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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 31st May 2020, 9:27 am   #1
Timeslip
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Default Need help with cable from vintage PSU to R1155 (D) receiver

The power supply unit is tagged KT547, but I have no idea if that's the serial number or the actual name of the unit. Three transformers, one valve, switchable between 300, 230 and 250 - I assume volts. Five pin output, HT and LT are correct voltages. Here's the catch. LT is AC not DC.

Some websites say that's ok, some say "should be ok, we've never tried it" and others say "own risk".

The cable was cut a long time ago, so I'm marrying it up with a cable with a connector to the R1155. This got complicated, because not all the pins were correctly soldered. Had to take the plug apart and resolder. Good job, too, as some of the wires were in a bad way.

There's two pins on the circuit diagram for the connector from transmitter (I think that's the right one to use) marked HT+. I presume both need connecting to the one wire from the PSU marked HT+.

There is a place to attach an earth on the PSU, and a wire that seems to ground the set that runs along the cable. I should probably set that up, but I've never grounded the set in the past with my old setup.

If all this looks ok, next stop is to give it a run.

I've used the receiver many times in the past, but using my father's home-made power supply for it, which has vanished and can be regarded as lost forever. Mind you, it was exceptionally dangerous.
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Old 31st May 2020, 1:41 pm   #2
Herald1360
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Default Re: Need help with cable from vintage PSU to R1155 (D) receiver

Have a look at this thread:

https://www.vintage-radio.net/forum/...ad.php?t=54747

Main thing to remember is that psu ht supply should be floating- ie no ground to ht- in pay.

AC for the heaters is fine.
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Old 3rd Jun 2020, 8:01 am   #3
Sean Williams
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Default Re: Need help with cable from vintage PSU to R1155 (D) receiver

Please do not ground the chassis of the R1155 - this will upset all the bias voltages for the receiver.

There will be 4 connections that are important from memory - HT+, HT- and Heaters.

Been an awful long time since i last played with an 1155.
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Old 3rd Jun 2020, 9:07 am   #4
M0FYA Andy
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Default Re: Need help with cable from vintage PSU to R1155 (D) receiver

There's no reason to be concerned about using an AC supply for the receiver heaters. The ground power supply for the T1154/R1155 combination supplied DC because it is required by the transmitter keying relay.

Andy
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Old 3rd Jun 2020, 9:58 am   #5
GW3OQK Andrew
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Default Re: Need help with cable from vintage PSU to R1155 (D) receiver

Timeslip, Sean, the chassis should be grounded to the psu and mains ground. The HT supply is just floating. That thread Herald gives is excellent.

Having DC heater volts would, I think, remove some hum picked up in the cable to my PSU +speaker amp.
73, Andrew
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Old 5th Jun 2020, 9:44 am   #6
AndyWright
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Default Re: Need help with cable from vintage PSU to R1155 (D) receiver

I use AC heaters on my R1155 with no hum problems. Like others have said, the HT- rail should not be connected to chassis.
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Old 5th Jun 2020, 10:28 am   #7
marty_ell
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Default Re: Need help with cable from vintage PSU to R1155 (D) receiver

On some 1115's I have found h.f. noise may be injected into V1 if heaters are supplied from a floating winding on a transformer without an electrostatic screen in the PSU unit. It's a small effect, but noticeable if you are aiming to tweak the 1155 for top performance.

The simple solution is to make sure the PSU's heater output wires are kept close together (better if strapped as a pair in the cable bundle, even better if twisted) and add an a.c. rated cap between pins 3 and 4 right inside the Jones socket, 10n-100n is fine.

I have also come across one 1155 where some previous owner had rewired the set's heaters to be completely isolated from chassis, I'm guessing this was because the PSU had one side of the heater output already earthed. A poor choice.

Cheers, Marty
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