09-12-2018, 08:52 PM
The 37-690X lives!
[Video: https://www.youtube.com/watch?v=xos2MnVxe-c]
I finished the recap on the weekend but didn't have any luck getting anything at all out of it. That's the way it's been since the first time I brought it up on the variac after finishing the amp/power chassis.
So today I decided to trace through the entire amp/power chassis and make sure I hadn't made any dumb mistakes.
Well it didn't take long for me to discover that I had (of course).
I discovered this wire coming off the transformer and with its end hidden under one of the bakelite block.
That there's your problem!
[Image: https://farm2.staticflickr.com/1849/4392...7ea4_c.jpg]
I still traced through the rest of the chassis and then reconnected it and....
[Video: https://www.youtube.com/watch?v=p4UO7o4LPX0]
What a relief to hear it working after going through the whole thing!
Status
Band 1 - Broadcast band works great.
Band 2 - Silent (as expected)
Band 3, 4 - Static
Band 5 - Silent (uh oh)
We'll see once I get things aligned but I would still expect to hear something on Band 5.
Sound out of both tweeters as well as the woofer obviously.
Volume control works well.
IF control works but is noisy.
Magnetic tuning - didn't try yet.
Bass control had no effect.
Audio Choke (Bass amplifier)
The bass control doesn't seem to do anything- and I'm pretty sure it's related to part 104 Audio choke (bass amplifier) being open. It's in parallel with Part 107 but I only measure the resistance of the resistor.
I couldn't find anything about that part (Part No. 32-7528) other than the DC resistance of 2000 ohms labeled on the schematic.
What inductance and current rating should I look for in a replacement? Any thoughts on if I should try to get it rewound or just replace it with a modern equivalent?
[Video: https://www.youtube.com/watch?v=xos2MnVxe-c]
I finished the recap on the weekend but didn't have any luck getting anything at all out of it. That's the way it's been since the first time I brought it up on the variac after finishing the amp/power chassis.
So today I decided to trace through the entire amp/power chassis and make sure I hadn't made any dumb mistakes.
Well it didn't take long for me to discover that I had (of course).
I discovered this wire coming off the transformer and with its end hidden under one of the bakelite block.
That there's your problem!
[Image: https://farm2.staticflickr.com/1849/4392...7ea4_c.jpg]
I still traced through the rest of the chassis and then reconnected it and....
[Video: https://www.youtube.com/watch?v=p4UO7o4LPX0]
What a relief to hear it working after going through the whole thing!
Status
Band 1 - Broadcast band works great.
Band 2 - Silent (as expected)
Band 3, 4 - Static
Band 5 - Silent (uh oh)
We'll see once I get things aligned but I would still expect to hear something on Band 5.
Sound out of both tweeters as well as the woofer obviously.
Volume control works well.
IF control works but is noisy.
Magnetic tuning - didn't try yet.
Bass control had no effect.
Audio Choke (Bass amplifier)
The bass control doesn't seem to do anything- and I'm pretty sure it's related to part 104 Audio choke (bass amplifier) being open. It's in parallel with Part 107 but I only measure the resistance of the resistor.
I couldn't find anything about that part (Part No. 32-7528) other than the DC resistance of 2000 ohms labeled on the schematic.
What inductance and current rating should I look for in a replacement? Any thoughts on if I should try to get it rewound or just replace it with a modern equivalent?
