[alf]

Hi All,

just working on a problem with my BG4000:

the 45rpm does not work !

replaced the speed relay with a modern smd one….no luck.

1TR7 and 8 tested fine, 1TR5 and 6 show 5.85 VDC and 23.8VDC at the collectors.

manual switching from 33 to 45 changes the bulb but platter motor stops.

switching back to 33 platter motor spins as normal again.

what else could be responsible for that issue ?

any pointers or help is most appreciated.

thank you

ALF

[spassmaker]

Hi Alf

Voltages that you measured are OK for 33 RPM.

The relay is in off position when 33 is selected.

If you switch to 45 can you hear the relay klicking? With the new one go to next with your ear to the relay.

If 45 is selected the voltage at TR 6 should drop to near zero volt, as the relais should engage.

The relay is switching the resistor networks 1R8 to 1R13

 

The following part of the circurit is same for both speeds as far as I can see.

A further possible fault could be the caps to the motor 0C6 4700uF and 0C7 150uF BIPOLAR

A hint is mentioned : I’m not sure but the lightbulb 1IL1 is used for the start of wien- bridge, so check if the bulb is OK

Recapping is recommended.

 

Regards Christian

 

[Dillen]

When in 45RPM, does the motor pulley vibrate if you feel with a finger, or is it completely still?

Martin

[alf]

Thanks Martin & Christian fir replying.

Yes, with the “finger-test” I can feel the motor vibrating but not spinning at 45rpm.

Question is what course of action I have to engage with ?

ALF

[hcraig244]

Alf

The service notes say “speed switching (33-45rpm) is performed by altering the values of R1 and R2 so that the oscillator frequency will be approx 42 and 59hz respectively” seems to me if everything works fine on 33rpm that the oscillator is working fine, could be wrong of course…….have you checked the trimmers and associated solder connections?

Craig

[Dillen]

Check the motor phase adjustment.

Martin

[hcraig244]

Martin

Whats the best way to do that?…..

Craig

[alf]

Hi Craig,

adjusting 1VR3 in combination with fine adjusting the 33 & 45 trimmers dud the trick.

if you listen to the motor noise you get a good feel when its right.

and thank you Martin, I feared there was more serious stuff to investigate…..

its back to working order 🙏🏼

ALF

 

[Author]

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