Sorry to bother you, but I have a problem with my GRUNDIG R20 HiFi receiver.
Namely, it spent a long time in the closet and my son decided to use it.
When switching on, after 10 years of use with the old speakers, the speaker on the right channel made a short circuit.
I understand that because it was stored in the garage for a long time (more than 20 years). To cut it short, my Darlington transistor G8004 burned out.
I replaced all output darlington transistors with new BDX54C / BDX53C and when they burned out (I was guiltyfor this) I also put new BDX34C / BDX33C.
I examined the correctness of the other transistors in the assembly and after some component replacements when adjusting biasing the quiescent (30 mV .... between test points x and y) current, the BDX33C exploded.
This happened when adjusting the quiescent current of the right channel to 30 mV.
I'm lost, now I install new darling transistors BDX34C / BDX33C (I have new BDW47/BDW42 .... this is for reserve).
I put new trimmers for adjusting ... 1kOHM.
I put trimmer to minimum and system operata .... no burning but I'm afraid to start adjusting more than 6mV.
My trimmer on the right channel was on maximum and I adjust biasing the quiescent to 6 mV
According to my calculation, the adjustment value should be a maximum of 9 mV and not 30 mV as recommended by Grundig in the HiFi Receiver R20 documentation.
I'm making a mistake somewhere with the settings or it's a problem that I don't see.
OK I can change the smaller trimmer but I'm not sure my darlin transistors will withstand 30 mV ..... as per the R20 documentation.
Please help if you can and thanks for your patience.
Best Regards,
BrankoPetra
Namely, it spent a long time in the closet and my son decided to use it.
When switching on, after 10 years of use with the old speakers, the speaker on the right channel made a short circuit.
I understand that because it was stored in the garage for a long time (more than 20 years). To cut it short, my Darlington transistor G8004 burned out.
I replaced all output darlington transistors with new BDX54C / BDX53C and when they burned out (I was guiltyfor this) I also put new BDX34C / BDX33C.
I examined the correctness of the other transistors in the assembly and after some component replacements when adjusting biasing the quiescent (30 mV .... between test points x and y) current, the BDX33C exploded.
This happened when adjusting the quiescent current of the right channel to 30 mV.
I'm lost, now I install new darling transistors BDX34C / BDX33C (I have new BDW47/BDW42 .... this is for reserve).
I put new trimmers for adjusting ... 1kOHM.
I put trimmer to minimum and system operata .... no burning but I'm afraid to start adjusting more than 6mV.
My trimmer on the right channel was on maximum and I adjust biasing the quiescent to 6 mV
According to my calculation, the adjustment value should be a maximum of 9 mV and not 30 mV as recommended by Grundig in the HiFi Receiver R20 documentation.
I'm making a mistake somewhere with the settings or it's a problem that I don't see.
OK I can change the smaller trimmer but I'm not sure my darlin transistors will withstand 30 mV ..... as per the R20 documentation.
Please help if you can and thanks for your patience.
Best Regards,
BrankoPetra
