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Old 18th Jun 2018, 2:48 pm   #1
dubsessive
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Default Marconiphone 4633 (actually a 4366) Speaker problem

Hi Guys, I'm glad I have found this forum! I’ve bought a Marconiphone Stereogram 4463 as a project to start to learn how to fix vintage equipment as I love the look of them but recognise they may need a bit of maintenance, however the RH speaker on my unit isn’t working. I think it may have stopped working after I tried my headphones, but I can’t be 100% sure.
A quick continuity test on the speaker suggested that it had failed, so I swapped them over to be sure, but then no sound came out of either side! When I plug the headphones in sound only comes out of the LH side in headphone as well. This is the same on for FM stereo and the turntable. I have tried the Balance knob and it seems to work as expected albeit with a broken speaker ie turn to the right, sound from the RH speaker turn to the left no sound. After spraying contact cleaner on everything the crackle has stopped on all controls. Now please be patient here as I am totally new to ALL of this. The wires that originate/terminate from the speakers and seem to go directly to the headphone socket. The headphone socket has three metal bars that when you push the jack in disengages two metal poles I assume this breaks the connections to the speakers and moves the connection to only provide sound to the Headphones. From the socket two of the wires have (sorry about this….) some sort of Resistor inline I assume that they have something to do with the balance but I could be very wrong. Could one of them be faulty. I can’t find any fuses or anything else that looks out of place. Has anyone got any ideas of where I could go from here?
I Am Sorry it’s a bit long I just wanted to get it all down? Thanks
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Old 18th Jun 2018, 3:28 pm   #2
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Default Re: Marconiphone 4633 Speaker problem

You have not done to bad to start with. However even if the speaker was bad, it would not affect your headphones! The speaker leads go to the headphone socket first. When a jack is inserted the pins on the other side switch off the speaker. And the sound is transferred to the headphones via the resistors which cut the volume to the headphones so you don't deafen yourself if you had the amp on loud.
So the only point that can cut out the Right channel is if the connection on the headphone socket, is: (A) poorly soldered (B) not connecting at all. This can happen if the contact has broken or a is not touching, because it is bent out of place.
You can test this with an ohm meter to see if it connects. Once this is eliminated. I think you are looking at a fault in the right hand channel. On the main amp section.
Trace the speaker wire back and you can identify the left and right channels. They are both the same only the power supply is different, which is unaffected otherwise both channels would be out. Resistance checks and voltage tests between the two channels should find the culprit. Remember the left channel tells you what is working. So any differences in the right readings in the same places, points to trouble.
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Old 18th Jun 2018, 3:56 pm   #3
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Default Re: Marconiphone 4633 Speaker problem

Thanks that makes sense I will give that a try tonight when I get back.
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Old 18th Jun 2018, 5:03 pm   #4
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Default Re: Marconiphone 4633 Speaker problem

I cant find any information on a model 4633 or mention of one.
Have you got the model number correct. Photos could be useful as there is probably a similar model (same chassis) under a different brand.
In case the fault is not in the headphone socket the circuit diagrams will be useful for anyone trying to help you.
Mike
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Old 18th Jun 2018, 5:13 pm   #5
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Default Re: Marconiphone 4633 Speaker problem

4463?

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Old 18th Jun 2018, 5:24 pm   #6
Edward Huggins
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Default Re: Marconiphone 4633 Speaker problem

I can't search this model number either. Speakers very rarely fail. If you want to test them in their own right, just use a 1.5v battery connected across the 2 connectors on the speaker chassis. The speaker cones should move and you will hear a scratchy noise, if so, then they are OK. I think they will have push on connectors on your model and you could gently ease these off, test and then push back. Your problem is more likely to be the wiring to the headphone socket. It's also worth checking if the 2 amplifier sections (LH and RH) are each fused.
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Old 18th Jun 2018, 5:26 pm   #7
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

I'm afraid I am really dyslexic LOL it is the 4366. I checked it three times before posting and still managed to get it wrong!
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Old 18th Jun 2018, 7:46 pm   #8
crackle
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

Still can't find any info on the 4366
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Old 18th Jun 2018, 7:49 pm   #9
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

Pics...

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Old 18th Jun 2018, 7:59 pm   #10
crackle
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

Ah, found it mentioned in the 74-75 R&TVS. It refers to the TCE 78S chassis covered in the 73-74 book on page 761.
AM FM Transistor radiogram chassis with stereo decoder IC. and with complimentary op transistors OP9A & OP9B whatever they are.
Ill scan the pages later if needed and add to my website.

