Philips B3X85U troubleshooting

[Abraham]

I recapped my b3x85u but I'm still not getting any sound. All tubes light up, but no sound checked speaker and works fine. Any ideas?

[Steve_P]

Are you sure all the capacitors are in the right places? One error... Also check the speaker and output transformer.

Check for HT first. The rectifier is a UY42 and check it's cathode for DC volts. Also is the Magic Eye lit. If it is and they are, then check for HT on all th valves. The output valve is a UL84 and there should be HT on the Anode and Screen Grid. (Pins 7 and 9). Als0o check the cathode resistor Pin 3.

There should be HT on the other valves too, the UBC81 (Pins 1 and 2) and the UF89 (Pins 8 and 9) and UCH81 (Pins 6 and 8). Again, check the cathode resistors too.

We don't have a circuit for this set to hand, but it's an easy one to work on.

If the Magic Eye is not lit and there is no audio, check for AC on the anode and check any anode feed resistor.

Hope this helps.

Cheers,

Steve P.

[vinrads]

I know it's a daft question but did it work in a fashion before you recapped it?

If not some basic fault finding will be req.

[Abraham]

Sorry for the delay, I was searching for new tubes, and just received them and had them installed, with exception of the magic eye, which I rewired since the tube socket was brittle and broke apart. All tubes light up fine. I measured the ohm on the transformer leading to the speaker and measured 1748 ohms. But I still dont get no sound at all not even an static whatsoever (dead). By the way connected the speaker with another radio an speaker works fine. Any suggestions. Would any picture or video help? Thanks again.

[Steve_P]

Abraham - do you have any test gear and any knowledge of radio repair? Just because a valve is lit does not mean it's working.

Tell us the level you're at and we can take it from there.

Cheers,

Steve P.

[Abraham]

I guess I'd call myself a beginner. As far as test gear, I only have a multimeter. I also have the schematics. When I recapped the radio, I only recapped the capacitors which were above 3000 PF which were about 15 of them, and the electrolytic capacitor which was the only cylinder coin like.

[Steve_P]

Fine. We'll do this in stages. Position the set so as you can get to the valves underneath. Make sure nothing can short out, Switch on and wait for about a minute. Meter to DC volts, 1000v range. Black to Chassis. Go round the pins of the O/P valve clockwise and tell me what is on pins 7, 9 and 3.

http://www.r-type.org/exhib/aai0038.htm

Then turn the set off and tell us what you find.

Cheers,

Steve P.

[Abraham]

Hi Steve, I checked the valve and it measured on
Pin #9 - 106.1V, Screen Grid
Pin # 7 - 122.7V, Anode
Pin # 3 - 5.68V. Cathode

This was on the UL 84 Valve. By the way what does the O/P stand for.

Thanks, Abraham

[Steve_P]

O/P stands for Output. Sounds like they are low, but that should work. Put a screwdriver on and off the center pin of the volume control. Do you hear a crackle in the speaker?

Check pin 2 of the UL84. If it's in any way positive, trace it back and you should find a capacitor going to the next valve, a UABC80. This is called 'That capacitor' and it probably needs changing if it hasn't already been changed.

Thanks Station X by the way.

Cheers,

Steve P.

[Abraham]

when I check pin #2 on the UL84 valve, how would I know it is Positive. Also, the capacitor that I traced to the next vavle was changed 10nf or10000pf.

On the volume control there are 3 pins on the bottom then another 3 pins above that, and another pin on the right side with a resistor attached that goes to a capacitor which I also changed.

[Abraham]

Here's a Photo of the back side of the radio

[Steve_P]

The meter should tell you. If it's a moving coil it would go forwards if it was a positive, back for negative. If it's digital, it should say on the display,

Touch both of the center pins. One is Tone, One is Volume.

Cheers,

Steve P.

[Abraham]

I also want to mention that there are some capacitors which I did not change since someone had said that those capacitors below 1000pf do not need to be changed. In total, they are 19 of them ranging from 4.7 pf to 470 pf which is the highest. Should I change those also? Thank again.

[Steve_P]

No. Let's find the fault rather than change parts willy nilly.

Cheers,

Steve P.

[Abraham]

The Pin #2 measures 4.4 and it is positive. The volume tone pins do not give no crackling noise whatsoever. It's a completely dead sound, like if it did not have a speaker.

[Abraham]

Please advise me if you need any particular pics.

[Steve_P]

Well check that capacitor again and make sure it's right. Check wiring and then try a new UL84 if you can.

Cheers,

Steve P.

[Abraham]

Is there a way of checking that capacitor? and the UL84 that I have it's brand new.

[Station X]

THAT capacitor will be connected to pin 2 of the UL84. Disconnect it from pin 2, but leave the other end connected. Bend the disconnected lead clear of the pin.

Connect your meter negative lead to chassis. Pin 2 should now read zero. Measure the voltage on the disconnected lead of THAT capacitor. If you get a reading THAT capacitor is faulty.

[Abraham]

Alright now, THAT capacitor does not give a reading, it measures 0. But pin #2 measures minus - 00.8