Any electronics experts here?

mhku

Super Moderator
Staff member
Joined
Mar 8, 2005
Messages
4,712
Reaction score
20
Points
38
My Satellite Setup
TM Nano ~ sg2100
My Location
Midlands
If there are I'll post the relevant photos but... how do I identify a thyristor on a PCB?
 

satelliteman

Administrator
Staff member
Joined
May 7, 2007
Messages
12,033
Reaction score
382
Points
83
My Satellite Setup
See signature
My Location
East Midlands, UK & Lanzarote, Canary Islands
Ok, post away, I had 10 years in the TV/VIdeo repair business. I don't mind taking a look but I may not be able to help after all :D
 

Llew

cerca trova...
Staff member
Joined
Jan 1, 2000
Messages
15,489
Reaction score
3,757
Points
113
Age
78
My Satellite Setup
Triple Dragon, Dreambox 8000, Echostar AD3000ip, TBS6522,6925,6983 PCie cards.
Gibertini 1.25m motorised dish driven by the AD3000, with either Inverto BU Quad or Norsat / XMW Ka LNBs . SMW 1.05m + 3 other dishes. Speccy: Promax HD Ranger+
My Location
The Flatlands of East Anglia
No markings on the case? A lot of them use TO (transistor outline) cases, so unless you know circuit details, it's hard to be specific.

A photo may help. What is the PCB for?

Llew
 

satelliteman

Administrator
Staff member
Joined
May 7, 2007
Messages
12,033
Reaction score
382
Points
83
My Satellite Setup
See signature
My Location
East Midlands, UK & Lanzarote, Canary Islands
Yes, from looking at any board, they can look just as a transistor and are also known as SCRs but of course they will measure totally different. They are about the size of a old bc548 but can differ in design to size of bu208
 

mhku

Super Moderator
Staff member
Joined
Mar 8, 2005
Messages
4,712
Reaction score
20
Points
38
My Satellite Setup
TM Nano ~ sg2100
My Location
Midlands
It's not a satellite question :)

Here's a PCB from a camera flash. Another model of flash (same make) can be adapted for variable power output by wiring a potentiometer across the thyristor. But it looks very different to this one.
 

Attachments

  • Resize of IMG_6873.jpg
    Resize of IMG_6873.jpg
    48.1 KB · Views: 62

Llew

cerca trova...
Staff member
Joined
Jan 1, 2000
Messages
15,489
Reaction score
3,757
Points
113
Age
78
My Satellite Setup
Triple Dragon, Dreambox 8000, Echostar AD3000ip, TBS6522,6925,6983 PCie cards.
Gibertini 1.25m motorised dish driven by the AD3000, with either Inverto BU Quad or Norsat / XMW Ka LNBs . SMW 1.05m + 3 other dishes. Speccy: Promax HD Ranger+
My Location
The Flatlands of East Anglia
That circuit looks like it uses a piezo transformer instead of a thyristor (the black rectangular component). I don't know of any way you can vary the output on those, haven't come across any circuit that can do that myself.

Llew
 

mhku

Super Moderator
Staff member
Joined
Mar 8, 2005
Messages
4,712
Reaction score
20
Points
38
My Satellite Setup
TM Nano ~ sg2100
My Location
Midlands
In the post #5 photo the clear LED at the bottom of the PCB is a sensor that can limit the output of the flash: when covered it gives full power, when partially covered power output is reduced.

On a similar flash a 100k potentiometer is wired across two sensor terminals (each end of the thin red wire in the photo below) to control power output (_http://www.websitetoolbox.com/tool/post/rtoyz/vpost?id=2324538) but this flash has different electronics and sensor.

As you can tell I know bugger all so it may not even be possible on the photo shown in post #5

Cheers for the replies (I had problems getting on the site last night) :)
 

Attachments

  • Resize of IMG_6872.jpg
    Resize of IMG_6872.jpg
    54.5 KB · Views: 37

Robbo

Retired Mod
Joined
May 17, 2007
Messages
6,424
Reaction score
5
Points
38
Age
54
Website
www.mbcsatellites.co.uk
My Satellite Setup
TM6800HD, TM1000, TM600 Linux,TM2200 motor, Channel Master 1.2m motorised, TD110 dish Meter=Satlook Micro+G2 NIT
My Location
Gravesend,Kent,UK
I think what you have there (The LED- not) is a photo transistor. The more light that falls onto it the more current it allows to be passed from one terminal to the other.