Mike

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Old 19th Jun 2018, 12:55 pm   #11
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

I am very familiar with the 78 chassis having cut my teeth on it!
It uses the MC1310 stereo decoder in a staggered pin arrangement. Which I got around by getting a staggered pin socket, that you could put a straight pin chip in.
The switchbank gave a lot of trouble with dirt on the contacts, but switch cleaner does stop it for a while.
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Old 19th Jun 2018, 3:02 pm   #12
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

BRC / Thorn used to use their own codes for semiconductors, allowing for the possibility of multiple sources. OP9A and B will be a complementary pair of output transistors, so probably AD-something or BD-something.
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Old 19th Jun 2018, 4:41 pm   #13
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

OK service information is scanned if it is needed. (boring night on telly) http://www.kbmuseum.org.uk/other_ser...phone_4366.pdf
I stitched the layout and schematics together at end of doc.

Mike
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Old 19th Jun 2018, 10:04 pm   #14
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

Thanks for the responses everyone.
I did a quick search on ebay and it appears you were right it looks remarkably similar to a Ferguson 3366.
I have been researching how to use a multimeter, without just randomly stabbing at odd wires (this may take some time) . So spent a few hours last night trying to wrap my head around everything. I tried with the mulitimeter but really couldn't figure out where the problem was. I think I would understand it better if I had a working one to compare it to! My unit seems to have only one fuse which was fine when I checked it. I followed the speaker wires back from the socket and they all go back to a plastic box on the chassis that is pretty tough to get a probe onto as even the back has no accessible solder
I am sure the RH speaker is blown I tried the Battery thing (good tip) and nothing on that one. Can I ask where people would go for speakers for something of this age?
Thanks for your help so far, please don't give up on me if I don't answer for a day or so I am probably working or trying to figure out what everyone is saying.

https://www.vintage-radio.net/forum/...pictureid=4052
https://www.vintage-radio.net/forum/...pictureid=4059
https://www.vintage-radio.net/forum/...pictureid=4055
https://www.vintage-radio.net/forum/...pictureid=4058
https://www.vintage-radio.net/forum/...pictureid=4062
https://www.vintage-radio.net/forum/...pictureid=4056
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Old 19th Jun 2018, 11:50 pm   #15
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

Quote:
Marconiphone 4633 (actually a 4366)
& yet in your 1st post you say you bought a 4463:

Quote:
I’ve bought a Marconiphone Stereogram 4463
If you could confirm which model it is: 4633, 4366 or 4463 ?
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Old 20th Jun 2018, 7:41 am   #16
dubsessive
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

Sorry, I really am Dyslexic I do try to double check everything before I post!

It's a Marconiphone 4366
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Old 20th Jun 2018, 7:55 am   #17
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

You do, in effect, have a working one for comparison!
As I understand it, one channel works, so you can use that as your 'good' example to compare with the faulty channel.
Having said that, if one speaker is dead, that will be part of the problem, of course.
Connect your meter, set on, say, its 20V range, across the terminals of the faulty speaker, and turn the unit on ( headphones unplugged). You should see no, or a very low, reading, indicating that the speaker isn't being fed with DC - it shouldn't be!
If that test is OK, try connecting the good speaker to the faulty channel, and see what happens.
If you do see a significant reading, that's likely to be what killed the speaker, so we'll need to dig further.
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Old 20th Jun 2018, 9:01 am   #18
crackle
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

I very much doubt the speaker itself is faulty. Dont go buying a new one till you have proved they are not working.

Early on you said that there was no sound in the left channel when you plugged in your headphones. This would tend to indicate a fault in the headphone socket, or the headphones plug, or a fault in the actual radio chassis/printed circuit.
Mike
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Old 20th Jun 2018, 1:12 pm   #19
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

That headphone socket doesn't look too good. The metal pins that run over the top should be a silver colour. Also some of the connections via the cables look at bit poor on the solder joints. You might have to resolder them.
A 1.5 Volt Battery across the speaker terminals should make it go pop. If you can't hear that then it is faulty.
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Old 20th Jun 2018, 9:23 pm   #20
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Default Re: Marconiphone 4633 (actually a 4366) Speaker problem

Ok thanks for your help so far, I checked the speaker with a battery across the terminal on the LH speaker it popped on contact the RH one nothing.
I put them both back in and turned on the radio, set the multimeter to 20v while music playing got a reading of LH 0.03 and the RH 2.21 that doesn't seem right to me.
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