philips: Philips B6X43A Bass and Treble Controls Not Functioning
I’ve replaced the electrolytic capacitors on this beautiful radio, but the bass and treble controls are not functioning in any mode. I have the schematic for the unit, but am unable to locate the controls on the diagram. The schematic and other literature I have on this model are in Dutch, further confusing things.
The radio has no paper caps, but instead Philips/Mullard “Mustard” capacitors which I understand are a type of poly and considered reliable. None of these have been replaced. If I could make sense of the schematic, I would undertake substituting some of these where relevant to the bass/treble circuit, but I don’t want to start replacing with no real direction.
I quickly tested a couple of sections of the tone controls and they seem to be varying resistance fine on an ohm meter. As both controls aren’t functioning, I don’t suspect that the controls themselves are faulty.
Interestingly, the radio has push button tonal controls which are functioning correctly. There are three selections labeled Fidelita (full fidelity), Modesta (medium fidelity) and Parola, suitalble for talk. I imagine these are useful with the AM broadcasts to quickly minimize RF noise.
Any help or insight would be appreciated.
Minutes after typing this post, I decided to recheck the literature I have on the radio. As I said, everything is in Dutch. Well, typing the following text from the manual into Google translate:
“Toonschakelaars wanneer een van de toonschakelarrs is ingedrukt, weekend de large en hogetonenregelaars niet” revealed the answer to my problem:
”Toggle switches when one of the key switches is pressed, the low and high speed controller do not work.”
That was enough for me to realize that the tone switches that I mentioned do not have to always be activated. If you ”half press” one of the unelected switches, they all become deactivated and the bass and treble control become active.
So, everything was working fine after all! Very happy here.
My only remaining question regarding this radio is that when using the tape input with an iPod, etc. the fidelity is not quite as good as when using FM. Mostly the bass seems distorted. I’ve tried this both directly and with an isolated audio transformer which boosts the gain, getting the same result. Sounds good, but not great.
1) If a mono input: use 2 x 33 Ohm between 3.5mm L and R and common to radio. Optionally add 68 Ohms to ground on L and R if there is distortion.
2) If a stereo input, then put 33 Ohm from L to ground and R to ground of 3.5mm jack and connect direct.
Some gadgets need a low resistance (30 to 200 Ohms) path from the output connection to the ground connection to work. If that is not needed, then the two combining resistors ( type 1a) convert stereo to mono. You'll get distortion if you short L to R to get mono.
Make sure there is no equaliser setting or app on any iPod, MP3 player or phone.
Thanks, Michael. I had tried adding various resistor values before this to no avail. I tried your specific values just now and the resistors seem to make no difference to the sound. Again, the sound is good, but the low frequencies (this radio does produce hi-if sound) are not quite solid when using the iPod/tape input compared to the FM quality. I can fool myself into thinking the iPod/tape input sounds fine, but when switching to a good FM station, the difference becomes immediately apparent. Adjusting the volume on the iPod headphone output helps, but at the best level, the quality still isn’t quite there.
The tape and phono leads are linked with resistors at the input jacks on this radio. I have to take a closer look to see what exactly they’re doing, though. There is one selector switch for “PU” (pickup), but two jacks. One is the stereo DIN connector I’m using for tape input, and the other is a banana type for phono. I may try circumventing the resistors at the jacks and feeding the iPod input directly to the coax cables to see if that helps. There may also be a capacitor in the path that needs checking.
Any additional thoughts, much appreciated.