1920s battery 3 valve power connections help please - UK Vintage Radio Repair and Restoration Discussion Forum

lloydwells · 3rd Aug 2020, 8:33 pm

I've acquired this huge very well put together 1920s set assuming a home brew job. I'm perplexed by the HT connections well more what voltages to attach them to. I have one HT+ going to each of the three transformers in it giving three separate banana plugs and two HT- connections ( one might be earth ) these are connected to a fuse bulb holder one side goes to the LT- rail the other being connected to the fuse bulb. Pics attached.

Ed_Dinning · 3rd Aug 2020, 8:52 pm

Hi lloyd, quite usual for 3 "earth" connections. These were GB+, LT- and HT-.
3 (or more ) HT + connections were not unusual in a multivalve set as well as several GB- connections
The SG valve (if used) often had an HT to anode and a lower value to SG.

When you post the pics we should be able to see if it looks like a kit and the makes of the majority of parts. That may give a clue as to the model of set

Ed

lloydwells · 3rd Aug 2020, 9:38 pm

As I did mention I have the GB and LT sorted it has two GB- one GB+. Those aren't the issue I have three transformers first is an R.I general purpose one HT+ is attached to this then out the back of the set I then have a Lissen super transformer again one HT+ cable attached and out the back of the set third is a Lissen Output transformer again HT+ lead attached and out the back of the set.

Ed_Dinning · 4th Aug 2020, 9:14 pm

Hi lloyd, output transformer will probably have 120v on it, The other 2 will probably go to 90 or so volts.
Note thta if you increase the HT voltage you will often need to increase the neg grid volts on that valve (and vice versa)

Ed

greenstar · 4th Aug 2020, 9:57 pm

Lloyd, you probably know, but don't change the GB voltage without disconnecting HT first. Having no GB even for a few moments isn't good.
Tony

lesmw0sec · 5th Aug 2020, 9:12 am

Another valid reason for multiple HT points is to achieve decoupling between stages, the battery acting as a big cap.

3rd Aug 2020, 8:33 pm	#1
lloydwells Heptode Join Date: Aug 2016 Location: Dumfries, Scotland, UK. Posts: 549	1920s battery 3 valve power connections help please I've acquired this huge very well put together 1920s set assuming a home brew job. I'm perplexed by the HT connections well more what voltages to attach them to. I have one HT+ going to each of the three transformers in it giving three separate banana plugs and two HT- connections ( one might be earth ) these are connected to a fuse bulb holder one side goes to the LT- rail the other being connected to the fuse bulb. Pics attached.

3rd Aug 2020, 8:52 pm	#2
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: 1920s battery 3 valve power connections help please Hi lloyd, quite usual for 3 "earth" connections. These were GB+, LT- and HT-. 3 (or more ) HT + connections were not unusual in a multivalve set as well as several GB- connections The SG valve (if used) often had an HT to anode and a lower value to SG. When you post the pics we should be able to see if it looks like a kit and the makes of the majority of parts. That may give a clue as to the model of set Ed

3rd Aug 2020, 9:38 pm	#3
lloydwells Heptode Join Date: Aug 2016 Location: Dumfries, Scotland, UK. Posts: 549	Re: 1920s battery 3 valve power connections help please As I did mention I have the GB and LT sorted it has two GB- one GB+. Those aren't the issue I have three transformers first is an R.I general purpose one HT+ is attached to this then out the back of the set I then have a Lissen super transformer again one HT+ cable attached and out the back of the set third is a Lissen Output transformer again HT+ lead attached and out the back of the set.

4th Aug 2020, 9:14 pm	#4
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: 1920s battery 3 valve power connections help please Hi lloyd, output transformer will probably have 120v on it, The other 2 will probably go to 90 or so volts. Note thta if you increase the HT voltage you will often need to increase the neg grid volts on that valve (and vice versa) Ed

4th Aug 2020, 9:57 pm	#5
greenstar Octode Join Date: Jul 2011 Location: Leicester, Leics. UK. Posts: 1,684	Re: 1920s battery 3 valve power connections help please Lloyd, you probably know, but don't change the GB voltage without disconnecting HT first. Having no GB even for a few moments isn't good. Tony

5th Aug 2020, 9:12 am	#6
lesmw0sec Octode Join Date: Jul 2009 Location: Carmel, Llannerchymedd, Anglesey, UK. Posts: 1,506	Re: 1920s battery 3 valve power connections help please Another valid reason for multiple HT points is to achieve decoupling between stages, the battery acting as a big cap.