HRO power supply to power a R1155

[deliverance]

Hi all, After fitting a mains transformer to the HRO power supply as the original fried its working fine can the supply be used to power a R1155 which a bought this weekend cheers Chris.

[g4aaw pete]

The heaters on the 1155 are wired in a series / parallel arrangement, so you'd have to rewire it for 6.3v.

There's also a requirement for a negative bias supply, not sure if that is available from an HRO psu.

[ms660]

Originally Posted by g4aaw pete

The heaters on the 1155 are wired in a series / parallel arrangement, so you'd have to rewire it for 6.3v.

There's also a requirement for a negative bias supply, not sure if that is available from an HRO psu.

Not unless it's been modified for the said.

Lawrence.

[deliverance]

Hi Thanks for your replies I am aware the the HT- in the HRO supply is direct to ground but with the R1155 the HT- it isn't .

[deliverance]

Just to add a 6V6 has been added with a output transformer so I need a supply just supplying HT and LT .

[GMB]

So apart from the HT grounding issue, the HRO has a lower heater requirement but higher HT voltage.

My data suggests HRO uses 240V 70mA HT and 3.4V LT
R1155 (with all valves) uses 217V 110mA HT and 4.7A LT

So not a great match.

[Silicon]

We need more information on the R1155.

Have the DF valves been removed and a 6V6 valve added added?
Can you measure the new HT current?

[deliverance]

Hi the DF valves have been removed and a 6V6 fitted to one of the sockets. I can't measure the HT current as i have no suitable power supply .

[majoconz]

in the HRO supply is direct to ground but with the R1155 the HT- it isn't .

Marconi WT used this arrangement in other receivers too, eg. the R1475. If you put a voltmeter from HT- to chassis you'll find that the voltage varies with signal - it's the AGC line in effect.

[deliverance]

Removing the DF valves saves around 1 amp of heater power apparently.

[M0FYA Andy]

Originally Posted by deliverance

Removing the DF valves saves around 1 amp of heater power apparently.

The BL63/VR102 alone consumes 1.27 A heater current! The two VR99As take 0.3 A each, so 1.87 Amps saved if all three are removed.

Andy

[Keith]

Originally Posted by g4aaw pete

The heaters on the 1155 are wired in a series / parallel arrangement, so you'd have to rewire it for 6.3v.

There's also a requirement for a negative bias supply, not sure if that is available from an HRO psu.

I'm afraid I don't agree with either of these statements. All the R1155s I've come across work with 6.3V AC on the heaters. Also there is no requirement for a negative bias supply - it is self generated by not grounding the HT negative.

[deliverance]

Interesting Keith I powered up the heaters on the 1155 yesterday from the HRO supply 6.3v ac and all glowed . But the HT from the HRO supply is still no good I take it.

[ms660]

Originally Posted by deliverance

But the HT from the HRO supply is still no good I take it.

What voltage is the HT out from the power supply when loaded with the working HRO ?

Lawrence.

[Keith]

If the HRO PSU produces somewhere around 220V HT it will be fine but only if you can isolate its negative rail from ground (RX chassis).

[deliverance]

Originally Posted by ms660

What voltage is the HT out from the power supply when loaded with the working HRO ?

Lawrence.

The HT on the HRO is around 230v DC Lawrence.

[deliverance]

Understood Keith thanks for the info.

[ms660]

Originally Posted by deliverance

The HT on the HRO is around 230v DC Lawrence.

The HT might rise a bit when connected to the R1155 but hopefully it should be ok.

Lawrence.

[deliverance]

Got it thanks Lawrence.

[deliverance]

Originally Posted by Keith

If the HRO PSU produces somewhere around 220V HT it will be fine but only if you can isolate its negative rail from ground (RX chassis).

How can you isolate the negative rail from ground to use it for the 1155 . I read somewhere that someone used the HRO supply and used a switch to use it with a 1155 but I can't find where I read it.