BX645A - follow up (Techniek Radio/TV)
door Pandu Rajan 
, 20.09.2024, 10:34 (62 dagen geleden)
Dear Mr Sieme
You were king enough to explain to me the working of the motorized band switch for the above set. As the set was under restoration I had not powered it ON. Recently I have completed the restoration and checked the voltages with all the valves in position. Then I decided to check the working of the motorized band switch. I carried out the following checks:
1. The band switch adjusted correctly to KW2a position.
2. Removed the EZ80 valve so that no HT to all the valves.
3. Released all the 6 switches of the 6 bands.
4. Fitted Z1 fuse.
5. Switched ON the power.
6. The motor runs continuously in forward and reverse direction without stopping. It should stop in part of the one revolution of the motor.
7. I checked Switch S7 and is always ON. Is this the reason for the continuous operation?
8. What Next I should do?
Regards
P.Rajan
BX645A - follow up
door Sieme , Niekerk, 20.09.2024, 16:53 (62 dagen geleden) @ Pandu Rajan
Dear Mr. Rajan,
This looks like a Sk7 failure ,short circuit.
It should open in a rather smal sector of each revolution of the outgoing motorshaft
in order to position the contacts of Sk6 , well in between open and closed. With all
bandswitches released ,stop should occur after each manual repositioning of the motorknob.
Turning the motorknob by hand with power to motor only should reveal the open sector,
if not,Sk7 has a sticking contact and will need open hart surgery,
Best wishes ,
Sieme
--
het experiment heeft altijd gelijk
BX645A - follow up
door Pandu Rajan , 22.09.2024, 07:23 (60 dagen geleden) @ Sieme
Dear mr Sieme
Thank you very much for your reply. I had loosened the disc screw mounted on the band switch and May be this was causing the motor to run past the open sk7 zone as there was no load. I opened the connection of sk7 and checked the switch and it is working correctly. Resoldered the connection of sk7 and readjusted the three discs. Now the motorised band switch is working correctly on kg2b to kg2d and kg3. On kg2a it is not working correctly as the motor does not stop. On MW the supply is tripping which I think there is some short which I have to check
Regards
PRajan