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

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Old 18th Oct 2021, 4:17 pm   #1
_Cosmic_
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Default Sobell S675 Record player

I was just wondering if anyone with experience with this simple amplifier (or any other vintage amplifier I should think) could help please? I think these Sobell amplifiers were also used in GEC radio grams after they bought the factory I read.

It has a capacitor, C1, value: 0.01 uF 300V a.c. 20%. It's marked on the component listing as a.c. The others are not. Is a.c. just for reference? When ordering a replacement it's not necessary to specify that somehow is it?

Also one capacitor, C6, value: 1800pF 3kV 20% that links the motor chassis to the on/off switch and tone pot that I imagine is the tone frequency filter has a rubber grommet on it for no apparent reason. The grommet is also marked on the circuit diagram. Would anyone know what the grommet is for? And is it really 3K volts as specified?

I know it's a simple circuit but I haven't replaced capacitors before. Apart from replacing electrolytic with electrolytic's and perhaps axial with similar is it a straightforward case of ordering similar values or as close as possible regardless of type ie polythene, polyester etc.

I've read the sticky about capacitors, I know how to solder, have multi-tester, done remedial repairs to decks, autochangers and replaced selenium rectifiers with resistor/diode etc but I haven't done a recap job yet. And I haven't replaced caps in a can.

I have tried to upload 2 .jpg's from my phone but they aren't showing in the folder so I can't upload them. I wonder if they are too big? That's all I can think of..
Thanks
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Old 18th Oct 2021, 4:39 pm   #2
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Default Re: Sobell S675 Record player

There is a guide to loading pictures to the Forum here:

https://www.vintage-radio.net/forum/...ad.php?t=77650

Cheers

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Old 18th Oct 2021, 5:25 pm   #3
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Default Re: Sobell S675 Record player

Circuit here:-

https://www.service-data.com/section.php/7572/1/s675

C1 is connected from one side of the PU cartridge to chassis. This is a live chassis player, so if the mains was connected the wrong way round and C1 failed short-circuit one of the leads to the cartridge would be at mains potential. Therefore I reckon it's failure mode should be to fail open circuit and it should be a Class Y type, but we'll see what others think.
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Old 18th Oct 2021, 5:26 pm   #4
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Default Re: Sobell S675 Record player

These are isolation capacitors and yes I should stick to those ratings. They are such for safety reasons. Depending on the exact type. They may or may not need replacing.
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Old 18th Oct 2021, 5:36 pm   #5
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Default Re: Sobell S675 Record player

C6 is connected between the amplifier chassis and the motor chassis.
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Old 18th Oct 2021, 7:16 pm   #6
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Default Re: Sobell S675 Record player

I've got the images to work this time.
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Old 18th Oct 2021, 7:18 pm   #7
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Default Re: Sobell S675 Record player

Quote:
Originally Posted by Station X View Post
Circuit here:-

https://www.service-data.com/section.php/7572/1/s675

C1 is connected from one side of the PU cartridge to chassis. This is a live chassis player, so if the mains was connected the wrong way round and C1 failed short-circuit one of the leads to the cartridge would be at mains potential. Therefore I reckon it's failure mode should be to fail open circuit and it should be a Class Y type, but we'll see what others think.
Yes thanks for that, I've already bought the circuit diagram.
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Old 18th Oct 2021, 7:45 pm   #8
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Default Re: Sobell S675 Record player

That’s obviously seen some damp. Does the output transformer test ok with a resistance meter?
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Old 18th Oct 2021, 8:04 pm   #9
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Default Re: Sobell S675 Record player

I suspect those caps will be fine.
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Old 19th Oct 2021, 3:26 pm   #10
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Quote:
Originally Posted by peter_sol View Post
I suspect those caps will be fine.
Yes they do look in remarkably good condition seeings how the chassis is so degraded. I'm rapidly going off the whole idea seeing how difficult it is to order small amounts of capacitors from the net. I went on to RS after trying most of the usual companies and you have to order packs of a thousand etc in the case of the cheaper ones. I'm trying to find an electronics shop near to me where I can just go in a buy them. Very difficult.
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Old 19th Oct 2021, 3:33 pm   #11
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Default Re: Sobell S675 Record player

I was getting a pretty loud hum on it and hardly any audio. That's why I thought I would recap at least some of it.

The hum seems to have diminished today. I'm getting a signal if I tap the pickup lead on the tab board but it doesn't seem to be very "bassey" I'm suspecting this TC8 has had it, as to be expected. Pity really as none of mine fit into the headshell.

