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 CHIEFTAIN valve radio 1950's.
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 Return to top of page · Post #: 1 · Written at 3:51:10 PM on 7 January 2022.
Chun's Gravatar
 Location: Melbourne, VIC
 Member since 7 January 2022
 Member #: 2477
 Postcount: 6

Hello everyone.
My first post on this forum.
I have found a Chieftain Battery/Mains valve radio. I'm guessing late 50's.
Tubes:
2x IT4
IR5
IS5
3V4
6X4

It was missing the IR5 and I replaced it with a DK91
Brought it up on a variac and replaced most of the caps.
The rectifier tube seems to work but none of the other tubes light up. There is a loud humming from the speaker, no signal.
The chassis when I move or tap it, echoes like a tin sound down a tunnel.

I can't seem to work out what is wrong. Any advice and help would be greatly appreciated.
Thanks: Chun


 
 Return to top of page · Post #: 2 · Written at 4:19:58 PM on 7 January 2022.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6663

The first five valves listed are battery types and have very lightweight heaters in them. Because of this, it will sometimes be hard to see if the valves are lit when there is bright light in the room you are in. Try checking the valves in a darkened room. The hum will most likely be mains hum and caused by dried filter capacitor(s) and these would need changing. The 6X4 is a mains rated valve for rectification an has heavier heaters in it. The heaters in this should be easier to see than the others and these will only be lit when the radio is working from the mains. It will be off when on battery power.

Off the subject, but the whole radio needs checking for safety reasons. Start with the mains cord if it is in any way damaged or it is single-insulated. Then move to the rest of the radio. When I refurbish a radio, I replace all electrolytic and paper capacitors as a matter of course. Then I check resistors but only replace any that are high. After this I then check audio and the tuned circuit.

I, and others here, often refer to monkeying - a term used to describe when a previous owner has tried to get a radio going via hap-hazard experimentation instead of a systematic servicing procedure that is generally known to work in most, if not all, cases. Having a circuit diagram for the receiver one is trying to get working again always helps, though circuits are easier to get for some radios than others. The radio clubs sometimes have copies of the harder to get ones.

When restoring a chassis, it is worth knowing that valves often live on for decades after other components fail. This seems counter-intuitive, given that valves are considered consumables and plug in rather than being soldered in because of this but they are quite indestructible under normal safe use and usually are only damaged by other components which are operating outside normal parameters or have worn out themselves.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 3 · Written at 6:53:56 PM on 7 January 2022.
Chun's Gravatar
 Location: Melbourne, VIC
 Member since 7 January 2022
 Member #: 2477
 Postcount: 6

Thanks Brad for the helpful reply.
I've changed all the electrolytic and paper capacitors and some high resistors. The only caps I have not replaced are the Mica caps. I am told these are very reliable..
I'm getting no frequency signal. Just the loud hum.


 
 Return to top of page · Post #: 4 · Written at 7:36:42 PM on 7 January 2022.
Johnny's avatar
 Location: Hobart, TAS
 Member since 31 July 2016
 Member #: 1959
 Postcount: 461

Have you checked the continuity of all the 1 volt valves.
Pins 1 and 7.
I think it may be model CP, need to find a schematic.
1R5 was always a common failing valve, but you have changed that.
Could be many reasons for your problem.
Will do some searching for a diagram/circuit.
JJ


 
 Return to top of page · Post #: 5 · Written at 9:05:37 PM on 7 January 2022.
Johnny's avatar
 Location: Hobart, TAS
 Member since 31 July 2016
 Member #: 1959
 Postcount: 461

No, It’s a model BP, AORSM 50 page 111.
Which I have not got.
But someone here will have it.
Found from valve line up.
JJ


 
 Return to top of page · Post #: 6 · Written at 12:01:00 AM on 8 January 2022.
Robbbert's avatar
 Location: Hill Top, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1553

I found that those battery valves sometimes you can't see the filaments glowing even in a pitch-black room, The only way to know is to measure the resistance of the filament of each valve (they are often wired in series), then follow the heater string and make sure the voltage drops by 1.4 volts across each valve. These sets are influenced greatly by even the slightest corrosion on the valve pins and sockets, so clean them.

The 1R5 is one of the most unreliable valves ever. When I checked my collection of them, half were dead.

You say the chassis is microphonic? I'd say that might be the first thing to start looking for. The 3V4 is the output valve, so check that, and the preamp that precedes it. Check the wiring in the area - something might be just touching something it shouldn't.

Does the hum or microphonics change when the volume control is adjusted?


 
 Return to top of page · Post #: 7 · Written at 10:38:29 AM on 8 January 2022.
Chun's Gravatar
 Location: Melbourne, VIC
 Member since 7 January 2022
 Member #: 2477
 Postcount: 6

Thanks everyone for the advice.
I checked the valves for continuity and they all seem fine.
The chassis is microphonic so I'll next check the wiring in the final stages. A schematic would help.
How strange is it that the radio does not even have a light for the dial area.


 
 Return to top of page · Post #: 8 · Written at 10:55:39 AM on 8 January 2022.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6268

.Chun: if you 'unhide' your email address via Control Panel, I'll send you the schematic.


 
 Return to top of page · Post #: 9 · Written at 11:08:39 AM on 8 January 2022.
BringBackTheValve's Gravatar
 Location: Linton, VIC
 Member since 30 December 2016
 Member #: 2028
 Postcount: 296

Very gentle tapping with your finger on the output and detector valves may reveal the microphonics source.


 
 Return to top of page · Post #: 10 · Written at 11:31:27 AM on 8 January 2022.
Chun's Gravatar
 Location: Melbourne, VIC
 Member since 7 January 2022
 Member #: 2477
 Postcount: 6

Thanks for that in advance. I've just unhidden my email.

Just tapping the wooden workbench creates the microphonics never mind tapping the output tubes.


 
 Return to top of page · Post #: 11 · Written at 12:59:16 PM on 8 January 2022.
Robbbert's avatar
 Location: Hill Top, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1553

Use a cotton bud or a toothpick instead of a finger, and just tap the suspect valve or area with the point.

Does it happen with the volume turned right down? If it does then you know the issue is with the audio side, and there won't be much to check.


 
 Return to top of page · Post #: 12 · Written at 2:10:06 AM on 10 January 2022.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6268

Schematic sent.


 
 Return to top of page · Post #: 13 · Written at 11:36:31 AM on 10 January 2022.
Chun's Gravatar
 Location: Melbourne, VIC
 Member since 7 January 2022
 Member #: 2477
 Postcount: 6

Thanks GCT. So much easier with a schematic.

An update. The microphonics goes up and down with the volume switch. I noticed a 0.0082mfd 600v clear plastic cap on the output tube that is noisy when I tap it. Should I replace this?. With what? cant seem to find one online


 
 Return to top of page · Post #: 14 · Written at 12:23:36 PM on 10 January 2022.
Johnny's avatar
 Location: Hobart, TAS
 Member since 31 July 2016
 Member #: 1959
 Postcount: 461

Cannot imagine that the value would be critical, at least not at this stage of the repair.
Just use a 0.01 630 volt cap, a common value.
What’s its position on the circuit anyway.
JJ


 
 Return to top of page · Post #: 15 · Written at 12:49:27 PM on 10 January 2022.
Chun's Gravatar
 Location: Melbourne, VIC
 Member since 7 January 2022
 Member #: 2477
 Postcount: 6

It's an Electrolytic cap between the IS5 and 3V4 output tube. I now have schematics for the Chieftain BP and the Chieftain 21 but neither has this cap mentioned.


 
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