Cossor 523A Quiet on FM

[gary_crutchley]

Hi all,

I've been looking at this issue again.

I changed C3, followed by C2 but there was still no great improvement on FM after either change. I am getting just one station, slightly louder than before and it appears undistorted. So there is some promise there.

I've now measured the voltages on V1 in the FM can with my Avo 7, clearly something is wrong:

1. 72V
2. -0.2V
3. 0V
4. 6.0V AC
5. 0V
6. 65V
7. 0V
8. 0V
9. 0V

The readings were taken with the set on FM, with chassis connected to negative. I think there are some remaining waxies under the chassis, and at least one Hunt's cap.

Any one got any ideas on what's going on?

Regards,

Gary

[gary_crutchley]

Hi all,

I changed first C3 then C2, but still little improvement in FM volume. I can get one station, but the volume remains low. The audio does not appear to be distorted.

I have now measured the voltages on Valve 7 (As per the Cossor service sheet), and got the following results:

1. 72v
2. 0v
3. 0v
4. 6.0v
5. 0v
6. 65v
7. 0v
8. 0v
9. 0v

The measurements were made with my Avo 7, with the set on FM.

Looking at the data for the 6AQ8 (I have an ECC85 fitted), that it looks like the voltages on pins 1 and 6 look low, everything else seems okay to me. Any ideas anyone?

Regards,

Gary

[Ambientnoise]

Suggest you check the voltages around V2 and V3 also, when switched to VHF. There are several switched functions around there.

The ECC85 voltages look a bit low but ok. I suspect that the resistors feeding it have gone somewhat high.

Ken

[gary_crutchley]

Hi Ken,

Thanks for your help. I will check the other voltages over the next few days and post the results.

Regards,

Gary

[gary_crutchley]

I meant to ask, in the table of voltages given in the Cossor service sheet, some readings are listed as "0", whereas others are "NR" (No reading). What's the difference and how would I differentiate please?

Regards,

Gary