Battery valve set

[rockinmark]

Hi I'm trying to find out if the valve set up would work the same as on the service manual, the marconi I think is a osram kt2 but has no markings the valves are what was in the radio when I got it
The valve 1 = detector is dead so this will have to be replaced. if anyone has one they want to sale please let me know

Mark

[PJL]

We would need the circuit to help as this will define the bias conditions. You appear to have 2 output valves PM2 and KT2 so you probably need valves for V1 and V2. I presume 'dead' means the filament is open circuit?

[Cobaltblue]

I'm guessing this is for the KB New Pup 362 in a previous post


Cheers Mike T

[rockinmark]

Yes Colbert for the pup dave check the valves on his tester for me no markings on the marconi one so don't know what it is

Mark

[PJL]

OK, found the thread. In your original picture the PM2 is in the V2 position and that would definitely be wrong. The Pup has no bias supply for V1 and V2 (not quite true as it is connected to the -ve filament supply) so it is important to use valves, like the PM1HL, that are designed to work under this bias condition.

[rockinmark]

PJL in the manual valves 1 and 2 are the same in not sure on what's the difference between pm1 hl and pm2 hl.

[PJL]

You need to look at the valve characteristics in the datasheets to understand why:
PM1HL http://g3ynh.info/valves/old/Data-Bo...G/MVG-p009.pdf
This valve is described as a detector.
PM2 http://g3ynh.info/valves/old/Data-Bo...G/RVG-p011.pdf
This valve is described as an output valve.

V2 has an anode feed resistor of 150,000 ohms. Assuming the design was intended to drop a maximum of 50V across the anode feed then the anode current must be less than 0.33mA when the grid voltage is zero.
Now look at the characteristic chart for the PM1HL and you can see that with grid=0V and Ia=0.5mA the anode would be about 50V and that sounds reasonable.
Do the same for the PM2 and the anode voltage would be next to nothing.

A PM2HL should be OK as it is intended to be a direct replacement for a PM1HL, but the valve in the picture appears to be marked PM2.

Trying the PM2 will do no harm as the 150,000 will prevent damage but I would expect it to perform very badly.

[Brian4radio]

Hi Rockingmark, yes you are correct. regarding the first two valves. Your paperwork shows that valve No1 and valve No2 should be PM1 -HL or equivalents and the valve No3 should be a PM22A or equivalent. If you try to purchase these valves just ask for PM1-HL or equivalent. Have you got any documentation with your radio to show where the valves should be installed in the set. Regards Brian

[cathoderay57]

Hi Mark, you might be in luck. My listings show the following used valves:
One KT2
One PM1HL
One PM2HL
One Pen220A
Tomorrow I will test them for you on the VCM163 and let you know if they are any good. The weather here is vile so not going out to the garage tonight! Cheers, Jerry

[rockinmark]

Hi Jerry yeah it's very wet and windy down here as well. It would be great if you have them. When you get time there's no rush if you PM me the cost

[rockinmark]

Hi PJL thats what I was not sure of, the amplifier valve 2 is a pm2 it looks like I have to change them all. Thanks

[PJL]

The PM1HL and PM2HL offered by Jerry are perfect for V1 & V2.
You can use the PM2 as V3 (output valve) but it requires a larger grid voltage of say -10V.
If the Marconi valve is a KT2 it should have 5 pins and should work as the set claims to be wired for pentodes and it claims to be an equivalent to the 220HPT.
I would avoid the PEN220A offered by Jerry as it is considerably more powerful than the PEN220 and might possibly damage the output transformer.

[cathoderay57]

Morning all; weather slightly better here so had a good rummage in the spares box; sorry, my list was out of date but I found one other contender (210HF) from your list. I've not bothered with the Pen220A based on PJL's advice: Here are the test results (spec values for a brand new valve in brackets):
KT2 - zero emission - scrapped
PM1HL - not found
PM2HL - Had a PM2A inside the box (Ia=7.6mA (5) gm=2.4mA/v (2))
210HF Ia=2.6mA (1.6) gm=1.1mA/v (1.5) metallised
Very sorry to build up false hopes - you have a PM re: 210HF. Assume you won't want the PM2A as it is a triode and you need a pentode for V3 (unless your KT2 works).
Cheers, Jerry

[PJL]

The PM2A is another output valve but you already have two. V3 appears to be wired for both triode (B4) and pentode (B5).

[davebms]

hello all,, the reason mark came to my place was he was having trouble
testing resistors, so he came with the complete set (not much point with just
a resistor) the problem his meter is rubbish !! reads some resistors some times ..so we changed two that were twice original value there are others
that have gone high but should work (mark will change them later)
the valves ,, Hl2 dead (no heaters)pm2 tested good ,wrong application
but we thought it may sort off work. the Osram I tested as a pt2 its ok
(if it is a pt2 ?)with an hl2 from my trf as first valve, no stations but
loud noise from speaker when touching grid second valve.. so I think
mark needs valve 1and 2

dave

[Luxman1050]

Mark just stumbled on your thread I have a brand NOS marconi HL2 never used as I bought it for a battery receiver I had but never got round to using it.
I'm happy to sell on to you if happy with price.
Here are some pics.
Chris

[rockinmark]

Thanks dave for all you help and glad that I now know my meter was rubbish and not my mind I have ordered some resistors. Just thinking there is not much left inside that's original but I'm enjoying the hobby and learning a lot from everyone as I go

[rockinmark]

Thanks jerry (cathoderay57) shame about the rest of valves but at least that's one just one more to get