet wire connects to ground, and the grey wire seems to control the voltage going to the Q1 base

Last edited by R_J; 11-09-2019 at 12:27 PM..
R_J is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2019
Powered by vBulletin ®
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 11:14 PM.
Did you find this forum helpful?