Manufacturer: General Radio Company (USA)
Model: 635-B, S#138
Vintage: 1935
Purpose: General Purpose
Condition: Unknown
Comments:
The 635 is the little brother of the 687. I say little because it does not include any amplifiers or a sweep generator. It could also be viewed as the cheapo version. The only tubes are the 906 CRT and a 2X2 rectifier. For electronic measurements it would require amplifiers and a sweep generator, quite cumbersome. It is safe to assume that if a company had the budget to buy a GR scope, it would have gone for the 687. The 635 has some specific uses but then simpler and cheaper scopes of that time would have worked too.
This 635 came from the STC radio factory in Botany Sydney NSW. Apparently it wasn't used much because it is in beautiful condition. The case is still solid and didn't even require much of a cleanup. The inside was reworked quite a bit. It was changed to accept 240Vac and controls for vertical and horizontal beam control were added. These two controls are the ones below the CRT. They are not original. Still, based on the potentiometers used, the modifications were made very early. Also a power switch was added beside the power connector.
One of the pictures shows the schematic, which was found inside the scope, behind the CRT shield. According to the paper, the modifications were made in 1947.
I am not aware of another surviving 635. Should you have one, please contact me. I would love to compare some of the components.
Model: 635-B, S#138
Vintage: 1935
Purpose: General Purpose
Condition: Unknown
Comments:
The 635 is the little brother of the 687. I say little because it does not include any amplifiers or a sweep generator. It could also be viewed as the cheapo version. The only tubes are the 906 CRT and a 2X2 rectifier. For electronic measurements it would require amplifiers and a sweep generator, quite cumbersome. It is safe to assume that if a company had the budget to buy a GR scope, it would have gone for the 687. The 635 has some specific uses but then simpler and cheaper scopes of that time would have worked too.
This 635 came from the STC radio factory in Botany Sydney NSW. Apparently it wasn't used much because it is in beautiful condition. The case is still solid and didn't even require much of a cleanup. The inside was reworked quite a bit. It was changed to accept 240Vac and controls for vertical and horizontal beam control were added. These two controls are the ones below the CRT. They are not original. Still, based on the potentiometers used, the modifications were made very early. Also a power switch was added beside the power connector.
One of the pictures shows the schematic, which was found inside the scope, behind the CRT shield. According to the paper, the modifications were made in 1947.
I am not aware of another surviving 635. Should you have one, please contact me. I would love to compare some of the components.
Documentation:
| catalog_h_1935_oscillograph_635-b.pdf |