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

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Old 18th Sep 2020, 1:05 pm   #1
FERNSEH
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Default Sobell SG678 radiogram made in 1964.

For a local customer I've accepted this smart looking stereo radiogram for repair and restoration.
Judging by the condition of the components the 'gram hasn't had much use.
After replacing the 0.02uF coupling capacitors between the triode and pentode sections of the ECL86 audio output valves and checking for any short circuits full mains power was supplied. The receiver does work but there are few minor issues to sort out. The BSR TC8S pickup should be replaced and the FM tuner needs adjustment to extend the frequency coverage to receive Classis FM. In NE England the station is transmitted on 100.3Mhz and the FM tuner in this receiver the frequency range is 88 to 100Mhz.
Also, when the volume control is turned down there is some background noises which go away when the audio printed circuit is flexed.

DFWB.
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Old 18th Sep 2020, 1:13 pm   #2
Edward Huggins
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Default Re: GEC SRG678 radiogram made in 1964.

GEC did not ever use a SRG model prefix and, sorry if I appear to doubt you, but are you sure that's a GEC Stereogram?
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Old 18th Sep 2020, 1:45 pm   #3
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Default Re: GEC SRG678 radiogram made in 1964.

Hi Edward,
I sure got that wrong, It's a Sobell SRG678.
Perhaps the moderators can change the title of this topic?

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Old 18th Sep 2020, 3:42 pm   #4
Edward Huggins
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Default Re: GEC SRG678 radiogram made in 1964.

This is still wrong. SRG is a BUSH code. There is no such thing as a Sobell SRG 678. Help us to help you please.....Do you mean a Sobell SG678?
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Old 18th Sep 2020, 5:03 pm   #5
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Default Re: Sobell SRG678 radiogram made in 1964.

5:03pm Just phoned the owner of the radiogram. It is indeed a model SG678.

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Old 18th Sep 2020, 5:30 pm   #6
Edward Huggins
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Default Re: Sobell SRG678 radiogram made in 1964.

Ah, so now we know the Make and Model. The FM Tuning range should be able to be "shifted" to a small degree, as distinct from extended. If you are going to replace the TC8S, there are more modern and better cartridges. Note these will of course have 4 connectors.
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Old 18th Sep 2020, 8:37 pm   #7
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Default Re: Sobell SG678 radiogram made in 1964.

For starters the hum and funny noises issue can be easily fixed by making a direct wire connection from the negative tag of the HT smoothing capacitor to the chassis metalwork.
This has already been tried and it solves the problem.
The two ECL86 output valves deliver excellent results from what is a simple circuit.

DFWB.
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Old 19th Sep 2020, 10:15 am   #8
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Default Re: Sobell SG678 radiogram made in 1964.

FM tuning range extended to >100Mhz by adjusting the local oscillator coil.
ClassicFM on 100.3Mhz now coming in loud and clear.
Tuning position of BBC Radio2 on 88.5Mhz is hardly effected.

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Old 19th Sep 2020, 1:11 pm   #9
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Default Re: Sobell SG678 radiogram made in 1964.

I'm guessing the confusion over the model number is because the gram cabinet and back panel with model number on was left at the customers house due to size and awkwardness of transportation and workshop space, with just the chassis being brought into the workshop for service.

A lot of these sets will just manage to pull Classic FM in right on the end of the scale without any readjustment, but obviously not in the case of this one.
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