Is there any way of testing a cartridge just using a multimeter?

I guess the only way I can think of testing the amplifier is attaching a known good cartridge to the inputs wires.
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Old 19th Oct 2021, 3:33 pm   #12
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Default Re: Sobell S675 Record player

ESR Electronics Station Road Cullercoats...??

Just a thought.
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Old 19th Oct 2021, 3:39 pm   #13
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Default Re: Sobell S675 Record player

Quote:
Originally Posted by Nickthedentist View Post
That’s obviously seen some damp. Does the output transformer test ok with a resistance meter?
Well the amplifier is sending a signal to the speaker.
To test this would I have to disconnect it then test the resistance on the primary and then the secondary?

Or test the voltages on the primary and the secondary with it turned on.
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Old 19th Oct 2021, 4:02 pm   #14
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Quote:
Originally Posted by martiR2R View Post
ESR Electronics Station Road Cullercoats...??

Just a thought.
Yes I did think of them when I was doing a search, but its a fair distance from me in Washington, 2x tyne tunnel fees then all the petrol. I will go over as a last resort. Dial, in some scruffy corner behind a garage, doesn't look promising and the one on Glover industrial estate just seem to do electricals. I sent them an email but they didn't respond.

I just discovered Canny Components in Sunniside. It looks like a general store on a housing estate on google maps. I thought I'd check by ringing them and they answered! Well, she was walking down the street anyways. They say they do have the shop and they took it over from the general store and google maps hasn't been updated yet. I'm sending them a list of the stuff I need and so fingers crossed.

I could do with lots of components as I have 4 bush srp 31d's I have got working but I would like to try experimenting to see if I can make them any better by replacing some of the parts, as much for my learning curve as much as anything else. Well, there's no practical course for this sort of thing is there. It's kind of start off doing small things then progressing to the electronics when you find testing live circuitry less intimidating.
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Old 19th Oct 2021, 4:55 pm   #15
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Default Re: Sobell S675 Record player

Quote:
Originally Posted by _Cosmic_ View Post
I was getting a pretty loud hum on it and hardly any audio. That's why I thought I would recap at least some of it.

The hum seems to have diminished today. I'm getting a signal if I tap the pickup lead on the tab board but it doesn't seem to be very "bassey" I'm suspecting this TC8 has had it, as to be expected. Pity really as none of mine fit into the headshell.

Is there any way of testing a cartridge just using a multimeter?

I guess the only way I can think of testing the amplifier is attaching a known good cartridge to the inputs wires.
If the BSR TC8H has failed you can buy a new manufactured clone - the "H TC8" at £38-00. Of course this will still only be suitable for 78s, 45s and old Mono LPs. Don't put a Stereo LP anywhere near it!
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Old 19th Oct 2021, 7:33 pm   #16
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Default Re: Sobell S675 Record player

Cricklewood Electronics are a good source for components, and very efficient.
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Old 20th Oct 2021, 2:17 pm   #17
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Default Re: Sobell S675 Record player

Quote:
Originally Posted by martiR2R View Post
ESR Electronics Station Road Cullercoats...??

Just a thought.
Hello Marti,
I just researched ESR a bit more. Its a double fronted old fashioned Aladdin's cave sort of shop. It looks fantastic. I think I will have a trip over there within the next couple of days. It also has quite a good website.

Many thanks for nudging me to take another look at them again.

Cosmic
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Old 20th Oct 2021, 3:27 pm   #18
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Default Re: Sobell S675 Record player

I've only bought a few things, over the years (by post) but have always been happy with the quality.

I would love to go and have a rummage!!

Quite rare these days to find a REAL (electronics) shop you can actually go and walk around?

Hope it is as good as it looks.

Regards
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Old 21st Oct 2021, 6:26 pm   #19
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Default Re: Sobell S675 Record player

Quote:
Originally Posted by _Cosmic_ View Post
Quote:
Originally Posted by peter_sol View Post
I suspect those caps will be fine.
Yes they do look in remarkably good condition seeings how the chassis is so degraded. I'm rapidly going off the whole idea seeing how difficult it is to order small amounts of capacitors from the net. I went on to RS after trying most of the usual companies and you have to order packs of a thousand etc in the case of the cheaper ones. I'm trying to find an electronics shop near to me where I can just go in a buy them. Very difficult.
Cricklewood electronics are fine for small orders.
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