ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
What do you measure at the connector for the keypad (P7) pin 6 when you press ">"? Do you get around 21V?
-sonavor
Excellent diagnosing
Martin
Okay, so that is about right. The ">" switch simply connects a 21V rail down through the 1R57 trimmer through diode 1D31 and to the base of 1TR24.But you are not seeing it reach base of 1TR24.
We must also have a miscommunication on the service manual adjustment for ">" and the 1R57 trimmer though. I thought you said earlier that you adjusted 1R57 so when ">" was pressed you measured 3V across the servo motor. I think you need to recheck trimmer 1R57 to see where its adjustment is set at. From what you are saying there is almost 20V on one side of the 1R57 trimmer so lets see what happens after it goes out of the trimmer.Press ">" and either measure the node of the 1TR24 base or measure across the servo motor. Or just measure the other side of the 1R57 trimmer (the node between 1R57 and the anode of 1D31). Adjust 1R57 and see whether you can get a voltage at either place.
My short term memory is going. I checked on the previous posts and you did say that you have no reading out of trimmer 1R57 for the ">" function.
So either the trimmer is faulty, not soldered in good or way off on its adjustment. As in my last post try that measurement for the ">" function again and monitor the measurement as you turn 1R57.
Yes, good. So the control voltages are there at the 1TR24 transistor but they don't get to the motor.
So now you can suspect the path from 1TR24 to 1TR23 to the motor lead. You said earlier that you replaced 1TR23 (it is one of those transistors in your photo that was marked in red). Why did you think the original 1TR23 was bad? Try putting the original back in place.Check the voltage from the 1TR24 emitter to the 1TR23 base to see what the voltage is there when ">" is pressed. Just to cover everything, measure what the voltage is on the collectors of 1TR23 and 1TR24. It should be about 21V.
In this case start with the power supplies of the Beogram 4002.
Turn on the unit and make sure all of the main voltages are present.
Always completely unplug the Beogram when changing something. Be it removing a component or moving a test wire. I like to use small micro test leads to attach to measurement points then attach the other end of the leads to my multimeter leads. Testing with a mulitmeter where you are manually holding the two leads on the wires you are measuring is too risky. One slip and you can short (and burn out something).Also be very careful on the Beogram of the four pin power connector that connects to the main board. The plug for those power wires are male pins. So if the Beogram is plugged in then those pins are live wires and very easy to short.
Some of your voltages have to be okay if the solenoid is operating. Check the places that should have 21 volts. The solenoid uses 30 volts so it sounds like that voltage is there.
It sounds like you are trying to diagnose too many issues at once.Also, when specifying the measurements please state the full designator. Otherwise it isn't clear. For example, when you just state a measurement at a pin number it doesn't qualify which connector the pin is on. So please state the connector and the pin. Same with transistors and diodes. You need to state the pin for the specific component.
Regarding the amber light as you put it, I take that you mean the arm position lamp 4D1. When you say it is not illuminating but functions with the "good" board do you mean that the lamp illuminates when the good board is plugged in? If 4D1 is not working then you will have about 10V at the collector of 4IC1. If 4D1 illuminates with the other board then I would suspect the 1TR18 transistor but you would need to verify what the DC voltages are at the 1TR18 collector and the base. The 1R88 trimmer must allow the base to turn 1TR18 on sufficiently to send enough current through 4D1 so that the 4IC1 device has 5 VDC at its collector.
On the servo motor voltage I would like you to measure each motor lead to ground instead of measuring across the two motor leads. I would like to see what each DC voltage is with reference to ground when ">" is pressed.The chart there on the service manual below the diagram for the servo motor (OM2) shows what the expected (approximate) DC voltage to ground will be for each operation (">>", "<<", ">", "<"). I think making those measurements will give a better picture of what is going on. So state the left side (">" side) measurement as P5-2 to ground and the right side of the motor ("<" side) measurement as P5-4 to ground. That will be clearer.
Hi The Motor voltages (OM2) with the negative terminal to ground are as follows:
OM2 motor
Off>> = 00.4v
On<< = 11.9
> = 11.2v
< = 10.2v
I will try to convey the information more clearly.
