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Radiogram record player very faint sound

ZJS

Sep 2, 2023
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Hi,

I have a 1954 HMV Radiogram.
When I first got my hands on it, it hadn't been turned on for a very long time and the power cable had been cut off. It has an external earth screw and a neutral and live wire which had been cut. I wired a mains lead, screwing the earth to the external earth screw and then connected the neutral and live wire to the mains lead. When I plugged it in everything powered up and all the lights came on. The radio function is all working fine (but on a high volume) and I have managed to tune it in to a couple of radio stations on MW. As for the record player, I turn the knob from the radio settings to 'G' which stands for gramophone which is the record player. When I press the start button, the platter spins around at the correct speed and the stylus automatically moves over the platter and lowers itself onto the vinyl record. But you cannot hear it at all.

After further inspection, I found that the two wires leading out of the record player inside the unit had broke off from the connector which slots in to a part in the record player. I soldered the wires back on to the connector and then powered it up. I put a record on the platter and press the start button and now, when you turn the volume up to max volume, you can very faintly and quietly hear the record playing through the speaker.

I then turn to the valves. It has 4 Marconi valves in it: N78, U709, DH77, N78.
One of the N78's was a bit dimmer and didn't get as hot as the other N78.
Because the N78 valves are the same I swapped them around, after doing that there was no sound from the record player on a high volume. So I figured that one of the N78 valves must me broken. I found out that the N78 valve that is not working was the one that was dimmer and not as hot. So, I ordered 2 replacement Marconi N78 valves which had been tested.

After I fitted the 2 new N78 valves, I plug it in and turn it on and the radio is louder on a lower volume and sounds very crackly and distorted.

I switch to the record player setting and test the record player but I cannot hear anything at all now even on max volume, I can only hear the speaker buzzing. However when I touch the needle, there is a very loud buzzing noise coming through the speaker.

In conclusion, the stylus is picking up the sound but it seems that it hasn't been amplified enough.
There is a small valve (DH77) which is the pre amp valve. I have not replaced that valve but maybe I should as it is 70 years old.
The U709 valve is larger than all the others and I think that is still working fine because when I remove it the radio doesn't do a thing.

Also, It has two removable styluses. One for 78's and another for 33's and 45's. The needle in the stylus that plays 33's and 45's broke so I am using the stylus meant for 78's on playing the records. I do not have any 78's but it does play the record fine be

Any ideas to what the problem is and what I should do next. I would love to be able to see it playing records again.

Thanks Zach.
 

kellys_eye

Jun 25, 2010
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so I am using the stylus meant for 78's on playing the records.
Show us the stylii you are using. There is a reason why they have different stylus for different records and it could be as simple as not using the right needle.
 
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ZJS

Sep 2, 2023
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image.jpg
 

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ZJS

Sep 2, 2023
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The 78 stylus is the one that I am using
I will try and get my hands on a 78 rpm record
 

ZJS

Sep 2, 2023
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Before the stylus broke though it still didn't produce any sound with the correct stylus.

thank you
 

kellys_eye

Jun 25, 2010
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Quite possibly an issue with dirty switch contacts when changing modes. Other than that, there might be a break in the audio path that requires further inspection. can you post pictures of the chassis/wiring?
 

ZJS

Sep 2, 2023
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Quite possibly an issue with dirty switch contacts when changing modes. Other than that, there might be a break in the audio path that requires further inspection. can you post pictures of the chassis/wiring?
Hi,
Here are the pictures of the wiring
 
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ZJS

Sep 2, 2023
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Wiring and chassis
 

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Martaine2005

May 12, 2015
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Get those old capacitors out of there.
Check the resistors too while you’re in there.

Martin
 
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Bluejets

Oct 5, 2014
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The radio function is all working fine (but on a high volume)
If the radio works, the amplifier must be ok so forget poking around the valves.

More likely the stylus or the selector grubby contacts.
 

ZJS

Sep 2, 2023
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Thank you
I do find it unusual though how when I put some new valves in the radio goes crackly and distorted and it also works on a higher volume? And also there is nothing coming out of the speakers on a high volume with the new valves.
But I would have expected some change in the record player with the new valves so the valves must not be the problem. I shall put the original valves back in it as it seems to work better.

Do you think that the capacitors will need changing and the resistors?
I have no idea how to test them sorry.

Thank you
 

73's de Edd

Aug 21, 2015
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Sir Zee Jay Ess . . . .