Just like a normal transistor except that the base current is supplied by the light source.

So, I would have thought that the device could be replace by a resistor. The max current through the will be in the region of a few tens of mA. So the resistor should not be too low in value, in the region of 1k minimum I would have thought, depending on the voltage accross it.

Robbo:)
 

Llew

cerca trova...
Staff member
Joined
Jan 1, 2000
Messages
15,489
Reaction score
3,757
Points
113
Age
78
My Satellite Setup
Triple Dragon, Dreambox 8000, Echostar AD3000ip, TBS6522,6925,6983 PCie cards.
Gibertini 1.25m motorised dish driven by the AD3000, with either Inverto BU Quad or Norsat / XMW Ka LNBs . SMW 1.05m + 3 other dishes. Speccy: Promax HD Ranger+
My Location
The Flatlands of East Anglia
Any chance of a rear view photo of the wiring?

Llew
 

HB13DISH

Retired Mod
Joined
Aug 13, 2007
Messages
3,764
Reaction score
1
Points
0
Age
75
My Location
Middle East - Israel
mhku said:
If there are I'll post the relevant photos but... how do I identify a thyristor on a PCB?

If you have a part which you know it is a thyristor and if it has some markings on it like part number or manufacturer's name or logo, it will be a step in the right direction, then just attach a photo/photos showing all possible info from different angles.
If there are no markings, then we need a part list of all the parts on the PCB.
If you have a PCB and you want to know which part is the thyristor, then I would like to see the same as above for all the parts, especially part numbers.
 

mhku

Super Moderator
Staff member
Joined
Mar 8, 2005
Messages
4,712
Reaction score
20
Points
38
My Satellite Setup
TM Nano ~ sg2100
My Location
Midlands
I'm soldering a potentiometer directly to where the photo transistor is soldered to the PCB. To quote Transformers "That was tingly!"... Back soon :)
 

Robbo

Retired Mod
Joined
May 17, 2007
Messages
6,424
Reaction score
5
Points
38
Age
54
Website
www.mbcsatellites.co.uk
My Satellite Setup
TM6800HD, TM1000, TM600 Linux,TM2200 motor, Channel Master 1.2m motorised, TD110 dish Meter=Satlook Micro+G2 NIT
My Location
Gravesend,Kent,UK
mhku said:
I'm soldering a potentiometer directly to where the photo transistor is soldered to the PCB. To quote Transformers "That was tingly!"... Back soon :)

Have you taken the photo transistor off?

Lets hope it doesn't bu99er it.:)
 

satelliteman

Administrator
Staff member
Joined
May 7, 2007
Messages
12,033
Reaction score
382
Points
83
My Satellite Setup
See signature
My Location
East Midlands, UK & Lanzarote, Canary Islands
This is getting interesting , lol
 

mhku

Super Moderator
Staff member
Joined
Mar 8, 2005
Messages
4,712
Reaction score
20
Points
38
My Satellite Setup
TM Nano ~ sg2100
My Location
Midlands
I managed to get another, bigger "sh*t!" shock from the capacitor but both I and the flash are still alive.

I'll post a photo later- it's not as tidy as I'd have liked: a potentiometer that can have the cable threaded through the centre (the axis) would have helped a great deal. Had to do some major surgery with a soldering iron :D
 

Robbo

Retired Mod
Joined
May 17, 2007
Messages
6,424
Reaction score
5
Points
38
Age
54
Website
www.mbcsatellites.co.uk
My Satellite Setup
TM6800HD, TM1000, TM600 Linux,TM2200 motor, Channel Master 1.2m motorised, TD110 dish Meter=Satlook Micro+G2 NIT
My Location
Gravesend,Kent,UK
mhku said:
I managed to get another, bigger "sh*t!" shock from the capacitor but both I and the flash are still alive.


