Cornboats
Dave
Last Activity: Today, 08:21 AM
Joined: 10-23-2010
Location: Worcestershire
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Thanks for the diagram. Did you just work out the schematic by looking at my photos? You are really clever if you did. I'll work thro and let you know how I get on. -
How do you delete photo's once published. 2 I've just uploaded are better....
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faulty loudspeaker amplifier-no sound output
I've several amplifiers of different sizes which are faulty. I haven't fixed them because I haven't a clue. This is the smallest culprit. 240v in (UK) and 12v dc to the board. Small neon lights when power button is on. Different dc voltages across all of the capacitors. Where do I go from here? -
Re: Garage door opener-safety cutout faulty
Les from electro-tech has pointed out pin 5 on the socket is broken. I'll resolder everything and once I've sorted out how to replace the broken pin I'll retest. 2 out of the 3 connections on the phototransistor are shorting aswell. The data sheet for CNY 70 shows I should be getting a diode test result so I'll check the known working operator to see if the result is the same.
I've attached my interpretation of the schematic for the small torque adjustment board. Could you explain how this design works to interpret torque of the...Leave a comment:
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Re: Garage door opener-safety cutout faulty
No I didn't try the operator with the other main board, only the torque setting board.
The transisitor is ZVN 330 6A
To test your theory on the bench could I connect to an oscilloscope, (I have an old analogue) to see the pulse width setting?
I've sketched a schematic of the torque setting board which I'll upload today which may help.Leave a comment:
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Re: Garage door opener-safety cutout faulty
Thanks for taking the trouble to reply
There was a black cover concealing the parts. I wrongly assumed this was a 1 piece component and so desoldered to lift off the board.The black cover prised off using a sharp trimming knife, but only after I'd desoldered the components.
I've serviced the operator for many years paying attention oiling to metal on metal parts. Alignment is ok and upper and lower limit settings are working. The limits aren't shown as close and open limits are installed on the chain track.
The door...Leave a comment:
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Garage door opener-safety cutout faulty
I have vintage Slavedor garage door opener that has stopped closing the door. If I disable the up/down current control to the motor it works fine. I've attached the larger control board which is for everything and the smaller current control board.
Normally the current control is set slightly above the maximum current normally used. If the door exceeds this it should stop and reverse when closing or just stop when opening. Can someone please explain how the current control board works so that I can try and repair or replace the defective parts.
I see my self as an interested novice... -
Re: Samsung 32 changes source on its own
Thanks for both of your suggestions. I'll look at both areas and report back asap.Leave a comment:
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Samsung 32 LE32B450C4WXXU changes source on its own
Samsung 32 LE32B450C4WXXU, manufactured 2009
This set changes source without being asked. Turn the set on and tv channel comes on for up to 20mins then set changes to ext1 for a couple of secs then PC for a couple of secs then back to tv for the same same. Then the cycle starts again. I turned on today and there were no channels saved so I had to rescan.
I'm guessing the faults on the main board so have included a photo.
Any thoughts or ideas would be welcome.... -
Re: EVO car radio -blank screen
Just an update. I found a transistor BD438 with a shorted leg. I've replaced but still have a dead set. There are 3 voltage regulators on the board 1 of which is adjacent to the transistor BD438 I've just replaced. I'll test these with the voltage on next. There is a smd transitor 3F P23 connected to the BD438 which is giving correct readings but then so was the BD438 until I pulled it. I'm reluctant to pull the smd transistor for fear that being so small I'll never get it back.Leave a comment:
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Re: EVO car radio -blank screen
Nothing happening. No sound, no light. If you take out the removable button the led flashes, which its supposed to.Leave a comment:
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EVO car radio -blank screen
I've had this in my Isuzu since I bought the truck in 2003. Stopped working and now on my bench for fault finding. Fuse at the back of the set is ok, testing using a 12v DC supply. 1st port of call was a disable button that you can remove which is supposed to deter theft. Looked at this first. When you insert it shorts 2 pins to make a circuit. Shorted pins out with white wire just to confirm.
2nd was the volume control which is pushed to activate a momentary switch to turn on /off. Test ok with ohmeter but ran white leads from pins just to check. Voltmeter shows 4.8v on to one of the pins... -
Re: Help reading this electrical schematic
Thanks to both your replies. I'm going to build my own controller based on the TDA 1085 as the ex washing motor I want to re purpose already has a tacho fitted on the end.
I haven't got the knowledge to design from scratch but can build from a drawing.
I'll search online to see if there are any I can use.
Many thanks for taking the trouble to reply.Leave a comment:
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Help reading this electrical schematic
I'd like to make a motor speed controller on an ex brush universal washing machine motor.
The motor runs for too fast so I'd like to reduce the revs down into the 10s. I've bought several motor controllers off Ebay/Amazon but the 240v version doesn't maintain the motor at low speed under load at constantrevs. The DC version I bought was good at low revs but I turned the unit on without turning the control potentiometer down first. This has blown something on the board and the fets/triacs aren't marked( Chinese) so I can't replace the obvious. I found this drawing on line and decided its... -
Re: Kareokee amplifier not working
So I checked every single capacitors ESR and found all within tolerance. The only one I changed was C27 which was across power to negative voltage regulator. The ESR on the old one was 23.00, average for this spec is 0.12. The capacitance should have been 470 UF but measured 86.7NF.
The crackling and sound distortion I managed to remove by turning down the echo and microphone volumes. All in all I treat this as a result. Many thanks for the Forums help. More broken and in need of repair items coming out of the box.Leave a comment:
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Re: Kareokee amplifier not working
Well done for that. Fitted an ac adaptor and negative voltage to the -voltage regulator is restored. Quality of sound at the speakers is not very good though. Could be the stand alone speakers. I'm going to connect up the amp thro a tv & dvd to see if its any better. There are loads of caps on the board, maybe some of those have dried out.
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Re: Kareokee amplifier not working
I think you're right. I just assumed as there was no bridge rectifier in the supply circuit it needed DC and having a battery backup hard wired into the circuit just confirmed my idea.
Model no is DVD K1 made by Accoustic solutions, Northampton, uk.
I'll dig out an ac adaptor, try it and let you know.Leave a comment:
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Re: Kareokee amplifier not working
voltage across c27 is 0 ( this is a new capacitor), voltage across c25 is 11.22v.
resistance across c27 is 3M and across c25 is 4M.
I pulled the KA7909 to see if that affected the readings but there was no difference so I soldered it back.
What puzzles me is that the negative voltage regulator requires a negative input voltage. How is this achieved from a positive dc supply?
Thanks for taking interest.Leave a comment:
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Re: Kareokee amplifier not working
I made a school boy error running track to + of capacitor. Please see last 3 photos attached. I removed tracks and capacitor to show existing track, then wired in new track from D5 linking at capacitor -C27 then to input of KA7909.
Still no joy I'm afraid.
Voltage readings taken are;
Across D3 0.73v, D3 + to grd 11.33v
Across D5 11.84v D5 - to + rail 11.84v
I'll remove KA7909 to see if was pulling down voltage....Leave a comment:
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Re: Kareokee amplifier not working
Thanks for taking the time to reply. I haven't put a jumper in, I've just followed the circuit board track exactly. To +capacitor c27 coming from -d5 M1 diode is long wire. From - capacitor c27 to pin 2 of KA7909 is short wire. I had to run new wires from both sides of the capacitor as the track terminals at the capacitor just disintergrated when I desoldered.Leave a comment:
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