New Pup KB 362

[crackle]

Its looking great, I bet you cant wait to see if it works now.
As a last resort I have a power supply to power it here, if you want to make the 50 mile trip to Basildon.

Mike

[rockinmark]

That would be great Dave PM sent I understand HT needs 120v and LT 2v but the GB- I'm not sure about Mike t said GB - (Green) this needs 6V at very little current the Positive connection goes to the HT- how do I give it 6v

[rockinmark]

Thanks mike yeah would love to see it work my first battery set that probably sounds funny. The power supply sounds a nice Idea for a later date did you make it yourself

[crackle]

Yes I made the one on Paul Stenning's site.
https://www.vintage-radio.com/projec...y-set-psu.html

Mike

[rockinmark]

Hi Mike that is great and doesn't look to hard for a novice like me it even gives a part list the only thing is unless I got it completely wrong it is for a 90v HT where I'm sure I would need 120v on the HT.
Mark

[crackle]

Oh yes I forgot that, but I would think it should work just about with a 90 volt HT.

Mike

[rockinmark]

Update: with the help from another forum member davebms. (Thanks dave for your help) I have connected a wire to HT- to give the GB+ would the original battery have this made up inside so you didn't need it on radio. We applied power but still no sound. Checking the output transformer and think it is dead. Is there a modern one that I can replace it with. It says it is 400ohm primary
Mark

[Ed_Dinning]

Hi Mark, some of the early HT batteries also had a GB section which would have had the link internally.
Note that you should not run the set with GB disconnected, even for a short time as it can damage valves and transformers.
Start at a high negative voltage and reduce; removing HT before changing taps and measure HT current if you can

Ed

[rockinmark]

Thanks Ed I have been doing that when checking the transformer on speaker it appears to be dead. That feeds the HT+ to valve 3 so I need to replace it but I don't know with what I can replace it with most I have looked at are not 400ohms can you still get one at 400ohms I think getting it rewound would cost more than its worth

[rockinmark]

Photo of what I need to replace HT is 120v

[ms660]

Originally Posted by rockinmark

Thanks Ed I have been doing that when checking the transformer on speaker it appears to be dead. That feeds the HT+ to valve 3 so I need to replace it but I don't know with what I can replace it with most I have looked at are not 400ohms can you still get one at 400ohms I think getting it rewound would cost more than its worth

The 400 ohms (440 in the manual) is the DC resistance, you need to be looking at the AC resistance (impedance) The recommended load impedance for the PM22a valve for instance is given as 15k:

http://www.r-type.org/pdfs/pm22a.pdf

If the transformer is faulty and all else fails then RS components still appear to supply a transformer that should do if space permitts:

https://uk.rs-online.com/web/p/audio...rmers/2106475/

Here's the data sheet for that transformer:

https://docs.rs-online.com/7d2d/0900766b80473a76.pdf

You can see from the data that it will match 15k to 3 ohms.

Lawrence.

[rockinmark]

Thank you for that Lawrence. Am I right I have to wire it up like this. Also if i only applied 90v to HT would i get some noise from speaker or should i give it the full 120v
Mark

[ms660]

I would connect as per the data sheet and I would operate the receiver with 120 volts HT and the correct LT and grid bias voltage.

Having said that are you sure the original output transformer is faulty? A simple resistance measurement of the primary winding and the secondary winding should confirm.

Lawrence.

[rockinmark]

I did a continuity check across the primary and didn't get anything so I'm thinking that that's the fault. Is the connections wrong on my drawing as I'm not sure how to connect the new one that you recommended I'm not that knowledgeable on op's I can have another look at the old OP transformer

Mark

[ms660]

Originally Posted by rockinmark

I did a continuity check across the primary and didn't get anything so I'm thinking that that's the fault. Is the connections wrong on my drawing as I'm not sure how to connect the new one I'm not that knowledgeable on pop's

Mark

If you were to use that transformer and the loudspeaker fitted is to the original spec, eg: a nominal 3 ohms (ish) then....

Primary 1 & 4 (13-15k)

Secondary C & D (3-4 ohms)

Lawrence.

[davebms]

Hello all Mark was at my house to use
My battery’s the 90 volt was just how
My battery’s were set at LT and grid bias
we’re correct. With the primary disconnected
There was no continuity on the primary
possibly it may be worth removing the
transformer to look if the broken wire
Can be re soldered ?

Dave

[rockinmark]

Thank Lawrence and dave. I will take it out and see if I can see any wire broken

Mark

[rockinmark]

I have taken the transformer off and couldn't see any brakes. From there I thought I have nothing to lose removed it from speaker and took it apart to see if I could see anything so the only way to find the brake would be to start unwinding it at this point I think easier to get a new one

[rockinmark]

I have just received the new transformer that Lawrence suggested the interesting thing is it fits inside the old one when I take out the old winding part. Got to clean it up but it will look a bit more original

Mark

[rockinmark]

Update I have now finished this pup trf radio been very interesting first of all I would like to thank everyone for their input in helping me finish this set thanks to dave, davebms for showing and teaching me a bit about it. And thank to ed dinning and jerry cathoderay57 for supplying the valves. Without everybody's help I wouldn't have finished it

Mark