Glad you are not dead mate.:-rofl2 That's the sort of stupid thing I would do, and then afterwoods think, mmm, maybe I should have discharged the capacitor first.:)

The question is though, does it work?
 

pgh13

Specialist Contributor
Joined
Apr 5, 2005
Messages
1,679
Reaction score
409
Points
83
Age
69
My Satellite Setup
XTrend ET8000, Dr HD 15, PC/twinhan combination. 80cm dish. GBPVR with 2 DTTV cards +hauppauge Media MVP +Raspberry Pi running XBMC
My Location
Midlands UK
I think that even after flashing you're still left with 90v, so still a bit tingly.

Lots of background info here on electronic flash circuits (including how to discharge the capacitor). Possibly older technology than the one you're working on judging by the circuit diagrams drawn with ascii characters
_ttp://members.misty.com/don/samflash.html

_ttp://repairfaq.cis.upenn.edu/sam/strbfil.htm
 

2cvbloke

Bulbs need shelter too...
Joined
Jan 5, 2006
Messages
9,768
Reaction score
1,806
Points
113
Age
35
My Satellite Setup
No satellite stuff for the moment (aside from a 43cm minidish that was on the house already), Samsung SyncMaster T27B550 Smart TV & Monitor, and a few computers...
My Location
Near Pontop Pike, Co. Durham
Are you building a Taser or something? It just reminds me of the "Taser glove" instructable which used a disposable camera's flash and a marigold glove covered in tinfoil....:-rofl2
 

mhku

Super Moderator
Staff member
Joined
Mar 8, 2005
Messages
4,712
Reaction score
20
Points
38
My Satellite Setup
TM Nano ~ sg2100
My Location
Midlands
It's alive! 'O'

The tingle may have been closer to 140-170V if it's the same as the trigger voltage (Vivitar 2800 _http://www.botzilla.com/photo/strobeVolts.html) which is why it won't be physically attached to the camera. Doing the trigger voltage modification might be next. I was lucky it the flash with the huge capactitor..

Anyway here's the (almost) finished article- the red cap covers the potentiometer which is attached with blue tac at the moment. Output is variable although I've read a 250k potentiometer is better (_http://www.krebsmicro.com/VIV283/index.html).

Total cost was:

flash - £3.21
potentiometer - 70p
knob - 94p
milk carton lid - free

A physically smaller potentiometer would have made the task easier and quicker.
 

Attachments

  • Resize of IMG_7197.jpg
    Resize of IMG_7197.jpg
    44 KB · Views: 31
  • Resize of IMG_7222.jpg
    Resize of IMG_7222.jpg
    66.3 KB · Views: 31
  • Resize of IMG_7224.jpg
    Resize of IMG_7224.jpg
    62.8 KB · Views: 34
  • Resize of IMG_7450.jpg
    Resize of IMG_7450.jpg
    51.5 KB · Views: 32
  • jm69a.jpg
    jm69a.jpg
    18.3 KB · Views: 26

Llew

cerca trova...
Staff member
Joined
Jan 1, 2000
Messages
15,489
Reaction score
3,757
Points
113
Age
78
My Satellite Setup
Triple Dragon, Dreambox 8000, Echostar AD3000ip, TBS6522,6925,6983 PCie cards.
Gibertini 1.25m motorised dish driven by the AD3000, with either Inverto BU Quad or Norsat / XMW Ka LNBs . SMW 1.05m + 3 other dishes. Speccy: Promax HD Ranger+
My Location
The Flatlands of East Anglia
Glad it's all come together mate. Yes, might be worth experimenting with the potentiometer - e.g. substituting a linear one for a logarithmic one if the scaling is 'cramped' at one end.

Llew
 

mhku

Super Moderator
Staff member
Joined
Mar 8, 2005
Messages
4,712
Reaction score
20
Points
38
My Satellite Setup
TM Nano ~ sg2100
My Location
Midlands
Cheers for the suggestion I'll try a few of higher value and a log one.
 
Top