[Boatanchors] SX-130 problem
imalowfer at yahoo.com
Wed Feb 1 12:24:13 EST 2012
Many thanks for all of the replies, re the SX-130 question!
I must apologize for not mentioning that this receiver does have a product detector (a 6BE6 pentagrid converter, as Bill mentioned). However, it uses carrier derived AVC, instead of audio derived AGC. I don't recall ever using a receiver with that combination (product detector and carrier derived AVC), so I don't have any experience with the results.
I assumed that the AVC bypass caps, and audio coupling caps were paper dielectric type, and I suggested that he replace them. He advised that they were disc ceramic types. He has also checked the IF transformers for leakage (which would upset the AVC), and he has replaced the resistors in the plate and screen circuits, of the product detector. The electrode voltages, on the 6BE6 are very close to those indicated on the schematic, except for the plate voltage (93 v actual vs 62 v, on the schematic).
The schematic diagram indicates that Hallicrafters used a capacitive voltage divider, to reduce the IF signal voltage by a factor of ~ 10, before applying it to the 6BE6 signal grid.
Again, any comments would be greatly appreciated.
73 de Ron N4GJV
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