Anyone else having a bad week?

[Mike Watterson]

I was fixing a CB and it had no RX audio on speaker, but speaker was OK. Audio out OK on amp. Mysteriously the earthy end of speaker went to mic socket, but the mic plug had no wire on that pin!
So went and found schematic for mic for that actual model and found the PTT switch earths speaker on RX and earths TX to on when pressed. Odd. But I left it as it was and wired the mic to suit. It did have a four core cable, but no connection on the normally closed on PTT and none on plug. Both ends 4th wire cut flush. Can't have been original mic?

[Paul_RK]

A Murphy B485 transistor. Spent a frustrating half hour getting it out of its "leather" carry case, why did they make these such a tight fit?

I don't think they did - if memory serves the stuff is called Neohide, and it shrinks. Somehow I've never had a B485, but its immediate predecessor the B385 is much the same set in much the same case, and my acquaintance with those stretches back about 54 years. I'm just about sure the one I had in 1969-70 slid in and out of its case with reasonable ease - worked nicely too, and I must have fed it several pairs of PP1s. By ten years later the case was decidedly tight, and the one I have now - it's as well that the wide black plastic escutcheon at the top isn't mirrored by a wide pedestal at the bottom, or the case could only be removed by surgery.

Paul

[Mike Watterson]

So like some celebs famous only for being celebs ...

[boater sam]

On the Murphy B485, decided I need a pair of output transistors.
They are XC131 and the leads are so rusty that they snap off when I look at them.
Listed equivalents are OC72, crazy prices, or AC128 which will have tin whisker problems and still daft money or 2N2431 which no one seems to sell.
Can any other suggestions of what will replace these at sensible i.e. cheap, price be forthcoming from our esteemed members?

Life is so much simpler with valves...........

[ppppenguin]

Try silicon and re-bias. Very ordinary devices like BC558 ought to work. Try what you've got in the spares box.

I've just looked at my stock of transistors and realised that I may be sitting on a fair bit of money. In practice I'm hanging on to them as potential spares for our professional kit at the BECG.

[Murphyv310]

Hi.
A bad week.......... A bad few weeks!
1, Heart problems..... Need a pacemaker.
2, Prostate operation..... On hold.
3, Spinal stenosis..... Numb in left leg and tingling hands.
4, Diamond X50 collinear antenna bought S/H duff.
5, ZL special antenna bought S/H duff.
6, Sold all my vintage collection, so less stress, that's one positive outcome. Just two to go now.
7, HMV 1804 to complete for a friend which is awaiting the return of the rewound EHT transformer, then to do more work on a 1947 Philips Radio/TV for the same person, then strictly no more vintage repairs for anyone. Had my fill and time for myself and family.

[Radio Fixer]

Mines been a good week.

Sorry for you Trevor, your health problems put it into perspective. Hope they turn out OK.

Gary

[boater sam]

The selenium diode stack gave inconsistent readings, so I have substituted a pair of 1N4007s.
I found a pair of AC128s and that restored the audio output. Setting the quiescent current is tricky now, the sliders are almost at the zero ends. In fact with them hard up against the stop there is still 0.8mA and it is impossible to get less than 2.2mA when they are moved away at all. I can live with that.
Difficult to arrange a heat sink, the XC131s are in their own dual heat sink that the AC128s will not fit. However running the set at high volume the transistors are still cold so I will just anchor them to the aluminium plate with hot melt.
Receives Gold on MW, twice! Nothing else and LW is silent. I suspect the twiddler has been here, the LW aerial trimmer is very loose.

[boater sam]

This set construction is terrible.

I thought I had replaced all the electrolytic capacitors, every one I have found is duff. Some have huge leakage, others are open circuit. Some think that they are resistors.

Thumbing through the service sheet I realised that I has not found C18, the de-coupler between the oscillator and the mixer transistors.
When I found it I wished I had not. Buried in the metalwork at the end the wave change switch, hidden  behind the external aerial socket which thankfully is held by only one hard to get at screw.
One end is completely inaccessible on a multiple earth tag, the other is through a rivet and wrapped, twice, round the tag on the paxolin of the switch.
Managed to unsolder one end, fatigued the ground connection to remove it and test. Totally useless as a capacitor. I have never before had a transistor radio  where every electrolytic capacitor is duff.
The replacement went in connected to the tag and another more convenient ground.
Stressed and out of time, seeing if it works any better will be for next week.

[Mike Watterson]

4, Diamond X50 collinear antenna bought S/H duff.

You can open them. There is usually a coil and capacitor in the base and the ceramic capacitor can fail either due to too much power or mechanical stress.