*‘Regarding the amber light as you put it, I take that you mean the arm position lamp 4D1. When you say it is not illuminating but functions with the "good" board do you mean that the lamp illuminates when the good board is plugged in’?
Yes that’s correct.
Yes 4IC1 is measuring approx 10v
1TR18 voltage at base = 00.1v
1TR18 voltage at the collector = 00.1v
Struer : Hi The Motor voltages (OM2) with the negative terminal to ground are as follows: OM2 motor Off>> = 00.4v On<< = 11.9 > = 11.2v < = 10.2v I will try to convey the information more clearly.
I need to see those measurements from both leads of the OM2 motor.
In otherwords -
From the black wire to ground will be one set of measurements.From the red wire to ground will be a second set of measturements.
Thanks,sonavor
Struer :Thanks for this. I’ve learnt a lot and now can see Some issue with the voltmeter. Slowly but surely Red terminal > = 11.2v Black terminal >=11.2v Red terminal Black terminal Red terminal < Black terminal < Red terminal >>=00.7v Black terminal >>= 00.7v
Some issue with the voltmeter. Slowly but surely
Red terminal > = 11.2v
Black terminal >=11.2v
Red terminal
Black terminal
Red terminal <
Black terminal <
Red terminal >>=00.7v
Black terminal >>= 00.7v
That sheds new light on this problem.
We have been looking at why ">" does not function and were observing that the voltage across the motor leads for that function was zero.However, you later reported that the voltage for the 1TR23 for ">" was around 11 VDC. So now we see that the opposite motor lead, that is controlled by 1TR20 and 1TR22, also has about 11 VDC on it. That makes the drop across the motor zero so the motor does not turn.
Now, 11 VDC for ">" is not a good voltage level. Per the service manual chart the ">" side of the motor lead should be at around 5.5V and the "<" side should be at around 1.4V. But that should be able to be trimmed out with 1R57.Meanwhile, the left side of the motor drive circuit appears to be where the failure is. Why is that side at around 11 VDC when it should be 1.4V ?1TR19 and 1TR20 was where I believe you saw remnants of some heat scorching of the circuit board.
Your ">>" voltage levels are not good though. You should have 1.4 V and 13.5 V.Can you fill in that service manual chart with your measurements?
Hi, having had very little luck the past few days, it seemed the repair may have been a step too far.
I decided to clean the board around some of the suspect areas, revealing some damaged traces. So I re soldered using two jumper leads between
R87 and the base of (1TR18) and another jumper between the trimmer (R88) and the base of (1TR18) . The result is that the arm position lamp 4D1 is now illuminated. The trimmer (R88) now increase and decrease in voltage (brightness of the bulb).
(>, <, >>, <<) are still unable to control the the servo motor (OM2)
The servo motor (OM2) voltage is now adjusted with variable resisters (R56) and (R57)
*I replaced (1TR18) with a new (BC547BTA NPN Transistor, 100 mA, 45 V, 3-Pin TO-92)
Struer : (>, <, >>, <<) are still unable to control the the servo motor (OM2) The servo motor (OM2) voltage is now adjusted with variable resisters (R56) and (R57)
That leaves me unclear on the exact status.The forward and reverse operations from the button panel don't function? But you can adjust voltage at the servo motor?So are you manually moving the tangential arm assembly so the Beogram will be on (so the arm position sensor lamp illuminates)?I am a little confused here.The R56 and R57 adjustments are for setting the voltage when "<" and ">" are pressed so if those don't function I don't see how those could be set.
Hi thanks for your input recently.
After taking a break from the problem and re addressing the main board at the output of P5, I replaced 1Tr23 again with one that definitely works. I also replaced TR18 with a new transistor.All is working now.
That leaves a faulty Board 8005017, I know this as it took out another board in the same way.
So the fault must have manifested in this board and caused the damage and burn to the main board under TR20. Is the cause most likely due to a failure of the right microswitch or the two resisters?
At this stage I’m not going to plug Board 8005017 back in and run any tests. It might be safer just to replace the two resisters anyway?
Thanks again for in depth diagnosis