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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 2nd May 2022, 2:32 pm   #121
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Default Re: 1936 Marconiphone 365 Radiogram

Very good!

I suspect the knob on the INTERNAL/EXTERNAL switch is fitted the wrong way round or something like that. It's unclear from the circuit whether it has two or three positions.
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Old 2nd May 2022, 3:01 pm   #122
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Default Re: 1936 Marconiphone 365 Radiogram

With switches in Internal and radio positions and reading clockwise from filaments

V1 pin 1 1.68V pin 2 75V pin 3 1.5mV pin4 350mV pin 5 1.68V

V2 pin 1 0.0V pin 2 262V pin 3 352V pin 4 4.5mV pin 5 74.6V

V3 pin 1 1.38V pin 2 74.1 pin 3 1.39V pin 4 0.5V pin 5 1.4V

There are three positions on the switch Position 1 is internal and 2&3 I can put bluetooth through.

All wiring looks original and untouched at the switch as with the rest of the radio
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Old 2nd May 2022, 3:16 pm   #123
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Default Re: 1936 Marconiphone 365 Radiogram

What about the voltage on the top caps?
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Old 2nd May 2022, 3:46 pm   #124
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Default Re: 1936 Marconiphone 365 Radiogram

Here are the pin numbers for the B7 valve base:

http://www.r-type.org/static/baseb7.htm

Lawrence.
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Old 2nd May 2022, 4:14 pm   #125
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Default Re: 1936 Marconiphone 365 Radiogram

Thanks ms660 for the pin numbers.

V1 269V
V2 0.98V
V3 270V
V4 5mV

I got carried away with the jazz music and forgot about top caps
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Old 2nd May 2022, 8:29 pm   #126
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Default Re: 1936 Marconiphone 365 Radiogram

There seems to be a distinct lack of screen grid voltage on V1 and V3. This derived from the potential divider R41/R42 which we visited earlier.

V3 should have a permanent screen grid supply. The screen grid supply to V1 and V2 is only present in RADIO mode and is fed from S16 contacts 5 and 6.

The screen grids of all three valves should be at the same voltage.
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Old 2nd May 2022, 8:54 pm   #127
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Default Re: 1936 Marconiphone 365 Radiogram

Graham, I think the pin numbering is wrong, there is 75V on V1 pin 2, V2 pin 5 and V3 pin 2. The pin numbers should read 7, 3, 7.
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Old 3rd May 2022, 10:10 am   #128
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Default Re: 1936 Marconiphone 365 Radiogram

Best to use the correct valve pin numbers.

V3's screen grid supply is switched along with that of V1 and V2 in the schematics I have.

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Old 3rd May 2022, 10:22 am   #129
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Default Re: 1936 Marconiphone 365 Radiogram

Agreed. I got confused following parallel lines.

I'll analyse the voltage readings later once I've reconciled the pin numbering.
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Old 3rd May 2022, 11:34 am   #130
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Default Re: 1936 Marconiphone 365 Radiogram

Apologies for causing confusion with pin numbering. I was unaware of the proper pin numbering until ms660 post.

As my late father said "ups and downs we've had a few but here we go again"
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Old 3rd May 2022, 1:45 pm   #131
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Default Re: 1936 Marconiphone 365 Radiogram

Quote:
Originally Posted by kinnego07 View Post
With switches in Internal and radio positions and reading clockwise from filaments

V1 pin 1 1.68V pin 2 75V pin 3 1.5mV pin4 350mV pin 5 1.68V

V2 pin 1 0.0V pin 2 262V pin 3 352V pin 4 4.5mV pin 5 74.6V

V3 pin 1 1.38V pin 2 74.1 pin 3 1.39V pin 4 0.5V pin 5 1.4V
From what I can make out, what the OP calls pins 1 ,2, 3, 4 and 5 are in fact pins 6, 7, 1, 2 and 3.

V1 VMP4G
Pin 1 Metallisation 1.5mV
Pin 2 g1 350mV
Pin 3 g3 1.68V
Pin 4 Heater
Pin 5 Heater
Pin 6 Cathode 1.68V
Pin 7 g2 75V
TC anode 269V.

V2 X41
Pin 1 a(t) 352V
Pin 2 g1(t)g3 4.5mV
Pin 3 g2, g4 74.6V
Pin 4 Heater
Pin 5 Heater
Pin 6 m, Cathode 0V
Pin 7 Anode 262V
TC g1 0.98V

V3 VMP4G
Pin 1 Metallisation 1.39mV
Pin 2 g1 0.5V
Pin 3 g3 1.4V
Pin 4 Heater
Pin 5 Heater
Pin 6 Cathode 1.38V
Pin 7 g2 74.1V
TC anode 270V.

Anyone disagree?
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Old 3rd May 2022, 2:08 pm   #132
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Default Re: 1936 Marconiphone 365 Radiogram

I would have expected to see a voltage on V2 pin 6 cathode, ie across R9 150R. Is a voltage present here on any of the five wavebands?
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Old 3rd May 2022, 2:44 pm   #133
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Default Re: 1936 Marconiphone 365 Radiogram

There is no voltage at pin V2 pin 6 (Cathode) in any ot the four wavelengths.

Resistance across R9 is 226 ohms

Your valve pin listings are correct apart from V3 pin 1 should be 1.39mV

Switching to Gram cuts grid supply to all three valves.

You are correct - the Int/Ext Knob is on the wrong way around
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Old 3rd May 2022, 3:17 pm   #134
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Default Re: 1936 Marconiphone 365 Radiogram

Error corrected.

Have you cleaned the contacts of the wave change switches with contact cleaner such as Servisol 10?

I would suggest replacing R9 which has drifted high. Also check R8 and replace if necessary. Replace C18 0.1uF if you haven't already done so.
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Old 3rd May 2022, 3:31 pm   #135
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Default Re: 1936 Marconiphone 365 Radiogram

No, I shall order some today. Is there any other readily available product I could use as a substitute?
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Old 3rd May 2022, 3:33 pm   #136
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Default Re: 1936 Marconiphone 365 Radiogram

Anything branded as "Contact Cleaner" will do, but don't use ordinary WD40.
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Old 3rd May 2022, 4:35 pm   #137
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Default Re: 1936 Marconiphone 365 Radiogram

Those V2 voltages suggest that V2's heaters aren't working, or if they are there's no emission.

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Old 3rd May 2022, 5:23 pm   #138
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Default Re: 1936 Marconiphone 365 Radiogram

So I have cleaned all the switches with contact cleaner but no change.

V2 pin 6 has no voltage. There is hum from the speaker which increases and fizzes when I touch V2 metallic coating
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Old 3rd May 2022, 5:25 pm   #139
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Default Re: 1936 Marconiphone 365 Radiogram

Is V2 lit up?

Check for an AC voltage across pins 4 and 5. Clean the valve's pins. Gently nip up the valve holder sockets if they're a loose fit.
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Old 3rd May 2022, 6:26 pm   #140
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Default Re: 1936 Marconiphone 365 Radiogram

4V AC present at pins 4&5 of all valves

I cleaned the valve pins and holders

I can not see any glow from the valve but it is metalized and in an awkward place to see. It feels warm to the touch but this could be radiated heat from the neighbouring valves.

I have to say that the quality of sound from the speaker is fabulous.
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