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Re: Philips Mod B5X34A/54 FM Reception
Geschreven door Richard Mensch - Pe2RM om 25. Jun 2001 10:55:41:
In reactie op: Philips Mod B5X34A/54 FM Reception geschreven door Ken Foshee om 19. Jun 2001 06:25:43:
> I can read a little Flemish but I am going to post this in English. I have a Philips Model B5X34A/54 Multiband receiver that I'm very proud of. It is a great receiver except for 1 problem. When I first got the radio it would not receive any FM stations and I replaced the ECC85 tube and it received stations all over the band. As the radio or tube warmed up, the tuned frequncy would go silent then I would tune a lower frequncy OK and then the same results until I had tuned to the lowest frequncy and then all frequinces were silent. I ordered a replacement tube and same results. I am an amateur collector/repair person and need advice on what to check next.
>All and any help is appreciated.
>Ken Foshee
>Alabama, USAHi Ken,
I have spend weeks with repairing an FM tuner, troughout completely rebuilding it, but after a few minutes of warmup the tuning keeps walking. The probleem was simple, the heatingvoltage of the ECC85 was dropped below a critical point (in this case 5.9 volts) and the oscillator became on a critical unstable point. The low heating voltage was caused by an bad (not blown) fuse.
If the tuned frequency suddenly goes silent (i.e. blops away), then the defect is almost a mechanical contact problem in the tube area of the tuner. Check the tube feet contacts, does they have a good contact with the tube (dust or dirty), are the soldere joints ok. If the tuner has variable capacitor tuning, check the little wiper contacts of the tuning capacitor, they can be very dirty due the grease of the bearings. If al these mechanical items are ok, then check the caramic tube capacitors of the tuner, try to use some coldspray on them (be carefull, there is at last 200-250 volts in de tuner unit.) I always try to spray in the tube of the capacitor to be sure that i cool down only the one i want. Don't freeze the capacitor body, just cool them. Don't be surpriced that some of the capacitors are very sensitive for the spray. the trick is to find the capacitor that restores the tuned freqency, with a very little spray. This capacitor looks good but can have an (invisible) crack in the ceramic body.
I hope my notes are usefull for you.
Best regards
Richard