3 observations here

Also, It has two removable styluses. One for 78's and another for 33's and 45's. The needle in the stylus that plays 33's and 45's broke so I am using the stylus meant for 78's on playing the records. I do not have any 78's but it does play the record fine be

And there you stopped . . .all in mid sentence . . . .
You DON"T want to use the stylus of a 78 size which is .003 in stylus tip radius on a 33 or 45 record as its groove is a mere .001 inch . . .OH the irreparable ruination that you will inflict on wallowing that record grove with a stylus 3 times larger . . . . . . or on a steeeee-ro record groove its only .0007 in .

Another thing
is that in looking at post 3's photo two you can see a ring terminal and its wire running down. Now that ring terminal connects to the cartridge elements metal shell and comes down as a ground.
You mentioned having to connect two... very fine . . . I'll bet . . . wires to the bottom of the cartridge and one will be ground and the other lead will be hot audio input.
I feel assured that on the cartridge, that of its two terminals, that one of its connections will have a mini strap going to the cartridge shell making a second ground.
There is a possibility that of those two wires going to the cartridge that your hot wire ended up getting connected to ground and the other lead also went to ground. Thus no or extremely weak audio, so transpose the two wires to see if that was being the fact.

Lastly
I say that its the cartridge output voltage itself . . . . . . it has deteriorated with time . . . . .70 yrs to do it in . On some Rochelle salt elements of the 40's-50's . . . . 5 yrs was good life . . . esp in humid and temperate environs.
Since you have two cartridges with specific record groove diameter stylii, try both of them, since apparently the one mentioned above has piezo output voltage from its cartridge element. ,
BUT instead of damaging a record to evaluate mount one unit and then rest the stylus on the center of your upturned index finger and pull that finger towards you a bit so that stylus tip will then be responding to being dragged over the up and down loops/whorl/arches on a fingerprint.
With volume control set to max, a good cartridges piezoelectric output will really SHAKE the speaker with rumblings / scratch sounds.
If its feeble . . .on both cartridges . . . .time to find a newer generation ceramic family of cartridge to replace it.

PENDING YOUR CONFIRMATION
The tubes used on that set are miniature pinned leads . . . if that was a 1954 model I would sort of expect larger octal tubes being used,
or that was being right at a transition time. Can you further confirm its model number. " Radiogram " was used on more than one model.

73's de Edd . . . . .

My only real goal in life is to fart loud enough to trigger a car alarm . . . . best, you now back away !

.
 
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ZJS

Sep 2, 2023
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Hi,
When I rub my finger it does scratch and buzz very loudly.
 

ZJS

Sep 2, 2023
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The valve tubes are correct though because there is a sticker inside of it which shows the model number of all the valves in it. i have checked and they all match up.

Thanks Zach
 

73's de Edd

Aug 21, 2015
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When I rub my finger it does scratch and buzz very loudly.
The large scratch reproduction was being exactly what was hoped for BUT the accompanying loud BUZZ / HUM was NOT expected . . .that sounds like the cartridge shell is not grounded and is picking up inter room radiated AC power wiring force fields from your body's fingers touch.
Instead, of finger touch revert to using a stylus tip scratch across the top of the rough surface of your thumbnail ( thusbeing electro-insulated).
Expecting the scratch noise only . . . . but if a finger touches the cart shell or metal of the stylus results in a HUMM . . .need to sort out that fault.
 

ZJS

Sep 2, 2023
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Hi

So I need to rub my thumbnail on the needle and expect a scratching sound?
There isn’t a scratching sound it is just my finger brushing against the stylus and causing a buzz

Also, if I touch any other metal component on the unit the speaker makes a little tapping sound ‘pop’

Thanks zach
 

ZJS

Sep 2, 2023
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When I touch any metal part of the cartridge with my finger the speakers make a loud buzzing sound. The metal underside of the cartridge makes an especially loud buzz
 

73's de Edd

Aug 21, 2015
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If the two wires that you reinstalled were very fine gauge wires ( in order to be able to flex VERY easily) . . . . I believe that you reinstalled them in transposed positions from the way that they had been installed at assembly time at the factory.
 

ZJS

Sep 2, 2023
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Hi

I will take out the record player and show you a picture of the soldering I did

As I say, those two wires that I soldered back on were the only two wires leading out of the record deck so they will be very fine wires.
 
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