1154/1155 question.

[G4YVM David]

My working pair has started playing up. The 54 still transmits but on the wrong freq - I'm sure it's a cap that's gone because everything works, just not where it should be!

However, whilst the receiver is still beautiful to listen to, as soon as I put the Tx power on everyone gets Dalek voices! Considering I have not done anything to the sets, not even moved them, in the last few weeks since last switch on, I'm wondering what this could be and whether it might be the harbinger of further woes!

I struggle with time as well as skill so if there's anyone who enjoys fettling the 55/54 I'd love to hear from you!

D

[GW3OQK Andrew]

David, I'm fettling my 54 at the moment and was thinking of asking for advice!

The Dalek voice sounds like 50/100Hz hum or buzz. Is the TX 6v still pure DC without ripple? I suppose that's the only live transmitter voltage when in off or standby position Do you hear it on headphones plugged into the 55 or from an external amp?

73, Andrew

[Keith]

Hi David,

When you say the 1154 is transmitting on the wrong frequency, what sort of discrepancy are you talking about? Worth trying some contact cleaner on the band switch and the variable capacitor rotor contacts, perhaps, before you start disconnecting things. Re the "dalek voices", I'd be surprised if it was caused by ripple on the 6V - some people run 1155 heaters on AC without problems.

[G6Tanuki]

Originally Posted by Keith

Re the "dalek voices", I'd be surprised if it was caused by ripple on the 6V - some people run 1155 heaters on AC without problems.

Agreed: I've used 1155s to receive CW/SSB and never had any problems running the heaters off AC.

I'd be looking for a source of ripple getting on to the local-oscillator or BFO HT . Could be worth trying to listen to the LO using another receiver (with its the BFO on), to see if there's any sign of roughness or wibbles.

A high resistance in the earth cables between TX and RX and PSU could be injecting AC hum from the TX filament current into the receiver HT; given the heater current of the TX valves you don't need much common-impedance between heater and HT wiring to cause a few volts to appear in the wrong place.

Also check the rectifiers in the PSU: in the past I've seen kit continue to work, after a fashion, when one of the rectifiers in a classic two-rectifier-and-cente-tapped-transformer has given up the ghost. Hummy HT and 'being a bit down on volts' being the only symptoms.

[GW3OQK Andrew]

Keith, I was referring to the Transmitter 6v which I believe has to be DC for the big relay. The Receiver 6v can be it AC or DC.

David switches on the TX PSU, (TX on standby, HT off, presumably) and the RX goes Dalek. That sounds like some AC/raw-rectified common-mode effect to me. I'd fix that before looking for an off-freq problem.

By the way I have modified my red-range MO to make it drift very much less on 80m so its better for CW, CW being my main operating mode. I'll start a new thread about it if anyone is interested.

73, Andrew

[G4YVM David]

Thanks chaps. Yes, tx on standby or even off, so long as its powered i get the dalek voices. Ill investigate but time is such a rarity.

When i say my tx is off freq its off by maybe a full megaherz or more. This rather happened overnight, so to speak. Mind you, so did the dalek voice.

D