T1154 re-awakening

[G4YVM David]

I thought I'd start a new thread for this because the topic has changed slightly.

I fitted two new PA valves to my Tx today and we (me and another chap who has much experience with military valved gear, though not '54s per se) fired it up.

No smoke,...always a good sign. Some Rf too...a few watts (2 to 4) on some bands, but after a mornings messing we got about 80 on 80m.

Strange few problems that need addressing but some folk might have a clue:

The worst is a very sluggish relay - CW speeds above about 8wpm -ish dont cause it to operate.. The relay flops side to side when the radio is tilted, but whether it flops enough...? So, not sure why it is very sluggish on changing over.

Low output power. Some bands a handful of watts at best.

On 40m band the right hand top blue capacitor has no dip effect at all - yet oddly the middle red one does. This also causes a total drop when it engages with the cam follower, so there's something electromechanical going on.

Finding a dip is difficult on most bands: impossible to get the amps below the green line!


Caps 15 and 16 - top and middle right hand side - if I engage or 'wiggle' them I can get crackling on Rx (the Rx RF goes through the Tx)

Some of the faults started to resolve themselves as we worked through the morning so we both suspected corrosion etc which was starting to wear off.

Anyway, there we are...it almost works.

David

[Keith]

Hi again David,

Glad to hear that you've now acquired a T1154 and are making progress. I wonder which model you have? If it's a T1154M like mine I can tell you the approximate PA settings into a 50 ohm load on 80m and 60m (haven't used mine on 40m). Obviously, if you're not getting a dip in PA current, then the tank circuit is not at resonance so you won't get much power out.

ISTR that the keying relay was a bit sluggish on mine and I added an additional light spring to give it a hand. Bear in mind that the 6V supply is used to return the relay to the receive position so worth checking this voltage under load. Using the relay, mine will key up to about 10 wpm but any faster and I think you need to use the bias keying arrangement mentioned in another thread. I think this means keying pin 14 on plug B but I'm not a CW man so I've not tried it.

73

[G4YVM David]

Thanks Keith,

Mines an M too. I really need 15wpm as a min, I'd prefer 18 -20 though so may have to do that mod.

Just rushing out...more later

D

[GW3OQK Andrew]

David, mine's another M and the relay is not floppy at all when power is on, pulling strongly to the receive side. Is your contact A7 ok? It operates at 20 wpm, provided I have short thick wires to the WT8Amp key. I used 6.3v DC with plenty of current capability so the voltage does not drop.

Sounds like you are well on the way to success
73
Andrew

[Keith]

David,

Tuned up my 1154M on 40m (7.1MHz) last night (into 50 ohm load). Settings were as follows:

Blue tap position - 2
Blue PA capacitor position - reference mark aligned with C on knob.

On 80m (3.615MHz), settings are:

Red tap position - 3
Red PA capacitor position - reference mark between M and L on knob.

X/N link - X uppermost

Both gave ~25W output in the RT position.

Hope this helps.

[G4YVM David]

Thanks all. I'll try shorter wires to the key.

Made two qso today on 80m, one on fone and one on cw. Very, very satisfying.

D

[trh01uk]

David,

the keying relay is somewhat unusual in that has three separate coil windings - see schematic. The manual says it will operate up to 25wpm, so clearly your relay is either faulty, or you have the wiring wrong, or perhaps your LT supply is not man enough for the job? I think the relay can take as much as 4 amps.

According to AP2548A, coil A is the receive coil and is always energised. You should hear the relay snapping into the receive position as you turn the power on. The B coil neutralises the field from the A coil when the key is pressed. Coil C is also energised with the key down, and provides the force to push the relay to the transmit position.

I would get in there with a DVM and make sure the voltage is as expected on all three coils.

Richard

[G4YVM David]

Thanks Richard, I shall in due course.

Yesterday, as the beast was being used again the relay got better - my qso was probably at 12-15 and it worked fine. I imagine the bearings are gunged or corroded. We'll get there...

My biggest issue now is why no 40m? The previous owner but one did a mod to gain top band at the cost of 40, which I thought I had reversed but clearly theres still a link either in where it shouldnt be or missing from where it should because i get zilch on 40.

D

[Keith]

Originally Posted by G4YVM David

My biggest issue now is why no 40m? The previous owner but one did a mod to gain top band at the cost of 40, which I thought I had reversed but clearly theres still a link either in where it shouldnt be or missing from where it should because i get zilch on 40.

First thing to check is whether the VFO is running on that range. You should be able to hear it on a nearby receiver. If not it has to be something to do with L1, C2 or the switching. Assuming the coil hasn't been messed with (?) then the previous owner must have added some capacitance to get down to 160m. What mods did you remove?

[G4YVM David]

Well the frequency counter and local rx do not hear the VFo. What mods... well, he said he simply connected the blue capacitor to the red one to get the range to cover topband. I found THAT mod (cut wire, solder wire, which I reversed) but I'm sure there must be a bit more that he's forgotten about because there's just no VFO oscillation at all that I can find when the range selector is set to 40m range. Of course, it could be poor connections through the selector... I really haven't go that far with fault finding yet... been too excited to get at least one qso on 80m!

David

[Keith]

David,

OK - I see what he did. I wonder if he did the same on the PA capacitors as you said that the red one was affecting the blue range dip (although maybe that was before you removed the mod).

The VFO is a simple inductive feedback circuit so not much to go wrong. Most likely the switch contacts are bad. Should be fairly easy to find. I wonder if the top blue range works as that would also eliminate some areas?

[G4YVM David]

Keith,

After the hiatus caused my my losing, then regaining the Tx, I'll recommence making slow progress on reversing this modification. Probably after my boys go back to school though in a few weeks. I'll do the relay mod first

D

David